I have an '86 IROC with the 305 TPI engine. Stock, it produces only about 190 hp and 285 ft/lbs of torque. I wanted to get the ZZ4 crate engine and drop it in to really improve performance, but I'm not sure if I want to spend almost $4,000 to do it right. How far can I take my 305 if I decide to keep it? It's got about 68,000 miles on it.

I'm putting on a Hooker Cat-Back exhaust system and headers (probably SLP).

I could always transfer over my stuff to a 350 block, correct? What would need to be changed (i.e. ECU) to allow for this, and would it even be worth it to do this?

Sorry for all the questions, but I'm new to the engine swap stuff... a friend of mine just got an '89 IROC and I want to meet/exceed his level of performance

 

Everything will bolt onto the ZZ4 crate engine. I even think your intake is drilled for the older style center bolts on the heads. Of course you will loose some of the advertised 355hp with the TPI. That 355 was gained with a large carb and open headers. A better computer chip will definately be in order, though the car will run with the 305 chip. I'd upgrade the injectors from the stock #19 to at least #22. Don't want the engine running lean. A good Adj FPR would help with the injectors.
Shop around. $4000 for a ZZ4 seems kinda high. I think I paid right at $2900 about 3 years ago from my local Chevy dealership. My autobody shop owner actually bought it under his shops name so I paid no tax!
Good luck

 

Yeah, I'll have to check to see where I can find a ZZ4 for the best price. If I got the crate engine, though, I would definitely go for a carburated setup... I'd only keep the TPI if I kept my 305.

 

Are you serious?
give up your TBI for Carb? Come to the TBI forum for a bit. You can have the benefits of a 350 with TBI!

 

Do you mean TBI or TPI?

 

Throttle Body Injection.

 

You had an LB9.... Even so.... Hmmm.
Still why not? TBI would give you the benefits of a wet fuel system and computer control!

 

If it was me, I'd keep the TPI. It has several advantages over carburetion.

1. Driveability. The a/f mixture will be more precise and is more street-friendly.
2. Gas mileage. All variables being equal, EFI will always get better gas mileage than a carburetor.
3. Cost. It would be less expensive to just keep the TPI. To convert over to carburetion, you'll need an HEI distributor, coil, carb, air cleaner, and fuel pump. For TPI you would need the SD base, bigger injectors, and a 350 knock sensor.
4. Labor involved. Going with a carb would involve a lot more work, like routing fuel lines and dropping the tank (40 psi to 5 is a lot for a regulator to handle).

I'll probably end up getting flamed for this, but it's my .02 and I'm sticking with it. I converted to carburetion from EFI and am pretty pleased so far so it's not like I'm biased or anything, but if I started out with TPI I would have kept it. Ultimately, it's your car, I'm just throwing out my opinion.

 

youre stock tpi intake will really choke off a ZZ4. if emissions aren't a problem your best bet would be to stick with a good carb. the intake that comes with the ZZ4 is enough to breathe through and accepts a vast array of good 4 bbls. if you were to keep the stock TPI setup, extensive porting, some computer work, different injectors, and siamesed runners, with a high flow throttle body would all be a nessesity in order to make a ZZ4 make its' full potential.

a carburetor thats well-setup with an operating choke shouldn't have any real drivability issues. with a ZZ4 you probably won't be looking at much more than 13-14 MPG anyway. it might be a little more expensive than just getting a carburetor, if you were to change the injectors, port the intake and get runners and a throttle body. swapping a carb isn't really all that much work, its actually really straightforward. inline fuel pressure regulators can be installed, theres really no need to drop the tank(which is really tough) unless youre looking to swap in-tank fuel pumps.

I swapped out an LG4 and put a 4 bbl carbed ZZ4 in its place. It went right in, although the SC has a carb from the factory. saving the TPI would be a good idea because its valuable at swap meets and worth a lot of cash. in my opinion it would be a better idea to stick with a carb, rather than use the inneficient TPI intake.

hope this helps

 

Yeah, the thought of keeping TPI with the ZZ4 had crossed my mind, but I did hear about how it limits the ZZ4 engine.

Another reason why I wanted to go with the carb setup was because I can get rid of the computerized injection entirely... I understand a great deal about computers but the "traditional" methods just seem so much simpler.

I have access to a 350; I think it's out of a '72 or '73 Corvette... I'm not sure of how much power it produces. Would it be a better choice to take this block and build my own ZZ4? How much money do you think I would save?

As for the TBI question... would that really produce more power than a good carb? Although, that is still dealing with computerized injection...