UPDATE: Compression numbers, comments on cyl #8

[My9302002]

1969 charger 440
440 rebuild sometime in the mid 90's (? Miles since rebuild, maybe
5,000?)
.30 over, 484 MP cam, 906 heads, holley 750, headers. No idea
on compression ratio.

All cylinders between 145-148 lbs, except cylinder #8 which
is at 120.
This cylinder (as well as the rest) holds it's  pressure very well.
This was done on a cold motor.
Any ideas for what's going on in #8?

[justcruisin]

Drop a bit of oil in the cylinder to see if the compression comes up. When you say it holds it's pressure very well, how do you know this? Have you done a leak down?

[My9302002]

Just looking at the gauge for several minutes after the pump
up.

[Cooter]

No way of knowing exact compression. Camshaft dur. Plays a huge role in bleeding off cranking pressure. That .484 cam is like 241@ .050...way lotta overlap.

[My9302002]

Agree. Just looking for opinions on why #8 is so off.

[justcruisin]

Most gauges have a one way valve in them to stop pressure bleeding out of the gauge, looking at the gauge to see if it drops will tell you nothing, if it does drop it means your valve in the gauge is leaking, no reflection on the cylinder.

[My9302002]

 I must verify the gauge, be back in a moment

[My9302002]

Buddy took it home, will have to check tmrw. It did say it was
a compression/ leakdown gauge...so should not have a one
way valve in it, otherwise how would it measure leakdown?

[cudaken]

Buddy took it home, will have to check tmrw. It did say it was
a compression/ leak-down gauge...so should not have a one
way valve in it, otherwise how would it measure leak-down?

My, not sure on the above part.

Why did you run the compression test in the first places?

I would do what Just Cruising suggested next. If compression stays the same it is a vale problem. If it goes up, ring or cylinder wall problem.

Not far off from the 20 PSI spread.

Cuda Ken

[My9302002]

Well the reason was that plugs 1,3 were oil fouled, 5,7 very white
lean looking.
Plugs 2,4,8 look ok, 6 oily.
Just a wierd burn pattern.
That'll be a new thread in a couple of days.

[My9302002]

Just cruisin is right, there was a valve ( switchable
for leakdown tests) that wouldn't release the pressure after
the motor stopped turning.
Anyway, next step is shoot a little oil in the cylinder and retest.
Then if no change, pull the valve cover and look at the rockers
and pushrods.
Agree?

[Dino]

Pull the covers now, doesn't take much but will make for much better diagnostics.

[My9302002]

Will do.
Update later tonight....

[My9302002]

 Compression up to 145 psi after a squirt of oil.
Bore scope through the spark plug hole, and pulling the valve
cover next.
Wonder if this will show the problem...or is pulling the head
off the only real way.

[cudaken]

My, sounds like a ring has gone bad. Only way I know to fix that will require the engine being pulled apart and either rebuild or try a quick ring job. Half ass rebuild.

What spawn you to start checking compression? Smoking, plugs fouling or just not running up to par?

Depending on the condition of the rest of the motor, replacing just the ring might be worth it.

Cuda Ken   

[My9302002]

Had some oily plugs. Not all mind you just
#5,7,2,6
Car runs great.
That was the reason I did it since the PO wasn't very knowledgeable
on the motor that was rebuilt right before he bought it in the
early 90's. I have just Summit receipts of all the parts, no
shop receipts.
Motor runs runs well though. I'm thinking manifold gasket
for the oily plugs?

[firefighter3931]

The oil fouled plugs could be either the intake gasket or valve seals. If all 8 were oily i'd suspect a defective PCV valve but this is not the case.

The "correct way" to do a compression test is to bring the engine up to operating temp and hold the carb wide open. I would re-test and see if the results are similar. 
 

Ron

[My9302002]

Will do Ron...
Maybe just a stuck ring.

[firefighter3931]

Maybe just a stuck ring.

That's my thinking as well.....the car sits a lot and probably doesn't see lots of extended hwy use. Carbon builds up and ring gets sticky in the ringland. That is the most likely explanation. Some run time on the engine will help to loosen things up....get her nice and warm. 

As we discussed ; i wouldn't be in a hurry to disassemble at this point without further investigation seeing as the engine runs so well. When you get a chance have a look at the valve seals because they are probably vulcanized and allowing oil to trickle down the valvestem. If you pull the intake manifold look at the ports for signs of oil leakage. If there is no oil in intake ports 5/7/2/6 then it's the valve seals.

Let us know what you find 


Ron

Ps. Here's the Lunati grind we talked about :

http://www.summitracing.com/int/parts/lun-10230703/overview/make/chrysler

[My9302002]

Thanks Ron...
I'll report findings of the borescope along with a repeat warm compression test.