No compression in #6 cylinder

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

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.

> wrote in message
oups.com...
> 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
>

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

> 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.

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.


--
- Yes, I'm a crusty old geezer curmudgeon.. deal with it! -

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