so i have a 1989 camaro rs...when i got the car it was in need of attention. still have the original 305TBI, but i wanted more power ....it now has a very nice 355...polished and balanced crank, .30 over aluminum je pistons, powdered x rods, melling hv oil pump with moroso pickup and 7qt moroso drag pan, vortec ported heads with lunati bracketmaster 2 cam lifters and pushrods, sealed power rockers, a performance products polished air gap intake, 750 edelbrock performer carb and mallory hei.
before anyone asks, yes it does still have electric pump. but is cut down with a regulator. its a 5 speed.. the problem is at high rpm (full throttle) it wants to bog like its lost fuel...runs great until then though, ive already changed carbs, and adjusted the time a million TIMES..and it still cuts out and will not hardly start back when its hot. It has a new starter, flywheel etc. i just need to find out the problem. please help

 

Welcome aboard thirdgen.org.

Most likely your in-tank electric fuel pump isn't keeping up with the demand. If it is the original factory pump, it isn't likely to be healthy enough to get the job done. If you don't have a fuel pressure gauge, get one installed on the reg outlet/carb inlet and watch the pressure as this happens. If it drops down, bingo.

(BTW, this is just a pet peeve of mine - it's 0.030" over, not .30" over.)

 

So here is my question now. If the in tank pump is the problem, I know on these cars you have to take the exhaust off to drop the tank, and I just had a brand new flowmaster system installed from the headers back, so there is no way in hell I'm cutting on it. Could I kill the power to the pump and mount a mechanical pump to solve the issue, or any other options?

 

The in-tank electric pump either has to work, or has to be removed. Making a poor mechanical pump try to suck through a dead electric will make the problem worse than it is now (if a weak pump is indeed the problem now).

By the way, what kind of regulator are you using? If it's something like a $25 Holley dead-head type, in-tank electrics can't handle that. They need constant flow to keep the pump cool. If they are dead-headed, they will suffer. Only a return-style regulator like a Mallory 4309 should be used.

If you are using a return-style regulator, you may be able to crutch it by adding a mechanical on the engine and keeping the in-tank functioning. You will still need a return-style reg after the mechanical pump. The two pumps together may be able to keep up with the demand (if a weak pump is indeed the problem now...). This would be my personal preference (with a healthy in-tank electric, though), with 2nd choice being in-tank electric only.

 

At this point the best bet for me is to go with the electric pump and forget about it. My regulator is a AEM I believe so it should be fine. What I don't understand Is why the pump hasn't completely quit, it just surges my pressure?

 

they slowly wear out over time, which means they deliver less fuel at high demands. did you have your new exhaust fully welded? id have the exhaust shop cut it and add in some band clamps to make it removable for future work. dropping the tank to replace the pump isnt all that difficult, but the exhaust needs to be out of the way.

 

They exhaust was fully welded bc I had no plans of taking the tank off anytime soon. I guess I will do what has to be done; considering my brother Is a pipeline welder. I'll have him weld it all back up. So what your saying is when I'm at full throttle, the pump is dropping from 7-8 lbs..to nearly nothing?

 

most likely. if its the stock pump its 23 years old. you cant expect a 23 year old pump to deliver under high demand.

like i said. id suggest cutting the pipe and using band clamps to reinstall. next time you have to do anything that requires the exhaust out of the way, youll just have to cut it again. theres nothing wrong with using band clamps.

 

Ok well I'm going to get a pump today and see what happens, any suggestion on brand..advance caries airtex & Bosch..I know Bosch is a little more expensive but it's also the better pump?

 

ive only use the walbro pumps so i cant vouch for the other brands. id ask to see if they carry any with an extended warranty. i got a limited lifetime with my pump. if it goes out, i pull it, take it back, and get a new one no questions asked.

 

just wanted to let everyone know i pulled my pump this afternoon. found out that the car was still equipped with the original AC delco pump from the factory its hard to believe that its over 20 years old. the new bosch pump will be in tomorrow, i will update and let you all know the results.

 

today i installed the new pump hoping to fix this issue, but it didnt. i was thinking today because it bothers me so much, that the computer is controlling the spark, I used the hot wire from the old coil and the distributor is being controlled by it..could this be my issue?

 

Assuming your Mallory HEI distributor is the vacuum and mechanical advance variety, no it isn't a problem, because the computer doesn't control the spark through the power wire. The two wires from the coil, the ignition-switched voltage supply, and the coil wire, can be connected directly to an aftermarket large cap coil-in-cap distributor and work just fine.

However, your initial timing at idle with the vacuum advance disconnected needs to be in the 8-12 degree advance at a minimum, unlike the zero degrees of the original computer system.

 

It runs fine until high rpm. Like otf for 3-4 seconds.

 

Did you hook up a fuel pressure gauge?

Where did you set the timing?