Well i have a 1971 331 stroker, and I have been having problems with it bogging down and sputtering. I just recently ran straight pipes off of it because when I had my exhaust hooked up my car would start slightly backfiering out of the carb, but it was more of a puff, arround 45mph. Well I have tryed messing with the jets, but when I open them too much it bogs more, but if I close them more I dont get any power out of my car at all. I need some help and im hoping you guys can help me =S

 

Im thinking its not fuel related...the backfire makes me think its another issue like timing or valves or plugs.

Do a compression test on each cylinder and write down the cylinder number and max pressure.

check the plugs too

Also check timing.

It could be fuel just as well its real hard to say with without seeing it...Im guessing not fuel for now.

-Gun

 

I cheacked me compression, its 150 on each cylinder, and my timing is perfect, I have had it in the shep 3 times for the timing, and I just replaced the plugs, and gaped them durring Christmas.

 

What cam and compression does it have? Compression testing an engine and getting 150 when it should have 200 would definately indicate a valve timing issue, prolly retarded. It could also be ignition timing. 95% of carbureted related problems are ignition problems.

 

how bout plug wires....For fun take s squirt bottle and set it to mist. Start the car and mist water around the dizzy and down each plug wire. Do it in low light and watch for sparks. If you forget to set it to mist and spary a sold stream of water on it im not responsible for your forgetting to use the mist setting.

Might want to check for vacuum leaks as well using a large propane torch. fog the raw unburnt gas around the carb base with the engine running. also fog around the intake manifold. If the engine changes tune then its a vac leak.

All simple and free test...do them before spending money.

-Gun

 

You say your timing is perfect. What is it? How do your plugs look. You really need to tune the carb via the plugs or an Air/Fuel sensor.

 

like everyone else I suggest timing.
You mention you went there 3 times, so you seem to believe in this as well.
1st make sure it's not the airfilter. any difference without?
if that does not help it's a known issue that harmonic balancers slip from time to time, which renders the timing marks on them useless.
So if the company you went to for timing does not know this fact then all their setting the timing was not helping much.
(i only learned here).
So here's a way on finding proper TDC
1. Turn your engine manually towards TDC
2. remove #'1 spark plug
3. push a wire like a welding wire (MAKE SURE IT CANNOT FALL INTO CHABER) into the chamber to feel top of piston.
4. rock the engine back and forth manually to determine TDC (piston highest point).
you might not be able to tell the exact degree, but should get you in a 5 degree range.
5. verify this TDC with what your marking on balancer says. if it's 10 or more degrees away, then this is most certainly your problem.

Another option would be to hook up a vacuum gauge on carb or manifold to measure vacuum.
Set idle timing to such that yoiu have the highest vacuum reading.
With this method you always end up being a few degrees advanced, but it should tell you if you're in the ballpark.

it's imperative that you check timing with vacuum hose to distributor disconnected and the hose plugged.
once you're finished hook the vacuum advance back up and check if timing changes. it should not.
If it changes by 5 or more degrees than you have the wrong port on carb for vacuum pickup. use ported, not full vacuum port onm carb

enjoy ...

Kalli

 

Ok cool, I think I might cheack for vacume issues because I have not even though about, and also ill cheack the harmonic balancer.
Thanks guys you have been more helpful than I have been, but ill let you know how everything turns out

 

If I were going to try Gun Jam's tests, think I would do the plug wire thing before the propane test, and keep my fire extinguisher close at hand!(lol)