Straightening a cylinder head - Chevelle Tech
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post #1 of 13 (permalink) Old Feb 8th, 20, 5:38 PM Thread Starter
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Straightening a cylinder head

OK, this is part 3 of a series and I will admit that I have not watched parts 1 or 2 yet. But this is an interesting shop technique. This guy certainly has a good feel for how to use a torch. I would expect that the straightedge would also get used on the bottom surface, too.

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post #2 of 13 (permalink) Old Feb 22nd, 20, 1:07 AM
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Re: Straightening a cylinder head

I really wish people could learn to hold a camera before making a video like this.

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post #3 of 13 (permalink) Old Feb 22nd, 20, 5:06 PM
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Re: Straightening a cylinder head

Follow-up to the now-deleted post.

1. You HAVE to straighten some heads rather than just planing the gasket surface. If the head warps, the overhead cam saddles go out-of-alignment. Straightening the head gets the cam saddles back in-line; or at least closer. The straightened head may need no align-boring/honing of the cam saddles, or will need less material removed which improves the chances of getting proper valve lash/lifter preload. Similarly, if the head is straightened before machinework, the valve guides are more likely to be concentric with the seats, again minimizing the amount of material needed to "correct" a warped casting.

2. True enough, after "straightening" the head, you'd probably need to at least skim-cut the head gasket surface. A proper straight-edge and a careful examination would tell that tale. Same deal with grinding the valve seats. They'd have to at minimum be tested for sealing, and likely "touched-up".

3. I had concerns about the torch screwing-up the heat-treatment of the head. But where he's pointing the torch isn't a wear surface; and it's possible the head wasn't heat-treated to begin with. Any quality aftermarket head for our old V-8s will be heat-treated ("T6" is the common result) but I wouldn't promise that the OEMs are doing that. At minimum, they don't tend to advertise it. Given a choice, I'd rather NOT use a torch. But I've been wrong before; and I've never personally straightened an aluminum head.

4. Of course he'd need to check the straighness/flatness of the BLOCK head gasket surface as well as the gasket surface of the head. Moderate chance the block needs work, too.

5. Yes, the chick has a screw loose, (perhaps SEVERAL screws loose) and the guy reminds me of Buddy Hackett in The Love Bug.


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Last edited by Schurkey; Feb 22nd, 20 at 5:21 PM.
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post #4 of 13 (permalink) Old Feb 22nd, 20, 7:47 PM Thread Starter
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Re: Straightening a cylinder head

Now you got me wondering what was in that deleted post. I had thought that with no responses for almost 2 weeks that this was certainly a topic of no interest to anyone.
I looked at the other videos and he does address the flatness of the head gasket surface and also the alignment of camshaft bores and binding of the cam if all is not well.
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post #5 of 13 (permalink) Old Feb 22nd, 20, 8:55 PM
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Re: Straightening a cylinder head

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Originally Posted by JWagner View Post
Now you got me wondering what was in that deleted post. I had thought that with no responses for almost 2 weeks that this was certainly a topic of no interest to anyone.
I looked at the other videos and he does address the flatness of the head gasket surface and also the alignment of camshaft bores and binding of the cam if all is not well.
I requested my post be deleted because it was pretty abrasive and probably would've statred an argument. The only thing I'll say here is that IMO the head is junk. Time for a new one. if the guy knew what the heck he was doing, he would've checked the under side of the head, (The deck surfaces) at the end of the last and final video AFTER he took a blow torch to it and AFTER he pressed it with well over 4 tons. You might as well drive over your heads with a HD3500 series dually pick up truck to fix them. LOL.

Did you catch what he said about what happened to another cylinder head after he pressed it? he said it "cracked" LOL...ya think???? What a hack. If you cannot mill the head to get it right, it's junk. Do you really think that once that head is back on the engine, and gets brought to ful operating temperature, it isn't going to warp right back to the bent shape it was before he got to it, or that it won't just crack from him placing 9,000 LBS of pressure on it from his hydraulic press? OK, I already said too much. But you wanted to hear it, so that's my opinion. I wouldn't even let that guy around my power tools let alone my engine. Buddy Hack it
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post #6 of 13 (permalink) Old Feb 23rd, 20, 12:28 PM Thread Starter
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Re: Straightening a cylinder head

Got it.
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post #7 of 13 (permalink) Old Feb 23rd, 20, 12:52 PM
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Re: Straightening a cylinder head

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Originally Posted by JWagner View Post
Got it.
Sorry if I was a little over the top JW. (I was worse in the post I asked to be deleted ). I just think it's a bad practice what that guy in the vid is advocating. Looks like that same chick has a bunch of vids on youtube. Personally I'd steer clear of all of them. JMO.

