Hey guys,
I am doing an engine rebuild for my 1996 z28. I am boring the engine 30 over, with an EGR delete, and an o2 sensor delete, with plans to make the car a nice DD. so my question is what are the main differences between the LT1 in the 94 Z28 and the 96 so i can know what to expect with this rebuild. Also I have been doing some reading and I saw a few forums that say that with a new bore on the engine and the EGR and o2 delete the PCM will need to be tuned. If that's true I would like to know of any company's near the Indiana area that tune them. I appreciate any help and advice that anyone has. Thanks guys!

 

The real (and maybe, the only) 'show-stopper' would be the failure to install a Crank Position Sensor on the '94 engine.

KW

 

To run OBD2 on the 94 engine you're going to need a lot more than that. The 94 LT1 doesn't have the hole in the timing cover for the crank position sensor. You can't just swap timing covers because the non-vented and vented optisparks use different seals. Here's the minimum you would need if you wanted to keep your 96 PCM:

vented optispark
OBD2 timing cover
crank position sensor
knock sensor
CPS reluctor wheel
vented intake elbow
intake fitting for vented opti
cam dowel of correct length or 95-97 cam

Now, converting an OBD1 motor to OBD2 wouldn't be too smart. OBD1 is extremely cheap to tune (you can do it with tunerpro, winflash demo, and an ALDL cable in your driveway for free) whereas tuning OBD2 can't be done at home for little or no money. OBD1 is a lot less annoying when it comes to emissions too because there are no downstream O2 sensors.

Here's all you'd need to convert your 96 car to OBD1:

94-95 PCM with part #16188051
OBD1 knock sensor (which should already be installed on the 94 LT1)

You can find that PCM in 94-95 Fleetwoods, Roadmasters, LT1 (not L99) Caprices/Impalas, F-bodies, etc. All of the OBD1 LT1 computers are the same, they just have different tunes.

 

For tuning purposes I would do everything possible to keep the car OBDI. Far simpler (and inexpensive) to tune.

Also I hope you realize that deleting the O2 sensors is an awful idea as they determine the fueling of the motor. Unless you're talking about the REAR O2s.

 

So basically, the front motor accessories of the '96 engine (which he already has) would go onto the '94 engine.......

KW

 

I plan on deleting the rear o2 sensors that are near the cat because I was told that it was needed if I do a cat delete(is this true?), unless its is not a good idea. So you are saying that the best plan would be to use the PCM off of the 94 with the 94 engine? Would I run into any major problems swapping the PCMs? The PCM came out of a 94 5speed z28

 

Based on what I have read I think I have decided to rebuild the 94 lt1 and use the OBD1 PCM, for easy tuning. Will the PCM swap be easy? Other than replacing the knock sensor? i have the OBD1 PCM but it came out of a manual(as did the motor and wiring harness) thanks for your help guys

 

Yes, but that requires pulling apart another engine. I was under the impression that the 96 motor is currently in the 96 car and pulling bits off of it would be a hassle. It all depends on whether or not the 96 car runs and drives.

It's not neccessary to get rid of the downstream aka rear O2 sensors when deleting a cat. You can leave them in or you can remove the sensors and plug up the holes, but it won't matter. You're going to have a check engine light without a cat either way if you reuse your 96 PCM because it's OBD2. An OBD1 PCM won't care.

The PCM swap is plug and play. There's a nominal difference in tunes but I wouldn't worry about it, that is unless the transmissions are different. Then you'll have to retune. Also, OBD1 and OBD2 have different knock sensors but your 94 motor should already have the proper one installed.

Things needed for DIY tuning:
ALDL to USB cable (OBD2 style plug, can be found on eBay for $60)
Tunerpro (free)
Tunercat Winflash (free demo for 30 days, can be uninstalled and reinstalled afterward)

And when you need a .bin tune file then just ask! I wouldn't be opposed to sending a few tunes via email and there are plenty kind people on this site who would too.

 

Good point.

KW

 

So just to clarify. Will the 94 PCM plug right up where the 96 PCM was? Also, the 94 PCM came out of a 94 manual 6speed car, would I still be able to use it even though the 96 that it is going into is an automatic? Thanks for all your input guys.

 

Yes and yes. The OBD1 and OBD2 computers can interchange BUT the tunes for automatic and manual cars are different. You'll have to reflash the 94 PCM with a tune from an automatic car which is pretty easy.

 

Would you mind walking me through what that takes?