Stumped! Anyone else have any idea.

[gofishn]

Bring any cylinder to TDC on the compression stroke - then put some compressed air into the cylinder through a plug hole and see where the air comes out. It has to come out somewhere - intake, exhaust, or crankcase.
IF it is coming out of the intake or exhaust, pull the rockers and see if it still does it. If it doesn't leak with the rockers off it is out of time, if it still leaks with the rockers off then you have a valve problem - seats, bent valves, etc.

Completely agree and what I meant in my first reply.

Pull #1 up to top dead center, yank the valve covers and start figuring out where that compression is being lost. There can only be soo many avenues for it to escape. RIngs, Cracks(Stress, Heat or otherwise) Gaskets, Valves (GUides seats etc)

I also agree, this would be a good engine to tear into and see just what the heck is going on.
Though, to be honest, I would want a couple of my super gear head friends around drinking beer and pointing out the not so obvious, to me.

 

[cheffrank_357]

Reading this is fun cause its a mystery!
My vote is timing
I would also check that pistons are indeed moving up and down
As is all the valves
And since nothing is a for sure thing at this point a new timing chain is a definite.



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[crash68]

Who all up for grabbing some beers and heading to @O3hemiram7 place for a teardown party? LOL
I'll throw in my $0.02 and guess the compression gauge is malfunctioning or bad? Something electronic has stopped the spark and/or fuel injection.

 

[Ppk1234]

One other item to check had a 74 Chevrolet 350 at a popping noise when I shut it off one day no compression on all cylinders. Everything looked normal until I took the head off and then I could see I had broken valve springs everything else was fine broke for no reason. Might be worth checking before you pull anything else apart .

 

[Hey Grandad]

Were you able to see if the key on the crankshaft was sheared or the dowel on the camshaft?? I have seen that happen before on different engine.

 

[demonram]

Since he lives in Arizona, I can't participate in the tear down, and I am no professional mechanic by any stretch, total shade tree, however, it sounds like (A)timing, but since everything seems to be functioning as it should, it sounds like that isn't the problem, (B)valve train, bent push rods, or valve springs. Just seems odd for all cylinders to not have compression.

 

[pacofortacos]

If I had to quess, I also think timing.
However, I find it better to diagnose that to guess if given an option

No matter what, the reason really can't be too complicated. It's just a matter of running the test to see what it is. Though it is possible to be 2 things at the same time - such as a sheared key way AND bent valves.

To the best of my knowledge, the hemi is an interference engine. And if cam and crank get out of sync, bent valves/pushrods/valve seats are the usual post carnage.

 

[cheffrank_357]

Pin is still in place.

View attachment 189992

That is one clean "original motor"

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[Marshall]

I would double check the compression gauge, just to be sure, if the crank key is gone, the timing marks would still line up as they should, but everything would be crunched as the chain would/ could slow /stop .
Blown head gaskets ? , but would have oil , coolant all over .
Interesting, Keep us up to date.
Pull the value covers sounds like the next thing.

 

[ford40]

I had a flax plate brake once almost tore the engine down because there was no compression but the engine was not turning over and no noise

 

[gofishn]

If I had to quess, I also think timing.
However, I find it better to diagnose that to guess if given an option

No matter what, the reason really can't be too complicated. It's just a matter of running the test to see what it is. Though it is possible to be 2 things at the same time - such as a sheared key way AND bent valves.

To the best of my knowledge, the hemi is an interference engine. And if cam and crank get out of sync, bent valves/pushrods/valve seats are the usual post carnage.

agree, again.
Suspect those pistons/valves are not moving or those push rods/valves are /brokebent beyond ability to do any good.

 

[Tadpole]

Like a few others have mentioned, imho the only viable answer is you have a bad compression tester.

Looking forward to hearing how this turns out!

 

[Bills86e]

I wonder if the pistons are going up/down. Pull it out will resolve this.

 

[shackman]

I used to own a auto engine remanufacturing facility from 1985-2005 .We ran into almost any and everything. If you have not yet confirmed that the valves are in fact opening and closing my guess would be a broken camshaft even though you can get the marks to line up on the chain that part is still supported by the cam bearing in the block. Since you have it down that far see if you can get the cam to move by putting the bolt back in a little and try to pull the cam out. If it's broke it will move.

 

[pacofortacos]

A broken flex plate could do it, but I am assuming that he has infact confirmed the engine is spinning over by watching the fan/etc. Might be wrong to assume though.

 

[ford40]

A broken flex plate could do it, but I am assuming that he has infact confirmed the engine is spinning over by watching the fan/etc. Might be wrong to assume though.

Thats what happened to me .I never thought to look to see if the engine was turning till was starting to remove it . just sounded like no compression.

 

[pacofortacos]

It is easy to do if doing a compression test by yourself and using the key.
And it would definitely account for no compression on all cylinders.

On the plus side, you have to remove the engine or trans (at least in most cases) to change the flex plate so at least you didn't waste all of your time haha.

 

[El Huapo]

How much st-re-tch in the timing chain? Original motor with 198K miles? If you have the cover off and roll the engine forward and them back with the marks at TDC, you may find there's a lot of difference in the start-to-move, meaning a badly stretched chain.

A broken camshaft would do it too, haven't seen that myself, but I do not understand how a broken flex plate would cause a loss of compression...? However, you said the rockers were rocking, right?

NOTE: I haven't been inside a new-type hemi, only the 1950's types so I may be way off-base here, apologies if so, but that chain stretching used to be a common problem at less miles than this.

Next thought: with that many miles, if you can afford it, pull the heads and get a valve job. You will be surprised at how much the engine wakes up (plus new timing gears and chain, of course, since you're already in there). My own experiences were at how much new back-pressure there was in going down the hills after a valve job, plus more get-up and go.

A last thought: IF, somehow, the engine was over-rev'd, and being that old, a whole set of bent valves isn't inconceivable. Maybe a missed shift...because of the tranny malfunctioning, natch! Good luck, hope the pistons are all OK.

 

[enforcer17]

I'm with shackman, based on the info provided, seems like the camshaft must be broken so no valves are moving but the chain is lined up and seems normal.

 

[crash68]

I'm with shackman, based on the info provided, seems like the camshaft must be broken so no valves are moving but the chain is lined up and seems normal.

Rocker arms are moving and the fact 4 of the cylinders were showing some pressure means the pistons are moving.
Quoted from the OP's original post:

We thought exactly what you are currently thinking pulled the valve covers and turned her over by hand all rockers are moving as they should, we pulled the timing chain cover and chain and tensioner look good and timing mark's are aligned as they should be. So I am at a total loss at this point. We did a wet test of the cylinders still nothing for compression.