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2.5l myths and differences.

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Old 03-11-2009, 11:00 AM   #1
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2.5l myths and differences.

ive gotten some mixed info on the 2.5 duke and what parts are compatible.
marine cranks, diffence in heads, super duty, cosworth.....
EDDIE this is kinda directed at you cause your the man..
lets clear this all up... what works and what doesnt, whats good and whats bad?
is there a difference in the heads in an A code and E code?which is better?
same w/ the intakes on the A and E, are the diff?which is better?
is there a electric water pump for these?
ive got more questions but im sure everyone else does too so
Old 03-11-2009, 11:38 AM   #2
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Re: 2.5l myths and differences.

http://ironduke7.tripod.com/index.htm
Old 03-11-2009, 11:47 AM   #3
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Exclamation Re: 2.5l myths and differences.

fab--

This thread is an excellent idea. It should be made a sticky, so it can be found and added to, easily.

I think, now, after many questions, that the Code E and the later, Code A, are so different, that they may be considered two entirely different engines. And, within THAT, there are, for example, THREE different Code A engines, just based on anti-smog regulations. We have the 49-state Code A, the California Code A, and a "mystery" Mountain Code A. What GM did to that last one, to make it run at high altitude, should make it a *hot rod* at sea level. "Sea level", as in where the ambient air is more dense.

Looking at it, the Mountain Motor probably has a different tune in the brainbox and mechanically, perhaps a different
MAP sensor and/or injector, although I haven't found it listed in the on-line parts catalogs from places like Napaonline...the MM is probably one of those "rarest of the rare" items, and as such, may not even be listed.

Where I am going with this: Can a lowly Code E engine be "converted" to a sea level MM with fairly simple mods like a MAP sensor swap?? You would still be strapped with all of the Code E deficits, like the headflow restrictions inherent to the design, but you would gain in output at sea level. Where the air is more dense. This all could be a dead end. However it certainly merits more research.

Last edited by Steady Eddie; 03-11-2009 at 11:54 AM.
Old 03-11-2009, 12:44 PM   #4
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Re: 2.5l myths and differences.

what exactly are the differences between the A and E? which one is better?
i want to know cause i have both(a 93 that was running like crap last time i heard it and an 85 that is running which is about all i can say, in my 86 longbox) and im lookin to rebuild or get one rebuilt, if one head flows better then the other one im obviously gonna wanna use it!lol
Old 03-11-2009, 01:31 PM   #5
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Lightbulb Re: 2.5l myths and differences.

Quote: Originally Posted by the_fabricator
what exactly are the differences between the A and E? which one is better?
i want to know cause i have both(a 93 that was running like crap last time i heard it and an 85 that is running which is about all i can say, in my 86 longbox) and im lookin to rebuild or get one rebuilt, if one head flows better then the other one im obviously gonna wanna use it!lol
========================
Somehow (depends on where you look), the Code A is rated at either 12 or 13 MORE horsepower than the Code E engine.

Where did this "extra" horsepower come from??

I don't know.

What I DO know is this:

The Code A has a different intake manifold with a different EGR valve. The gaskets are different.

The Code A has a different throttle body (TBI).

The Code A has a different Brainbox with different bin tuning.

The Code A has the better valve springs.

vs. your 1985 Code E, the '93 Code A has a stronger cast block.

vs. your '85, the '93 Code A has "crankshaft counter-balancing" so it should be a smoother engine.

And the list goes on.

Does the Code A head swap onto a Code E motor?? I don't know that, either. But if it does fit, you'd for sure need the matching intake.

Last edited by Steady Eddie; 03-11-2009 at 01:37 PM.
Old 03-11-2009, 03:09 PM   #6
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Re: 2.5l myths and differences.

so it sounds like the a code is the way to go
Old 03-11-2009, 03:11 PM   #7
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Re: 2.5l myths and differences.

any links for superduty stuff?
any info for crank swaps?
Old 03-11-2009, 05:22 PM   #8
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Lightbulb Re: 2.5l myths and differences.

Quote: Originally Posted by the_fabricator
any links for superduty stuff?
any info for crank swaps?
=========================
The SD stuff is here in the Archives, but save your typing fingers....SD stuff mainly fits SD engine blocks...the headbolts are fully 1/2"--the spacing is different, too. While the SD cast iron head WILL fit on a Code A or a Code E, there is some machine shop work needed to the block to get it on there.

The crankshaft swaps ARE doable, too. We just do not have (at this time) any Members that have been there and done that. Folks that could post up a "how-to" guide.

