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 Post subject: Can't find the miss!!!
 Post Posted: Sun Jul 20, 2008 10:02 pm 
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Joined: Mon May 01, 2006 12:58 pm
Posts: 59
Location: Ft. Worth, Tx
We just rebuilt our short block due to a destroyed piston and scarred cylinder. The only change to the engine was boring the block and putting in a 14.2 to 1 set of pistons from a 12.9 to 1 set. Compression is good in all cylinders. Everything else is the same. At idle it sounds like it is hitting on about 5 or 6 of the 8 cylinders. When you bring the revs up it sounds fine. We have checked the plug wires all test good, replaced the dist cap and rotor, 2 different sets of plugs, double checked our valve settings and we don't know where to go next. The ignition is a Msd Digital 6 with an HVC coil and a locked out pro billet dist. Could a problem with the carburetor be causing this problem? Any suggestions on where to look next would be appreciated.

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 Post subject:
 Post Posted: Fri Oct 31, 2008 11:20 pm 
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Joined: Mon Oct 22, 2007 9:33 pm
Posts: 46
Location: Chandler Arizona
Was your increase in compression from a much larger piston dome?
Any chance the dome is closing the gap on some of your plugs?
I see you have tried a different set of plugs. Where the gap closed down on any of the old ones?
Have you tried killing each cylinder individually as the engine is running to determine which cylinders are missing?
Best of success in finding your problem.

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 Post subject:
 Post Posted: Sat Nov 01, 2008 9:17 am 
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Joined: Mon Oct 29, 2007 7:07 pm
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Location: Florida
Try a step colder on the plugs and back the timing down.


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 Post subject:
 Post Posted: Sat Nov 01, 2008 3:59 pm 
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Location: NJ
DID YOU CHECK PISTON TO VALVE CLEARANCE ?

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 Post subject: PLUGS
 Post Posted: Sat Nov 01, 2008 5:18 pm 
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Joined: Sat Nov 03, 2007 4:44 pm
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Location: Clawson, Mi.
Did you index your plugs???????

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 Post subject:
 Post Posted: Sun Nov 23, 2008 8:11 am 
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Joined: Wed Oct 24, 2007 6:36 pm
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Location: Blanco, Texas
The fact that it runs better as you increase engine speed suggest a lean condition at idle, getting better as you rev it up.

I would look for a vacuum leak.  If you don't find one try richening up the idle mixture.  

A lean mixture will run at idle but miss on different cylinders as it runs, not just one dead cylinder.

Let us know what you find,

Donee


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 Post Posted: Wed Feb 25, 2009 10:36 am 
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Joined: Mon May 01, 2006 12:58 pm
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Location: Ft. Worth, Tx
A bad Vacuum leak where the intake fastened to the head on the R/bank.
Thanks for your help.

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 Post Posted: Wed Feb 25, 2009 10:53 am 
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Location: Blanco, Texas
Glad you found it, and it was a cheap fix! =D>

Thanks for letting us know what you found.

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