Low Compression after Head Gasket Job (SOLVED)

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Alright I wish I didn't have to make this thread but I am at a loss. Here is the story:

My 80 has 170k miles and I just started to notice a head gasket leak. Some oil in the coolant, some coolant in the oil, and a rough idle for about 15 seconds on cold start. So I ordered the kit from Wit's End and started tearing it down. Sure enough, cylinder #6 had a crack in the firing ring part of the gasket, direct path to one of the water jackets.

Anyway, I cleaned everything the best I could, had the head checked for flatness, checked the valves for leaks, and put everything back together. I made sure the cams were in time with everything, all marks at TDC. I just finished putting everything together last night. I turned the engine over by hand to verify the timing was correct and that there was no interference before I buttoned it all up. I cranked it over and it sounded like there was zero compression :/

I did a compression test on cylinder #1 and it's bringing up about 63psi which is super depressing. So at this point I feel like I've made things worse. I double checked the cam timing with the crank pulley and it seems to be in time. I can only assume that the head gasket did not seal properly. I torqued the head bolts using the method outline in the factory manual.

So what do you all think? Did the head gasket just not seal properly on all cylinders, or is the timing off somewhere?

I feel like it would be a timing issue if all cylinders have low compression but the marks line up so I'm not sure.
Thanks in advance.
 
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Put a cap full of oil in each cylinder. That should help the rings seal. Chances are the rings are totally dry from cleaning the block.. if the oil doesnt bring up the compression you may have valve train issues.. or maybe it wasnt head gasket after all..
 
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Put a cap full of oil in each cylinder. That should help the rings seal. Chances are the rings are totally dry from cleaning the block.. if the oil doesnt bring up the compression you may have valve train issues.. or maybe it wasnt head gasket after all..
Hmmm you bring up an interesting point. I will try putting some oil in the cylinders. Definitely an HG issue since I saw the failure on the old gasket myself.

Didn't even think about putting some oil in there though. Thank you.
 

SNLC

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Alright I wish I didn't have to make this thread but I am at a loss. Here is the story:

My 80 has 170k miles and I just started to notice a head gasket leak. Some oil in the coolant, some coolant in the oil, and a rough idle for about 15 seconds on cold start. So I ordered the kit from Wit's End and started tearing it down. Sure enough, cylinder #6 had a crack in the firing ring part of the gasket, direct path to one of the water jackets.

Anyway, I cleaned everything the best I could, had the head checked for flatness, checked the valves for leaks, and put everything back together. I made sure the cams were in time with everything, all marks at TDC. I just finished putting everything together last night. I turned the engine over by hand to verify the timing was correct and that there was no interference before I buttoned it all up. I cranked it over and it sounded like there was zero compression :/

I did a compression test on cylinder #1 and it's bringing up about 63psi which is super depressing. So at this point I feel like I've made things worse. I double checked the cam timing with the crank pulley and it seems to be in time. I can only assume that the head gasket did not seal properly. I torqued the head bolts using the method outline in the factory manual.

So what do you all think? Did the head gasket just not seal properly on all cylinders, or is the timing off somewhere?

I feel like it would be a timing issue if all cylinders have low compression but the marks line up so I'm not sure.
Thanks in advance.


Cams out of phase?

Cheers
 

SNLC

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If the dots are not lined up correctly and checked when installing the cams they may be in out of phase. Out of phase cams will result in low or no compression because the valves are open at the wrong times.

Cheers
 

flintknapper

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Assuming you have everything in 'time' and you saw factory cross-hatching on all cylinder walls, your rings are just dry.

Fog the cylinders real well while turning the engine over by hand. Then crank the engine and let it run for awhile.

Retest cylinder pressures with the battery on a battery charger so you get full starter output for each cylinder and I think you'll find noticeably better figures and no need for concern.
 
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OK so I have good news: I am simply dumb :doh:

The intake camshaft was 180 degrees off.... I matched the yellow dot to the two stamped dots on the exhaust.... so yeah, that was it.

Compression on all 6 cylinders is around 200 psi, all within a few psi of each other. This was after I squirted some oil in each cylinder. Very happy with this number considering the spec is 120-171psi (IIRC).

It's all buttoned up now and it runs super well thankfully, except for a nice exhaust leak coming from the rear downpipe; one of the nuts stripped so I couldn't get it off, that's gonna be fun to fix tomorrow. I need the thing off-road ready by Thursday morning so we're almost there!

Thank you everyone for your insight. Super helpful.
 

flintknapper

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If the dots are not lined up correctly and checked when installing the cams they may be in out of phase. Out of phase cams will result in low or no compression because the valves are open at the wrong times.

Cheers

^^^^^

Good call. Turned out to be the problem.

Despite the OP having 'checked the cam timing twice', going back revealed the cams were not in fact phased correctly.

Glad he got it sorted and that the knowledgeable folks here were willing to help. Good job guys!
 
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^^^^^

Good call. Turned out to be the problem.

Despite the OP having 'checked the cam timing twice', going back revealed the cams were not in fact phased correctly.

Glad he got it sorted and that the knowledgeable folks here were willing to help. Good job guys!
Yep, I did not see the double dot mark at all on the intake... Oh well, I'm glad my own installation was the problem and not something actually wrong with the engine.

Just drove it to work today and all is good! Water temp is good, I put a radiator flush in there to get all the oil out so I'll drain that probably this weekend. Fixed the exhaust leak, and I'm going to change the oil again tonight. Smells a bit oily but I'm sure that's from all the penetrating oil I used on the exhaust manifolds.

Could not be happier with the result. Thank you again @SNLC for the tip.
 

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