The 181 cu. inch Marine Crank will fit, one is available with the correct rear crankshaft seal, but then you get into the issue of what rods to use. Pontiac made forged pistons for the Turbo 301 V-8 that drop in. The 181 crankshaft is cast, however, and not forged. But you wind up with a 3 Liter 4-banger...there are 327 V-8 Chevy rods that are "supposed" to work, with minimum machine shop work. These are available as forged rods, via the aftermarket. A 3 liter should be dammed near blow-up proof...

Last edited by Steady Eddie; 03-11-2009 at 05:25 PM.
Old 03-11-2009, 05:50 PM   #9
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Re: 2.5l myths and differences.

can i use the crank w/ stock everything else? im not intrested in getting any more machining than what is needed.
are the pontiac 301 rods price compatible w/ oe replacements?
Old 03-11-2009, 06:15 PM   #10
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Re: 2.5l myths and differences.

where can i find a 181 crank?
Old 03-11-2009, 07:21 PM   #11
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Re: 2.5l myths and differences.

fab--

Most all of this stuff is in the Archives..

That said, here is a video of a newly rebuilt 181 Marine engine--note that it IS NOT our S10 Iron Duke, but it is based on the 153 cu. in. Chevy II 4-banger.

http://videos.streetfire.net/video/C...-on_178833.htm

All you want is the correct rear seal 181 crankshaft, OUT of a motor like the one shown...

The vid shows "how" a rebuilder correctly "breaks a motor in".

There is no way I have heard to do this 3 L crank swap WITHOUT machine work....$$$

Last edited by Steady Eddie; 03-11-2009 at 07:22 PM.
Old 03-11-2009, 07:40 PM   #12
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Re: 2.5l myths and differences.

neat video.
you have alot of really good info on these duke, if you have links to all your information would be great
Old 03-11-2009, 08:19 PM   #13
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Re: 2.5l myths and differences.

fab--

Being ignorant, I always wondered how in hell you could buy a "broken-in, fully-tested" crate rebuilt motor and when it arrived it had NO black carbon in the exhaust ports. Now we all know, they do not fire 'em.

I ran across this link a while back, with comments from KRP's rep guy:

http://www.thedirtforum.com/ubb/Foru...ML/000786.html

Far down in this interesting thread he says he'll sell you a fully-prepped 181 crank (for swapping) for $800--race ready.

THEN he says what rods to use..BINGO???

Last edited by Steady Eddie; 03-11-2009 at 08:21 PM.
Old 03-11-2009, 08:30 PM   #14
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Re: 2.5l myths and differences.

So say that i blow up my 87 2.5, i can purchase a 2.5 from a 1993 and drop it in ?
Old 03-11-2009, 08:48 PM   #15
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Re: 2.5l myths and differences.

Yeah, why not, may not make advertised power, may need a different intake.

Eddie, you my friend must be retired or have way too much time on your hands. :-)
Old 03-11-2009, 09:02 PM   #16
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Re: 2.5l myths and differences.

The marine crank swap is problematic but not impossible. definitely start with the one piece seal unit.
Here is a photo of an early 2pc seal marine crank. Note how far the flywheel (actually drive plate) flange extends past the oil slinger/rear seal area.

Sorry I didn't take take any pics of my duke crank when I had it out, but here is a pic of my 3.625 (181) SD crank. uh no it's not for sale

This is the business end. If you can find a 1 pc seal marine crank on ebay or somewhere note how much of the end of the crank would have to be cut back. Necessitating the drilling of new holes for the flywheel. Alternately one could adapt a flywheel and space the trans back to accomodate. Not a super clean solution.

Maybe someone could post up a 2.5L OEM crank for comparison.

BTW While I sold that marine crank, I still have the rods from it. Can't recall the length, but could be used with a mercruiser crank and pistons (press fit) to make a combo if someone was intent on doing it.
Old 03-11-2009, 09:28 PM   #17
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Lightbulb Re: 2.5l myths and differences.

mafia---

If the motor mounts all carry the same part number, then it should drop in. The two engines are physically the same size.

But I have read that sometime in there, about 92 or 93, GM changed the plug-in for the injector. They went to a new, improved version. I DO know that a Code A injector carries a different part number and has a different receptacle on it. So what could that mean? It might mean that GM changed them ALL, so that your Code E harness would not work. If it only means that they changed just that one connector, then you could steal the one from the Code A donor rig, and splice it into your harness.

