2mm Stopper MHG Too Thick?

[Supra0089]

Going to meet with my Toyota dealer friends tomorrow to discuss the MHG install with them, and I have a 2mm hks stopper coming in the mail tomorrow with ARP studs. This is a new 7mgte engine (10k miles) without a bhg, but am replacing the HG for upgrading purposes.

Here is the questions:

Even after the head/block is machined, will the 2mm stopper mhg be too thick? Or do I tell them to machine the head/block to a specific amount?

From what I've read (thanks IJ and others), the total distance from top of head to main bearing saddle should be 315.87mm (Stock HG = 1.37mm compressed+Stock head = 116mm deck to valve cover surface+Stock block = 198.5mm from deck to main bearing saddle). So if it sits at that amount now, and I'm installing a gasket that is .63mm thicker than the OEM, then I need them to machine off that difference between the head and the block (i.e. .40mm off head, and .23 mm on block)? Am I on the write track here?

One more question that is thrown into the mix here...do the stopper mhg's compress? If so, how does that all factor in here?

Maybe I'm just paranoid, or really thickheaded.

Sorry for another HG question...I was just getting dizzy after reading all the threads from multiple forums.

Thanks in advance.

 

[IJ.]

No they don't compress

It may drop your compression slightly ie 8.5:1 to 8.25:1 from memory in the real world you will never tell or measure a difference.

 

[Supra0089]

No they don't compress

It may drop your compression slightly ie 8.5:1 to 8.25:1 from memory in the real world you will never tell or measure a difference.

So just have them machine enough to make it flat, and then install it without making it all exact, and it will be fine?

 

[CajunKenny]

Your MHG has a minimum RA (roughness) requirement and your block and head surfaces need to be machined to that specific RA.

That is more important than slightly lowering your compression.

 

[lewis15498]

Wont be a big deal. its turbo, any lost compression can be made up for with more boost. but even at stock boost, a drop from 9.5 to 9.25 shouldnt be noticable. However, it would decrease the results of a compression test 2.6% in theory so your numbers would be 4-5 psi lower, so don't panic if you see this.

 

[IJ.]

So just have them machine enough to make it flat, and then install it without making it all exact, and it will be fine?

Flat and very smooth!

I wouldn't be super paranoid I've ran a 2mm then a 3mm MHG in the same engine and didn't notice any huge differences other than knock threshold on pump fuel.

It's not like you're building a class car that has to deliver every last hp.

 

[Supra0089]

Flat and very smooth!

I wouldn't be super paranoid I've ran a 2mm then a 3mm MHG in the same engine and didn't notice any huge differences other than knock threshold on pump fuel.

It's not like you're building a class car that has to deliver every last hp.

Thanks guys. I was debating on sending the 2mm back for a thinner one. It sounds like there is no harm in the 2mm as long as toyota does the job right. This car is just intended to reach 350-400hp and will be used mainly as a summer daily.

 

[disturbed1]

ive got a 3mm hks mhg and its soo gutless off bost its not funny.

t also makes fuck all power for the boost and turbos its running

 

[rayall01]

ive got a 3mm hks mhg and its soo gutless off bost its not funny.

t also makes fuck all power for the boost and turbos its running

You got something else wrong, cause that won't make that much of a difference.

 

[Supra0089]

ive got a 3mm hks mhg and its soo gutless off bost its not funny.

t also makes fuck all power for the boost and turbos its running

making me nervous...hopefully its not the gasket...

 

[GrimJack]

I wouldn't be super paranoid I've ran a 2mm then a 3mm MHG in the same engine and didn't notice any huge differences other than knock threshold on pump fuel.

Unrelated question, but what effect did this have on the knock threshold? I'd expect it to be able to run more power before hitting knock, but that's just an educated guess on my part.

 

[IJ.]

I managed 30psi on pump with a 3540r and no knock Dave

 

[gaboonviper85]

ive got a 3mm hks mhg and its soo gutless off bost its not funny.

t also makes fuck all power for the boost and turbos its running

Then you have a personal problem! That headgasket isn't going to effect power enough to notice.

 

[IJ.]

Goon: Going to a 3mm will make a difference, not discounting what Disturbed is saying but even at 8.5:1 a 3.0L I-6 in a 1500+Kg car is NEVER going to be "snappy"

Mine was doughy off boost as well but it's just degrees of sogginess between 2mm and 3mm.

 

[gaboonviper85]

From my limited experience, most turbo cars are crappy off the line...but that headgasket may effect power by 5-6 hp but that is so minor it's not worth the trash talk of "gutless". My point is don't make it sound like the car was a smoke machine with the stock gasket turned granny mobile from a very slight drop in compression. The car will get up and go just fine with a thicker gasket within reason.

 

[Hmong_1G]

Only thing is that You are reusing or didn't do a proper torque procedure. Never reuse any headgasket. Many have succeed, but rule of the thumb is once its crushed down... thats it. There something else wrong.

 

[gaboonviper85]

You aren't going to crush tempered steel shims which is pretty much how good mtl gaskets are made...different thickness steel plates stacked on top of eachother...they are certainly reusable if you don't bend, warp, scratch, bhg, or anything of that nature!

 

[jdub]

Only thing is that You are reusing or didn't do a proper torque procedure. Never reuse any headgasket. Many have succeed, but rule of the thumb is once its crushed down... thats it. There something else wrong.

A MHG in good shape can be reused as gaboon said. You will have to strip off the old Viton and give it a couple good coats of copper spray as a substitute.

 

[disturbed1]

i was making 440 hp on 18 psi with a gt30r. with a 1.2mm hg (compression was about 185 psi)

head gasket leaked so rather then rebuilding, moved all my go fast bits onto a mates motor i bought off him which had a 3mm hg and only other difference being a ported head.

that motor made about 370 on 18 psi. (about 145 psi compression)

ripped that turbo off and bolted a t78 and it made 430 hp on 19 psi

whether its the hg thickness or not, the one with 3mm hg felt a good 500 hp laggier then the other 1 when both had the gt30 one.

the motor with the 1.2mm hg was awesome. very reponsive and pretty much instand boost from whenever u put your foot down.

in saying this, the 3mm hg motor is stock everything bar the gasket and porting. even has stock rods albiet were replaced with brand new ones when it was built about 8 years ago. previous ower was running 25 psi +50 shot of nos with a garrett t04z for 460 hp all on pump fuel. the fact its still alive might be cause of the low compression.

ian - what u think u could my motor as i described above on pump?

23/24 psi? should go very close to 500 hp if that were the case