Im going to check out the vac adv diaphram and take it out tomorrow night and see how it does.Im thinking lean too but because the intake valve isnt opening or opening properly or something .Its only that cylinder and there is no coolant smell or anything, I just took a look. I gave that rocker another 1/4 turn too and added some MM Oil.
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Bad lifter ?
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Originally posted by antmnte View PostVac gauge is steady and Vac advance is working . I just had it out and the problem is still there. Just fine when accelerating then level off to speed and it starts popping.
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I have had Unilite dizzy's go bad in short time acted goofy would pop and snap but mostly when hot at most speeds cold it was fine.
I have a good HEI I use when I think there is a problem just to rule it out but ya do a leask down and check everything over keep us posted
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Flying south, with a flock of bird dogs.
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Years ago I bought a 87 HD F250 that had a carbed 460. I got it real cheap because literally it was running on 1 cylinder and the owner was totally frustrated. I had planned on using the truck to haul stuff out to PA. Since the trips planned were 150 miles one way and the truck was unknown, I went through the engine. I replaced the carb because the $450 the guy paid the mechanic to rebuild the carb with a can of gold spray paint and clogged up the air bleeds. It ran now but still rough. I replaced the plugs, wires and timing chain mostly so it wouldn't skip while out on the hiway. It ran pretty well except for a steady misfire at idle and wouldn't pass emissions. It ran fine other wise, nice and smooth. I had even compression and the plug was firing but still had that misfire. I thought about it and the only thing I could think of was a bad intake gasket...and that's exactly what it was. 1 cylinder had a piece missing which would cause that cylinder to be too lean at idle and misfire but once under way ran fine. With the new gasket, that 460 was one sweet running motor that idle so smooth and passed emissions with flying colors.
I say you have a bad intake gasket causing that cylinder to lean out too much at idle and misfire.Last edited by Huskinhano; September 20, 2011, 08:47 PM.TomOverdrive is overrated
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Great point on the intake gasket - they can fail on top where you can see them upon careful inspection with a flashlight - or they can fail out the bottom into the lifter valley and you'd never know without pulling the intake.
If they fail up - sometimes you can hear that cylinder sucking air while cranking the engine with the starter.... you need a starter button or a friend to crank while you're under hood listening - I had an EFI 302 in an '88 truck do that once.... once apart I was amazed it ran at all - nearly half the gasket between the upper and lower EFI manifolds was GONEThere's always something new to learn.
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All right ,I took off the manifold heres what I found ,the gasket is intact but its got oil all over it (Both sides of the motor) so it seems it wasnt sealing properly (didnt show me that on the vac gauge) the backs of valves also are really cruddy. So what am I looking at here? The heads were milled when I had them done so that might explain the oil.Thanks again !Last edited by antmnte; September 21, 2011, 06:45 PM.
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