Head Gasket thickness selection

IJ.

Grumpy Old Man
Authorized Seller
Contributor
Joined
Mar 30, 2005
Messages
38,726
Likes
4
Location
I come from a land down under
#81

enjoyer

New Member
Authorized Seller
Joined
Mar 28, 2009
Messages
164
Likes
0
Location
Lithuania, Klaipeda
#83
1mm = 40 thou

.4mm = 15 thou

55 thou = 1.39mm, you add this to 1.37 to get 2.76mm, closest you'll find is a 3mm MHG, never seen a 2.8mm.
So, i actualy calculated corectly. Just wanted another opinion from the supra god, i mean IJ. So, i milled everything to fit a 3mm HG. OK,now the next question. I've red a lot of different discusions about HG manufacturers and still i'm not sure witch manufacturer is a better choise. I've got an option of custom made HG, but that's a bit expensive. If any of you have bought 3mm HG, could you give me any feedback, and where to look for them(with links for buying). I found some myself, but i just want some second opinions.
 

Chello

New Member
Authorized Seller
Joined
Jun 8, 2011
Messages
104
Likes
0
Location
Victoria, Australia
#88
Awesome thread, great information. I am in the process of building another motor due to BHG.

Is there a prefered material? I.e copper or MLS? That's assuming anyone does a Copper head gasket.

Is adding a sealing agent a no no? I heard spray-on holymar was a good thing, anyone had experience with it?

I'm yet to get the machining place to measure the head and block heights but have to wait until I get the pistons so they can do the boring and surfacing at once, before they can measure it for me
 

jdub

<B>Official SM Expert: Motor Oil, Lubricants & Fil
SM Expert
Authorized Seller
Contributor
Joined
Feb 10, 2006
Messages
10,730
Likes
2
Location
Valley of the Sun
#89
Use MLS - copper would have to be wired around the cylinder for a seal. Way too much work for zero gain.

Never, ever use any kind of spray on sealer on a new MLS HG. It already has a viton coating - the spray sealer will destroy it.
 

IJ.

Grumpy Old Man
Authorized Seller
Contributor
Joined
Mar 30, 2005
Messages
38,726
Likes
4
Location
I come from a land down under
#91
Thanks for the reply jdub.
What do you mean by wired around the cylinder?
Usually a Copper HG is used with "O-Rings"

These are a stainless steel wire that sits in a groove machined into the deck surface, there isn't enough room to do this on a 7M due to the close bore spacing.

Where in VIC are you?
(Central here)
 

Chello

New Member
Authorized Seller
Joined
Jun 8, 2011
Messages
104
Likes
0
Location
Victoria, Australia
#92
Thanks for the reply IJ.

Half the problem with mine was, the last owner, who did the head gasket put a 1.2mm HKS gasket on it which would have bumped the comrpession up a fair bit and then machined the head ontop of that, they didn't get the block surafced either.

Just trying to make it reliable as humanly possible as it's in a Hilux 4x4 ute, so don't really want to be stuck in the middle of nowhere with a BHG

Mildura, North West Vic here
 

IJ.

Grumpy Old Man
Authorized Seller
Contributor
Joined
Mar 30, 2005
Messages
38,726
Likes
4
Location
I come from a land down under
#93
Thanks for the reply IJ.

Half the problem with mine was, the last owner, who did the head gasket put a 1.2mm HKS gasket on it which would have bumped the comrpession up a fair bit and then machined the head ontop of that, they didn't get the block surafced either.

Just trying to make it reliable as humanly possible as it's in a Hilux 4x4 ute, so don't really want to be stuck in the middle of nowhere with a BHG

Mildura, North West Vic here
If you haven't got around to measuring it by early October let me know as I have to go to Berri in SA and intended going through Mildura so it's no probs to bring my big Digi Vernier along!
 

Chello

New Member
Authorized Seller
Joined
Jun 8, 2011
Messages
104
Likes
0
Location
Victoria, Australia
#94
I will let you know, thanks for the offer. Much appreciated

With any luck they should have it measured this week, just thought it would be easier for the machine shop to measure it seeing they have to bore and surface the block and port and surface the head.

Is it acceptable to go a little lower in the thickness of the gasket? Just to get a little more compression without going over-board. Obviously not to the extreme that was in it initially, more say the thickness of the gasket was to be 1.8mm to bring it back up to standard specs, how low could I go before it would start to cause problems? 1.6mm be ok? I know it's a bit of a how long is a bit of string question until I know exactly what size I need, was just curious about it for now.
 

suprajztwenty

New Member
Authorized Seller
Joined
Nov 5, 2009
Messages
369
Likes
0
Location
corinth tx
#97
great sticky here! just saved me a hunt over on sf.

i have a question about the titan headgaskets...are they still just cometic rebranded?

will a cometic gasket hold up as well as an hks when shooting for 500+?
 

