BovineZro

iTrader: (11)

I wanted to reach out to some of the experts here for a quick sanity check on a project I'm putting together.

I have my car (91 Z28) with the factory 700R4 and a "mystery" TPI V8 (I know nothing about the engine). I also purchased a '90 RS with an LO3 TBI 305 and a T5 manual. The LO3 has been recently rebuilt, runs great, and has Vortec heads and an aftermarket cam (not sure of the exact model). I would like to move the entire drivetrain from the '90 RS (which aside from the engine is not worth anything) into my '91 Z28. However, I have to keep all emissions equipment as well (Colorado emissions testing is a bummer). My thought is swap the motor and transmission (along with all hardware for the conversion from auto to manual) from the '90, retaining the TPI system and emissions gear from the '91.

If I've done my research right, I'm gonna need the following major items (this is where I'm looking for suggestions and/or a sanity check):
A Scoggin Dickey intake to get the TPI runners mated to the Vortec heads
A set of Dyno Don headers with AIR tubes and the Corvette-style provision for recirculating exhaust gas back to the intake (I've seen generally positive reviews but I'd welcome more feedback)
Custom tuning to account for the engine/transmission combination since my computer is tuned for a 305 TPI/700R4 combo (probably)

Am I on the right track here? I did some searches but I haven't found anyone who has done this swap AND kept emissions.

Thanks in advance!

aliceempire

iTrader: (14)

Before you go too far, check casing numbers on the TPI v8 now, that'll tell you at least what heads and displacement you have. If it turns out you have good heads on a 350, then switching to a 305 might be a downgrade. Also want to find out what injectors you have to know if they'll work on the RS's engine.


Past that, you're SURE the L03 has VORTEC heads? Meaning there are 4 bolts holding down the manifold on each side, 8 total. Not 12 total bolts like the older style heads. Reason I say this is because a lot of people think or are told that the older swirl port heads are "vortec". They are not. That'll change if you need a different manifold or not. Next, if they are actual vortec heads there is no heat crossover port meaning you'll need to plumb a exhaust tube from the header to the egr port on the vortec tpi manifold to stay emissions legal. That's where Dyno Don's headers will be perfect. They are really good units.
Custom tune won't be needed to run, but won't likely pass emissions without.
You'll have to change some wiring around for the trans swap, but that's not that difficult and check the stickies for more info on that. It's only for neutral safety wiring and reverse light.


Not much to it really. Seems like a lot of things but in the end it's not. Other than trans wiring, it's mostly pull one engine out and put a different one in. GL

BovineZro

iTrader: (11)

Thanks for the response, glad to know I have the right idea on the emissions side of things. Also good to know I'll need to get plan on a custom tune. I keep seeing good things about Dyno Don's products, so I'll plan on a set of those headers. I had not considered the injector sizing, that's something I will definitely look into. Might lead to a whole new set of questions!

I am 100% certain that the TBI motor has Vortec heads. I counted the intake bolts just as you suggested when I bought the donor car, I didn't believe the guy selling it either. He did a fair amount of work on the 305 already, and it runs really well. I should clarify that it is NOT the original engine in the '91 (so I can't just check the option codes), and it is in serious need of a rebuild. I will check the numbers as you suggested to see if it's worth keeping.

I've already done a lot of reading on the T5 swap (this site is great!) and I think that I have that well enough understood. Plus, I can always take measurements from the donor car and get pictures of how everything is put together and wired.

Thanks again for the input!

aliceempire

iTrader: (14)

I think you have a good handle on things. Checking the part number on the vortec heads may be helpful for you. If they are the 906 or 062 350ci castings the compression ratio may be low. Unless you know what pistons are in there. If they are the 059 (I think that's the number) 305ci castings, the compression will be a bit higher.

Last thing I can think of is what cam is in the RS's 305? Tuner will want/need to know that. Especially if tuning without the car in their hands.

BovineZro

iTrader: (11)

Thanks, always good to get a little feedback before attempting something different like this. I will look into the head casting numbers as well.

The previous owner did say he replaced the cam, but I'm not sure if it was a stock replacement or something a more aggressive. I'll try to contact him and get a part number or something. Otherwise I might have to replace it with a known quantity.. Might make sense to do anyway if I'm swapping from TBI to TPI, any thoughts on that?

aliceempire

iTrader: (14)

If that tpi in the z28 turns out to be factory yet, use that cam. Much easier to have a chip burned if you can't get a tuner locally. It's not a bad cam from the factory. Or look for a used fbody LT1 cam. I wouldn't suggest spending a bunch of money on this 305 that you don't have to. If you just can't stand that money in your pocket and have to buy an aftermarket cam..I usually suggest a 8-500-8 on a 305 with a factory intake and street driven application. There are SO many cams you could use but if it were me, I'd stay with the tpi cam i that's there. The 91-92 cams were pretty good. And i'd spend as little as possible.

BovineZro

iTrader: (11)

Well, the previous owner was able to tell me it's an "RV" cam (which apparently means it's designed to build torque for towing), but he didn't have more specific info. I guess I'll pull both cams, check them with a micrometer, and do the math (hooray) to figure out what I've actually got. Then I'll just pick the most appropriate of the two.

Thanks yet again!

Edit: might not be that simple. Looks like I'll need all sorts of tools to figure out duration. I'll plan on leaving the existing cam in there for now unless I can get more info on the TPI motor.