i just recently replaced my stock headgasket when replacing the cylinder head on my 88-t and i used all stock hardware and the gasket is the stock type one (no metal headgasket or arp studs or anything) and i am wondering what is safe as for amount of boost and types of mods i should do to it, it is completly stock right now.
what is safe and what is not
- Thread starter 88SupraTurbo
- Start date
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JerzeySlowpra
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i know somoene that was boosting 18psi on OEM gasket with 75 ft tq on the head bolts and was fine, like aye mate said its the factory tq setting thats the problem.. bu twhy didnt you go MHG if you went through all of that
you wasted your time and money not using ARP studs 
i hope you atleast toruqed the bolts to ~76ft/lbs
i hope you atleast toruqed the bolts to ~76ft/lbs
88SupraTurbo said:
i would...i give it about a week before it blows... torquing STOCK bolts that much WILL stretch them and they will give out and cause more problems...
not only that but if it DOES hold...boosting much more then stock will be a daily adventure.
all that apart and you couldnt spring an extra 250 bucks? to do it right and never have to worry about it... :dunno:
eh if you dont have high hp goals your gonna be good probibly to around 14 lbs as long as you are careful. in all honesty a mhg and some arps (or just arps ) woulda been better, just make sure you check the headbolts after 500 or so miles to make sure everything is good and tight.
Idealsupra said:
ummm as for stock bolts being unrealiable i have been running the originals on an oem hg at 74 lbs and theres realy nothing to worry about, beyond 80 yea they will stretch and into the 90s they snap. it could hold 15 psi. notice i said "COULD" not that it will forever.
in terms of reliability the oem and stock bolts will do you good up till you hit fuel cut, and that will be pushing it a little. if you run stock parts like that you will be limited to stock performance, generally true.
i wish i did a cometic swap but at the time of hg swap i had owned this car for 3 weeks and didnt know how to do an oil change so my knowledge was limited.
americanjebus said:
just like with resurfacing for hg in the other thread... theres a difference between USABILITY and RELIABILITY.
USABILITY: being able to use something for the job ...it could work fine and dandy..OR it could fail miserably.
RELIABILITY: being able to use something for the job and have it work ALL the time. meaning 0 percent chance of error.
the STOCK bolts (especially REUSING stock bolts) and being torqued that much have a tendency to fail. dont misunderstand me...im not saying its GONNA happen..even though i kinda did originally but it wasnt meant specifically like that. my point is this... if you use stock bolts..and torque them much more then the tsrm says...they DO stretch... and because of this you have the possibility of them failing on you.
I bought my car with a BHG. Replaced it with an OEM head gasket and NEW Toyota head bolts. torqued to 76ft/lbs and then re-torqued at 500 miles. It held with daily 9 PSI boosting for 15,000 miles until I developed rod knock. The head still had a good seal up till I rebuilt the engine. The main thing is, if your going to use OEM head bolts you need to use NEW ones. The olds ones are stretched and not suitable for reused. Fortunately for $30 more dollars you can just get ARP's.( I used OEM bolts because the previous owner had already bought them, so they came with the car.) Use ARP’s which are stronger and can be reused. The reason it’s bad to use the old head bolts, is because the torque values cannot be trusted. They are already stretched and cannot provide an accurate reading.
the fact i reused my bolts has always been a splinter up my ass, sometimes i feel like redoing the hg just for shits and so i can sleep at night.
Hate to say this, but there is some misinformation in this thread. Check out Reg writeup on the stock bolts here:
http://www.suprasonic.org/public_html/sonictech/mk3/mk3_pmtn.html
What this means, is that you can use the stock headbolts to 72 foot pounds without stretching them, thus, they can technically be used over and over again, as long as they are still in good condition.
As for the usefulness of the stock head gaskets, let me say this: I am running 17-19psi on my stock head gasket. I drive my car HARD - I race it regularly. Guess what? I have never blown a head gasket. Whenever I pull my head, which I seem to do about once a year, the head gasket it always in pristine condition. Admittedly, I do have some extra insurance in the form of ARP head bolts torqued to 95 foot pounds, and as always, your mileage may vary.
The good Doctor has always said, it's all in the tuning, and I agree 110%.
http://www.suprasonic.org/public_html/sonictech/mk3/mk3_pmtn.html
What this means, is that you can use the stock headbolts to 72 foot pounds without stretching them, thus, they can technically be used over and over again, as long as they are still in good condition.
As for the usefulness of the stock head gaskets, let me say this: I am running 17-19psi on my stock head gasket. I drive my car HARD - I race it regularly. Guess what? I have never blown a head gasket. Whenever I pull my head, which I seem to do about once a year, the head gasket it always in pristine condition. Admittedly, I do have some extra insurance in the form of ARP head bolts torqued to 95 foot pounds, and as always, your mileage may vary.
The good Doctor has always said, it's all in the tuning, and I agree 110%.
