MHG question

[1StTurbo]

Ok i have read a lot about the MHG, now here is the issue. My buddy who i swear was born in a Toyota in 64 helped his brother in law do a HG, They did the head but not the block, BHG a year later, same car in shop getting new MHG and i asked if he got the block decked and he replied no. Buddy swears block is steal so no need. By the way new MHG lasted less then a month an is leaking again. ( I enjoyed a i told you so on this) but i am the dummy he is the mechanical one (snicker)

Also what is a SAFE max boost on a new OEM HG if i use arp studs.

 

[CyFi6]

He is probably just not well informed, but he should take a hint that something is wrong having to go through this again. It doesn't matter that the block is cast iron, it can warp and it can get what they call brinelling where basically the head gasket cylinder sealing rings dig into the surface of the block over time. This is the most important area to seal and if the deck is worn around these areas you will have less and uneven clamping on the gasket. After 20+ years of being on that block and going through BHG's it needs to be surfaced properly to seal. We are also assuming here that he is using good hardware and properly toqueing the head down.

Stock gasket has proven to be good even in high HP applications with a very safe tune, but detonation will kill them quickly.

 

[hvyman]

Need a smooth flat machined surface for mhg to seal. Ditto on cast iron doesnt mean shit.

And ya if you have a good tune you can hit a good amount of power with a stock hg.

 

[VegaSupra]

I knew virtually nothing about the head gasket with my previous Supra. (But remember, this was basically pre-internet days... sorta kinda).

I had intake, hks dp, test pipe, hks catback, bov... so I must have been somewhere around 300hp I suppose. It sure felt like at least 300 anyway.

I ran that combo for quite a while and the HG was fine. It did eventually blow but I believe that's because it was only torqued to factory specs by the dealership (too low of course). I bet if it was torqued down properly (and especially with ARP studs) it would have held fine at that level and maybe even with more power.

 

[Turbo Habanero]

I beat the crap out of my supra and ive messed with boost all the way to 13lbs and its got a OEM headgasket with ARP studs to 90 ft lbs. and its holding up like a champ. last HG job was not done by me have no idea what it was bolted down to but i know they didnt use arp's and it blew the gasket after 6k miles of my driving Completely stock setup.

My setup and im no mechanic just all the amazing people on this site helped me out with the info.

OEM HG bought from Drift motion.
ARP Studs also got from Driftmotion
Toyota Engine Gasket Kit From Driftmotion
$350 after shipping roughly

My head had to be cleaned/decked/had to get new valves and valve job. $490

Did all the pulling apart and putting back together my self. (2 days after i got my head back) (some of the turbo lines are where a bitch took me 4hours to get one of the banjo bolts in lol.)

All in all after doing it for the first time i think the HG job is more intimidating then anything. pretty simple.

 

[suprarich]

Boost level has little to do with the capacity of the head gasket.

I usually see about 350 rwhp on a stock type hg with arp's and a tune as my personal threshold. Any more than that and I would rather use a metal gasket.

 

[1StTurbo]

Cool i have heard all kinds of number i can boost on a stock HG, I am putting on a slightly bigger turbo and was told i could run 20pds boost on a stock HG i was thinking to set it in the 15 range as i would rather error on the safe side.

 

[suprarich]

Again, "boost" level has little to do with the capacity of the head gasket.

 

[VegaSupra]

Again, "boost" level has little to do with the capacity of the head gasket.

suprarich,

I started a thread about switching to metal even if oem isn't blown yet.

my concern is to blow the stock on and cause damage at the same time. what would be your answer to my thread question here?

Head Gasket?

 

[hvyman]

You need to machine the block which means you need to disassemble the block. Whether it blows or not it doesnt matter so long as you dont get a cracked head or block.

 

[NashMan]

all add to this

in most case's the stock block finish will be there and be fine BUT but it all depends...... I find that the hks bead seal alot better then the less forgiving cometic/titain/sip gasket's because of it's stain less steel shim it uses

and the greddy gasket fits the best out of all of them but i never held one in my hands but this has been shown in many pic's

and second alot of the times the front timing cover will be proud on one side of the block and will need to be filed down to match the block or it wont last long

 

[Poodles]

You need to machine the block which means you need to disassemble the block. Whether it blows or not it doesnt matter so long as you dont get a cracked head or block.

Don't forget about the risk of annealing the head.

 

[hvyman]

Yup that too. Most people dont even check that.

 

[1StTurbo]

Interesting, Well when i get ready to do a MHG some day i am going to ask you guys for a list of questions and answers i should expect from the shop doing it

 

[VegaSupra]

What about this idea? Purchasing ARP studs and replacing the head bolts and torquing down correctly? Is that even possible without taking it all apart and resurfacing the head and resealing the gasket?

 

[Poodles]

Threads MUST be chased int he block for studs. They use the entire threaded hole, while bolts only use about half of it.

 

[VegaSupra]

Threads MUST be chased int he block for studs. They use the entire threaded hole, while bolts only use about half of it.

Hi Poodles,

I am sorry but I don't know what you mean by this. Let me ask this way...

Right now.. stock everything under the hood. 69K miles. Original owner had head bolts torqued down to much tighter specs than factory at 46K miles.

Here's my question.... if I purchase ARP studs/bolts and hand them to a mechanic and say "Hi, can you please replace my head bolts with these and torque them down to xx.xx?"

Can this be done without pulling the head apart and machining it? Or is it the case that once you loosen those bolts to remove them, you MUST machine the head, regardless of whether or not the gasket is blown?

Why do I persist in asking this? Because if I can spend $120 on the studs and whatever it costs to torque em in... wouldn't that be at least better than leaving it as is?

Again, thanks for your advice!

 

[hvyman]

You could change the bolts one at a time in the torqueing sequence but only with bolts. Not really worth it.

Studs the head needs to be off and you must bottom tap the holes. There is about 1/4in or so that needs to be threaded down to the bottom. Each hole has to be clean as well. The studs should be able to reach to the bottom smoothly.

 

[suprarich]

all add to this

in most case's the stock block finish will be there and be fine BUT but it all depends...... I find that the hks bead seal alot better then the less forgiving cometic/titain/sip gasket's because of it's stain less steel shim it uses

and the greddy gasket fits the best out of all of them but i never held one in my hands but this has been shown in many pic's

and second alot of the times the front timing cover will be proud on one side of the block and will need to be filed down to match the block or it wont last long

All the above mentioned head gaskets are made from stainless steel, not just the hks.

 

[1StTurbo]

Sure have learned a lot from my stupid little thread question