$1500 dollars, 2 blown mufflers SAME PROBLEM?
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Elder User
Joined: Apr 2016
Posts: 854
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$1500 dollars, 2 blown mufflers SAME PROBLEM?
Bogs down and pops through exhaust and carb under hard acceleration.
Runs great at idle,.great throttle response when sitting. Drives and accelerate perfect at part throttle.
Step on the gas hard, and all hell breaks loose. Popping, missing, backfiring and bogging out.
1978 351m. Rebuilt Jasper engine with lower miles. Complete new ignition. New duraspark box. New efelbrock intake and 650 carb.
Timing set at 0. Moved it a little in each direction, same results.
All vacuum lines hooked up correctly.
I have spent 1500 in new parts and hours if research trying to correct this problem. It's no different than when I started.
Any ideas would be great. Thanks
Runs great at idle,.great throttle response when sitting. Drives and accelerate perfect at part throttle.
Step on the gas hard, and all hell breaks loose. Popping, missing, backfiring and bogging out.
1978 351m. Rebuilt Jasper engine with lower miles. Complete new ignition. New duraspark box. New efelbrock intake and 650 carb.
Timing set at 0. Moved it a little in each direction, same results.
All vacuum lines hooked up correctly.
I have spent 1500 in new parts and hours if research trying to correct this problem. It's no different than when I started.
Any ideas would be great. Thanks
Cargo Master
Joined: May 2009
Posts: 2,587
Likes: 47
From: Eagle River, AK
I believe the distributor should be set between 8° and 12° BTDC (engine dependent).
If you are set at 0° BTDC, the spark is getting there too late and that could be why it is popping out the exhaust.
Senior User
Joined: Oct 2014
Posts: 130
Likes: 1
From: Pilot Mound, Iowa
X2 on timing 12 deg is norm at 0 it will pop and bang and buck like a bucking bronco ....
Jeff
Cargo Master
Joined: Nov 2011
Posts: 3,354
Likes: 49
From: Great American SouthWest
Since you didn't mention the "timing set" (gears and chain) I presume you're talking about the timing mark on the crank. That should not be zero, but should be around 8-12 degrees before TDC at idle
My 351m ran like crap at the factory idle mark, so I timed it with a vacuum gauge and tachometer. Disconnect and plug the vacuum advance to the distributor. Attach a vacuum gauge to full manifold vacuum. Alternately rotate the distributor and blip the throttle until you get the highest, steadiest vacuum at your preferred idle speed. After you reach the maximin, back it off a couple degrees.
Remove your testing equipment, hook the vacuum advance back up, and take her for a spin. It might not be perfect, but it'll be a lot closer than zero is!
My 351m ran like crap at the factory idle mark, so I timed it with a vacuum gauge and tachometer. Disconnect and plug the vacuum advance to the distributor. Attach a vacuum gauge to full manifold vacuum. Alternately rotate the distributor and blip the throttle until you get the highest, steadiest vacuum at your preferred idle speed. After you reach the maximin, back it off a couple degrees.
Remove your testing equipment, hook the vacuum advance back up, and take her for a spin. It might not be perfect, but it'll be a lot closer than zero is!
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