S-10 Forum banner
1 - 20 of 29 Posts

·
Registered
Joined
·
23 Posts
Discussion Starter · #1 ·
I have a 95 4.3l 5-spd 2wd with a throttle body injection system and i was just wondering if it was possible to switch it to a CPI system and what parts do i need to do so if it is possible.:D
 

·
Got Fuel Rails?
Joined
·
4,539 Posts
You could, but why? The reason the cpi makes the power is mostly due to the camshaft, it is considerably more agressive.

That is the only advantage i see, and you can put a camshaft in a tbi. Also, tbi's have upgradeable injectors, and they don't have fuel leakage problems that the cpi units have. It is also easier to upgrade a tbi to better '96 up vortec heads than it is on a cpi injection setup.
 

·
Lotsa parts, Lotsa brands
Joined
·
24 Posts
The CPI also had lighter, performance pistons (made by Mahle) that year, which the TBI never got.

The CPI air intake will need to be donated, and you'd also need the CPI's high pressure fuel pump, and likely the computer as I think the 94-95 year change also saw the OBDI to OBDII changeover (not sure the OBDII can run the 94 CPI.

I've got the 94 CPI.
It's a very nice engine.

Not too sure you can truly "convert" a TBI to a real CPI, may be easier to just find a donor CPI, and swap the engine.
 

·
Registered
Joined
·
498 Posts
Why on earth? You must be a glutton for punishment. My 93 Vortec has kept me broke for the ten years I've had it. The injector has been replaced twice, two egr valves and constant cleaning, two fuel pumps, with one complete assembly, timing codes and problems several times, not to mention the other typical GM stuff that fails. . Yes, it runs great when it 's right, and at 200K miles it's still strong, but there's no excuse for these same defects in these poorly designed items. I'd trade for a good old reliable TBI in a heartbeat!
 

·
Registered
Joined
·
23 Posts
Discussion Starter · #5 ·
rat said:
You could, but why? The reason the cpi makes the power is mostly due to the camshaft, it is considerably more agressive.

That is the only advantage i see, and you can put a camshaft in a tbi. Also, tbi's have upgradeable injectors, and they don't have fuel leakage problems that the cpi units have. It is also easier to upgrade a tbi to better '96 up vortec heads than it is on a cpi injection setup.

Where is the best place to get those upgraded injectors i am having problems with mine right now and it seems that getting those and a new cam may be my best bet. Thanks
 

·
Got Fuel Rails?
Joined
·
4,539 Posts
socki said:
Where is the best place to get those upgraded injectors i am having problems with mine right now and it seems that getting those and a new cam may be my best bet. Thanks
Depends on how wild you are going. I would just replace them with stockers if you are going mild. If you are going to forced induction, or a big cam with some good flowing heads and intake manifold then you can upgrade to 350 injectors.

If you are changeing the cam you probably need a tune. If you change injectors you really need a tune for sure.

The trick with selecting injectors is that you want them just big enough to fuel the ammount of air you are moving at wot. Getting to big will cause idle tuning issues.
 

·
A4, A5, A6, A8 ASE Cert
Joined
·
374 Posts
CPI also has the MTV, Manifold tuning Valve and the wind tunnel effect like an internal ram jet, sort of putting on a aftermarket intake pletunem for a tbi or carb system. You could change it but fincally its not worth it. new wiring harness, upper and lower air pletneums, which are 800-900 a piece. a new computer, and intake systems.
 

·
UNBANNED BITCHES!!
Joined
·
2,007 Posts
Mix-n-Match said:
...and you'd also need the CPI's high pressure fuel pump,



I've got the 94 CPI.
It's a very nice engine.
i beg to differ i am using my trucks stock 2.2 fuel pump with my CPI......


ive got the 93 CPI.
and YES its a very nice engine.
 

·
yes, that is a v6
Joined
·
2,628 Posts
Mix-n-Match said:
The CPI also had lighter, performance pistons (made by Mahle) that year, which the TBI never got.
where did you read this?


anyways, the TBI's have alot more options and is much easier performance wise
 

·
Got Fuel Rails?
Joined
·
4,539 Posts
TnHombre said:
i beg to differ i am using my trucks stock 2.2 fuel pump with my CPI......


ive got the 93 CPI.
and YES its a very nice engine.
If your 2.2 had high pressure fuel injection this is obviosly ok. However going from a tbi to a cpi you are going from 13psi to 60psi, i don't think the pump will flow enough at this high pressure.

s10ls said:
where did you read this?
From: http://www.babcox.com/editorial/ar/ar40047.htm
It is also a sticky.
PISTONS
There have been five different pistons used in the 262 along with two versions of the lightweight piston.

