New to the forum and I hope this is posted in the right place. I have a 57 bel air with an 89 corvette tpi, map speed density setup. I'm having issues driving it. the symptom is very little power under load past 1/4 throttle and intermittent pops through the intake. The fuel pressure is 40 steady with fpr disconnected. I pinched the return line and it shot up to 60 till I let go. I have checked for and not found any vacuum leaks. It revs fine in neutral but under load it does not want to accelerate. Thanks for any help you may have to offer!!

 

Restricted exhaust?

Are you getting spark advance?

Trouble codes set?

 

Exhaust is all new from headers to tail pipes, no codes. I advanced the base timing from 6-8 and it ran better, 8-10 and better still. I know the spec is 6 but if it runs better there I want to leave it. What do you think? Is this just masking another problem??

 

Hook a fuel pressure gauge to it and take it for a drive. The pump might be going south or something is plugged. If that checks out, borrow a scanner (Snap -On or similar) that can read timing and see if you are getting timing advance with change in throttle position and MAP.

 

I had a balancer spin on me and every time you would try to set it it would sputter and ruin like ****. I timed it by ear and it ran wayyy better. Then when I got close up on the balancer I could see that it spun on me.

Could of also jump time on you too.

 

Mine did the same. Was the pump going out. Would hold pressure without a load.

Might also check your pcv.

 

Check the timing.


As stated above, it sounds like it's not advancing.

 

Thanks for the replys! I will try to get that scanner and check what the advance is doing if anything. As a side note I did notice that the air intake noise from the throttle body was crazy loud but after advancing the timing it got much quieter. I know they have a tendency to be loud hence the ugly intake mufflers but this was bad. Now I barely notice it.

 

First off the regulated fuel pressure is low with the vacuum line off......What engine do you have under the 89 converted speed density setup?? Is it the stock L98 aluminum head corvette engine? What Memcal are you running, should have a 4 digit number similar to ACUN stamped on the Memcal. Could have a 305 Memcal or worse a V6 memcal and that could explain the poor running. Also 40 PSI is a bit low, my 1986 TPI setup I swapped onto the Vortec 350 in my G20 van had the regulator factory set at 46 PSI. I swapped the 22 lb/hr injectors for 24 lb/hr LT1 injectors after carefully grinding down the fuel rail stands on the intaketo allow for the shorter injectors. I made the stock regulator adjustable and pushed the pressure up to 50 psi to feed my thirsty production LT4 cammed Vortec 350 with tri-y headers and 2.5" dual exhaust.

 

I always thought you could only change the timing on early tpi, because the speed density tpi contains the esc inside the memcal. Or so I thought