I have a 89' IROC with a 350 tpi. Last year it g-teched 14 flat with the minor boltons that I had done to it. But it spun a rod bearing and I decided to buy a whole new short block from GM. It is just the stock replacement nothing fancy, but I put Edelbrock centerbolt performers (old style), crane compucam (194 intake/ 204 exhaust @ .050in.), crane fully rollerized gold rockers, hardened pushrods and a 165 degree thermostat. Aside from that it already had a crane adjustable fuel pressure regulator, edelbrock headers, catco cat, and a flowmaster muffler. Yet I am running worse. At the track my best was a 15.5 with .7 react and it just g-teched today at 15.1! The car has never been so slow! Did I accidently choose a bad combination? I am beginning to look for problems. So far I checked the compression and it was at 225psi but I don't know how to make a ratio out of it so I don't know if that is okay. I have played with the timing between 6 advanced and 8 advanced but there doesn't seem to be much difference. I have my fuel pressure set to 55psi and the plugs appear nice and gray so I don't think that is a problem. It accelerates strangely, at first it goes well then it seems to slow down around 2000 but the power comes back again around 2500 all the way up to about 4500. Is the stock ignition not up to the job? Also under light acceleration it seems to "skip a beat" were it just misses for a split second. My only other thought is that at first I was foolishly running 30lb injectors before I realized that it was total overkill and that may have clogged the cat. One of my friends is a mechanic and he hooked it up to his scanner and it seems to be in perfect working order. I am totally frustrated and confused as to why many thousands of dollars went to a make a pokey car. Please help me!!!!!

Thanks

 

Couple of things I see amiss..

55psi
30lb/hr injectors

combination of 55psi and 30lb/hr injectors

 

Small cam too. Smaller than stock. That sounds like the peanut cam. Not good for a 350 I wouldn't think.

 

I agree...

 

A guy I used to work with used that exact same cam in his formula 350. He went from running around a 14.6 with the stock cam to a low 15.

I'm not saying for sure that's the reason you are running slower, but that's not the best cam in the world for the TPI 350.

Have you checked fuel pressure. How old is your fuel pump?

 

i agree with these guys. the cam is is on the conserative side. the FP is too high. set it to stock and start from there. your injectors are too large. run some 24# injectors and have the PROM burned for 24#'s. also the heads on the plain crate motor may be swirlport heads. those are garbage. they are worse than stock l98 heads. so that will also lead to peformance trouble. you might want to check that as well. best of luck

 

If the short block had dished pistons then your compression ratio would be lower. A step backwards. The cam is small.....

A stock TPI cam should have around 203 to 207 deg @.050"

Something around 203 to 212@.050 intake duration would be better. both crane and comp have EFI compable cams about that size for this application. You compression test is pretty high.
Did you mean 125psi?

I believe the factory TPI engines used flat top pistons, 64cc heads and thin .015" shim head gaskets.
If you installed your performer heads on a dished piston replacment motor with composite type (.040") gaskets, your compression ratio would be quite a bit lower.

What was the MPH on the time slips? this MPH is a better indicator of Horsepower than the ET.

 

Well, I pulled off the 30lbers a while ago and put the stockers back on...they are set to 55psi. As far as the compression test..yes it is at 225psi which is more than likely a result of carbon build up from when I had the 30lb injectors on. Does anyone know of something that I can pour into the throttle body to break up the carbon? I know they make something like that for carbs. Anyway I will replace the cam once I have so of these other problems figured out.

Thanks

 

Actually a small, low duration cam will increase cranking compression. So 225 is possible just from that.

 

Is there anyway to tell if I do have a carbon problem with out pulling the heads off. I will be pulling off the intake anyway to replace the cam. Can I tell by just looking into the ports?

 

one way would be to pull your plugs...what do they look like?