What's good? I just bought a 7mgte motor for my cressida. I'm having a tough time trying to figure out what size mhg I should use, HKS 1.2mm/2.0mm? Does any one know the difference? Also, what else should I do before installing the motor?
The gasket thickness will be determined by how much material your machinist removes while prepping the deck surfaces. He will measure the block height as well to ensure that there has not been previous machining.
If you're not planning to visit a machinist, don't break the seal. Install it as is and run. If you have bought one that had a headgasket issue already, the machine shop visit is nearly unavoidable.
ummm...let me see...no. If you replace the gasket and do choose stock bolts, it will fail if and only if you do not know to torque to a minimum of 70 ft/lbs, or because your machinist didn't surface the decks correctly, or a combination of the two.
Umm lets see yes!!!, the toyota head bolts are known to have problems. If you plan on running a good amount of boost (which I assume you do since you put a 7mgte in a cressida) you will want to get the arp bolts. The stock ones are known to stretch to much over a period of time. Look it up on any of the supra forums there's pages on this old problem. I personally used the HKS 1.2mm with arp bolts and run 19psi all the time on a CT26 60-1. It's been 6 years and I still haven't had any head gasket problems!
They are not known for problems. They are torqued incorrectly from the factory. A long time before most owners were old enough to know WTF a supra was, a well known Toyota tuner named Reg Reimer sent them out for engineering and metalurgical analysis. Guess what...he confirmed they were fine for the application, though Toyota did indeed undertorque them from the factory, and in the TSRM specs. Now, if a bolt is stretched, it is because they were overtorqued, or reused after a number of heat cycles. If you reused a bolt or overtorqued it and expected it to hold up in a high power application, you are an idiot. Even the ARP's really shouldn't be reused, though most have had success.
Now, if someone has gone back and redone these tests and found a real problem, feel free to quote that analysis and we can benefit from the revised knowledge. Otherwise, stop misinforming people. The ARP's are a superior fastener, but Toyota ones were not a problem.
Look I'm not misinforming anyone. I'm trying to help this guy from redoing a head gasket again in the long run. If your going to buy new head bolts you might as well dish out a couple extra dollars and get the arps to be extra safe. In stead of buying OEM bolts, torqing them to factory spec of 58ft (which is too low), when a metal gasket properly needs to be torqued near 75-80 ft.lbs and having it fail later on. That's all I'm saying. Do it right the first time.
Yeah, when you take your head and block in to get resurfaced, make sure your machinist keeps a detailed record of what he takes off of both. The stock gasket thickness for a the 7mgte is 1mm, so just add whatever he took off and thats what you need. I went through cometic, and had a custom gasket made to with .005" of what was taken off. And yes, the stock bolts are fine. They need to be tourqed higher, and then they are fine. If your doing the head gasket and the resurfacing, may as well go with arp if you got it apart.
Last edited by SupraTuned; 03-04-2009 at 10:26 PM.
I went through cometic, and had a custom gasket made to with .005" of what was taken off
+1
I had cometic make me a custom MHG for mine too. I believe mine was .042 Yea... yikes. Had head and block surfaced. Old owner had the HG fixed at one point but it was fixed wrong and made it worse...
ummm...let me see...no. If you replace the gasket and do choose stock bolts, it will fail if and only if you do not know to torque to a minimum of 70 ft/lbs, or because your machinist didn't surface the decks correctly, or a combination of the two.
I know you're the moderator and all and are very full of useful information, but the head bolts on our MKIII are TTY (Torque To Yield). Which means they torqued till they stretch to just about there breaking point. However, once they've been torqued to the factories weak point, they've already stretched, the engine is then ran, the aluminum heads pull against them more, which stretches them more. Once used and stretched, they are not reuseable or retorqueable. TTY, it is not a good thing.
I've seen threads suggesting that these bolts can be torqued to 70 ft/lbs, the man who posted this helpful thread was using new bolts, not used, but then he suggested tightening the old bolts in your engine to that torque. That is not kosher, that is very bad, having new bolts tested for tensile strength is not the same as old bolts that have already been torqued to yield as that changes everything.
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Light moves faster than sound. That is why someone may appear to be bright, until you hear them speak.
1987 Toyota Supra Turbo.
The torqure to yield I understand. However, testing confirmed that the factory torque point is not the yield point, but is far short of it on stock bolts. It's the whole reason why the bolts back off and gaskets failed back in the day, and still to those unfortunate enough not to have stumbled across that information. The yield point should be in the range of 72 ft/lbs per the testing that was performed by Reg (I may be off a couple of lbs on the exact number). I indeed never stated they were reusable in any conceivable way, nor that I agree with the retorque many others do on them. Actually, nobody brought up the idea of re-torquing bolts until now. If by refering to them as stock someone thought I meant used as opposed to stock versus aftermarket, it was not my intention.
The torqure to yield I understand. However, testing confirmed that the factory torque point is not the yield point, but is far short of it on stock bolts. It's the whole reason why the bolts back off and gaskets failed back in the day, and still to those unfortunate enough not to have stumbled across that information. The yield point should be in the range of 72 ft/lbs per the testing that was performed by Reg (I may be off a couple of lbs on the exact number). I indeed never stated they were reusable in any conceivable way, nor that I agree with the retorque many others do on them. Actually, nobody brought up the idea of re-torquing bolts until now. If by refering to them as stock someone thought I meant used as opposed to stock versus aftermarket, it was not my intention.
Aww, I got you now, I misunderstood what you were saying, thanks for clearing that up. That is what I meant by saying the factories weakiest torque spec, what they were using, some 50 ft/lbs or so. I read an article Reg did and his advice was "up to" 70 ft/lbs for new OEM bolts and "around" 80 ft/lbs for ARP bolts. For some reason, he clearly said "do not use ARP studs"... not sure why as from what I've seen all over the net many have used them with no problem whatsoever. I've seen they're a pain to put on with the block in the car, but someone had done by installing the last two at the firewall with the head already seated (but not torqued) without problems.
__________________
Light moves faster than sound. That is why someone may appear to be bright, until you hear them speak.
1987 Toyota Supra Turbo.
I never knew why he hated studs beyond the fitment either. I always figured if someone was that far into the engine, it was going to have to go to the machinist anyhow, so the head could be installed on a stand if it was that much of a pain.
I never knew why he hated studs beyond the fitment either. I always figured if someone was that far into the engine, it was going to have to go to the machinist anyhow, so the head could be installed on a stand if it was that much of a pain.
I completely agree. I've installed studs on chevy engines that were still in the car, but as someone had said on another supra forum, the trick is just not install them all, leave some out and manipulate it. ARP's instructions on stud installations is to do them hand tight, so just laying the head on and then sliding the studs through works just fine. Though, I'll admit, I've never installed studs hand tight, a little tighter is always good, but no more than 10 ft/lbs.
__________________
Light moves faster than sound. That is why someone may appear to be bright, until you hear them speak.
1987 Toyota Supra Turbo.
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, HKS 1.2mm/2.0mm? Does any one know the difference? Also, what else should I do before installing the motor?
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