Head Gasket thickness selection

[IJ.]

Seen this question asked on many occasions, here's the HG's for dummies version

1) Stock HG = 1.37mm compressed

2) Stock head = 116mm deck to valve cover surface

3) Stock block = 198.5mm from deck to main bearing saddle

If 2 and 3 are less that amount needs to be added to 1 to retain the stock compression ratio and squish/quench.

When resurfacing the Block be sure to take the Timing Case along to have it done at the same time or your new HG will fail in miles.

Block measurement = 198.5mm/7.81"

 

[kamikazemkiii]

i already have my 1.2mm MHG from HKS
would it be ok to use since the head is resurfaced?
if not what would happen?

 

[rayall01]

i already have my 1.2mm MHG from HKS
would it be ok to use since the head is resurfaced?
if not what would happen?

If the stock gasket is 1.37mm, then the HKS is already to thin for stock surfaces. Since you have already machined the head, (and hopefully the block as well), You will need to get a much thicker gasket to maintain the correct compression ratio, or you will get detonation issues. And if you haven't done the block, then don't even think about using a metal gasket, because it will not seal.

 

[kamikazemkiii]

If the stock gasket is 1.37mm, then the HKS is already to thin for stock surfaces. Since you have already machined the head, (and hopefully the block as well), You will need to get a much thicker gasket to maintain the correct compression ratio, or you will get detonation issues. And if you haven't done the block, then don't even think about using a metal gasket, because it will not seal.

i havent decked the block just resurfaced the head
my wiseco's are 9.1 compression
what size would you reccomend?

 

[IJ.]

Measure the Head and Block.

 

[CyFi6]

How much is considered safe to remove off the head/block before either is considered junk? I see this question often and it always seems to be unanswered. Also, why did HKS make a 1.2mm head gasket/ in what case should it be used?

 

[SBM713]

thats helpful thanks for the info and sticky

 

[suprahero]

Measure the Head and Block.

Sometimes the answer is right in front of you, but you just can't see it...........:3d_frown:

 

[IJ.]

How much is considered safe to remove off the head/block before either is considered junk? I see this question often and it always seems to be unanswered. Also, why did HKS make a 1.2mm head gasket/ in what case should it be used?

Going by the factory specs very little but in the real world 20 thou off either seems to work fine and possibly more off a late Heavy/Thick Block.

 

[nsngarage]

Yeah i'd love to know when a head is considered unusable.. I have 3 of them that have come off of BHG cars, and they've all been resurfaced before. I'd much rather not use one that's gonna cause me MORE headaches lol..

 

[max-89supra(t)]

hey if you measure the stock head gasket after it has been pressed its actually a lot thinner the the 1.2mm hks, keep that in mind, and ya its better to resurface both head and block when going with a mhg, found that out the hard way:cry:now i got my head resurfaced and will get my block resurfaced this weekend, will post pics soon

 

[IJ.]

Stock composite gasket is 1.37mm compressed.

 

[Ice]

If the stock gasket is 1.37mm, then the HKS is already to thin for stock surfaces. Since you have already machined the head, (and hopefully the block as well), You will need to get a much thicker gasket to maintain the correct compression ratio, or you will get detonation issues. And if you haven't done the block, then don't even think about using a metal gasket, because it will not seal.

So i'm planning on using Fel Pro's MLS (multi-layer steel) gasket, and by what your saying i need to resurface the block as well or the gasket won't seal? Could i just clean it up with ..say..sand paper and a scraper? I have pulled the head off on my car bc of a BHG but im not looking forward to have to remove the block.
A sooner than later reply would be helpfull. Thankyou

 

[chefma70]

sorry to ask this but how the fuck do you measure a block and head???!

im using my dads ancient carpenter tools.so excuse my lack of knowlege for the newer tools

 

[IJ.]

I use a pair of Digi Verniers.

 

[chefma70]

I use a pair of Digi Verniers.

oh yea i have one of those...

takes a sip of gatoraid

puts bottle down.....well my machinist recommended a 2mm mhg cause my head has been decked before so i just going to listen to him.

 

[jb dock]

just put a mhg hks 1.2 mm in my 87 supra running at 15 lbs of boost for 1 month now no problems .not using any kind of drugs [just budlight].

 

[rayall01]

So i'm planning on using Fel Pro's MLS (multi-layer steel) gasket, and by what your saying i need to resurface the block as well or the gasket won't seal? Could i just clean it up with ..say..sand paper and a scraper? I have pulled the head off on my car bc of a BHG but im not looking forward to have to remove the block.
A sooner than later reply would be helpfull. Thankyou

No, unless you mean you're going to do what I did. Read my build thread.

http://www.supramania.com/forums/showthread.php?t=92669

 

[jdub]

just put a mhg hks 1.2 mm in my 87 supra running at 15 lbs of boost for 1 month now no problems .not using any kind of drugs [just budlight].

That's a great idea...just pull a number out of your arse and use it. Base your recommendation on a whole month of use too. Highly credible post sport.

Since you appear to be new guy, these kind of posts are not tolerated in the Tech section. Especially one that has potential to cause damage.

To keep stock compression, the MHG needs to be at a thickness that will make up for the material removed from the block and head decks. Unless you know what you are doing, increasing cylinder compression and increasing boost is a sure fire way to blow your engine.

 

[Drake69]

Okay, PLEASE forgive my ignorance, but from the way I read this, there are two choices....

1: Pull the head apart, inspect the head and block for warping or damage, take the head to a machine shop to get it milled if it needs it, measure how much of the head was shaved, jump online, order the appropriate MHG or HG with studs (if they are even in stock!!!), and wait for it to ship? (And I'm not even talking about how to mill the BLOCK yet, like taking IT out or trying to mill it in the shop...)

2: Buy an MHG ahead of time with more width than stock (like 1.5~2.0mm) with studs, pull the head apart, inspect the head and block for warping/damage, take the head to machine shop to get it milled irregardless of damage to match the amount of the MHG you just bought (equal to what the head and block had to be milled to to match the width actually), and them reassemble everything.

Since this is a HG for Dummies thread, what exactly is the recommended way of doing this, factoring time constraints and cost of this endeavour? For some of us, we're using our MKIII's as daily drivers, and as such can't be down for weeks at a time doing all this. For others, they won't/might not have the garage/shop space to take up for weeks at a time doing this. As a preventative measure, it makes perfect sense getting the HG done NOW and done RIGHT to avoid any headaches later on down the road, so more people will want to do this themselves or with friends who know motorwork. Or should the newbie just chuck all this and get it pro done and get raped by a stealership/machine shop in the process?

Again, forgive my ignorance and/or asinine tone. It's frustrating worrying about a BHG and not being able to do much about it but let it happen when you can supposedly prevent/postpone it.