I have a '86 Z with a 305 TPI. I want to swap the 305 for GM's ZZ4 crate motor while retaining the TPI, however, I here that this combination will not pass emissions. I have also been told that by adding an additive containg isopropyl, I will be able to pass. Is there any truth to this? If not, is there anything else I can do to pass emissions. Please help.

 

There is a bunch of stuff on this board if you do a search. I have had no problems passing but that is just me.

 

How extensive are your emissions requirements? If a simple sniffer, you should be able to pass. If inspection is involved, make sure you have all of the required equipment in place. If the car is on a dyno, everything had better work properly as well.

I have a bud who started with that engine, then went nuts on it (ZZ9 cam, 1,6 rockers, CNC head porting and extrude honing, decking, runners, base, ported plenum, larger TB & injectors, chip, etc.). We have visual inspection and the dyno test, which can measure NOx - the EGR valve MUST work! He ran a tube up from the exhaust manifold to the intake to feed the EGR. When he took it in for emissions, it was clean enough to be accepted via "fast pass".

For the sake of how well it runs, you should at least port the base & plenum, use shorter runners, and consider chip work.

 

My dad has a 90 Formula a ZZ4. The car has 1 5/8 inch hooker headers, Hooker Super Comp 2 1/2 inch catback system . The car also has 1:6 roller rockers, a linfelter(can't spell it) intake, Bosch 40 pound injectors, SLP runners, and more stuff I forgot. We live in Wisconsin. The car passed emissions. Not sure why but I bet the fact that the car has the stock 2.73 rear helped alot. It kept the rpms down.

 

Just throwing the stock tpi unit on there will hurt the claimed hp! As far as the sniffer tests, i do not know. I doubt that mine will pass since i have added the hot cam, but i am keeping all of the smog equipment, so we will see! I know that NJ is real strick, if you go to a state inspection.