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Need some help (2) issues: exhaust pop and timing jumping

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Old 02-08-2018, 12:50 PM   #1
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Default Need some help (2) issues: exhaust pop and timing jumping

I have two issues. Carb’d and HEIdistributor On LQ9 running straight open headers. New timing chain, plugs and plug wires.
Fired it up for the first time Sunday and it fired instantly. There was a random pop out of exhaust. We adjusted the carb for richer fuel mix and it was running like a top and we hadn’t even messed with timing.
So, we hook up my Bosch timing light and the timing appears to be jumping all over the place. Mind you, there is no longer a pop out of any pipes and that is at idle and revved up.
Turn it off and call it a day. Excited that it sounded so good.
Come back Tuesday and fire it up and the popping has returned??
any ideas as to the popping? It was cheap 87 octane out of a gas can. I know most of these engines prefer better quality so I will get some but I can help but wonder why it stopped popping after the initial carb adjustment.
And the timing light. What could cause that? I’ve heard using a digital gun should be avoided when running an HEI set up but that doesn’t explain the light bouncing all over the place.
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Old 02-08-2018, 07:26 PM   #2
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Popping out of the exhaust can be caused by an exhaust leak. It can also be caused by a misfiring cylinder, unburned gas passes than ignites the next time it does fire. I've never run short pipes like that so not sure how that affect things.

Viscous looking car by the way, you have some quality hours into that I can tell.

But I guess I would also worry that maybe the timing light is accurate and your timing is really jumping all over. That could cause exhaust pops. Something mechanically loose in the distributor or drive system could cause the timing to wander. Everything seated right? Also is the vac advance disconnected when setting the timing?

As for the timing light, how is it hooked up, to a plug wire? I would think that would be pretty bulletproof, digital or not.

I assume no carbon traces inside the dist cap? That can cause cross firing.

Worst case maybe there is not enough separation in the plug wires and you are getting some cross firing from that. Easy to separate them for a test, say over the valve covers? Nobody likes looking at plug wires but they need to be separated for a reason.
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Old 02-08-2018, 07:52 PM   #3
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Thanks Pop N Wood! I will check some of these things tomorrow when I get back in town. Yeah the car has come a long way since last year when I started. Couple pics
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Old 02-08-2018, 08:38 PM   #4
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Gotta agree with Pop N Wood! CLASSIC Hot Rod look with modern power! Nice job!
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Old 02-11-2018, 12:16 PM   #5
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Default Wegner Distributor Drive

Hi Jack, I have seen problems with the Distributor Drive Gear.

I supply the Ford 302 distributor to Wegner to fit the GMPP front drive.

I have not seen a GM HEI front drive ?
What side of the camshaft is the gear on ?

Lance
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Old 02-12-2018, 02:37 PM   #6
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Quote:
Originally Posted by Pantera EFI View Post
Hi Jack, I have seen problems with the Distributor Drive Gear.

I supply the Ford 302 distributor to Wegner to fit the GMPP front drive.

I have not seen a GM HEI front drive ?
What side of the camshaft is the gear on ?

Lance
Lance, it is not a GM HEI distributor. It is a SBF unit.
Also, I found the culprit of the misfire. I neglected to hook up a solid ground after I had done some “tidying” up🙄
all working now
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