Stumped
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Lead Driver
Joined: Aug 2003
Posts: 6,305
Likes: 18
From: Boulder Creek, Ca
Stumped
Installed a 68 302 with 4v Holley 1850, and Dura Spark ll ign. in 65 F100 about 6 yrs. ago. Went to town and the truck ran fine but on the return it started running ruff; popping/backfire and sounded like it was coming from the passenger side exhaust. Timing checked out okay. Pulled passenger side valve cover and valve trane looked okay. Plug wire resistance checked out. Ran a compression test, one cylinder is at 149 and all the other running between 155-160. My initially compression test found driver's side #2 cylinder was running about 1/2 as all the others and after pulling valve cover and valve trane checked out retested compression and found #2 cylinder actually running at 149.
It has got me stumpted,
I just can't fiqure what appears to be effecting just the one bank. I am not familar with the Duraspark ll and whether it could be the source of the problem. Considering swapping the carburater, have another Holley 1850 I rebuilt. Anyhow, suggestions, comments, input appreciated.
It has got me stumpted,
I just can't fiqure what appears to be effecting just the one bank. I am not familar with the Duraspark ll and whether it could be the source of the problem. Considering swapping the carburater, have another Holley 1850 I rebuilt. Anyhow, suggestions, comments, input appreciated.
Moderator
Joined: Jan 2001
Posts: 57,014
Likes: 2,751
From: Virginia
Could be a piece of dirt covering one of the jets inside the carb. Depending on what type of manifold you have, they split the engine in half, though most intake manifolds split the cylinders randomly, and not side to side.
Thread Starter
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Lead Driver
Joined: Aug 2003
Posts: 6,305
Likes: 18
From: Boulder Creek, Ca
It's an edlebrook dual plane intake, using a ported spacer, did not occure to me until you mentioned it, carburation split between the two sides. However, now with the new plugs, rotor, etc. the engine is no longer backfiring. I have a 'backup' Holley 1850 that I swapped and still getting the surging but now acquired a screeching sound, as if a fan belt was loose. I removed the belts to where the crank was only turning and did not eliminate the sound. I am going to focus attn. on possible vacuum leak, bought a quality gasket set and will see if it solves the problem? Also found the local auto parts store carries the Holley rebuild kit, that will likely be the next step. I hate it when it's not obvious, it usually means end up replacing components until the problem is solved. Not familiar with the Duraspark ll ign. and whether it could be contributing to the problem; in the meantime, the saga continues. Thank you Dave, appreciate the input!!
Thread Starter
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Lead Driver
Joined: Aug 2003
Posts: 6,305
Likes: 18
From: Boulder Creek, Ca
Purrring like a kitten. Wish I could say for certain what I did to correct the problem. Took your advice; decided to pull the carb in order to clean air and fuel passages. Installed the carb using the new gaskets then probed, pulled/pushed various electrical components and the truck started right up. Did not get into resetting throttle clearances, etc., may do it later; although, as it's said, if it aint broke leave well enough alone. Thanks for the suggestions!!.
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