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Cylinders failing
https://slantsix.org/forum/viewtopic.php?t=35552		 Page 1 of 1
Author:  Avenger2040 [ Wed May 27, 2009 5:14 pm ]
Post subject:  Cylinders failing
I really need some help with my Slant, the story is this.

Engine was working right but with some carb problems (1 bbl Holley carb) and small lubrication problem in the head, solved this with another carb and 1 week later solved the lubrication problem.......but in the meantime of carb to lubrication problem, the engine started to work roughly.

Engine was hard to turn on, not a smooth idle, was a little "jumpy", just after the week my slant six was basically working only with 4 cylinders, checked compression in failing cylinders (Number 2 and 5) and was for 95. Car fails under low RPM, but in higher RPMS the problem is null!!.

My mechanic insist in a bad cylinder compression and nothing more, but I really don´t think that can be the problem, can be a valve issue?. I really need help to solve this, many thanks in advance.
Author:  Aggressive Ted [ Wed May 27, 2009 7:45 pm ]
Post subject: 
It would be easy enough to see by rechecking the valve lash (.010 intake and .020 exhaust) cures it. A valve might not be sealing well/leaking and causing the low compression.

Buy another valve cover gasket and re-lash the valves.
Author:  Avenger2040 [ Wed May 27, 2009 9:54 pm ]
Post subject: 
Thanks for the reply Ted, valve lash was checked today and is under correct setting (.010 intake/ .020 exhaust). I was thinking to take off the engine head and check the valves.
Author:  Rug_Trucker [ Thu May 28, 2009 5:15 am ]
Post subject: 
Quote:
Thanks for the reply Ted, valve lash was checked today and is under correct setting (.010 intake/ .020 exhaust). I was thinking to take off the engine head and check the valves.
Do a leak down test. No need to pull the head to test it.
Author:  ceej [ Thu May 28, 2009 6:51 am ]
Post subject: 
What was the lubrication problem?

CJ
Author:  66aCUDA [ Thu May 28, 2009 7:40 am ]
Post subject: 
95 psi is not too bad. What are the other cylinders? As long as they are not more than 20 psi different, run it.
You could indeed have a valve problem.
As Ceej asked what was the lubrication problem?
Frank
Author:  68barracuda [ Thu May 28, 2009 10:56 am ]
Post subject: 
Hya Frank!
If I am not mistaken Mopar specs is between 110 and 140 psi with no more than 20 psi diffrence 95 is a bit low
Author:  ceej [ Thu May 28, 2009 11:14 am ]
Post subject: 
And what do you mean "under correct setting?"

Tighter than .010" and .020"?

If anything, set them slightly loose. .011" or something like that. Does it have a stock cam?

CJ
Author:  Avenger2040 [ Thu May 28, 2009 1:19 pm ]
Post subject: 
The rest of cylinders are running a 110 compression, the lubrication problem was almost none oil in the Rocker Arms and Valve Springs area, engine in fully stock. Remembering numbers in compression Cylinder 2 got 92 and Cylinder 5 got 95, the rest are in 110
Author:  Rug_Trucker [ Thu May 28, 2009 6:31 pm ]
Post subject: 
Quote:
the lubrication problem was almost none oil in the Rocker Arms and Valve Springs area
I saw that on my slant in the Dart! It was a rag in there blocking the oil screen!! I hope yours isn't bad!

:shock:
Author:  slantfin [ Thu May 28, 2009 7:35 pm ]
Post subject: 
You might be able to clear the oil passages in the rocker arms with compressed air, or spray lubricant, if you take apart the rocker assembly. It's cheap and easy if it works, the way we like 'em. 8) Also, Rug_Trucker has a good point, a careful compression and leak down test are necessary. Leak down is a compression test with oil sprayed into the cylinder to seal the rings. If the numbers are the same in both tests, the problem is in the cylinder head. If the oil raises the compression, rings are worn. Don't forget to open the throttle plate in the carb while testing compression.
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