Another sad head gasket story (1 Viewer)

[72LANDI]

I am the owner of a 4/72 FJ40 with the original F155 engine. I purchased it in 4-2019 and right away I could tell it did not run well. After a long process to figure out what was ailing it, it turned out to be blown the head gasket.

Took the head to a shop I have used in the past and had the head rebuilt and flattened (it was warped). Cleaned the block head gasket surfaces, cylinders, piston tops and chased and cleaned all threads. Checked the block for flatness and found no issues. The cylinders looked OK so I did not have the block rebuilt or resurfaced.

I purchased an $.O.R. head overhaul kit but noticed the head gasket was not as good quality as the metal one I removed. Installed it anyway with no problems, torqued it in three steps to 90 ft./lbs. using A.R.B Ultra Torque on the head bolts. Adjusted the valves per the FSM. Now when I check the compression it’s very low (30 to 60 PSI) on all cylinders.

Any idea where I went wrong?? I am out of ideas. I was hoping to just get it running so I could drive it. My plan was to eventually replace the F engine with something else as there is so little parts support available.

 

[Steamer]

A thorough leak down test would help you track down where your lost compression is going. Rings could have been bad all along. Did you happen to do compression check before the head job?

 

[fyton2v]

Seems odd that you’d have the problem across all cylinders. I’m not an expert so don’t listen to me, but are you sure your valves are closing all the way? Perhaps increase the rocker arm clearances on one of the cylinders just to be sure. If not clearances, did you redo your valves and seats to ensure they seal properly?

 

[pb4ugo]

A thorough leak down test would help you track down where your lost compression is going. Rings could have been bad all along. Did you happen to do compression check before the head job?

Yep, or at least a wet compression test

 

[brian]

what was the comp before the work?

 

[Pighead]

I might double-check the accuracy of your compression tester

 

[72LANDI]

Thanks for all of the responses fellow Cruiser Heads. I created this chart when I took a compression check on 11/7 & 12/17/21. I put MM oil in the spark plug holes on 11/7 and let it soak a couple weeks. Compression did get a little better but the leakdown test on 12/23/21 told the story. The head gasket confirmed it when I pulled off the head.

I adjusted the new valves per the FSM cold with the intake .008 in. and exhaust .014 in. Valves, guides and seats were all new. I am going to take Fyton2v's advice and loosen the rocker arms on cyl. #1 and see what happens. It had the lowest compression. It seems as though it would make sense that I do this with the leak down tester plugged in. I will keep you all posted.

Thanks!!

 

[mrboatman]

I would place my bet on the valve adjustment being to tight.

 

[72LANDI]

Thank you for yiur comment. I agree completely. The information I used to adjust the valves was posted here on the site, It is page EM-5 ENGINE MECHANICAL - ENGINE TUNE UP. Maybe this is incorrect for my F155 engine.

 

[Steamer]

I’ll post this chart in case you don’t have it, or for others that might not.
Is there any chance the half and half method (A & B) got switched when adjusting them?

 

[72LANDI]

Yup. That's exactly how I adjusted the valves. Thanks for the info.

 

[72LANDI]

The only other thing I can think of is when I had the valve push rod side coverer off and the head removed, I pulled each valve lifter one at a time, cleaned the varnish off the exterior, oiled them up and slid them back into place. They seemed to go back exactly where they were originally. Could I have created a problem?

 

[middlecalf]

A thought… somewhat uneducated but from a small bit of practical experience.

This ran before you did the head job, right? “Not well” from your first post. Was it smoking out the exhaust, specifically blue smoke? Was it consuming oil? If yes and yes, it’s possible that your head job stopped the leaking of oil wrt the valves (or possibly head/gasket) into the cylinders, and as a result you now have low(er) compression because there’s no longer the oil to help seal up old and tired rings. That’s one of the things you do when performing a compression test, is if one or more cylinders have low compression you add a little oil to those cylinders and retest - if compression goes up that points to sad rings. Just a thought. GL.

 

[DougAustinTx]

It would have been a good idea to check the valve seal against the seats before you installed the head. When I do a valve job on any head (I have both a Sioux valve facer and seat tool), I always either pull a vacuum on each valve, or pour lacquer thinner or gas into the port in the head for each valve, and push the head of the valve against the seat using just pressure from my thumb (before installing the springs). If there isn't a perfect seal, then it's time to use a little fine grinding compound on the leaking port, or redress the valve face or seat. It takes me several hours to do a valve job on a head, but knowing for sure that the valves are seated eliminates that as a variable in a case like yours. It's not impossible that the shop didn't do a proper valve job. Maybe set the angles wrong on the valve faces or the seats. I agree with the earlier posters that you either have your valve clearances way off, you put the head gasket on wrong, or my idea about the bad machining on the head work.

 

[72LANDI]

It ran poorly when I got it and continued to get worse over time. Hard or impoosible to start when cold, irratic idle, lack of power. then it started to spew a black sludge out the tail pipe. A leak down test confirmed a blown head gasket as did the bubling in the radiator. When I took the head off, I cleaned the block off and poured marvel mystery oil down the cylinder bores to see if the rings would hold the oil. They held the MM for days before it was gone. Cylinders looked ok with minor scoring that could not be felt with the fingernail. I agree with the valve adjustment. I did per Steamers info above. To rule out a bad valve job, I am going to put the enigine to TDC on #1 cylinder and loosen the rocker arms and compression test the cylinder to see what the pressure is. I was also considering running smoke through the cylinder and see where it comes out.

I was hoping to get this F engine running enough so I could get it back on the road. This would give me time to decide what I wanted to replace the F engine with. I don't see any value in rebuilding an F engie as the part support for this engine is dwindling dailey.