Chello

New Member
Authorized Seller
Joined
Jun 8, 2011
Messages
104
Likes
0
Location
Victoria, Australia
#98
Okies, got back from the machine shop, they seem to think there will be around 40 thou all up removed from the block and head over time, will have to wait until they measure it properly, they are still porting the head before they deck it
 

IJ.

Grumpy Old Man
Authorized Seller
Contributor
Joined
Mar 30, 2005
Messages
38,726
Likes
4
Location
I come from a land down under
#99
great sticky here! just saved me a hunt over on sf.

i have a question about the titan headgaskets...are they still just cometic rebranded?

will a cometic gasket hold up as well as an hks when shooting for 500+?
As far as I know Cometic make the Titan MHG, 500 is well within it's limits, keep it out of detonation and make sure it's torqued down correctly and retorqued and that the surfaces are flat and smooth.

Okies, got back from the machine shop, they seem to think there will be around 40 thou all up removed from the block and head over time, will have to wait until they measure it properly, they are still porting the head before they deck it
I see a 3mm MHG in your future :)

What sort of HP are you aiming for on this motor?
 

Chello

New Member
Authorized Seller
Joined
Jun 8, 2011
Messages
104
Likes
0
Location
Victoria, Australia
Not a great deal of HP, it's in a hilux 4x4, so more building it more for torque than straight out power. So getting them to port the head out a bit, has .50 mm over pistons.

They took 10 thou off of the block, the head has been milled 20 thou previously and they estimate maybe another 10 thou has to come off of it to make it flush.

So.. I guess I will be looking at around a 2.4mm, depending how much ends up coming off of the head, which I can't see it being 10 thou, but they said it as more of a safe guard I think
 

Chello

New Member
Authorized Seller
Joined
Jun 8, 2011
Messages
104
Likes
0
Location
Victoria, Australia
Well, 40 thou ended up coming of the block and head all up, so I will be up for a 2.4mm.

Just a question, 10 came off of the block and the rest off of the head over time, will that bring up the comrpession ratio by much? Seeing that the compression bowl is smaller
 

Chello

New Member
Authorized Seller
Joined
Jun 8, 2011
Messages
104
Likes
0
Location
Victoria, Australia
Thanks for the reply IJ
So do you think the 2.2 or 2.4? Will 2.2 be pushing it a little much seeing not really any sort of fuel control other than the standard ECU?
 

suprajztwenty

New Member
Authorized Seller
Joined
Nov 5, 2009
Messages
369
Likes
0
Location
corinth tx
i believe the sip is just a cometic gasket, same with titans gaskets. i ended up with a hks3.0, THICK ass gasket...you just dont appreciate it untill you hold it (thats what she said)
 

Chello

New Member
Authorized Seller
Joined
Jun 8, 2011
Messages
104
Likes
0
Location
Victoria, Australia
Ahh damn, well maybe a couple of weeks lol, I think I have to go to Ballarat end of next week for work for a few days anyway.

I have stuff I am doing on the Hilux at the moment anyway so a bit of extra time will be fine
 

Needboost

New Member
Authorized Seller
Joined
Mar 2, 2009
Messages
312
Likes
0
Location
danville, virginia
i soon will be taking my block an head to be machined for a mhg what Ra values should be done. and what exactly are Ra values? and i am planning on running probe pistions and saw on the thread that dish changes compression also. i guess im just confused on the compression ratio i would like to stay as close to stock to prevent problems. sorry if this is off subject
 

eraezer

Member
Authorized Seller
Joined
Nov 6, 2008
Messages
765
Likes
1
Location
Stockholm, Sweden
Needboost: it's a arithmetic mean value of the surface roughness.


Now I need a little help to decide on a MHG.

As far as I know there is no MHG size between 2.0mm and 3.0mm, is this correct?

My block is now: 197.4 or 197.6mm (I don't have the exact number in my head, but somewhere in between).
My head is now: 116mm (unsurfaced so far)

Stock piston protrusion: 0.5mm
My protrusion value: 0.5+ (198.5-197.4) = 1.6mm (Max. value)
My protrusion value: 0.5+ (198.5-197.6) = 1.4mm (Min. value)

Combustion chamber volume: 37.5cc (forums) or 40cc (Arias)
I have been grinding away some hotspots so my combustion chamber is a bit larger than stock.
And I'm not sure which stock value is correct? On the piston paper from Arias, they say 40cc

Let's say that during surfacing of my head I'll end up removing 0.5mm
Let's also say that the combustion chamber opening is the same as the stock bore: 83mm. Just to keep it simple.
The volume removed will be:
pi*r^2*removed material = pi * (83/2)^2 * 0.5 / 1000 = 2.705 cc

So 2.705 cc is removed if the head is shaved 0.5mm
Let's say that my grinding has added 1cc/cylinder
This gives me:
Min : 37.5-2.705+1 = 35.795 cc
Max: 40-2.705+1 = 38.295 cc

Piston Dish: 19cc (stock)
My piston dish: 16.09cc (Arias)

If I would use a 2.0mm MHG I will have the following clearance between piston and head:
Min = 2-1.6 = 0.4mm
Max = 2-1.4 = 0.6mm

And with a 3.0mm MHG:
Min = 3-1.6 = 1.4mm
Max = 3-1.4 = 1.6mm

The stock clearance is 1.37-0.5 = 0.87mm

How much does the Eagle rods stretch during max rpm?

