Head Gasket leak?

[Dave WM]

One more thing, Maybe I should look at the valve guide seals for the oil in the cylinders. Most of the test running it idle, and this engine has a very high vacuum. I check it today at was 20in/Hg while idling. I suspect that could pull in a pretty good amount of oil on the intake valve seal.

[Dave WM]

Ok now I can join the removed head bolts without breaking any club (already a member of the spindle pin removal club).

I used my old hand powered impact tool working from the outside towards the center, to motivate them. They all succumb to a combo of that and a 1/2 breaker bar. I got the nice satisfying squeak on all but the center long. it was kinda stuck and did not release after one turn like the others. I presume some corrosion on that one, but it came out. I did remove the 2 small bolts that clamp to the timing chain cover. I will prob leave the exhaust manifold on to aid in unsticking the head. Waiting on the timing chain jam tool before removing the timing chain. I set it to TDC on #1 and noted the shinny chain link is right over the #3 mark on the gear. The slot is centered in  the V on the viewing window.  took pics so I can reassemble. I am reserving judgement on how far I want to go. I want to get the head off and examine for cracks/leaks/warps. I have a new head gasket on the way (felpro). IF all looks good I will prob just clean up the head and reinstall to see if that stops the exhaust gas in rad issue. I did another video (did not post) where you can clearly see the yellow tint in the test fluid.

If the head not cracked but warped I will prob fully tear down the engine and take to a machine shop for hot tank and head work. Have them check the bores, of not bad, ball hone and new rings, bearings etc...

I guess if the head is cracked I will do some research on my excellent looking MN47 head. IIRC dished pistions and maybe a 2 millimeter (double thick) head gasket to get the compression where I want it. I do not want to have to run premium fuel.

 

 

 

Edited May 21, 2019 by Dave WM

[Zed Head]

You can make your own tool from a piece of wood.  Not much to them.  

Head gasket seems most likely.  I haven't seen much about cracked heads, especially the later years.  But, it's usually overheating that causes the HG to leak, which also causes the head to warp.  But, also, I found that it really doesn't take much force to bend the head.  You can "reflatten" it with a single head bolt and a short wrench.  

[Dave WM]

1 hour ago, Zed Head said:

You can make your own tool from a piece of wood.  Not much to them.  

Head gasket seems most likely.  I haven't seen much about cracked heads, especially the later years.  But, it's usually overheating that causes the HG to leak, which also causes the head to warp.  But, also, I found that it really doesn't take much force to bend the head.  You can "reflatten" it with a single head bolt and a short wrench.  

can you elaborate on that re flatten? I presume you put spacer of some kind on the and then bolt pressure to reverse bend? I have shim stock handy if that would work.

Edited May 21, 2019 by Dave WM

[Zed Head]

I got curious about the need to shave or skim the head if it was out of spec. for flatness.  My head was at the limit, bowed up in the middle, so I put it back on with no head gasket and tightened it back down to see how much it would take to make it flat again.  It didn't take much to close the gap.  I'm pretty sure that the How to Rebuild book uses a wider range also, I seem to recall .007", not the .004" that Nissan uses.

The resurfacing has always bothered me because it leaves the valve train spec'ed to a different surface than the bottom of the head after skimming.  The valve train is still warped.  But if you tighten it back to flat using bolts then the valve train should straighten out also.

Just a thought.

[Dave WM]

if I had to machine it flat I would have them do both sides. I have a head saver shim kit ready to go.

IIRC read that shimming (as in your case .001 shims on far ends to pull the bow down in the middle) followed up with a heat cycle was something that was mentioned. Need a oven to heat it up, again cant recall the exact temps 250f maybe? hold it there for hours then let cool off. Something about even SKILLFUL use of a gas torch with a flame spreader to gently heat the entire head. Seem like the oven would be better for long term setting (hours then a cool down).

Agree with not liking the idea of skimming and shimming etc...

Fingers crossed I don't have to cross that bridge.

[Zed Head]

I think that the process is described Honsowetz's or Monroe's book, or both.  

I've thought that  torque plate would be best for machining.  It would take some ingenuity, maybe counterboring or even threading the bolt holes.  But then you could flatten it via bolt torque to the top surface and skim just the odd high spots on the mating surface.  When it's bolted on to the block it will be the same as on the torque plate.

[Dave WM]

This morning I pulled up the one "sticky" head bolt (long one center cam tower) all loaded up with black carboned up goo around the threads. Maybe the head leak area? The ones I pulled from the MN47 head were nearly perfectly clean looking, and prob what I will use, unless someone tells me they should not be reused. I can see I will need to get a flat bottom clean out tap.

[Zed Head]

The head gasket usually tells a story.  Check it carefully.

[Dave WM]

will do, will post up some videos as I go.

did notice my spray bar had a partial failure of one of the gaskets when I removed it, so they need to be redone as well. I did not notice any significant wear on the lobes, but the was a lot of sludge build up, esp in the head bolts, guess that is typical.

[Dave WM]

went out to shoot some video, noticed the head was already lifting up (weight of manifolds I presume) so looks like its going to go easy, Just waiting on the jam tool now. will go a head and remove the manifolds while waiting. I was concerned about all the horror stories of stuck heads.

[Dave WM]

progress. the head was indeed loose (see the end of the video) I have since then removed that Tstat housing and the manifolds, and have the chain tool (came in the mail later) install. All that is left is to remove the gear and pull off the head.

 

Edited May 22, 2019 by Dave WM