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post #8 of 13 (permalink) Old Feb 23rd, 20, 4:50 PM
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Question Re: Straightening a cylinder head

You can cut the cylinder head gasket surface flat on a overhead cam cylinder head and still have a warpage in the cam journals which then has to be fixed too.
After cutting the gasket surface flat,the OHC head could be flipped over and then the cam journals can be bored/honed & straightened ? I would think.I don't know which area would have to be done first and is that critical ?
But what really had me thinking of how & what that guy was doing, straightening the head had me wondering if once it got torqued down and hot,would it then relax and return to its original warpage ? What would keep it in its newly straightened shape ?

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post #9 of 13 (permalink) Old Feb 23rd, 20, 5:05 PM
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Re: Straightening a cylinder head

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You can cut the cylinder head gasket surface flat on a overhead cam cylinder head and still have a warpage in the cam journals which then has to be fixed too.
After cutting the gasket surface flat,the OHC head could be flipped over and then the cam journals can be bored/honed & straightened ? I would think.I don't know which area would have to be done first and is that critical ?
But what really had me thinking of how & what that guy was doing, straightening the head had me wondering if once it got torqued down and hot would it then relax and return to its original warpage ? What would keep it in its newly straightened shape ?
Sure, but either way,placing 9,000 LBS on it with a press, is the caveman way, and if you decide to resort to such measures, then you have to flip it over to check the gasket surface with a straight edge and he did NOT do that in the vid AFTER he heated it and pressed it. That's why I said the guy is a hack.

And I agree with you that there's a chance, (prolly a good one) that the head would just flex back to the warped state that it was in, and heating it with a torch isn't helping the heat treat that the factory put on it.But even if there's a question about whether or not the heads were heat treated from the factory, you're fatiguing the aluminum by heating it with a torch and even if the trch was placed on the webbing only, it;s all one piece and if enough heat was applied to make it easier for the entire head to be altered with the hydraulic press, then it's very lkely causing that entire head to be fatigued. It just looks like a bad practice all the way around. Ya gotta wonder how much that guy is charging his customers to do that.

He said that he's "saving money" for the customer, hahaha.
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post #10 of 13 (permalink) Old Feb 23rd, 20, 5:41 PM
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Re: Straightening a cylinder head

Either way that's something the import guys and ferds have to worry about, not us

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post #11 of 13 (permalink) Old Feb 23rd, 20, 5:53 PM
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Re: Straightening a cylinder head

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Originally Posted by 71350SS View Post
Either way that's something the import guys and ferds have to worry about, not us
Yeah, it's only a supra, right?
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post #12 of 13 (permalink) Old Feb 23rd, 20, 8:37 PM
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Re: Straightening a cylinder head

Back in my machine shop days, I remember sending heads out and having them bolted down to cast iron blocks to be heated in an oven and then cooled to get them back to flat. When they came back, we surfaced them, checked the cam bores, and did the valve job. Don't recall any problems doing it that way, but that was 30 years ago. Maybe that doesn't work with the junk being produced now.

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post #13 of 13 (permalink) Old Feb 23rd, 20, 9:48 PM
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Re: Straightening a cylinder head

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Originally Posted by dyno jonn View Post
Back in my machine shop days, I remember sending heads out and having them bolted down to cast iron blocks to be heated in an oven and then cooled to get them back to flat. When they came back, we surfaced them, checked the cam bores, and did the valve job. Don't recall any problems doing it that way, but that was 30 years ago. Maybe that doesn't work with the junk being produced now.
Yeah John, someone else just told me the same as what you just said. Thanks for chiming in. Apparently some of those heads on the old foreign cars were very prone to warpage because I just remembered that I had a Subaru back in the 80's and the repair manual said that it was part of a routine tune up on those cars to re-torque the cylinder head bolts due tjem being so prone to warp.

So perhaps it's true what was said earlier that some aluminum heads weren't even heat treated from the factory.

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