Been working on friends Challenger that has a 440 engine. He dropped it off and said it just started smoking out exhaust.Swap carburetor out to rule running rich. Compression check only showed 90 to 95 dry. Wet only increase reading by 5 lbs. The engine has only has twenty thousands miles on it. The reading seems low to me anyone one know the numbers I should be seeing. I was told it was built with 6 pack pistons.

You should be seeing 160-170 min. I gotta question the test basics: all plugs removed? Throttle open? Battery charged? Battery charger hooked up? Engine warm?

Did you do an oil test to see if readings improved?

The fact the readings were consistent is good, the fact they are that low is not.....hence the questions

Yeah that's pretty low. I healthy motor should be in the 130-140+ range...and fairly consistent between cylinders.

Were all cylinders this low or just two? If it's two adjoining cylinders, it could be a blow head gasket. If it's pretty much all of them, new rings are probably needed.

However if it just started smoking all the sudden, I would suspect a blown gasket or (hopefully not) cracked block. Check the oil and make sure it doesn't look like a milkshake indicating coolant is getting into the oil which is bad news for the rest of the motor.

Good luck.

Warm engine ,one plug at a time, good battery spins engine great, couple of shots of oil in cylinder only increase reading by 5

Oh man. One plug at a time? You need to do it over. Pull all plugs, open throttle and test.

Remember to disable ignition!

smokes all the time or on decell or? If "just started" that makes me think valley pan tin gasket leaking

Thottle was wide open, The instructions with compression tested said one plug at a time. What is advantage of removing all plugs To make the engine spin over faster. The engine is spinning pretty good as is.I understand the open thottle to help draw air in. But what does the other cylinders have to do with the one I have the gauge hooked to.

Already changed valley pan gasket. That is was my first move

Wrong stagger on the piston rings......

Numbers this low will not come up to acceptable with proper ring stagger.


Smoke can come from a minor mark in a cylinder wall. For the same reasoning that a compression test is not a good tool. It's a quickie to tell if a motor is great or shot, like burnt valve shot.

That engine needs a cylinder leak down tester with compressed air, 2 gauges and a regulator.

It sounds like the cam was installed dot to dot and not checked for cam timing, it is probally retarded 2 to 6 degrees Did you get to drive it before the smoking? If so was it lazy and not real responcive to the throttle? If so check the cam timing to make sure it is installed correctly

All the plugs have to be removed for the engine to spin fast enough to get a proper reading. You will never get the proper reading out of it by leaving them in and pulling just one plug at a time. I think you may have misunderstood the instructions. Yes, you are checking only one cylinder at a time, but with ALL of the plugs removed.

Big cam, low compression ratio will give low readings across the board. Second thing is check with the same gauge on a known good motor. Gauges can be inaccurate. Seen plenty of motors in the 125 psi range with low compression ratios. The first thing I'd check is a poor fitting intake manifold.
Dou

If it has 6 pack pistons in it that is an extremely low reading. What cam is in it?

Seen that b4.


Yep. My 8.x:1 440 with the MP 509 cam was pulling 110psi on all eight (cam was straight up).

first we gotta fix the smoking. secondly improper breakin might have fubared the rings. You might read "breakin secrets" at www.mototuneusa.com for my take on that. As said I would do a leakdown. keep us updated

if the rings are shot, can he ball hone the cylinders and slap some new rings on and be good to go? or do we think we need to remachine the block?

I don't see why not. I burned up #3 twice (cast pistons w/ 6psi of boost) all I did was pull the old unit out hit with quick hone and slap it back together. Do a leak down 1st. How do the plugs look?

I believe so with the correct grit on the ball hone. (I'd want file fit plasma moly rings and Brush Research Manufacturings' recommendation on the grit). You would wanna check taper/out of round & you'd sure think it'd be good with that few miles but I would square up a ring gap & use it to check out of round/taper at least on 1 cyl just to see where you are at or if the block is coming out then have your shop use a dial bore gauge for a spot on check

I don't think its rings or it'd have come up more than 5 PSI with oil. 95 PSI is LOW no matter how you cut it.

How does the engine run and what cam is in it? I'd suspect that the pushrods are too long or lash adjusted wrong if it has adjustable rockers. OR it doesn't have six pack slugs in it.

Are you sure the gauge is good?