Knowing that the Code A injector was "different" I tried to find out if it had a higher flow rate, and there was the greater HP...I could not find it on any flow charts ???
Old 03-11-2009, 09:37 PM   #18
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Re: 2.5l myths and differences.

blowd--

GREAT pictures--thank you..
Old 03-11-2009, 09:52 PM   #19
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Re: 2.5l myths and differences.

whats the part number on that wood box/crate?
Old 03-11-2009, 10:14 PM   #20
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Re: 2.5l myths and differences.

dime,
That's a 10093312 You wouldn't believe what I got with it, but that's another thread.
If your into SD's and don't have it already google on HotrodSD4guide.pdf It's posted a couple of places but I don't recall off the top of the ole noggin'. Big download but it's the cliff notes/bible for SD's most of the p/n as well. Betcha Eddie knows where to get it.
Old 03-11-2009, 10:33 PM   #21
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Lightbulb Re: 2.5l myths and differences.

Here is a side by side, the SD crank that blowd has is the one on the right.

http://ironduke7.tripod.com/Crank_Compare.jpg

You can see by looking, how puny the OE crankshaft is...

Last edited by Steady Eddie; 03-11-2009 at 10:36 PM.
Old 03-11-2009, 11:25 PM   #22
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Re: 2.5l myths and differences.

Link dont work man
Old 03-11-2009, 11:48 PM   #23
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Re: 2.5l myths and differences.

Quote: Originally Posted by lesterl
Link dont work man
Fixed it...sorry about the delay, I was out looking for that Hot Rod Magazine article--lol...
Old 03-12-2009, 09:10 AM   #24
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Re: 2.5l myths and differences.

awsome blowd! love the pics!
believe it or not the was a difference in the wireing harness's between an 85 and 86, there was one plug from the 85 that wouldnt fit into the 86 brainbox.
as for the 93, if it where me(and its gonna be) i will take the brainbox from the 93 when it comes time to drop it in. you might get away w/ some splices, or swaping your 87 harness. when i dropped the 85 in i had to use my 86 harness.
Old 03-12-2009, 09:32 PM   #25
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Re: 2.5l myths and differences.

Quote: Originally Posted by Steady Eddie
Fixed it...sorry about the delay, I was out looking for that Hot Rod Magazine article--lol...

Eddie, it still doesnt work... it was too long since you posted to edit. Might try reposting.
Old 03-12-2009, 09:54 PM   #26
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Lightbulb Re: 2.5l myths and differences.

Quote: Originally Posted by lesterl
Eddie, it still doesnt work... it was too long since you posted to edit. Might try reposting.
======================
les---

It works on my end--Browser=Cuil/Firefox OS=XP Home Edition.

I did change the link from attempting a [img] pic[/img] to just an http: Link...maybe your Browser is showing a (ahemmm) rather elderly post...try refreshing the page and go for it again.
Old 03-12-2009, 10:13 PM   #27
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Re: 2.5l myths and differences.

i wish there were people around me that were interesting in building 2.5's up. Hell ive had a 91 A code motor sitting in my garage taking up space for allmost 2 years now.. not one person will even offer me 50 bucks for it.
Old 03-12-2009, 10:24 PM   #28
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Talking Re: 2.5l myths and differences.

Quote: Originally Posted by 98layinframe
i wish there were people around me that were interesting in building 2.5's up. Hell ive had a 91 A code motor sitting in my garage taking up space for allmost 2 years now.. not one person will even offer me 50 bucks for it.
====================
Dave--

I believe you've come to the right place to sell it. Nice to see ya dip in here, welcome aboard!!

BTW: Was that a little Freudian slip there? I am sure you meant "interested"--lol---but on the other hand, we DO have some interesting folks here, too...

Last edited by Steady Eddie; 03-12-2009 at 10:28 PM.
Old 03-12-2009, 11:18 PM   #29
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Re: 2.5l myths and differences.

Copied and pasted link into new browser window, works fine, hmm....... IE7 MICROSHAFT products!!!!!!!!!!!!!!!!
Old 03-13-2009, 12:31 AM   #30
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Re: 2.5l myths and differences.

Quote: Originally Posted by 98layinframe
i wish there were people around me that were interesting in building 2.5's up. Hell ive had a 91 A code motor sitting in my garage taking up space for allmost 2 years now.. not one person will even offer me 50 bucks for it.
$100 shipped?

If you were closer id take it....
Old 03-13-2009, 10:01 AM   #31
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Re: 2.5l myths and differences.

ide take it for 100 shipped if i wasnt gettin a whole 93 for 150, not to mention its right next door!
Old 03-14-2009, 12:45 AM   #32
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Re: 2.5l myths and differences.

