Engine cut out while slowing down....

[Mtl-Diesel]

The hard part is knowing where the compression was leaking now that the head is off. With it on you can do a leak down and figure it for sure - as you pressurize a cylinder through the plug hole you listen for where the air is escaping. If though the crankcase vent, it's rings, if through the cylinder next over, it is a head gasket or crack in the head. And so on. Without having done that you are down to inspecting everything. A machine shop will help a lot. They can check flatness pretty easily. And they'll know what to think about valve issues.

All great advice! Guess I'll bring it in for inspection. Should I reassemble and bring the whole engine or just the head?

 

[Rick Stephens]

All great advice! Guess I'll bring it in for inspection. Should I reassemble and bring the whole engine or just the head?

Start with the head. See if they find the issues.

To do anything with the motor you'll have to pull it and remove the pan. Then pop pistons out, pull rings and mic the gaps.

 

[Mtl-Diesel]

Start with the head. See if they find the issues.

To do anything with the motor you'll have to pull it and remove the pan. Then pop pistons out, pull rings and mic the gaps.

Will do. I’ll circle back with an update as I learn more. Thanks so much!

 

[Mtl-Diesel]

Hey folks,

Happy spring to y'all! I wanted to circle back with an update. I took the head in for evaluation. At first glance they seemed impress with the look of condition. Once they tore it open, a different story. Head was at the border of tolerance for flatness. The valves were not sitting well allowing pressure to escape. Head had a crack starting to form which they were able to fill and repair. Whole new valve job and now ready to put it back on the block. I'll give an update once I check compression with new numbers.

Thanks again to everyone for the help & guidance!

 

[kenny nunez]

You should remove the distributor cap turn the engine by hand and check how the push rods are acting. Wedge something between the alternator and the block to keep the belt tight so that you can use a 15/16” wrench on the alternator pulley nut. Also check if the rotor lines up with the #1 wire position in relation to the timing marks on the balancer. There is a possibility that the timing gears may be the problem since you heard a noise and the compression was really way off.

 

[Mtl-Diesel]

You should remove the distributor cap turn the engine by hand and check how the push rods are acting. Wedge something between the alternator and the block to keep the belt tight so that you can use a 15/16” wrench on the alternator pulley nut. Also check if the rotor lines up with the #1 wire position in relation to the timing marks on the balancer. There is a possibility that the timing gears may be the problem since you heard a noise and the compression was really way off.

Awesome! I'll do this. It has been changed over to EST so rotor alignment is out.

 

[Mtl-Diesel]

Ok. Putting everything back together and just noticed I have one pushrod that is slightly bent. Having difficulty locating a new one here. Is there an automotive equivalent? Mercruiser part #34532

Thanks!
Rod.

 

[alldodge]

The 3.0 is a marine and industrial motor only. Was never put in a auto app.

Only needing one, should be easy enough. BAM has 2 available for 10.93 each
https://www.mercruiserparts.com/34532-push-rod

 

[Mtl-Diesel]

The 3.0 is a marine and industrial motor only. Was never put in a auto app.

Only needing one, should be easy enough. BAM has 2 available for 10.93 each
https://www.mercruiserparts.com/34532-push-rod

Agreed. Easy to find in US. Add the shipping to Montreal, Canada and it's nuts!

 

[alldodge]

Take some accurate measurements and verify they are 3/8 x 9.75 length. Then find ones which will work. I did some looking at summitt racing and found a few, but not sure about the tip.

 

[Mtl-Diesel]

OK. So finally got the head put back on! Did a compression test:
1 - 45
2 - 65
3 - 65
4 - 75

When my problem happened originally I had
1 - 40
2 - 0
3 - 0
4 - 40

Am I looking at a combination of I had a blown head gasket, valves not sealing correctly and now piston ring issues? I was hopeful the rebuilt head would be a win. :-(

 

[Rick Stephens]

Unless you have the rockers run down too far it sounds like heads were the least of the problem.

 

[alldodge]

Unless you have the rockers run down too far it sounds like heads were the least of the problem.

Agree

Did you check clearance of the collapsed lifters?
Basically the lifter is fully collapsed and tool is used to see if there is still room to insert the gauge. If its unable to insert then a different length of rod is needed

 

[alldodge]

The procedure above is also how the rockers should be tightened to spec. Manual states if not done this way it can bend push rods

 

[alldodge]

Have been looking at parts from the old 140 to the new 3.0 and the studs, nuts, push rods have been all changed to the newer 3.0

Seeing a different cylinder head part number but that's about it @Bondo have any thoughts?

 

[Mtl-Diesel]

Interesting. I followed the manual to adjust the rockers. 3/4 turn after lash was eliminated. Should I have run the engine for a few minutes before testing compression? It has not been turned over since late August 2020.

Maybe I should try backing off the rocker nut an 1/8-1/4 turn to ensure they aren't too snug?

 

[Rick Stephens]

I keep hearing different philosophies from folks about what equals zero lash. Zero must be vertical play in the rods. No twisty turn type feel. I was taught early on to turn a rod, took years of having to redo valve adjustments to learn that feeling up and down is the key.

 

[achris]

Should I have run the engine for a few minutes before testing compression?

Absolutely. Compression should be tested warm, not cold.

Maybe I should try backing off the rocker nut an 1/8-1/4 turn to ensure they aren't too snug?

Did you turn the pushrods to find zero lash? (Incorrect) or did you find zero lash by lifting and feeling for VERTICAL movement? (correct method)

Chris...

 

[Mtl-Diesel]

Yup. Following manual I did the spin test. I'll redo today using vertical movement. I did a quick test again last night backing off an 1/8 turn on one and pressure went from 40 to 100. Fingers crossed it is something as silly as that!

 

[Mtl-Diesel]

So readjusted the rockers as per the proper lash setting (up & down). Did a compression test. I'm now thinking my gauge is inaccurate. Without changing anything, I got different readings from the same cylinder 5 minutes apart. 50 psi difference. Picking up a new gauge tomorrow to confirm.