2.8 3.1 stroker ???? - S-10 Forum
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2.8 3.1 stroker ????

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Old 07-02-2006, 10:02 PM   #1
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2.8 3.1 stroker ????

I have a 86 jeep with a gm 2.8 v6 that is shot (330,000 hard driving KM's)
I'm looking to do a auto wrecker stroker motor, 2.8 block 3.1 crank and whatever rod's and pistons i need

camero/firebird 3.1/3.4's are being sold for way too much around here
I have access to tons of 2.8's f/rwd and 3.1/3.4's (fwd only) what would be the best setup(block, crank, rod's, pistons, head's) to go with.

it is a rwd carbed application and I don't want to have a bunch of fabrication as it is my d/d right now so it has to be a 1 day swap (after the motor is assembled obviously)

any tips links or write up's on this would be greatly appreciated

Thanks in advance
Mike
Old 07-02-2006, 10:42 PM   #2
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Re: 2.8 3.1 stroker ????

you need a rwd engine. get a 2.8 and put a 3.1 crank(any 3.1 crank will work) you will need 3.1 rods and pistons(they need to be iron head pistons)
Old 07-03-2006, 02:33 AM   #3
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Re: 2.8 3.1 stroker ????

Quote: Originally Posted by pare_john
you need a rwd engine. get a 2.8 and put a 3.1 crank(any 3.1 crank will work) you will need 3.1 rods and pistons(they need to be iron head pistons)
is there no alum heads that will bolt up without fab work for the intake?
or is there any particular iron heads that are better than others? (bigger valves, better ports, etc)

so i could use a 2.8 block(rwd) with 3.1 crank/rods with pistons from a iron headed 2.8

thanks for the info
Mike
Old 07-03-2006, 03:25 AM   #4
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Re: 2.8 3.1 stroker ????

The pistons need to be from a 3.1. The 2.8 pistons would hit the heads with the longer stroke. I did this stroker thing using a 3.1 out of a Lumina van and an 88 2.8 block. It cost me about $500 total with the rebuild. The Lumina van has iron heads so the pistons work but the block doesn't have anywhere to mount the rwd starter. I'm quite impressed with the results. My S10 4x4 will top out around 105 mph now and pulls real good and that's with the Rochester carb that nobody seems to like.

Last edited by Hayseed; 07-03-2006 at 03:28 AM.
Old 07-03-2006, 04:58 AM   #5
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Re: 2.8 3.1 stroker ????

Quote: Originally Posted by Hayseed
The pistons need to be from a 3.1. The 2.8 pistons would hit the heads with the longer stroke. I did this stroker thing using a 3.1 out of a Lumina van and an 88 2.8 block. It cost me about $500 total with the rebuild. The Lumina van has iron heads so the pistons work but the block doesn't have anywhere to mount the rwd starter. I'm quite impressed with the results. My S10 4x4 will top out around 105 mph now and pulls real good and that's with the Rochester carb that nobody seems to like.
ahh I see now i thought all the fwd applications used alum heads.
the only thing I dont know now is about the heads, are any better than the others?

I dont know I would want to push mine anywhere near 105 (75-80 maybe and I dont even know about that)
right now i'm lucky if i can hit 110......km/h(68.75mph)


thanks Mike

Last edited by mike86xj; 07-03-2006 at 05:03 AM.
Old 07-03-2006, 09:46 AM   #6
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Re: 2.8 3.1 stroker ????

All iron heads off injected motors are the same and have the bigger valves. A porting job helps quite a bit.
Old 07-03-2006, 10:31 AM   #7
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Re: 2.8 3.1 stroker ????

As stated any 3.1 crank can be used, RWD or FWD, same goes for the 3.4 crank, since it is the samed as the 3.1 crank. Both use the 3.31" stroke.

All 660 rod used from '82 to '04 are the same, all are forged steel all are same dimentionaly. After '04 the same rod was still used, but particular engines, like the 3500 and 3900 had a different crank used, with larger rod pins, and I beleive a length change which makes these ones impossible to use, so it's easier just to say "up to '04".

The pistons must be from an iron head application, when using iron heads, other wise the static compression ratio will be in the toilet, if aluminium head pistons are used with the iron heads. Around 7.0:1. The iron heads have a chamber size of 56cc, the aluminium heads use a chamber size of 28cc, quite the difference.

Your best bet, if you can't get a complete iron head 3.1 is to use the FWD crank and get some aftermarket stock replacement pistons, for the iron head 3.1.
Old 07-03-2006, 12:59 PM   #8
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Re: 2.8 3.1 stroker ????

OK i think this will be my last 2 question's

do 88+ all use a neutral balance flywheel?

and 85.5 up got the large journals correct?

thanks for all the help
Old 07-03-2006, 05:38 PM   #9
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Re: 2.8 3.1 stroker ????

