Author Topic: No carbon in exhaust port of 396.  (Read 1473 times)

SS396

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No carbon in exhaust port of 396.
« on: March 17, 2010, 09:36:54 PM »
Bought a rebuilt 396 just recently but cant get it to run properly. There is no carbon in no. 8 cyl exhaust port whatsoever, clean as a whistle.Took rocker cover off to see if valves were opening and closing on that cylinder which they were so it has me stumped. I thought if the cyl wasnt firing you would still expect to see some residue or petrol in the port. Any ideas.

tmodel66

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Re: No carbon in exhaust port of 396.
« Reply #1 on: March 17, 2010, 11:14:59 PM »
If it's not firing you won't see any on a new motor. Sounds like you have a dead plug. Did it flood before it  started?  Pull the plug and make sure it's firing and check the compression. Is it a solid or hydraulic lift.? If its hydraulic you might have a lifter bad or not primed.  PM me if you can't get it going


Daniel
Daniel  
'69 SS 350/4 speed  Fathom Green--POP

SS396

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Re: No carbon in exhaust port of 396.
« Reply #2 on: March 18, 2010, 01:02:04 AM »
Thanks  tmodel66. Theres carbon in the header tubes except no. 8, thats how I noticed this problem. Cam is hydraulic. Swapped plugs around and they are all new but its still the same. It has new leads and rebuilt dizzy so I don't think it's electrical. Next thing will be to check lifter and compression.

Ed_B

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Re: No carbon in exhaust port of 396.
« Reply #3 on: March 18, 2010, 04:00:33 AM »
A blown head gasket (or a cracked head) will do this. Water gets into the cylinder and "cleans" the carbon out. (Don't ask me how I know!) Are you loosing water from the radiator? Do a leakdown test and see what you come up with.

Ed

SS396

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Re: No carbon in exhaust port of 396.
« Reply #4 on: March 18, 2010, 09:22:08 PM »
Water level in radiator is pretty constant and doesn't overheat. Motor is supposed to have been rebuilt so I would not have thought this would be a problem in case I got a dud.

tmodel66

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Re: No carbon in exhaust port of 396.
« Reply #5 on: March 18, 2010, 10:10:47 PM »
Have you made sure the plug wire is fireing.  Put a plug in the  end of the wire and make sure it's fireing. If it is check the compression. You could have a warped push rod. Has the rocker stud pulled up out of the head any ? There is so many things you really have to go thru a step by step process.
Daniel  
'69 SS 350/4 speed  Fathom Green--POP