Bent cylinder head help

[tig321]

I just bought a 1990 supra turbo a few weeks ago and have blown the headgasket. My plans are to build the engine for 350+ rwhp and build some custom parts with my miller dynasty 200dx tig welder. :icon_bigg
but since I just bought the car I can't afford that right now.

My problem is that cyl head is out about 15-17 thou across both the cam and combustion sides. (bent down from the heat too much heat I geuss) Its still a decent head aside from this.

I have heard of people heating/bending other heads straght but I'm having are hard time finding solid info.

Has anyone here tried this?

I am a welder who works in a machine/welding shop and I have access to the equipment needed Including a small 5ton and not so small 80ton press.
I also have a junk head to practice on so if anyone has any tips, or links I'd really appreciate it.
The machinists I work with all think Its a bad idea, but I'm sure I'ts been done before.

Should I just pull the block and buy a used JDM engine?

I'd like to give bending a try since I have nothing to lose anyway.

 

[GrimJack]

My machinist baked mine flat - fastened it down to a flat block of steel, then threw it in the oven overnight.

Before you do anything, test it for hardness on the exhaust side. If it's going soft, don't bother trying to fix anything, just find a better one.

 

[supra90turbo]

Just put it under your knee and pull, kind of like when you're trying to break a branch. Hold it there for an hour or so while your buddy holds a propane torch to the other end.

 

[Satan]

I had a warped one "baked" as well. Dunno the specifics to the technic, but the head seemed good for the 2-3 years following that. I eventually sold the complete engine and never heard about any problems. Dunno about you doing it yourself... I'd just pay to have it doe by ppl who've got the experience... remember to use some ARPs on there when U R done.

 

[GrimJack]

supra90turbo was kidding.

 

[Joel W.]

I had to have my head surfaced also. It only required .006 Inches to be removed. But my question is if the head surface is warped, It would seem to me the cams would also be stressed from the warping. So if you make the head surface flat again by only machining it, the cams would still be stressed from warp? Yes, no, maybe?

 

[NDBoost]

^ yes

 

[Joel W.]

Cool ND, Should I be concerned with .006" ? It's been that way for 3 yrs now(40k miles).

 

[3p141592654]

Measure it. Two things help. One is that the cam journals become very loose once the mystery babbit goo wears away (Toyota wear limit is 5 mils!). Two is that the cams are shorter than the deck surface and so the warp can be less than measured at the deck. I had 4 mil deck warp and less than 1 mil cam journal warp.

I think the cam journal warp is probably the least of your worries. Plastigage the journals and see how loose they are (especially the exhaust side). The oiling arrangement in the head is dismal. It comes up through a convoluted path from the block and exits into the front cam journals. The hollow cam then takes that oil and pumps it to all the remaining journals. Once the journals start to open up the oil pressure at the rear journals starts to drop, and wear accelerates. If this gets bad enough you can deveop a startup clatter almost like a leaking hydraulic adjuster (like the 5MGE engine used to do).

One possible solution is to lap the bearing caps, since most of the wear is on the top of the caps from the opposing valve spring pressure. I'm always surprised that I never see any discussion about the cam journals on these forums. They are definitely a weak point on the car (5mil wear limit on a 25mm journal tells me that Toyota new they had a problem too).

 

[GrimJack]

IIRC, the max allowable is 5 thou...

 

[tig321]

Thanks for the help.
After some calling around I found a shop with an oven. I geuss the technique is to either bolt it to a flat plate and shim the high spots (if it needs it).Hoping it comes out straight, when it cools.
or
Heat it and bend it in a press.

I was told If I heat it bolted to a plate, I could do it at home in a 200F oven or a BBQ (kinda ghetto). I'm told people have done this before, but I won't be one of them.
The deck of my block has been damaged by the gasket. You can just barely feel it with your finger nail. I'll have to pull the engine. I may go over to Vancouver this weekend to find a decent JDM engine cause I can't afford a full rebuild right now and from what I read a stock block will handle my goal of 350+ rwhp.

 

[Jspec7m88]

supra90turbo was kidding.