[willisjdeck15]

Got my 79 280zx up and running on all cylinders (stuck injectors) only to get a lot of white smoke out the exhaust after getting the 4th cylinder to fire. Inspected with a Boroscope to find some coolant leaking into the cylinder, so it looked to be head gasket time.

Pulled the head and the gasket was intake but worn out, and the mating surface on the block was pretty gross. After cleaning up the block and head surfaces, I checked for warpage using a machinist straight edge. Block is straight as an arrow but the head has around 0.01” warpage between cylinders 3 & 4. As background I ran a dry compression test and got 170 across the board +/- a couple.

I’m trying to weigh my options. From what I’ve read, milling isn’t really the solution. It seems like I will need a shop to bolt down the two center bolts on a steel plate and put it in an oven to unwarp both the inner and outer surface of the head. The only problem is that these shops are charging quite a bit to disassembled the head and some won’t reassemble at all.

I’m not experienced disassembling/assembling cylinder heads so I’d like to avoid it unless it’s something I can be talked into doing. Another option is buying a used head which may or may not be true either. And remanufactured ones are quite pricey.

The question I want to know: is there a chance the warpage will address itself during the in to out tightening process? I mean, this is aluminum so I figure it’s possible to tighten down the center 2 bolts pretty tight and then retorque them after a few engine cycles. Or is there a head gasket in particular that might help? Any advice is appreciated.

 

[pilgrim]

If it's only one-thousandth, I'd use a premium (thick) gasket and expect it to seal OK. I confess that I might add just a couple lbs/ft to the torque readings on that spot in the head.

But with the head off, I'd also have the valves done and have new valve stem seals installed.

 

[willisjdeck15]

What would be considered a premium gasket? I have a new Felpro one. It seems to have elevated metal rings around the cylinders which might help prevent any leakage. If I have the valve seals done do I need to worry about the piston rings? I think I read that somewhere

 

[Dave Datsun Tech.]

0.010” is no big deal. Just take it to a machine shop and get it resurfaced. They may have to remove more than that to clean it up. They may have to surface the top of the head too. If so, there are shims you can buy for the cam towers, to make up the difference.

 

[theghosttanker]

I believe the rule of thumb is you can take off up to 020 without having to shim the cam towers. I agree that you can just get it milled flat removing minimal thickness and put it back together.

 

[pilgrim]

What would be considered a premium gasket? I have a new Felpro one. It seems to have elevated metal rings around the cylinders which might help prevent any leakage. If I have the valve seals done do I need to worry about the piston rings? I think I read that somewhere

"Premium gasket" is probably an outdated term. It used to refer to a thick head gasket rather than a thin metal one.

 

[Tango#2020]

I too, would go with a light skim of the head surface0.001 ain't much, and have new valve guides pushed in and the reassembly isn't too massive a job. but even if you took less than the 0.001, just skim the head and then retorque going just slightly more, and agine Use the best head gasket you can find, and use 'New' head bolts. Never skimp on head bolts, get the best you can afford. You only plan on doing this once, Right ?

 

[pilgrim]

Use the best head gasket you can find, and use 'New' head bolts. Never skimp on head bolts, get the best you can afford. You only plan on doing this once, Right ?

I strongly agree.

 

[Dave M]

I picked up some OE looking head gaskets of a guy local to me on ebay, pretty sure they had asbestos in them, the good stuff. Its what I plan to use next time I pull the head for any reason. IIRC he bought out a warehouse full of such stuff.

 

[kpitts]

Here in Central Kentucky we have a shop that will straiten in the oven then machine the head. Mine was out .005 after the bending.Then machined and reassembled with great results. If you need any more info about them DM me.

 

[willisjdeck15]

I found a shop who was willing to work on this and had experience. Most shops in the Detroit area only work on domestics so it’s actually not easy to find people to work on an older Japanese car.

And just to reiterate, it was warped 0.01” (10 thousandths) not 1 thousandth.

 

[pilgrim]

And just to reiterate, it was warped 0.01” (10 thousandths) not 1 thousandth.

Thanks for catching my error in math. Agreed, that's enough that you need to correct it.

 

[zmanofwashington]

Don't forget to check the top of the head with a straight edge as well. Like someone else said you may have to cut both top and bottom. .010 is enough to cause cam bind which can cause premature failure of the cam. I strongly urge you to have the head pressure checked as well. If these heads crack it's usually on #3 or #4 cylinders. Let's suppose the heads cracked and you don't have it pressure checked so you deck the head and put it back on only to find out that it's still pumping coolant into the cylinder. Imagine how happy you'd be then. One last thing, it may be an optical illusion from the picture but it looks like #1 cylinder is not at TDC. In that case you'll have to put the head back on, then turn the engine a little to get to TDC on #1, then remove the cam gear, turn the cam a little to #1 TDC and put it back together again. Z man of Washington