Quote: Originally Posted by mike86xj
OK i think this will be my last 2 question's

do 88+ all use a neutral balance flywheel?

and 85.5 up got the large journals correct?

thanks for all the help
That is correct.
Old 07-06-2006, 01:51 AM   #10
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Re: 2.8 3.1 stroker ????

ok I lied i have 1 more question

since i'm building this for a carbed app, when did they delete the mechanical fuel pump mount on the 660 block?
I know that the 3.4's dont have the mount for it but what about the late 2.8 s-10 and camaro blocks

thanks
Mike

Last edited by mike86xj; 07-06-2006 at 01:52 AM.
Old 07-06-2006, 04:52 AM   #11
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Re: 2.8 3.1 stroker ????

1985

There are no large journal blocks with the mechanical fuel pump provision.

You'll be farther ahead to use an electric pump with a newer block.
Old 07-06-2006, 06:39 AM   #12
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Re: 2.8 3.1 stroker ????

Quote: Originally Posted by The_Raven
1985

There are no large journal blocks with the mechanical fuel pump provision.

You'll be farther ahead to use an electric pump with a newer block.
I should have dug around a bit more before asking the last question

I don't know if this information is correct or not but i would think so(being that it is from a major parts supplier)
going from federal mogul's parts lookup https://mfr.activant.com/mfrserv/ext...pplier=FMOFull

84-85 cherokee and 82-85 s-10's 2.8's use 7241ma bearings (for 2.4937-2.4946 std size)

85-86 cherokee's and 85-93 s-10's use 7242ma bearings (for 2.648 std size)

and according to this site http://users.spec.net/home/emxjc/block.html
the late 85 blocks have large journal's and are caburated (did gm use a electric pump?)

is there any way to tell if a block has large journals while it's still installed?

Last edited by mike86xj; 07-06-2006 at 06:43 AM.
Old 07-06-2006, 12:36 PM   #13
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Re: 2.8 3.1 stroker ????

Actually yeah, sorry I was getting ahead of myself, there is a very limited number of blocks that have both large journal and mechanical pump prvisions.

I should have thought about it a bit more and explained it... I was also thinking of most of the rest of the GM line-up that went to EFI in 1985. Kinda funny that I own an '85 that was carburated when I got it, I should have known best. LOL

These blocks are half year only and will be difficult to find without tearing it down to a bare block.

I will suggest just going with a larger journal block, '86+ and using an electric pump, it will be easier to find, since there are a lot still around and possibly cheaper, not that I would say the half year only block would nessisarily be worth any more, but some people have some pre-conceived notions about "rare" items.
Old 07-07-2006, 05:02 AM   #14
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Re: 2.8 3.1 stroker ????

yeah i stumbled across all that when I was trying to figure out if my jeep has the large journal's
usually whe one company sells a item to another, they sell the older technology so i was suprised to learn the jeep changes at the same time as the s-10's

so is there any way to id the large journal blocks when it's still in the vehicle. casting numbers, date codes, etc
just cause you never know what was swapped into that after the motor blew up
Old 07-07-2006, 10:18 AM   #15
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Re: 2.8 3.1 stroker ????

Quote: Originally Posted by mike86xj
yeah i stumbled across all that when I was trying to figure out if my jeep has the large journal's
usually whe one company sells a item to another, they sell the older technology so i was suprised to learn the jeep changes at the same time as the s-10's

so is there any way to id the large journal blocks when it's still in the vehicle. casting numbers, date codes, etc
just cause you never know what was swapped into that after the motor blew up

I haven'[t heard of a way to ID the block with it still in the vehicle.

Some say that the type of rear main seal will be an indication, but would still require at least removing the engine and/or tranny, to get to that part.
Old 07-08-2006, 08:40 PM   #16
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Re: 2.8 3.1 stroker ????

Yea a one piece seal indicates large journal. If you find and EFI vehicle your pretty safe anyway. If I were you though I would be looking for 88 or later. They are all internal balance which is much nicer.
Old 07-09-2006, 02:16 AM   #17
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Re: 2.8 3.1 stroker ????

well i may allready have a complete 86 camaro motor all I'm going to use is the block and maybe the cam(more on that later).
with 1990-95 lumina or transport van internals(the crankwould be internally balanced)

and i have a set of recently rebuilt heads from a 1986 pontiac 6000 ste (looks the same as camaro injection)

now onto the cam question
this motor will be used for d/d and weekend off roader
now wich cam should i use? the one from the original motor or one from the camaro block?
basically my question is where is the powerband with the camaro cam and where is it with the stock cam?(with a well running motor, not mine obviously)
Old 07-11-2006, 10:59 PM   #18
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Re: 2.8 3.1 stroker ????

If you ahve to use a stock cam the Camaro Cam is much nicer than the S-10 Cam. I use the Camaro cam and it isn't half bad. However a wiser choice would be a Crane 260 Cam.
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