[87camaro307]

Hey guys, i'm new to the site and i was hoping to get started off with a question that has been puzzling me. One day i got off the highway and my car(1987 camaro with an old rebuilt 307) just started running like garbage, no power and lots of hesitation. I noticed there was a massive exhaust leak from the exhaust manifold. since that day, i have fixed the leak, gave the car a tune up, changed the o2 sensor, put a used,but good, holly 650cfm carb on, and hollowed out the cat. Now the car runs much better than before, but still hesitates before 3000 rpm. The hotter the motor the smoother it runs but never gets perfect. Also the car backfires out of the exhaust when i let off the gas, it's a 5 spd manual. Any bit of information would help a lot. Thank you for your time and hope to hear a reply soon. Thanx

[DoubleVision]

I`m afraid your question has me somewhat puzzled, you installed a different small block, installed a Holley carb in place of the TBI or electronic carb that was on the car, yet retained the computer? changing the O2 sensor did no good and may as well have been a waste of money, the computer can`t function correctly without all it`s connections active, so that would leave the throttle position sensor plug flapping in the breeze. If you still have the newer HEI without vacuum advance, your best bet would be to change over to the older HEI with vacuum advance and mechanical advance, the computer controlled HEI that came in your car has no mechanical advance and without the computer`s aide it would run like crap, so installing the older HEI would be the first starting point. also, if the computer is still active as your post would leave me to believe, what knock sensor did you use? the bore size of the 307 is different than the many engines that came in your camaro and that would put it even further out of whack when the car detonated. bypass the computer and install a older HEI and go from there, if the problem remains then take a closer look at your carb. and while I`m thinking about it, what intake are you using? did you use the factory intake and use a adapter to bolt on the holley? if so what kind of adapter, open or 4 hole? or did you use a spreadbore Holley?

[1975BlueTransAm]

If it is an older motor, the timing chain may be worn out causing it to jump a tooth

[CraigDGE]

your problem could be from the O2 sensor. In the past in my dad's shop, when we use aftermarket sensors they do not always match the exact calibration specs as the OEM ones. Another possibility is that your computer is mad at the fact that the catylytic converter is hollowed out. I can't tell you for sure, but some computers get pissed off when you change the exhaust backpressure. You could try like a Prom, or an O2 sensor, but I might be wrong on both counts. The computer could be at fault too-some of those 80s computers had trouble with circut board delamination.

[keithrock]

I am a troll and I have nothing constructive to say. Put me on your "Ignore" list. Edited by willys36@aol.com

[hotwheels55]

Originally posted by keithrock
I am a troll and I have nothing constructive to say. Put me on your "Ignore" list. Edited by willys36@aol.com

[79transam]

Sounds like a vacuum leak but most likely is carburator problem. Check your primary metering. It probably runs better after 3000 rpm because the secondaries are starting to open up and improve the mixture.

[CraigDGE]

Before you start throwing parts at this car, make sure that you have already checked the following:
1)Vaccum advance on the distributer-your car has one and it could be retarding the timing due to a vaccum leak
2)Fuel pressure, and flow. You can find the procedures for this in a Chilton Guide or similar shop manual. Your Holly carb may have different flow requirements too. You may want to talk to Holly. Try throwing a fuel filter at it, its cheap and it can't hurt.
I also agree that your jetting could be faulty. Remember that your average Q jet carb uses very small primary, and very large secondary jets. The Holly will have larger primaries, and slightly larger secondaries. Give this all a check before you start just guessing. I still think that you could have a computer problem as well, but I wouldn't go guessing at that sort of thing if the Check Engine light is not on.