1) The original, heavy piston used in the 262 was the same as the one that was used in the 350 V8 except that the pin boss was opened up slightly for the offset rod. It weighed about 745 grams with the pin and had a 9.1:1 compression ratio. It was used in all of the light duty engines without the balance shaft from ’85 through ’94 and in the VIN "Z" balance shaft motors from ’93 through part of ’95.

The parts catalog identifies the ’95 VIN "Z" engines with this heavy piston as the "second design" version even though they were built during the first part of the year. They will have one of the following engine codes: ALH, ALA, ALB, ALC, ALD, ALF, ALH, ALJ, ALL, ALP, ALS, AJS, AJT, AJW and AJU.

2) The lightweight piston weighs about 675 grams with a pin. It was used in all the high output, balance shaft engines (VIN "W") from ’92 through ’98 and in all the VIN "X" engines from ’96 through ’98. It was also used in the "first design" VIN "Z" engines that were built during the latter part of model year ’95, including those with the following engine codes: AAB, AAC, AAF, AAJ, AAK, AAL, AAP, AAS, AAW, AFC, AFD, AHC and AHD.

The lightweight piston was originally a Mahle, full-round design (p/n 2753), but GM switched to its own "RPM" (Revised Permanent Mold) design with a short slipper skirt and a narrower pin boss in ’95. Both of these pistons have very short skirts, so the clearance must be right or they tend to make noise at startup.


3) There was a heavy duty engine offered for trucks and vans with over 8500 GVW from ’89 through ’95. It used a heavy duty, Zollner piston that had an 8.3:1 compression ratio and weighed the same as the regular heavy piston.

4) There was also a high output, VIN "B" (LU2) engine offered in the Astro van in ’90 and ’91. It used a special, hypereutectic, strutless piston that is available from GM under p/n 10181389 in standard, or from Zollner as a H-8269-D. It weighs about 745 grams, just like the rest of the heavy pistons.

5) There was one more piston used in the 262. It’s a low compression (8.6:1), strutless, hypereutectic piston with a deeper dish that was used in the turbocharged Syclones and Typhoons from ’91 through ’93. The OEM standard piston is p/n 12508702 and the Zollner number is a H-8269-E.

All of these pistons are specific to the application, so they should not be interchanged. Building an engine with pistons that have the wrong weight or compression ratio will guarantee a comeback, so it’s better to play by the book.
 

·
Lotsa parts, Lotsa brands
Joined
·
24 Posts
When I had the engine on a stand, I flipped it over (minus the oil pan), and stuck a small flashlight in and checked the underside of the pistons: Yup, "Mahle" stamped right on them, on the inner side of the skirts. Even managed a dig. pic. of the writing...

Got all the CPI deets from the posted sticky (as noted).

Also read "somewhere" that the cpi 4.3 was originally spec'd for a 3" exhaust, with 2.25" downpipes. And with those specs you get the higher torque/HP figures.
So I used those dimensions with mandrel bend pipes.
Anyway, a truly fine exhaust note as a bonus!
 

·
UNBANNED BITCHES!!
Joined
·
2,007 Posts
Mix-n-Match said:
All read "somewhere" that the cpi 4.3 was originally spec'd for a 3" exhaust, with 2.25" downpipes.
So I used those dimensions with mandrel bend pipes.
A truly fine exhaust note!
got more info on this OR pics?:D
 

·
Lotsa parts, Lotsa brands
Joined
·
24 Posts
Pics of my exhaust? Yes, probably, but still need to learn to post images here (gimme a break!)...

The "somewhere" in this case is a conversation with a very well informed automotive "super-tech"

(edit)
Hmmm... Pics and FTP program on the work PC, I'll dig up something tomorrow.
 

·
Lotsa parts, Lotsa brands
Joined
·
24 Posts
(hope this don't count as a thread hijack...)

Thanks for the "howdy".
Currently located somewhere in the Great White North.

..another lurker gets outed.
 
1 - 20 of 29 Posts
Top