ENGINE compression issue

[toddbracik]

Hey guys! It’s been awhile since I’ve posyed but I need some advice. I’ve been driving my D24 for a number of years now without an issue. Labor Day weekend, however, I got a ride home in a rollback.

 

short story: I had some overheating problems on 300 mile journey to and from Michigan. Thankfully on the very last 60 miles of my journey, I heard some rattling coming from my engine, blue smoke came out of the tailpipe, and she died immediately at a stoplight.  I didn’t want to chance it so I had her towed the last 60 miles home.  I’m greatful because Hagerty covered the tow.

 

today I finally got a chance to do a compression check.  Here are the results:

 

1= 82
2= 35
3= 71
4= 80
5= 35 plug oil soaked
6= 53

 

Plugs all looked fine except for 5.

 

I was able to start it and it ran smooth but after a few revs something started rattling inside the engine again so I turned it off as soon as I could get to the key.

 

any advice on a next step would be appreciated. Thanks!

[Plymouthy Adams]

could be that you have some piston ring land or ring itself broken off and bouncing around...with poor compression....I would inspect by pulling the head as first order of business...sorry to hear you having issues

[knuckleharley]

Compression is really low in a couple of the cylinders,so my best guess is to agree with Plymouthy Adams,and also suggest you start budgeting a ring and bearing job on your engine at minimum.  Maybe a rebore.

 

If you go that far you might as well take the whole ride and go for new timing gears,valve job,and oil pump. Do it right once and never have to take it apart again.

[sser2]

2 hours ago, knuckleharley said:

go for new timing gears,valve job,and oil pump.

Knuckleharley - a question for you. Is it common for timing gear to wear so bad as to need replacement? 

[knuckleharley]

17 minutes ago, sser2 said:

Knuckleharley - a question for you. Is it common for timing gear to wear so bad as to need replacement? 

Yes,even with modern vehicles using the MUCH better oils of today.  I have seen some that come off of modern cars that were so sharp they could have been used for throwing stars.

 

One major consideration for ME when working on this old stuff is the thought "What happens if I take shortcuts now,and need to do more a few years from now when it is even harder,or maybe even impossible to find the parts?" Yeah,if you have the money and are willing to spend it,you can get anything made that you need,but isn't it smarter to just go ahead and do it all at one time and have a reasonable expectation that you will never again in your entire life have to go into the engine again and THEN have to look for parts you can't find?"

 

Plus,when/if you ever go to sell it,it can really help the sale down the road when you or your heir can show the potential buyers receipts for parts and machine shop work that are dated and in your name. It can also get you a better price.

[knuckleharley]

26 minutes ago, sser2 said:

Knuckleharley - a question for you. Is it common for timing gear to wear so bad as to need replacement? 

I apologize. Doing two things are once and breaking up a cat fight got me distracted,and somehow my original reply to you was posted separetely.

[sser2]

I was asking because in two P4 engines that I took apart there was hardly any sign of sprocket or chain wear. Chains in Mopar flathead six engines are so massive and overbuilt compared to what is being used in modern engines! Shop manual describes checking procedure for valve timing, which accounts for combined wear in camshaft and timing gear. I believe that if valve timing is correct, replacing timing gear is waste of money.

Edited September 17, 2018 by sser2
Grammatic error

[knuckleharley]

3 minutes ago, sser2 said:

I was asking because in two P4 engines that I took apart there was hardly any sign of sprocket or chain wear. Chains in Mopar flathead six engines are so massive and overbuilt compared to what is being used in modern engines! Shop manual describes checking procedure for valve timing, which accounts for combined wear in camshaft and timing gear. I believe that if valve timing is correct, replacing timing gear is waste of money.

Ok.

[dpollo]

It is possible that the head gasket has been leaking for a long time and finally failed at #5  but I agree with PA and KH that you had better have a look at the pistons and rings.

[Dartgame]

Easy to check the chain. While still assembled and the chain cover off, see how much slop there is in the chain using your fingers to move it on the side not driving the cam, if its floppy, replace it. I know - not technical, just a mechanical feel one acquires. The big deal with chains wearing is the distance from the two sprockets. Flat heads are really close compared to a lot of v8’s, and the older ones use a really beefy chain, less likely to wear. I talked with George Asche about timing sets and he said the gears don’t usually need to be replaced, only the chain when they go bad.