No compression in #6 cylinder

Jan 11, 2005 3 Replies
M

I have a '66 Mustang with a 289 rebuilt about a year and a half ago. It has run very well until a couple of days ago when it felt like it had lost a cylinder. My local mechanic did both dry and wet compression tests and determined I have no compression in the #6 cylinder. He says the problem could be in the head but he needs to take the head off to find out the problem and would like to charge me



1800 bucks to rebuild the engine. The heads are stock and I was planning to replace them eventually just not yet. I am running an Edelbrock intake with a Road Demon carb on a stock 289 motor. What else besides the head could cause this problem? Should I just buy new heads and replace them myself? I would take it back to the shop that rebuilt the engine but they only warranty it for one year. I am getting dry readings of 150 psi on cylinders 1,2,3 and 160 psi on cylinders 4 and 8 and 170 psi on cylinders 5 and 7. The wet are 160 on
1 and 2, 170 on 8 and 180 on 3,4,5,7. This is my daily driver so any help you can give me would be great.

Thanks,



Mike



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J

The likeliest cause would be a valve problem.... broken spring, burnt, bent... since you aren't complaining of a backfire in the intake... likley the exhaust valve. You could have the cylinder leaked to determine where the pressure is going. Removing the PCV valve and observing any blowby should indicate ring/piston condition. Removing the valve cover will reveal any valve spring/rocker arm problems.

Word of advice... diagnose the problem BEFORE you try to fix it.

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B

Jim Warman opined in news:xELEd.93234$KO5.51726@clgrps13:

No compression wet, (while having no pre-detonation ping before the problem) almost certainly a valve, notable puffing on that side exhaust, no backfire.. almost certainly exhaust valve, like jim Says

Pull the valve cover and look close.

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M

The valve spring broke. It gave me an excuse to dump the stock heads and install Edelbrock Performer RPM heads and ceramic coated headers. Thanks for the info guys!

Mike

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