66' F135 Compression Test, ADVICE NEEDED

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Rock40

Rock40

10 Year
Joined
Feb 21, 2012
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Location
Snohomish, WA
All, I'm currently working on this: 1966 FJ40 Frame-Off Build (3rd Generation Owner)

Roughly 2oz of coolant came out when I drained the engine oil and the rear coolant passages are blocked up (no coolant draining from the drain cock)

My next plan is to pull the head and inspect the head gasket. The engine has approximately 70,000 original miles on it but #4 cylinder is definitely out of spec. #4 does hold pressure pretty well, it bled off about 10psi in 20 minutes or so.
IMG_3986.webp

Here are the compression test numbers:
Dry, cylinders 1-6: 150, 149, 152, 129, 150, 156
Light oil (WD40) cylinders 1-6: 153, 152, 155, 132, 155, 158
Clean engine oil, cylinders 1-6: 165, 170, 170, 142, 165, 170
I trust this compression tester, I've owned it over 20 years and it's of good quality.
IMG_3987.webp

Really looking for some advice here before proceeding
 
You already know you're pulling the head. Why not pull it, tell us what you see, show us what you see, and then ask for advise?
 
65swb45 said:
You already know you're pulling the head. Why not pull it, tell us what you see, show us what you see, and then ask for advise?
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Fine, but that is just not nearly as fun. I suspect there is a compression ring issue on #4, we'll see
 
Yes but, there's a lot of F135 owners that WISH they had 140 PSI on their cylinders.

One of the smoothest running motors I ever owned had less than 120 across the board. It could run circles around my rebuilt engine. It was so LOOSE!:lol::lol::lol:
 
Well, that is good advice. Frankly, I'm curious if we can get away with having the head magnafluxed and the head gasket replaced. I'm assuming the cylinder walls are going to look just fine. I can always acid flush the block to clear up the coolant passages.
 
I'd be absolutely thrilled with those compression numbers. I agree totally with Mark's assessment and comments. No coolant from the drain cock (not a plug?) on the driver side of the block? Unthread it and stick an awl or something in there to be sure the threaded hole is just not blocked with crud. Interested to see how you proceed. Good luck!
 
shmukster said:
I'd be absolutely thrilled with those compression numbers. I agree totally with Mark's assessment and comments. No coolant from the drain cock (not a plug?) on the driver side of the block? Unthread it and stick an awl or something in there to be sure the threaded hole is just not blocked with crud. Interested to see how you proceed. Good luck!
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X2. The drain holes can get plugged up pretty good.
 
Yeah, the drain is plugged tight with crud and I've spent several hours over the course of the teardown cleaning it out. I've managed to get it pretty clean but only a few drips have come out. The nearest freeze plug is not very close on this older 66' block. I'm hoping that with the head off, I may be able to get at the coolant passages from above.
 
shmukster said:
I'd be absolutely thrilled with those compression numbers. I agree totally with Mark's assessment and comments.
Click to expand...

Thanks, that's encouraging. The consensus is still pulling the head to address the small amount of coolant in the oil and inspect the cylinder walls correct?
 
I am dealing with coolant in the oil on a rebuilt 2f. The head is coming off as soon as I get time to pull it.
 
OK, the head is off....and I don't think this is the first time either. The valve rocker retention nuts were not JIS along with the ghetto screw clamp holding the oil union in place. The oil feed tube is also pretty bent/buggered up.
IMG_3996.webp


The coolant passages are really bad and there is some evident water intrusion in each cylinder, most obvious in #3 and #4
IMG_3997.webp


IMG_3998.webp


IMG_4001.webp
 
This was a win...I was able to unclog the rear coolant passage from above which allowed me to actually drain the coolant from the block. I spent hours working on this alone
IMG_4002.webp


This is what the cylinders look like. I inspected the head gasket and it appeared to be intact. So...with coolant in the oil should I be suspecting a cracked head? Should I be taking the head in to be inspected/magnafluxed next?
IMG_4003.webp


IMG_4004.webp

IMG_4005.webp


Thoughts? Suggestions at this point?
 
Have the head checked. Be prepared for the worst.

Did you notice the head gasket was on backwards? Should have been a no-brainer. So that's probably what the PO was.

I Have an NOS oil delivery tube for sale in the classifieds. Also have the F135 head gasket set in stock.
 
I did not notice that the head gasket was on incorrectly. What/where is the indication of that? Head will go out this week for inspection.
 
Rock40 said:
I did not notice that the head gasket was on incorrectly. What/where is the indication of that? Head will go out this week for inspection.
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Match the ports between the head gasket and block where the oil tube is. You can see it in the second picture.
 
White Stripe said:
Your about an hours labor from having the block disassembled. How about sending the bock to a machine shop to have it hot tanked or whatever to clean the Coolant jackets? While that's being done u could have delta grind u a little better than stock profile camshaft.
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Well, it would probably take me a bit longer than that once everything was bagged and tagged. This is Jason's truck (not mine) and I'm doing the work for him so how he wants to proceed is his choice. Either way, the coolant passages seriously need to be addressed. They look like this...
IMG_3799.webp
 
Splangy said:
Match the ports between the head gasket and block where the oil tube is. You can see it in the second picture.
Click to expand...
Got it. That makes perfect sense, thanks
 
Did you check both sides of the head gasket? Between block and gasket

Looks to me like it may have been seeping right under where the head bolt is that nobody ever retorques is :meh:

Poor neglected head bolt ... he's always left out
 
JohnnyC said:
Did you check both sides of the head gasket? Between block and gasket

Looks to me like it may have been seeping right under where the head bolt is that nobody ever retorques is :meh:

Poor neglected head bolt ... he's always left out
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I looked at it again and you just might be right. I doubt any of the head bolts were re-torqued as required. The head is off at a local engine rebuilder as we speak, I should know by the end of today of it's cracked or not. He's going to magnaflux it after tearing it down.
 
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