Little sumthin sumthin I came across...SD stuff from GM Performance parts

http://www.s-series.org/htm/tech/GMP...ts/160-164.pdf
Old 03-14-2009, 10:37 AM   #33
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Re: 2.5l myths and differences.

Quote: Originally Posted by 92 s10 project
Little sumthin sumthin I came across...SD stuff from GM Performance parts

http://www.s-series.org/htm/tech/GMP...ts/160-164.pdf
Old 04-04-2009, 11:39 PM   #34
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Re: 2.5l myths and differences.

Quote: Originally Posted by Steady Eddie
========================
Somehow (depends on where you look), the Code A is rated at either 12 or 13 MORE horsepower than the Code E engine.

Where did this "extra" horsepower come from??

I don't know.

What I DO know is this:

The Code A has a different intake manifold with a different EGR valve. The gaskets are different.

The Code A has a different throttle body (TBI).

The Code A has a different Brainbox with different bin tuning.

The Code A has the better valve springs.

vs. your 1985 Code E, the '93 Code A has a stronger cast block.

vs. your '85, the '93 Code A has "crankshaft counter-balancing" so it should be a smoother engine.

And the list goes on.

Does the Code A head swap onto a Code E motor?? I don't know that, either. But if it does fit, you'd for sure need the matching intake.
The heads can swap but you have to have the intake to match the head model. I am running an 89 motor with an 85 intake, but I had to make an adapter plate to make the ports match. The ports on the head are half an inch higher than the ports on the intake manifold, but the bolt holes are the same.
Old 04-05-2009, 08:22 AM   #35
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Thumbs up Re: 2.5l myths and differences.

Quote: Originally Posted by 85 Orange Dime
The heads can swap but you have to have the intake to match the head model. I am running an 89 motor with an 85 intake, but I had to make an adapter plate to make the ports match. The ports on the head are half an inch higher than the ports on the intake manifold, but the bolt holes are the same.
=====================
85OD--

Thanks for posting that...it is another difference.

On eBay, you will see rebuilt heads where the guy says his item will fit "all" 2.5 Liter GM Iron Duke Engines. While that may be, that it will fit the block, you have to consider that the intake may NOT fit. Our little engines are proving out to be one of GM's most changed "but the same" engines ever.
Old 04-06-2009, 05:45 PM   #36
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Re: 2.5l myths and differences.

Quote: Originally Posted by Steady Eddie

This thread is an excellent idea. It should be made a sticky, so it can be found and added to, easily.
Done
Old 04-09-2009, 08:30 AM   #37
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Re: 2.5l myths and differences...cylinder heads...

Here's a link that shows the differences between Stock and the Super Duty stuff...
http://images.google.com/imgres?imgu...icial%26sa%3DN

Steady Eddie
Old 04-15-2009, 08:11 PM   #38
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Re: 2.5l myths and differences.

Hey guy's im new here but i have a 1986 s-10 with a 2.5l iron duke. it had about 167,789 miles on it and finily broke a timing gear so i rebuilt it from the bottom up all new parts. as for The fabracator you could do what i did and have the head worked (head gaset mached on the intake side and the headside,and the intake matched too both timing gears steel slash cut) most people want to put v8's in the s10 but for me that is too common,i like to do thing differnt.
Old 05-05-2009, 03:10 PM   #39
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Re: 2.5l myths and differences.

