Ailing engine (Updated after teardown)

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Coyote Jack

Coyote Jack

Member #55, I'm old
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I started my 340 up this spring and noticed a **** load of blow by. I finally got around to doing some tests on it today. Compression is all over the map. There is light blue smoke coming out of the tail pipes. And you can see the amount of blow by in the video. The plug check showed all cylinders a little rich except #6 which showed a little oil fouling. The car still pulls like a freight train. Keep in mind this is 340 with a roots 6-71 blower on top. I am pretty sure a complete refresh is in order. Rings, bearings and a hone job for sure.

Compression test results:
1------128
2------121
3------120
4------118
5------122
6------95
7------112
8------168

What do you think?
 
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Pulses in the blowby almost seem like it is just one cylinder, maybe a blown head gasket at number 6. Number 8 is confusing though. Was compression that high when fresh?
 
qkcuda said:
Pulses in the blowby almost seem like it is just one cylinder, maybe a blown head gasket at number 6. Number 8 is confusing though. Was compression that high when fresh?
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I can't remember what the initial compressions were, that was 11 years ago. #8 had me scratching my head as well. Did it again and was the same.

Jack
 
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The others are so close, they are either all good or the rings are all worn out .
 
Maybe head gasket.Do a leak down on and listen where the air goes.Or borrow a smoke machine leave the plugs out and follow the smoke.#8 maybe a big blob of I burned oil(carbon) taking up space
 
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Getting that much blow by makes me think head gasket. I didn't watch the video at first, but that looks like a good possibility. Light blue out the tailpipes could be valve stem seals or guides, seals usually will smoke at startup in my experience.
 
This 340 was pulled out for a swap only because of blowby - out the breather in valve cover , no exhaust smoke , did not run poorly - just puffin' out the breather. It was a fogger. 2 weak compression cylinders , and a unhappy # 5 piston. Broken rings in every cylinder.

IMG_1625.jpg


IMG_1630.jpg


IMG_1626.jpg


IMG_1629.jpg
 
Michael Siple said:
This 340 was pulled out for a swap only because of blowby - out the breather in valve cover , no exhaust smoke , did not run poorly - just puffin' out the breather. It was a fogger. 2 weak compression cylinders , and a unhappy # 5 piston. Broken rings in every cylinder.

View attachment 1716251183

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Ouch.

Would pull the plugs and bore scope. The pressure numbers could be all over the board due to the valves not fully seating from carbon buildup. Would for sure pull the valve covers, give the valves a slight tap with the dead blow as your working through the cam timing to close the cylinder for each leak down.
 
I'd say it's time for a refresh at the least. That #6 compression is definitely out of range, as is #8. I would suspect #8 is probably getting oil in the cylinder. What kind of rings did you go with, Jack?
 
RustyRatRod said:
I'd say it's time for a refresh at the least. That #6 compression is definitely out of range, as is #8. I would suspect #8 is probably getting oil in the cylinder. What kind of rings did you go with, Jack?
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That was 11 years ago, (I just looked it up), Rob. My memory does not recall the type of rings, only that they were a softer metal than what a n/a engine would use, but that only applied to the compression rings.

Jack
 
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I got it taken apart today. Here are the photos.

Jack

HEAD GASKET004.jpg

I didn't see anything obvious damage wise. The one thing I really noticed was how much cleaner #6 was compared to the other pistons.
HEAD GASKET005.jpg

There was no scoring of the cylinder walls and no ring ridge.
HEAD GASKET006.jpg

The cam lobes looked great.
HEAD GASKET007.jpg

#6 here is the middle cylinder. Notice the cleanliness.
HEAD GASKET009.jpg

#6 is on the right. Looks like it was pushing the gasket into the lifter valley.
HEAD GASKET010.jpg

#4 is on the left here. Looks like it was headed for the lifter valley as well.
HEAD GASKET012.jpg

Here is the reverse side #6 on left.
 
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Wow! I think it's time for a head gasket upgrade. Maybe o-ring the block and go with copper? I know it's been fun though!
 
The head gasket is what I figured, but that still doesn't explain the high number in number 8
 
qkcuda said:
The head gasket is what I figured, but that still doesn't explain the high number in number 8
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It was either getting water or oil in. Caint compress either one of them. lol
 
Here are my thoughts. It appears that #6 has just completely pushed the head gasket out. Number #4 is not far behind. Looking at the pressures again I would say that #7 is headed that way as well. The cylinder walls still have crosshatch on them and I didn't see any scratches. There are no obvious problems with the pistons either. It looks like I may have caught it in time that a new set of multi layer head gaskets will fix it up.
@jimjimjimmy ; @RustyRatRod
@missing linc ; @Scody21;
Jack
 
Coyote Jack said:
Here are my thoughts. It appears that #6 has just completely pushed the head gasket out. Number #4 is not far behind. Looking at the pressures again I would say that #7 is headed that way as well. The cylinder walls still have crosshatch on them and I didn't see any scratches. There are no obvious problems with the pistons either. It looks like I may have caught it in time that a new set of multi layer head gaskets will fix it up.
@jimjimjimmy ; @RustyRatRod
@missing linc ; @Scody21;
Jack
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I wouldn't go any less than Cometic and I would CALL them and see what they recommend for your application. Let them know the boost amount and the whole nine yards. They may have something that can do the job without o-ringing the block. That sure would be convenient.
 
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