Cylinder Head Flatness

[Jerry VanOoteghem]

How flat does the head really need to be? Yes, perfect would be nice, but what have you found to still be serviceable?

I have a gasket leak. There may have been other reasons for the leak, (like it wasn't retorqued after warm-up, but only later, after it was found to leak combustion). However, upon checking the head, it appears to be out by .004", (on a freshly re-decked head), making the gasketed surface concave. So, what did it? The .004" out-of-flat, or allowing the gasket to leak and thereby ruining it?

Since time is of the essence, (upcoming tour), I'm tempted to clean things up, put on a new gasket, and torque it down, (the right way). Just curious as to what I'm likely to have as a result. I know, there's no definite answers here, until I actually do it.

A little more background...
-Stock, cast iron, high head
-Copper sandwich gasket
-50 ft-lbs torque
-Some small deformities on the gasket fire ring.
-No real tell-tale marks or degradation on the gasket, except for a simple blackening near the valve areas on all 4 cylinders.

[Dan McEachern]

Did you torque it from the center out in a pattern or just randomly tightened the bolts? Not retorquing it initially may have added to the problem.
T head gaskets are pretty forgiving in most cases, but they do need to be retorqued.

[Norman Kling]

I like to run it until warm and then re-torque. Then I will drive it slowly for a mile or so until it warms up again and then torque it again. I keep doing this until it holds torque. I found one problem with one of my cars which continually would leak in a certain spot. I finally found out that the bolt was bottoming out before it completely torqued to the head. The torque wrench would read 50 but it was not actually pushing the head. I put a thin washer under the head of this bolt and since then haven't had the problem.
Norm

[Jerry VanOoteghem]

Did you torque it from the center out in a pattern or just randomly tightened the bolts? Not retorquing it initially may have added to the problem.
T head gaskets are pretty forgiving in most cases, but they do need to be retorqued.

The head was not initially torqued by me. I have every reason to believe however, that it was torqued in the correct "center out" sequence. I assumed that it had been subsequently re-torqued by the installer. I should not have made that assumption. Upon hearing the tell-tale chirp of leaking combustion, I only then re-torqued, using the correct sequence.

[Randall strickland]

Wondering how it was torqued down when it was milled?

[J and M Machine]

Quote " However, upon checking the head, it appears to be out by .004", (on a freshly re-decked head), making the gasketed surface concave. So, what did it? The .004" out-of-flat,"

It could of been machined that way, if you just installed the head and already blew a gasket then I would speak with the machine shop.

To answer your initial question .004" is the limit on a four cylinder engine for cylinder head to be out .

[CudaMan]

If you haven't already, make sure that any crud in the bottoms of the head bolt holes is cleaned out. Then, check the lengths of all the head bolts and run them down into their holes without a head gasket to make sure that they clamp the head without bottoming out in their holes first.

[Jerry VanOoteghem]

Quote " However, upon checking the head, it appears to be out by .004", (on a freshly re-decked head), making the gasketed surface concave. So, what did it? The .004" out-of-flat,"

It could of been machined that way, if you just installed the head and already blew a gasket then I would speak with the machine shop.

To answer your initial question .004" is the limit on a four cylinder engine for cylinder head to be out .

By "what did it" I don't mean what made the head .004" out, I meant what made the gasket leak. Was it being out of flat, or was it damage to the gasket by not being re-torqued.

As to answering to my original question, thank you, that's what I was looking to determine.

[Tmooreheadf]

Do you use copper plus on the gasket when installing it?

[Jerry VanOoteghem]

Do you use copper plus on the gasket when installing it?

I use the Permatex brand copper spray.

[Norman Kling]

I suspect a combination of things caused the problem. The head was milled down so it is entirely possible that the top of the block was also surfaced when the engine was rebuilt.
This being the case, the bolts might be a bit too long. After cleaning out the threads with a bottoming tap and blowing out the holes, Try the head without a gasket and tighten down all the bolts. Just to where they bottom out. They should be touching the head all the way around. If one is too long, grind it down so it will tighten touch the head when tightened. Then check all the bolts and grind them to the same length. This will assure that you are measuring the torque against the head and not against the bottom of the hole.
Now place the gasket and torque. Torque again several times after the engine has warmed up until it holds torque.
Norm

[Joe Bell]

As some one comment on I have had to shorten the bolts from block and heads being milled so bolt does not bottom out.

[RGould1910]

I've had issues with the new generation gasket material not holding torque. You shouldn't have to retorque but once.

[J and M Machine]

I've had issues with the new generation gasket material not holding torque. You shouldn't have to retorque but once.

Unfortunately this is what the head gaskets are today. Same with Model A and V8 gaskets. Must be retorqued after 5 minutes of running time as they will loosen up. We tell our customers to constantly check torque on new engine. Typically we've gotten feedback saying around five times that they no longer move.

[Jerry VanOoteghem]

I'll be using an older stock gasket, but will still do multiple checks.

[Susanne]

Check the flatness of the block. Might be raised around some of the head bolt holes where someone tried to retorque it a bit too much over 80 years and, well, yeah.

Someone SKILLED with a flycutter mill that doesn't have clapped out cutters, etc., can skim a block or head .001 at a time until they're flat. Takes time to set it up right and to skim it over and over, but... you get a decked block without losing too much of it. Do the same with the head, and you're back in business.

[George Mills]

Maybe I'm reading into this something that isn't there and was never there?

There is probably an even chance that whoever put that head on may have actually 'drawn' the copper up in the area you mention where you 'think' there was a bypass leak? The old head bolt-down sequence? The premise is to walk out any micro burp that may come back to bite you in the butt later.

Sure the bolt engineering is all wrong in a technical sense, but they took a cannon to swat a mosquito in the first 500 field fixes...and...15 million later it still worked with no reason to go back on it. (the 3/8-24 head bolts and the separable head in use...as an engineer yourself keep in mind that they also thought part of the chronic weep was the water outlet being mounted to the head from the top with longer 2 head bolts! Which today even modern engineering 101 would say was never a part of the problem.). I mention this because...1st and foremost you NEED to have every bit of tap depth in the BLOCK possible WITHOUT bottoming out the bolt. The active threads produced in a perfect world of a 7/16-14 by THE EXACT SAME DEPTH SPACE that was designed for 3/8-24 means the real expected torque level was the SAME as a 3/8-24, once you actually run the numbers! Further proved to me by no one ever changing the length of the head wrench in that same 15 million run...in a world before those things called torque wrenches. That's my view...no one else quite wants to ever agree with me most of the time. Make sure the heads are squeaky clean and follow people like Joe Bell in their own methodology for getting the bolts ready.

Head milled flat within 004? Would not actually concern me...unless the block was decked with similar results on the same mill? Luck of the draw says 'somewhere' is then going to be 008. Worth at least a look see with a good straight edge.

Copper coat on the gasket? Good, a secondary something is needed as the clad surface today on the gaskets I 'think' is a little too hard to fill surface finish anyway.

Retorque...look at it this way...bring it in way tight to begin with and you may have no room to draw it up tighter later while at the same time you might run the risk of stripping a block tap (my standard advice for the 50 #--ft and over crowd.) I don't use a torque wrench, but believe that I pull them in somewhere between 35-40 and usually no leaks or weeps or real need to draw much tighter after a heat/cool/ cycle and one retorque seems to nail the occasional errant.

Bolt sequence...now that could go on for days as there are in fact many ways recommended, even by Ford! Don't forget the premise...walk out any flutter in a way that does NOT pinch the thin areas between. Here is the late Herm K's way...

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