GrimJack said:
ive said it before...and for some reason a lot lately...and ill say it again... USABILITY AND RELIABILITY...
why do something that MIGHT work...when you can do something that WILL work...
people have jumped off 10 story buildings and lived... are you going to do that because SOME people have lived?
thats my point...i NEVER said that using stock bolts and torquing them to X amount of lbs and using a stock hg with X amount of boost would not work... i just said youre playing with fire....
to each his own
EDIT: id also like to say ive seen that reg info before...and i 100% agree with his findings as it makes perfect sense...HOWEVER.. his plasticity regions and tensile strength before going into plastic regions are ADMITTEDLY calculations...with that said i would give any calculation some leeway in either direction...meaning it COULD be a slightly lower value...and you torque to 72 and bam youve reached the plasticity region...which would start the process of stretching...
all i gotta say is... WHY risk ANY of this? when it could be avoided so easily while youre doing the work anyways....
Sorry about that GrimJack. For some reason I could have sworn the 7M head bolts were TTY(Torque To Yield). Guess I was wrong. Glad you were there to catch me on that. While I would never question Reg's numbers on this matter. Those numbers are for the bolts. But it doesn’t take in to account what might occur due to metal fatigue from thermal expansion over an extended period on a bolt torqued well beyond factory spec. Then again there may be no effect, these bolts are made from some really hard metal. And Toyota does like to seriously over engineer their stuff.
Ideal - I agree on most points, especially when you consider that ARP head bolts are essentially the same cost and will take a LOT more torque. My local Toyota dealer quoted me $7 each for the headbolts. That's $98 total - I got my ARPs from Mopac for $95. My point is, folks running the stock head bolts shouldn't worry about sleeping at night.
Dirgle, no worries, I was busted on this very same point many moons ago.
It's my personal theory that the BHG madness on the 7M engine has caused people to go overboard in the opposite direction. I know people who put down 270 hp per litre at the wheels on their DSMs with stock composite head gaskets, never having a problem. (Ok, not entirely true, the DSM guys blow up transmissions all the time, and suffer from crankwalk the same way we do rodknock)The DSM crew doesn't seem to think that MHG are worthwhile until well in excess of that. That translates into over 800 hp on a 3 litre 7M that should be attainable reliably with a composite gasket.
The thing is, if I'm building an 800 hp engine, a couple hundred bucks on a MHG is the least of my expenses, so why wouldn't you put one in?
I'd love to know what the highest hp someone has run reliably on a composite head gasket is. I think the only way I'm going to find out is to buy an SP61 and crank my boost.
Back on topic - I wouldn't worry about boosting your car to 13-14psi. Heck, even if you blow another gasket, that just gives you the opportunity to redo it with ARPs.
Dirgle, no worries, I was busted on this very same point many moons ago.
It's my personal theory that the BHG madness on the 7M engine has caused people to go overboard in the opposite direction. I know people who put down 270 hp per litre at the wheels on their DSMs with stock composite head gaskets, never having a problem. (Ok, not entirely true, the DSM guys blow up transmissions all the time, and suffer from crankwalk the same way we do rodknock
)The DSM crew doesn't seem to think that MHG are worthwhile until well in excess of that. That translates into over 800 hp on a 3 litre 7M that should be attainable reliably with a composite gasket.The thing is, if I'm building an 800 hp engine, a couple hundred bucks on a MHG is the least of my expenses, so why wouldn't you put one in?
I'd love to know what the highest hp someone has run reliably on a composite head gasket is. I think the only way I'm going to find out is to buy an SP61 and crank my boost.
Back on topic - I wouldn't worry about boosting your car to 13-14psi. Heck, even if you blow another gasket, that just gives you the opportunity to redo it with ARPs.
i have been running about 10.5, sometimes even 11.5 psi on the stock hg. I wouldn't worry till it blows The real thing you need to worry about is rodknock issues. You have done the headgasket, you know how it goes on now, it should be cake for you. A lot of rumors are going around about putting a little more oil in the motor than the recommended amount(4.7 i believe). I put in about 5.5 quarts of oil in my motor cause i have been told that may keep your engine from being susceptible to rodknock . It should be more of a concern in my book, because it is a lot easier to change a headgasket then fixing a rodknock issue. Somebody back me up on this.
The real thing you need to worry about is rodknock issues. You have done the headgasket, you know how it goes on now, it should be cake for you. A lot of rumors are going around about putting a little more oil in the motor than the recommended amount(4.7 i believe). I put in about 5.5 quarts of oil in my motor cause i have been told that may keep your engine from being susceptible to rodknock . It should be more of a concern in my book, because it is a lot easier to change a headgasket then fixing a rodknock issue. Somebody back me up on this.
im just curious what the actual difference between the stock bolts and the arp's is. i know there is a huge one but what is it, the way they are heat treated, quality of metal used, or is it a metal alloy wut is it.
Idealsupra said:
your wrong ideal... many people have torqued stock bolts to 72 or higher without problems (myself included)