compression Numbers

[1979 Quartermasters]

I had a long thread going about hydrolocking and was not getting any responses.

To make a long story short: Hydro locked when cold, pulled sprark plugs, water in number 4 and a little in the pan. Oil level didn't rise but the oil is a little milky.

Pulled manifold and elbow, visually looked fine but have not tested them yet.

Compression test, first number dry, second wet: #2 170/175, #4 160/165, #6 165/170, 165/170.
Does the comp test rule out head gasket. Could the head or block still be cracked.

I have not over heated or froze this engine as it sits in a heated shop all winter. We have been using this boat since April and this condition just started in the last couple of weeks.

I did bend a starter bolt but have had the starter serviced and new bolts.

I'm trying to locate a leak-down tester and may be able to get one tomorrow.

I would really like some answers so I could get this thing running and get a few more trips out of it this year.

I'm thinking I will see if i can get the manifold and elbow preasure tested tomorrow and do a leak dowm test aswell.

I'm confused because there is only water in one cylinder.

Ken

 

[NHGuy]

Re: compression Numbers

Go to harbor freight and get some line clamps. Block off all the inbound and outbound cooling water lines except 1. Take the unblocked line and pressurize the cooling system to about 20 psi, it should hold a while. I did the pressure fitting which is 1" ID hose by taking a round plug with a hole down the middle. I took a bicycle tube and cut out the valve with a "skirt" around it. Put the valve through the middle of the plug with the skirt around the outside of the plug. Then put this valve/plug rig in the end of the cooling hose and clamped it off with the tube material trapped between the hose and the plug so it would hold air. This will check the motor cooling system.
That's the first test. I am pretty sure I answered you about this in the other thread.
There is a chance that the gasket for the elbow leaked water, and there is also a chance that the manifold leaked the water from a rust through. If you don't find out why you will kill your motor.
Do some reading at the top of the forum in the stickies for how to test the manifold. Check the elbow gasket for visible leak tracks. If you think it's the elbow gasket, put in a new one, run the motor til it warms up, shut it off and wait. After a good wait-more than 30 minutes, pull the spark plugs. If they are bone dry you might be OK.
Compression test does indicate good head gasket.

 

[1979 Quartermasters]

Re: compression Numbers

I did the elbow gasket and even had the elbow refaced to eliminate that possibilty. Still water in #4 only. I guess I'll do that lineclamp test tomorrow.

Thanks for you response....

Ken

Your right, post 25 other thread. More detail this time. Thanks

 

[thumpar]

Re: compression Numbers

A head gasket leak would be very small normally and not show much on a compression check. Try a leakdown test and as NHGuy stated to pressurize the cooling system and listen.

 

[1979 Quartermasters]

Re: compression Numbers

I was looking a little closer at the exhaust manifold and found some white streaks in the corner leeding to #4. I just refaced the surface on the elbow and new gaskets and torqued to 25lbft. Here is a picture of what I found.



What do you guys think....

Ken