popping through the exhaust at 4500 rpm or so.. HELP!

[Zedyone_kenobi]

Too soon to tell on AFR. But they look about the same. Maybe a bit better. It certainly idles better and starts better

[Bonzi Lon]

I would like to know if the bead of grease trick around the throttle shafts I suggested had made any difference.

Bonzi Lon

[Zedyone_kenobi]

Drove the car more today. BIG improvement can be confirmed. Car feels great at any throttle position.

At about 5000 rpm at part throttle it still had a popping but I could only get that to happen in second gear not first. If I was not so anal I could live with this just as it is because under normal driving it is butter smooth. It still leans out as rpm goes up with part throttle but not nearly as fast. There was no doubt a vacuum leak in that gasket

Normal driving AFRs are about 13 :1 at steady throttle. I could probably run it richer and not worry about it but that is most likely masking the real problem

I will drive it more and report back

[Zedyone_kenobi]

Clarification, popping is definitely there

Again only at part throttle. More evident rise in AFRs in 3rd at part throttle, and again in 4th. . Next step carb swap

[Diseazd]

I'm betting it's electrical now.......plugs, points, condenser......maybe a bad plug wire.....I once had a similar problem with almost new plug wires. When I put a new distributor cap on there was a green electrical corrosion where the wire snapped into the cap.

Edited January 29, 2012 by Diseazd

[Zedyone_kenobi]

We took some shots at the electrical system. I bought new plugs and wires and installed and measured the resistance through all of them. I swapped out dizzy with a good pertronix and a coil with a known good car. I even replaced the balast resister even though it is bypassed. I ran a jumper from the battery to the coil to take the tach out of the picture. I swapped out a cap and rotor as well

Edited January 30, 2012 by Zedyone_kenobi

[Zedyone_kenobi]

So does anybody else think it could be valve seals leaking air into cylinder

[doradox]

So does anybody else think it could be valve seals leaking air into cylinder

Think about what might accompany that air if they were indeed leaking enough to make any kind of difference.

Steve

[steve91tt]

On a 40 year old motor, leaky valve seals are as common as wet tires in the rain. If leaky seals could cause the symptoms you describe this wouldn't be 12 page long thread.

Edited January 30, 2012 by steve91tt

[Travel'n Man]

What about your fuel return line? Are you running a return or is it deadheaded? Maybe if that were it the problem would be more consistent at all RPM's.........just thinking out loud.

[Travel'n Man]

What was your AFR at WOT?

[Zedyone_kenobi]

At WOT THe AFR stays around 12.9 to13.5

Steve, Doradox, You guys are probably right. Those were the words of a desperate man talking...

I have rulled out the 12V power side of the coil getting enough power with the jumper trick. However, I have not checked to see the quality of the coil ground. Although I think that would be just as evident at WOT as it is part throttle.

Edited January 30, 2012 by Zedyone_kenobi