Well guys and gals I have never posted anything anywhere on any forum until today. I guess that makes me a "Newbie"? Ive been reading S10 as well as Fiero forums for years about the mysterious "Marine" crank in the 2.5 block and Ive got to tell you Ive gone everywhere from laughing to crying when I read some of them. Unfortunately much (if not most) of the info about this topic floating around on the forums are "rumors" disguised as "facts". Now I dont mean any of this is intentional but just an example of when something is repeated enough times by enough people it seems to become a "fact". I am here because I JUST COULDNT TAKE IT ANY LONGER! I have personally done this conversion and drive, on a daily basis, an 89 S10 2.5 with the "153" (3.25" stroke) marine crankshaft. I have also converted it to the "A" code head, intake, cam, and throttlebody. I have considerably more power and torque as well as getting as high as 30MPG (I average about 28 on most trips) on regular fuel. It even passes California smog inspections. I know how to overcome the rear main seal issue, what rods to use, what pistons, what head modifications, injector and the biggest issue of all "the flywheel". I have also installed a "181" (3.6" stroke) marine crankshaft in the S10 block as well (although I chose to go with the 153 crank instead [at least for this time around]). The reasons that I chose the 153 instead of the 181 crank are "mainly" as follows:
1) This needed to be a California smog "legal" engine and I was concerned about the extreme cubic inch increase not passing the test.
2) Unless I used a Super Duty head (which wouldnt pass Ca smog) I didnt feel the stock head would flow enough to properly feed the beast.
3) Last but not least, AND THIS IS THE KEY TO THE 181 CRANKSHAFT CONVERSION IN THE IRON DUKE, you must use at least a 6.200" rod or the engine will self distruct!
The reason you need at least 6.200" (6.25" preferably) rod is this:
When GM cast the Iron Duke block it shaved weight everywhere it could. One of the places was in the height of the cylinder walls. The 151 only has a 3.00" stroke therefore it only needed a cylinder wall tall enough to accommodate the 3" stroke. When you install the marine 3.6" stroke crank (and rods) in the Iron Duke block you will literally pull the wrist pin to the very bottom of the cylinder wall at the bottom of its stroke. The piston will then "cock" itself in the bore breaking the piston and then probably send the rod through the side of the block. The stock marine 181 rod is only 5.7" (same length as a Small Block Chevy). There are no "off the shelf" rods that I know of that will fit that crank and are long enough. The cost of having custom rods made also played a part in my S10 decision. The later (one piece seal) marine crank will also work but requires extensive machining of the seal and flywheel area (not to mention the filling if the original flywheel bolt holes). I do have another 2.5 that at some time I will do the 181 conversion for a Street Rod or something. I also have a Super Duty engine and parts so I am very familiar with both engines. None of this info is second hand as I have actually "done this myself", along with the hand machining of the custom flywheel. Ive left out a lot of "details" for now but just gave you enough info to chew on for awhile! StrokerS10
Old 05-06-2009, 11:57 PM   #40
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Re: 2.5l myths and differences.

That has to be in the top 10 of the 'most informative threads' I have ever read.

Thanks a lot stroker, I hope you will inform us some more before this post loses it flavor
Old 05-07-2009, 10:21 AM   #41
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Re: 2.5l myths and differences.

^^X2^^

Keep the info coming, Stroker, what a helluva *first* POST!!!
Old 05-07-2009, 04:55 PM   #42
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Talking Re: 2.5l myths and differences.

