Thicker Head Gasket Recommendations Please

[WindyCityZnut]

The head gasket on my race car blew recently (280ZX, T-4 Turbo motor). I took the head to a local engine builder to get checked out. Got the news today. The head is warped .013, needs new valve guides and seals.

 

The previous owner told me that he had this head shaved .008-.010. So, if I get it shaved another .013, I thinking I will need to get a thicker head gasket, right? I am concerned about too much chain slack or even throwing the timing off.

 

The engine builder recommended getting a Cometic .060 thick gasket. I did a ton of searching on the internet and could not find a Cometic gasket for this engine. I did find some discussion of Cometic gaskets being made out of copper and that you would need to o ring the block.

 

I did find a Tomei metal head gasket that comes in 1.2mm, 1.5mm, or 2mm thickness. Anybody ever heard of this one or used one?

 

So, what would you guys recommend?

 

Thanks,

 

 

Marty

[Xnke]

0.060 is about 1.5mm. I would either run the stock gasket and some head-saver shims, Or the 1.5mm thick gasket.

[Tony D]

with 013 warpage, you should check the TOP of the head as well. Likely it is warped as well, and getting to the point where tower bind is getting possible.

 

One way or the other it looks like you will be shimming the towers after a matching cut top and bottom...you could possibly be looking at a cam drop relative to crank centerline of 1mm (010+013+013=036" or roughly 1mm worst-case if the head was not decked top-and-bottom the first time)

 

I would get a head thickness reading and make the decision from there. I would keep a standard gasket (if the CR remains sociable) and shim the cam towers to get the right cam-to-crank centerline dimension restored. Or go with the Kameari Adjustable Chain Idler assembly ($500?+)

 

Tomei makes top-notch-stuff. I'd have no reservations using any of their componentry, but what you have may not require anything special other than the cam tower shims. That way you have 'standard parts' for a consumable for your racer and not something you will have to wait to order in when it breaks again...

[WindyCityZnut]

with 013 warpage, you should check the TOP of the head as well. Likely it is warped as well, and getting to the point where tower bind is getting possible.

 

One way or the other it looks like you will be shimming the towers after a matching cut top and bottom...you could possibly be looking at a cam drop relative to crank centerline of 1mm (010+013+013=036" or roughly 1mm worst-case if the head was not decked top-and-bottom the first time)

 

I would get a head thickness reading and make the decision from there. I would keep a standard gasket (if the CR remains sociable) and shim the cam towers to get the right cam-to-crank centerline dimension restored. Or go with the Kameari Adjustable Chain Idler assembly ($500?+)

 

Tomei makes top-notch-stuff. I'd have no reservations using any of their componentry, but what you have may not require anything special other than the cam tower shims. That way you have 'standard parts' for a consumable for your racer and not something you will have to wait to order in when it breaks again...

 

 

The shop checked the top of the head and it is flat and the cam spins freely. It was milled top and bottom the first time.

 

I will have them measure the head. A search revealed that a stock head thickness is 107.9mm, correct?

 

The Tomei gasket has a 91mm bore, where the block has a 89mm bore. Someone here has run that in a track car successfully. The other concern is that the head gasket may hold up, but it may blow other engine components, like rings, pistons, etc. with detonation. There was a lot of detonation showing on the old gasket. I can't tell if that was happening before or after I had it dyno tuned. I have to assume that it was before since it was running really crappy, barely running at all actually. It would be better to be safe with a stock gasket, like you suggest.

 

By the way, this is a P90 head and the boost is set at 15 PSI.

 

Will shimming the cam towers require other changes in the valve train?

 

Thanks,

 

Marty

[WindyCityZnut]

I talked to my machine shop again this morning about putting in cam tower shims. He said he could not get them from his suppliers any longer. He recommends going with a head saver shim.

 

This sounds like a simpler solution. He thought that there was no technical advantage for cam tower shims over head saver shims. He said they use them all the time in his industry. He may be able to get the head saver shim. Do you guys have an opinion on which is a better method for L6 engines?

 

Thanks,

 

Marty

[2eighTZ4me]

MSA sells the cam tower shims, as does a member on this board. Your machinist doesn't appear to have the "proper" connections. Let me guess - he does a lot of small block Chevys......

 

http://www.thezstore.com/page/TZS/PROD/10-1151

 

Go with the "proven" method of realigning cam geometry. I don't know what these "head saver" shims are - but I've not seen them and I'd go with the tried and true method of fixing what ails your motor.

