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Old 05-14-2014, 06:47 PM
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4.3 to a 5.7 swap

i have a 94 gmc 1500 sierra that currently has a 4.3, my friend just removed his 5.7 from a 95 silverado i was wondering would i need his computer and wiring also to make it work? what else would i have to change? i know mounts are different, also i was looking to rebuild that 5.7 before installing it would i be able to do any upgrades to the block as far as cam and head work? i heard those that tpi runs like crap with any upgrades ?

Ps. I'm new to this site so bare with me lol

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Old 05-14-2014, 08:29 PM
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There could be a few issues with this swap. #1 is that the 94 is an OBD1 system.The 95 is a transition year between OBD1 & OBD2.Some refer to late 95's as OBD1.5.I'm not real sure what all problems may surface,(different wiring/sensors,etc),but'I would do some research before diving in headfirst. #2 You don't say which trans you are using,but,there are some differences between the 94 & 95 4L60E. 95 is a standalone year for that trans.It can be worked around,but,IDK how much is involved.The 95 use PWM valve & has differences in solenoid control.If your swapping engine & trans into your 94,using the wiring harness & ECM from the 95 would be the best bet.If swapping the engine only,you could possibly use a PROM from a 94 5.7/4L60E in your controller & be OK provided the wiring harness is compatible.Again'do some research befor diving in.Also'neither of the vehicles you list used TPI.They were both TBI.Big difference. The TBI doesn't like modifications such as big cams w/ a lot of overlap w/o some custom tuning.Bigger cams & more HP means you need more fuel.Again,do some research to see if you are willing to take on all the requirements & have the budget before diving in.You have several cans of potential worms there in front of you.
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Old 05-14-2014, 09:56 PM
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@ jockerz71 yea thats what i meant tbi, i do have the trans still connected to that 5.7 but no harness , my buddy said he was going to use it for his new set up, the trans with the 5.7 would need a rebuild also if i used it. if i did manage to get the computer?
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Old 05-15-2014, 06:07 AM
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You need the ECU for a '93-'94 IIRC. The '95 is different tho it is still TBI. The engines are compatible.. Extend nessasary wires, use the 5.7 knock sensor and it should run with the right computer.. On the Fullsizechevy site, there is a guy who parts out OBS Chevys and has done tons of '93-'94's and probably has what you need
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Old 05-15-2014, 11:23 AM
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The 1995's came both ways.Either flat tappet or roller.Both have the holes drilled and tap for a roller set-up.The upgrade considering your going to rebuild is the hydro roller cam.Also from 1996 to 2000 good set of heads that are not cracked.


The Vortec 5700 L31 (Vin code 8th digit "R") is a V8 truck engine. Displacement is 5.7 L. It is the last production Generation I small-block from Chevrolet. The cylinder heads feature combustion chambers and intake ports very similar to those of the LT1 V8, but without the reverse-flow cooling. As such, the L31 head is compatible with all older small-blocks, and is a very popular upgrade. It offers the performance of more expensive heads, at a much lower cost. It does, however, require a specific intake manifold (A 5.7L, 350 CI L31, Vortec engine has eight bolts attaching the intake manifold or four per head, as opposed to the traditional six bolts per head twelve in total found on older Chevrolet small blocks). The L31 was replaced by the 5.3 L 5300 LM7. The 2002 model year was the final year for the L31 5.7 L small block V-8 whose origins date back to 1955. The Vortec 5700 produces 255 hp (190 kW) to 350 hp (261 kW) at 4600 rpm and 330 lbft (447 Nm) to 350 lbft (475 Nm) of torque at 2800 rpm. It is currently being produced as a crate engine for marine applications and automotive hobbyists as the 'RamJet 350' with minor modifications. Known as the GEN 1+, this was the final incarnation of the 1955-vintage small block, ending production in 2005 with the last vehicle being a Kodiak/Topkick HD truck. Volvo Penta and Mercury Marine still produces the L31. The "MARINE" intake is a potential upgrade for L31 trucks. Using this "MARINE" intake will allow the use of common types of injectors with various flow rates while still maintaining emission compliance.

L31 applications:

1996–2002 Chevrolet Express/GMC Savana full-size vans
1996–1999 Chevrolet/GMC C/K full-size trucks
1996–1999 Chevrolet Suburban/GMC Suburban full-size long-wheelbase SUVs
1996–1999 Chevrolet Tahoe/GMC Yukon (and 2000 Tahoe Limited and 2000 Tahoe Z71 models) full-size short-wheelbase SUVs
1999–2000 Cadillac Escalade
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Old 05-16-2014, 05:16 PM
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i actually have a 350 block with vortec heads and a 490 lift comp cam in it, the block is bad i cracked an ear where the trans hooks up to , i wanted to transfer those heads and cam to that 95 engine after the rebuild but then i hear those tbi don't like any mods , so its starting to sound like its a little bit more of a headache then what i had imagined.
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350, 5.7, obs, sbc, swap

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