Ok boys and girls here is a little more info on the 2.5 "Iron Duke" engine for any of you that really care. For years and years there has been lots confusion over the difference between the "Chevrolet" 153 (3.875" bore x 3.25" stroke) and the "Pontiac" 151 (4.00" bore x 3.00" stroke). Everyone seems to want to call both of these an "Iron Duke". There has been a long going debate over whether that nickname started with the Chevy II 153 or the Pontiac 151 (2.5) engine. I can tell you from personal experience (since I am an "old fart") that it wasn't until Pontiac started building the 151 in 1977 that it became known as the "Iron Duke". The "Stovebolt" 153 was originally built by Chevrolet between the years of 1962 and 1970 for use in the Chevy II as well as the 63-67 Chevrolet (Economaster?) van. It was for the most part a shortened 230 cu. in. Chevy six cyl. It was also produced by GM for OMC Marine from 1964 -1992 until OMC sold out. At around that time Mercury Marine (Mercruiser) took over the use of this engine with GM building a bored and stroked (4.00" bore x 3.600" stroke) 181 cu. in. version albeit with a new better casting for the block. Both of these engines (153 and 181 [UP TO 1993]) used a non crossflow head (Intake and exhaust on the same side), a two piece rear main seal (same part # as Small Block Chevy), a Chevrolet bellhousing bolt pattern (same as Small Block, Big Block, Six cyl., and the 4.3 V6), and a Chevrolet flywheel/ring gear and starter (also the same as a Chevy V8). The 1994 and up 181 "Marine" block and crank used the "one piece" rear main seal therefore the block and crank were different. The 153 and the 181 were also used in industrial applications like forklifts as well.
In 1977 Pontiac started building their own "version" of the four cyl. engine. They obviously "based" their original design on the Chevrolet 153 but with a different bore and stroke (and with rods and pistons like those found in the 301 Pontiac V8). As I recall they, for only the first 2 1/2 years (1977 through mid year 1979 in the Monza and Astra), stayed with the Chevrolet bellhousing bolt pattern, two piece rear main seal crankshaft and the non crossflow head design as the 153 and 181. The crankshaft in this engine would drop right in a 153 (or vice versa) as long as you used the proper rods and/or pistons. This is when the circle trackers took advantage of the larger bore of the 77-79 151 by installing the 153 crankshaft yielding 163 cu. in. (same bore and stroke of the famous 327 Chevrolet) in the 151 block. For them this was a bolt in no brainer. Now starting mid year 1979 until 1993 the block, crank and heads were changed to accommodate a one piece rear main seal and crossflow (intake and exhaust on opposite sides [better flowing]) head. Now this part I am not 100% sure about (only about 95%), my memory tells me this is also when they changed the bellhousing to the "Small Corporate (60 degree V6 [2.8])" bellhousing bolt pattern (the same as ALL 2.5 S10s). Because of these changes you could not anymore just "bolt in" the 153 or the 181 crankshaft in the later (79 to 93 2.5) block without a custom rear main seal adapter, a hand made flywheel and special rods/pistons. Nor could you just bolt in a 153 or 181 engine into your S10. It can be done but you would need to change the bellhousing, flywheel, clutch, hyd. clutch, and starter just to name a few. You would also need to fabricate engine mounts as the block is of a completely different casting, your accessories wouldnt bolt back on and you would still be stuck with the non crossflow head (along with several other differences to deal with).
Now Pontiac has made several different versions of the 151 with all sorts of changes over the years which has caused lots and lots of confusion. They built "2", "5", "R", "U", "E" and "A" code engines (I may have even left out a few). The one you mainly need to stay away from for your S10 is the "U" code engine as the crank is 1 1/4" shorter and the block is different as well. The "U" engine also requires a different head gasket even though some of the head casting #s are the same (IIRC they moved one of the bolt holes). I believe all of the others are of the correct dimensions but you need to watch out for those that dont have the front water pump machining for your S10. Some of the front wheel drive (as well as the Fiero) blocks only have a "Hole" on the drivers side to acommodate their side mounted water pump. This hole can be covered as long as the block still has provisions for the front mount pump (some do some dont) for your S10. Many of these engines have "balance shafts" and "Gyro" type oil pump systems. Now it has also been rumored that the S10s have stronger blocks than the passenger car engines. To be honest with you I dont know for sure but what I do know is that they have different casting numbers and to play it safe I would recommend staying with an S10 block in your S10 since at least you will know everything will still "bolt on" when you are finished. If you do try a pass. car engine look to the "R" engine but make sure you do all of your homework first. Other than a Super Duty block I would recommend the later 10044311 (88-93 S10/S15/Astro/Postal Vehicle) roller cam block in your S10.
IIRC when Pontiac built their first "Indy Fiero" they used a stock Fiero (no stronger than your S10) block with a Super Duty crankshaft and head and pumped out 232 hp. This should tell you that the little 2.5 block in your S10 can handle more than you might think (they did upgrade to 1/2" head studs and maybe even 1/2" main cap bolts as well). The crankshaft (along with the rods) on the other hand are another story (maybe to be continued [its up to you!]). I know I have left out lots of block and crank details in this but I am just getting started and I dont think you need to know everything (just too overwhelming) right now. If you really, and I mean REALLY want to know more about building up a 2.5, then you need to post some more replies or you never know I might just "Fade Away". StrokerS10
Old 05-07-2009, 07:30 PM   #43
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Re: 2.5l myths and differences.

P.S. For those of you interested there is a real Super Duty 4 crankshaft on EBAY set to expire 5/12/09. This will drop right in your 85-93 S10 block. Go For It! StrokerS10
Old 05-08-2009, 12:06 AM   #44
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Re: 2.5l myths and differences.

In my last long post I had mentioned that I was 95% sure that the Iron Duke bellhousing bolt pattern changed in mid 1979 to the Small Corporate Pattern. I had thought that it had changed at the same time the one piece rear main seal and the crossflow head were introduced. Well after further thought and review I seem to recall that 1980-83 Jeep CJ as well as the 1980-83 AMC Spirit, Concord and Eagle used the Iron Duke but still with the "Chevrolet" bolt pattern. So in other words the Iron Duke used the "Chevy" bolt pattern from 1977-1983. At least I "Think" thats right. StrokerS10
Old 05-08-2009, 02:15 AM   #45
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Re: 2.5l myths and differences.

Stroker--

Keep 'em coming, you are doing good. :-)
Old 05-08-2009, 03:10 AM   #46
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Re: 2.5l myths and differences.

I for one would really really like to know all I can about building up the 2.5. It is not common and very different which is very appealing to me. The fact that it costs more or not is not the point here.

I love the info you are providing us with here Stroker, keep it coming and please dont fade away!