[WindyCityZnut]

MSA sells the cam tower shims, as does a member on this board. Your machinist doesn't appear to have the "proper" connections. Let me guess - he does a lot of small block Chevys......

 

http://www.thezstore.com/page/TZS/PROD/10-1151

 

Go with the "proven" method of realigning cam geometry. I don't know what these "head saver" shims are - but I've not seen them and I'd go with the tried and true method of fixing what ails your motor.

Actually, he does a lot of Hondas,and Toyotas along with a bunch of Chevy's. They just don't see these engines anymore, since they all rusted away years ago around Chicago.

 

As he explained the head saver shim to me, it is made out of steel, about .020" and gets sealed in place just like a gasket. It builds up the mating surface to make up for what was shaved off. It almost sounds like a metal head gasket. You then put your head gasket on top of that.

 

The Pro's that I see are: 1) It is easier to install than the cam tower shims; 2) it won't change the CR; and 3) when used with the stock head gasket, it still gives you the safety of having the gasket blow before internal engine parts break, if you went with a metal head gasket.

 

The Con's that I see are: 1) it might just create another area for potential leaks; 2) it is an unproven fix in the Z world.

 

He is checking to see if he can still get one. If he can't, well, it makes that decision a whole lot easier.

 

But, like you said, it is probably better to go with the tried and true method.

 

Thanks for the input.

 

Marty

[ozconnection]

Oh man,don't make it more difficult than it needs to be.

 

Tony D gave it to you straight and I would follow his advice closely. he's got all the credentials any of us would ever need to do the job correctly.

 

Take his advice. Do it once and do it right. What you want to do isn't that complicated!

[WindyCityZnut]

Oh man,don't make it more difficult than it needs to be.

 

Tony D gave it to you straight and I would follow his advice closely. he's got all the credentials any of us would ever need to do the job correctly.

 

Take his advice. Do it once and do it right. What you want to do isn't that complicated!

 

Relax. The last thing I want to do is make this more complicated! I already stated that I was going with the tried and true cam tower shim method. I was just responding to 2eighTZ4me's comment that he had never heard of "headsaver shims". I was just telling what I learned from the shop and the relative merits of using this as an alternative for discussion purposes. Personally, I like to error on the side of too much info, as opposed to not enough.

 

I am ordering the cam tower shims today.

 

Thanks for the help!

 

Marty

[Tony D]

The Con's that I see are: 1) it might just create another area for potential leaks; 2) it is an unproven fix in the Z world.

 

 

Addressing in turn the cons:

1) Yes, but dressing properly will stop that issue.

2) Uh....no, that is not a correct statement. I'm not going to get into it here, but it is a complex answer to a simple problem. a 0.020" head saver shim is not worth the effort.

 

I'm not at liberty to discuss anything other than that right now, but it is a proven quantity. Just was overkill for the situation at hand. Which is why I went with the course of action I suggested.

 

Want a more valid con: If you DO blow a head gasket, you have a flapping 0.020" piece of steel exposed to directly exhausting combustion gasses. What do you think it does to a flimsy 0.020" peice of steel in that environment? Like I said, 0.020" is not worth it in this case. Now, you got a 0.040" peice in there, and it starts holding up O.K... one that is 8.2mm thick really has no issues at all holding up!

 

But I've said too much already...

 

shhhhhhhhhhhhhhh!

[ozconnection]

I wont mention the L20B front cover Tony, OK?

[Noddle]

I wont mention the L20B front cover Tony, OK?

 

How much taller is the L20B cover ?,

I assume you could run very high boost with a thick head shim and the L20B cover to drop the compression.

 

or am I barking up the wrong tree ?

[ozconnection]

How much taller is the L20B cover ?,

I assume you could run very high boost with a thick head shim and the L20B cover to drop the compression.

 

or am I barking up the wrong tree ?

 

Tony and I had a discussion when he was at my place about a brainchild of his.

 

I don't really want to spill all his ideas because he could do that himself, obviously.

 

Nigel, just think of the possibilities of an L20/24/28 block that was 8.2mm's taller than standard ie L20B size!

 

(Sorry Tony if I've said too much It's just such an AWESOME idea,I couldn't help myself )

Edited July 2, 2010 by ozconnection

[Tony D]

Before anything else transpires: No it is not an LD28 that is being discussed.

 

Don't even go there!