Compression loss 440

[fatecaptured]

I have posted in other threads about my 72 rallye w/1971 440 HP. Now i'm getting into it. I decided to do a compression test on all 8 cylinders. I'm going by the "72 dodge service manual CD Rom". Although it said to tighten the intake bolts to 50 foot pounds (which I didn't see till after I completed the test). I could be wrong, but I don't think that makes a big difference.The motor hasn't ran since i've had it, and previous sell said it ran for a short time when he was checking it out. I wanted to check the condition of the engine before trying to start it. Anyways here's what I came up with:

Drivers side (front to back):
1). 110 lb's
2). 110
3). 70
4). 100

Passenger side (front to back):
1). 60
2). 85
3). 50
4). 85

Now the manual says for a 400/440, that 100 pounds should is where they should be and not vary more than 40. But it also says"Many conditions which are difficult to control cause variations in compression readings. An engine should not be disassembled to determine the cause of low compression unless some other malfunction is present".

So what the hell do I do then? LOL It goes on about changing plugs and wires . This is all under tune up procedures. But with the big difference in readings , I can't help but feel like there's something fishing going on.

Any thoughts???

 

[Meep-Meep]

Are these numbers with the engine hot or cold? I've always done the compression test with a warm engine and the throttle open. Go through 5 cranking cycles per cylinder and the first reading should be at least half the total. Then go back and do a wet check and see if the numbers change drastically. A wet check means squirting some oil into the plug hole so it can temporarily seal the piston. If the reading changes a bunch then you have worn rings. Or do a leak down test and listen where most of the air is escaping. Your numbers don't look to good and I would suspect valves are at fault or the engine is just worn out.

 

[69Bee]

He said the motor has not run for him, so I'm geussing cold...:icon_wink:

Like Meep said, try squirting a small amouont of oil in the cyl to see if there is a problem with the rings. Problems include:

1) Broken rings
2) Stuck rings
3) Worn seats
4) Stuck valves
5) Burnt valves
6) Bent valves

The 110 to 100 readings seem to be worn symptoms, but the 50-85 is a problem symptom to me. So it might be prudent to pull the heads and see.

 

[fatecaptured]

Should I even try to run the engine like that? Yes it was cold when i checked it. The fuel line was disconnected and the fuel pump was sucking gas threw a water bottle (wtf). And allot of the plug boots are split. Fresh headers were on it. Doesn't look like any of the pain has been burnt off. Coil was disconnected and alt is all spliced with tape. So I was hesitant on trying to start if. Looks like new freeze plugs and the lower radiator hose was leaking. Got a new one and have a set of accel plugs to a b electronic conversion kit still in the box. So if u think i shoud fire it up. I guess i can give it a shot.

 

[69Bee]

For the price of gaskets, and piece of mind, remove the heads and have them evaluated. You can also see it there are any issues with the piston tops (harder to evaluate the rings). You could also look thru the valley holes and see if the cam looks okay. If it was wiped, this would be another way to have lower compression as the valves are not opening properly.

 

[fatecaptured]

Well I suppose I better just put this one on hold. I need to get my coronet up and running before i tackle another engine build. I already know the cost of that avenue. Spent around 7k on the 440 build in that car. Should of just bought a damn crate engine after all said and done. Live and learn right.

Thanks for the advice guys.

 

[Garys1969RR]

What I find strange is that #6 cylinder (the 3rd one back on passenger side) always goes first! Every big block I ever had, there was some kind of problem on that cylinder. From burnt ex valve to just lowest compression as in your case. Any body else ever see that happen? I usually try to at least fire up an engine and run it a little before evaluating it. But in this case, looks as though there are some serious probs due to the wide variation in compression pressures. If they were all 90 to 110 you prob be ok. Well good luck!