Whenever I get around to actually doing something, you are going to save me a whole lot of time and money because I am not doing all this buying and fitting and measuring and researching myself.

I very much appreciate what you are doing. If you know of any place that has any pictures posted those are always awesome but so far you are painting a beautiful picture.
Old 05-08-2009, 08:24 AM   #47
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Re: 2.5l myths and differences.

You cant be serious with post #42, you couldnt pay me to sift through a lump like that, its the hugest paragraph in the history of the earth.

Youve given multiple people headaches...lol
Old 05-08-2009, 11:09 PM   #48
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Re: 2.5l myths and differences.

42 Was kinda painful, but I read it top to bottom and enjoyed the info, keep it comming.
Old 05-09-2009, 06:34 PM   #49
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Re: 2.5l myths and differences.

Greetings ladies and germs another day and another lesson. Sometimes these lessons can be somewhat "painful" as SweetloveS10V8 pointed out but sometimes when you endeavour to go down a road less traveled or especially to blaze a new trail altogether, you've got to know where you are, in order to know where you are going. Homework and research are the key to success. So now that we "think" we know where we are lets try and go forward.
Like someone that I personally met some years ago said "A mans got to know his limitations". This is true of the Iron Duke engine as well. Its horsepower is limited by its lower end, mainly the crankshaft and then the rods. What happens to the 2.5 when pushed above say 130 or 140 (close guess) horsepower the lightweight crankshaft starts to flex (bends) distorting the rods and causes them (the rods)to eventually crack and break. This crankshaft was not designed for anything but economy and acceleration not horsepower. In order to build more horsepower in a stock 3" stroke Iron Duke to say 125hp or more you must increase its rpm's range some. Building horsepower is not the problem, keeping it together is (this is true of most engines). If you were to bolt a Super Duty head and intake to the stock Iron Duke lower end along with a camshaft, carburetor and exhaust to match you could easily build 200hp (for about 5 minutes) until the lower end would "self distruct". In my opinion adding good forged aftermarket rods to a stock Iron Duke is about the absolute minimum you should do if you want to build much more than say 125 horsepower. This does not stop the crankshaft from flexing but the better rods can take more of the abuse. I still would limit the stock crank to a maximun of about about 150hp. From my experience the absolute best way to gain decent horsepower in the Iron Duke is to "STROKE IT". you will build more torque and horsepower without even needing to increase its rpm very far.
The absolute single greatest upgrade for a real Iron Duke performance engine (that will stay together) is the addition of a forged Super Duty crankshaft with a good set of connecting rods. In my estimation this gives you a bottom end that can easily withstand 200 to 225hp (or more) in a stock S10 block with no problems. Unfortunately these crankshafts are scarcer than hen's teeth and expensive if you do find one. Fortunately they do use Small Block Chevy connecting rods that are plentiful and relatively inexpensive. A Super Duty crankshaft in a Super Duty block can handle 500+ hp (I have a non-asperated [with webers] SD that dyno'ed at 374hp) without any problems. In truth, strength wise, these crankshafts are actually somewhat of an overkill in a stock S10 block.
Enter the "marine" crankshafts. Although these crankshafts are nodular iron, not forged, they can handle far more than a stock S10 block can and therefore strength wise are a perfect match for a stock block S10 build. Whereas the SD crank (with SBC rods) including the use of the stock S10 flywheel is a true bolt in, the marine cranks are not. 153 and "early" (up to 93) 181 marine crankshafts will drop right in these blocks (the 181 requires about 1 min. with a die grinder to clearance the dist. boss in the block). The only item needed to fit these "early" cranks into the S10 block is a two piece rear main seal adapter. This consists of two half moon shaped adapters that fit in the block in place of the original S10 one piece rear main seal. The inside of these pieces are machined to accept the early (SBC and marine) two piece rear main seal. These adapters where once made by Kansas Racing Products (same people that took over the production of the SD 4 block). I do not know if they still make them today. I think I might still have a "few" of them somewhere here in my shop though. A machine shop should be able make you a pair if you supplied them with the right dimensions. After properly putting either of these "early" crankshafts in a S10 block it still requires that a custom flywheel be made. The early crankshafts not only have a much larger flywheel bolt pattern but are also .800" longer (to the flywheel mounting surface). The Chevy flywheel that fits these cranks will not fit into the S10 bellhousing let alone the clutch or the use of the S10 starter. Modifying and redrilling the S10 flywheel will not work either as it would still move the clutch .800" to the rear and the starter ring gear will be too far to the rear as well. There have been some who have cut off the crankshaft and have had it remachined to work but it still requires a custom flywheel. I do not recommend this mainly because it weakens the crankshaft to flywheel mounting area (too small a bolt circle). The solution that I have used is to start with a factory Chevrolet V8 (10.4") 153 tooth flywheel, casting #3973455N (1963-69?), and remachine it to fit. (EBAY)
