Interesting head gasket experience

[Dire McCain]

Here's a cut to the chase.
1988 N.A.

HG was blown. Head had been machined twice before. Third time left it too thin to be in spec. Installed a steel head gasket shim sealed on the block side with copper spray. Used a genuine Toy HG.

Torqued the new headbolts down to 75 lbs in four steps.

Fired it up...ran beautifully. Except for the white smoke blowing our of the exhaust, the pressure in the radiator overflow hose, and the oil pouring our from the front a rear main seals. Oh yeah, no water getting to the heater coils either.

2.5 hours later with the help of air tools, yanked the head and found water and oil on both sides of the toyota head gasket...water and oil in all six cylinders...and a metal shim that looked perfectly fine...

If it was leaking under the shim you sure can't tell it.

I'm thinking the head had been shaved so many times that even with the
.020 shim it was so thin that the head bolts bottomed out and didn't really tighten the head. I've never seen that much water in the cylnders and I've done this job before...with 10 years in between them...

Stock height is 116mm...mine is closer to 115mm...

Hmmmm..add a washer under each head bolt...? I'm tempted to ry it just to
experiment. Then again, my fingers are already bloody..I could just pop for another head and say f it.

Live and learn...


Live and learn.

 

[Poodles]

The stock headbolts won't bottom out (they only use about half of the threads in the block) so something else is up...

 

[Dire McCain]

Interesting. I screwed one down in the block to check it out and there was still some bolt thread showing above the block- about one turn- when it seemed to bottom out..it wouldn't go any farther...stock headbolt from Toyota...

 

[CyFi6]

It might have a thread sticking out when bottomed out but that doesnt really mean anything. Measure the thickness of your head (from the deck surface to the valve cover sealing surface), then add the shim thickness and you should be relatively close to 116mm (stock head height)

 

[thorpedo]

Check to make sure the front aluminum cover is not holding the head up.

Compare your new head bolts to your old head bolts to verify they are the same. (may I ask why you got new ones btw?)

Did you clean the threads in the block out? the bolts shouldn't be bottoming out that close to where they would fully tighten.

Edit: Also are you remembering to use the head bolt washers?

 

[gofastgeorge]

Well, copper spray between a steel shim, and the block is a failure waiting to happen.

If it had a formed bead, that would be another subject,
but if used with a stock head gasket, that isn't a good mix either.
It is doubtful if a stock head gasket would put enough preasure on a beaded steel gasket to make the steel one seal, before the stock one started to squish out of place.

Mixing styles of gasket is not good.

Either get a thick all metal gasket, or get a new head.......
I've seen GReddy gaskets up to 3mm.

How thick do you need it to be ?

 

[Dire McCain]

I purchased new head bolts from toyota becxasue 1. the old ones had been used twice
by me, and again before I bought the car and 2. because they are one of the least expensive parts you can buy- cheap insurance.

And apparently you are right that the toy HG was squiching around quite a bit...it was a real mess. Like I said. Live and learn. But those head saver shims have been around a long time and have been in use- even in production automobiles (Ford) for some time...
I had a bad feeling about it but tried it anyway...

 

[IJ.]

Considering you already had fresh surfaces I'd have gone to a 3mm MHG and called it a day.

Don't get the "shim" it's another level of failure waiting to happen.

 

[ganesht]

what material are the oem toy hg made out of?

 

[thorpedo]

While I agree with the others (you may as well use a MHG at this point) I've seen many engines use shims with a stock head gaskets without any problems. With your shim there should have been an instruction sheet with a permatex or equivalent part number to apply to the shim prior to installation. If it squished the gasket that bad you may have an inaccurate torque wrench or you're not using it correctly. (don't let that offend you, i just thought I'd mention it because they are a tricky thing to be accurate with)

The stock gasket is a fiber type with stainless / copper rings around the combustion chambers and water jackets.

 

[Poodles]

Interesting. I screwed one down in the block to check it out and there was still some bolt thread showing above the block- about one turn- when it seemed to bottom out..it wouldn't go any farther...stock headbolt from Toyota...

Yes, but when actually tightened through the head they only use about half of the threads. main reason studs are better as they use all of them.

 

[IJ.]

Yes, but when actually tightened through the head they only use about half of the threads. main reason studs are better as they use all of them.

If there's Oil/crap in the threads they can hydraulic giving a false torque reading then bleed down over time and loosen leading to the leaks.

 

[Poodles]

Yarp

 

[ganesht]

The stock gasket is a fiber type with stainless / copper rings around the combustion chambers and water jackets.

sorry if this is a noob question but when would a bead type mhg be better than the oe hg? would there be any point on a fully stock motor w/ stock twins?

 

[Dire McCain]

Yes, I researched the shim concept and found that many engines do successfully use shims. So for $44 I decided to give it a shot. I followed the instructions from the shim manufacturer to the letter.

I am very careful and diligent with the torque wrench. It is a Craftsman
wrench that 'clicks' when the value is reached. I also double checked each head bolt with another Craftsman wrench- the old 'dial' type and made sure all the bolts were at 75 lbs.

I cleaned out all the bolt holes an cleaned the threads. There was no oil in the block holes, but there was light 30-weight oil on the bolts and under the washers.

But it was a real mess. Tonight I pulled the shim off and it was wet and sloppy and oily underneath it as well...something was wrong- read the next paragraph.

I have an acquaintance who is a mechanic and a Supra enthusiast who was kind enough to have a look at the head...it took him about 30 seconds to sight down the head and notice that it is shaped somewhat like a banana.

I took the machine shop's word that it was flat. I also took the machine shop's word that they 'straightened' the head...and charged me for it twice.

This is the same shop that left a pit in the sealing ring surface of number six...at precisely the point where the HG blew.

I am not a particularly big fan of cylinder head shops in Jacksonville, Florida, at the moment.

 

[thorpedo]

If you can see it is banana shaped your head is likely toast...

Too many food refrences

 

[Dire McCain]

The banana shape isn't especially obvious but one you see it, you can't miss it. Put a straight edge along the valve deck and...yep, it confirms the visual.

Looks like I need a new head.

 

[amichie]

Banana shaped heads can't be much fun for cams. Straightening is going to mean even more machine shop dramas. See if you can find another head.

 

[IJ.]

The banana shape isn't especially obvious but one you see it, you can't miss it. Put a straight edge along the valve deck and...yep, it confirms the visual.

Looks like I need a new head.

You needed a new head 2 cuts ago as it's more than likely been warped the whole time and just cut flat each time leaving the saddles misaligned.

I'm willing to bet that the exhaust side is annealed.

 

[Poodles]

More than likely the straightening was done with heat, meaning the entire thing is probably annealed...