Okay, I haven't posted here in a long time, but I'm hoping someone could maybe give me some insight to this problem.

I'll start by saying my car is a 1985 GS, with 152k miles approx. I recently put a weber 45dcoe on it, and after a lot of headaches I finally got it running okay enough to drive. But when the engine was under certain loads while driving (RPMs would vary for this to happen in each gear) it would make this abnoxious loud banging/rattling/grinding sound. Its really hard to describe it, it won't typically happen at all in first gear even aft 7000 rpms, but in second gear at anythign past half throttle it will start to make the noise around approx. 5500 rpms. Then in third gear it will be doing it by 4500 rpms, but it will only do it when the throttle is about halfway down. This will also cause an extreme loss of power, and hte car will struggle to even pull forward with half of the power it had before.

I've been through a lot getting rid of burnt out cats, etc. thinking maybe these were the cause of the noise, current the exhaust is a straightrhough with a racing
beat header, with only a resonator and a muffler in it. And the resonator is brand new.

Earlier on I think something had happened to my distributor because in order ot even get the car to say the timing was right, the timing had to be off almost 180 degrees. So I went ahead and just grabbed a remanufactured distributor, throw on the cap and rotor etc. made sure the timing was dead on, and tried to crank the engine. As soon as I cranked it the car started to backfire like crazy. Sounded like someone started shooting off a shotgun in my neighborhood. I even tried swapping the old dizzy back on, and still the same thing. So needless to say it wont even start at this point. And I am running out of ideas

If anyone can possibly help me with this I would really appreciate it, and if more details are needed I will happily give them. Thanks a bunch

 

There is a thread in the archives for finding TDC, that should get you lined up for the dizzy.

What are you running for a fuel pump and regulator. Sounds like it's running out of fuel and going lean, that's why it gets worse in each gear at a lower rpm.

 

Thanks a bunch, I'm using a 4.5 psi fuel pump I found at a checker auto parts, with no regulator currently. I'll find hte specs of hte pump and post them, I should probably get a fuel pressure regulator, I jut wanted to try to get it to at least drive down the road. Hopefully it was jut me cheaping out then that is causing the problem.

 

sounds like ur describing a rotary spark knock. retard the timing a bit. with the dist stabed correctly, factory setting shoud be with the mounting bolt centered in the slot on the dist. mine was doing the exact same thing when i had it too far advanced. it still seemed to do it even after retarding the timing down to factory setting. only after pulling the trailing plugs did i find it had broken the ceramic on the firing side of the plug. luckly nothing got into the engine and after replacing those plugs i had solved the problem. needless to say, i WONT be running that far advanced anymore.

 

Just thought I would update you guys. I still have traces of that annoying sound at high loads, in higher gears, around high rpms, but only after half throttle. I played with the timing and got it dead on 0, I will probably tweak it a bit more later, but as it stands the car has come to life, in the first few gears when I can floor it with no problems. =D Oh how I missed that rev buzzer.
And thanks again for the advice/help guys, I appreciate it.

 

Still sounds like a timing issue. To find out for sure, just rotate the dizzy a little bit counter-clockwise and try it again. If the noise is gone then you'll know...

 

Not sure what psi the Weber needs, when was the last time you changed the fuel filter? If that doesn't help, either the pump doesn't have enough flow, or there may be a partial blockage in the pickup tube.

 

You were right. The car runs like a dream now. Thanks a bunch everyone for your help. I'm off for a long over due drive =D

 

Glad to hear it man!