Modify flywheel and trans. as follows:
(You may want to take at least three aspirins about now...lol)
This requires the use of a lathe and someone who knows how to use it. First you machine down the diameter of the flywheel (mainly for the starter gear area) until it is the same diameter as the S10 flywheel (so that the S10 starter gear will fit). Second you machine the flywheels crankshaft mounting surface (I believe it was about .125") to move the starter gear forward enough to duplicate the original S10 starter gear location. Third you surface the flywheel face itself about .125 (its way too thick and heavy for a four cyl. anyway) to move the clutch as far forward as possible but still leaving ample room (at least a 1/16") between the clutch hub springs and flywheel mounting bolt heads (I used part #14052 Mighty Mite [Ford] bolts as the heads are thinner). Fourth you redrill the flywheel for the smaller S10 pressure plate bolt pattern. Fifth you shorten the front bearing retainer on the transmission 1/2" so that it will not hit the clutch hub (or you can just buy a Camaro/Astro van bearing retainer as it is 1/2" shorter already). Sixth you shorten the slave cyl. actuating rod 1/2' (Since the pressure plate has still moved 1/2" closer to the rear). Seventh you make an 1/8" shim to go between the trans and the bellhousing or you will run out of splines on the input shaft just as the trans seats to the bellhousing or you can replace the input shaft with one from an Astro van which is 1/2" shorter and not need the shim. Eigtht, and this is optional, lighten up the flywheel by drilling or milling recesses on the outside/engine side of the flywheel (If you do this the new flywheel will be very close to the weight of the original 2.5 flywheel). Just make sure you stay away from the new pressure plate mounting holes you have drilled.
Modify the "early" marine crankshaft as follows:
The early marine crankshafts are not drilled or tapped for a balancer bolt. I drill and tap mine to accept the metric S10 bolt and washer. I also drill the depth at the rear of the crankshaft with about a 5/8" bit an additional 1/8" or so as I found that even with the trans shim the pilot end of the input shaft would just touch the crankshaft when installed. You could cut 1/8" off the end of the shaft but I choose to countersink the crank a little instead. If you use the Astro van input shaft you will not need to do this.
The "other" marine crankshaft option is to use the "later" 1994 and up 181 crankshaft. This crankshaft is machined at the rear the same as a one piece SBC crankshaft. In stock form this crankshaft will not fit in the block because the large diameter of the seal area is just to big fit (much larger than a stock S10 crank). The solution to using this crankshaft is to modify the seal/flywheel area of the crank until it is exactly the same as the 2.5 crank.
Modify the "late" marine crankshaft as follows:
One, plug the 6 7/16" flywheel bolt holes by epoxying in grade 8 bolts (use a good epoxy). Two, shorten (machine) the end of the crank to the same length as the 2.5 crank. Three, machine the diameter of the seal area until it is the same as the 2.5 seal area (yes you will be cutting into the bolts you epoxied in). Four, redrill the crankshaft to accept the S10 flywheel (in between the old pattern). Five, install a Speedy sleeve over the end of the crank (in order to cover the outside of the exposed bolts). Six, if necessary machine for pilot bushing (some cranks are machined some are not). Seventh, if the crank is not drilled and tapped for the balancer bolt do so.
The advantage to modifying this "later" crankshaft vs the "early" crank is that, after machining, it will accept the stock S10 flywheel and also does not require any trans. input mods. or shims.
So now that you have a "real" crankshaft in your S10 block "What do you do about Connecting rods? Pistons? Head? Camshaft? Etc.?" OMG!
Now for any you light weights that might still be out there, take my advice, swallow a few more aspirins, dont worry, relax and ly down for a while...lol.
"Maybe" to be continued "Its up to you!" StrokerS10
Old 05-10-2009, 01:03 AM   #50
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Re: 2.5l myths and differences.

The main reason it was "painful" was that you left no room between paragraphs and such, it was just a continuous blurb of characters that after a while seemed to run together.

I had to highlight each little bit I was reading just to see where I had already read.

The info was great, just its format was kinda hard to take.

Keep it comming, and might try to add some spacing to make it easier to take (with fewer asprins.)

Thanks. :-)
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