Very Strange Phenomena - Need Advise

[chevyaddict]

Hi all;
I have a strange phenomena happening. We are working on a 302 (bored to a 306) Ford motor. Fast! At idle, you can put your hand on the #7 cylinder and its cold and also at steady rpm it seems to be misfiring as well out of #7. Here are all the things we've tried so far and none of them have remedied the problem:

1. Checked/switched around plugs and wires - no change.
2. Switched with a new distributor - no change.
3. Messed around with different carb settings and jets (its a 670 Holley) - no change.
4. Ran a compression check in the cylinder - no problem.

Now under acceleration, the tube starts to get hot and when you are on it, it runs like a dream. However, it is misfiring under no load. WHY? At this point we are thinking its something with the manifold. Here is the manifold that is being used:

http://cgi.ebay.com/ebaymotors/Typh...tegoryZ36474QQihZ008QQitemZ180086917676QQrdZ1

What else is there to check? Any thoughts??? :confused

 

[gmjunkie]

Valve adjustment,(Some 302's are adjustable,Depending on year)Weak Valve spring,Bent valve,Cracked head,Vacuum leak at intake runner!!

Hi all;
I have a strange phenomena happening. We are working on a 302 (bored to a 306) Ford motor. Fast! At idle, you can put your hand on the #7 cylinder and its cold and also at steady rpm it seems to be misfiring as well out of #7. Here are all the things we've tried so far and none of them have remedied the problem:

1. Checked/switched around plugs and wires - no change.
2. Switched with a new distributor - no change.
3. Messed around with different carb settings and jets (its a 670 Holley) - no change.
4. Ran a compression check in the cylinder - no problem.

Now under acceleration, the tube starts to get hot and when you are on it, it runs like a dream. However, it is misfiring under no load. WHY? At this point we are thinking its something with the manifold. Here is the manifold that is being used:

http://cgi.ebay.com/ebaymotors/Typh...tegoryZ36474QQihZ008QQitemZ180086917676QQrdZ1

What else is there to check? Any thoughts??? :confused

 

[chevyaddict]

Valve adjustment,(Some 302's are adjustable,Depending on year)Weak Valve spring,Bent valve,Cracked head,Vacuum leak at intake runner!!

Well, the motor only has about 6000 miles on it (or less) and was professionally built. Wouldn't a weak valve spring or bent valve show up in the compression check? We've checked the vacuum - seems to be fine and I doubt its a cracked head... the car runs too good and fast under load.........

 

[gmjunkie]

Well, the motor only has about 6000 miles on it (or less) and was professionally built. Wouldn't a weak valve spring or bent valve show up in the compression check? We've checked the vacuum - seems to be fine and I doubt its a cracked head... the car runs too good and fast under load.........

It should!!! It could have a Casting Flaw in the Intake on #7 runner, or the Intake gasket it self at head!! Depending on where the crack in a head might be would determine if it would change compression or not!!

 

[geekinavette]

Does it use hydraulic lifters? I've seen a lifter do weird stuff like that.

Bill