The cylinders are now 83.49 mm

gasket bore is 86mm

With this calc: http://www.csgnetwork.com/compcalc.html

and these values:

Enter Cylinder Bore Size 83.49
Enter Piston Stroke Length 90.98
Enter Head Gasket Bore Diameter 86
Enter Compressed Head Gasket Thickness 2
Enter Combustion Chamber Volume In CCs 35.795
Enter Piston Dome Volume In CCs Negative For Dished Pistons (Use '-') -16.09
Enter Piston Deck Clearance Negative If ABOVE Deck (Use '-') : -1.6

I get the maximum static compression of
With a 2mm MHG 10.10526513241693 : 1
With a 3mm MHG 9.231210911947521 : 1

and these values:

Enter Cylinder Bore Size 83.49
Enter Piston Stroke Length 90.98
Enter Head Gasket Bore Diameter 86
Enter Compressed Head Gasket Thickness 2
Enter Combustion Chamber Volume In CCs 38.295
Enter Piston Dome Volume In CCs Negative For Dished Pistons (Use '-') -16.09
Enter Piston Deck Clearance Negative If ABOVE Deck (Use '-') : -1.4

I get the minimum static compression of
With a 2mm MHG 9.543791078210202 : 1
With a 3mm MHG 8.769627288645353 : 1

Since the combustion chamber, according to arias, is 40cc and that is bigger than my max
I added a static comp ratio for that too:

I get the minimum static compression of
With a 2mm MHG 9.30101738082517 : 1
With a 3mm MHG 8.568338122041688 : 1

Until I have measured my final combustion chambers, these are the values I have to work with.

My max. static comp. ratio with a 2mm MHG is 10.105:1
My max. static comp. ratio with a 3mm MHG is 9.231:1

My min. static comp. ratio with a 2mm MHG is 9.301:1
My min. static comp. ratio with a 3mm MHG is 8.568:1

I'm not planning on using huge amounts of boost.
I will use my supra mostly on the street and on the occasional track-days.
The largest turbo it will see is probably a GT-35 or BW S200.
It's already stand-alone
BC stage 2 cams, BC valve springs+retainers and 1ZZ-FE COP's are on it's way.

What's the closest piston to head clearance I can run?

Should I just go with a 3mm MHG and be over with it?

What's your suggestion?

Thanks/Marcus
 

eraezer

Member
Authorized Seller
Joined
Nov 6, 2008
Messages
765
Likes
1
Location
Stockholm, Sweden
I went with a 3mm MHG.

The easiest equation is stock block + stock head + stock gasket - new block - new head = new HG
This should give a comp ratio slightly higher than stock and since I'm using 9:1 pistons so I should be around that.
 

nofx230

Member
Authorized Seller
Joined
Jan 24, 2012
Messages
132
Likes
0
Location
Colorado
ok bare with me here, my heads already been shaved .020 from PO and is probably going to need another .015-.020 taken off thats almost 1mm of thickness problem is i wanna run a composite head gasket because pulling the block isn't an option right now, but with 1mm of thickness to make up due to machining whats my CR going to be at? also can i even run the car like that and what would i need to do to actually get it running properly
 

Needboost

New Member
Authorized Seller
Joined
Mar 2, 2009
Messages
312
Likes
0
Location
danville, virginia
ok i have had my head and blocked machine and decked. block is bored .20 over

HEAD BLOCK stock head gasket 1.37mm before total- 315.87mm
before-116mm before- 198.5mm after total- 313.918
after- 4.560in. = 115.824mm after 7.799 in.-198.094mm equals = 1.952 mm gasket that i need?

if i have the caculations correct what head gasket will i need?
 

Needboost

New Member
Authorized Seller
Joined
Mar 2, 2009
Messages
312
Likes
0
Location
danville, virginia
2mm will do it fine if your math is correct.
ok i have had my head and blocked machine and decked. block is bored .20 over

HEAD BLOCK stock head gasket 1.37mm before total- 315.87mm
before-116mm before- 198.5mm after machine total- 313.918
after- 4.560in. = 115.824mm after 7.799 in.-198.094mm equals = 1.952 mm gasket that i need?

if i have the caculations correct what head gasket will i need? the machine shop did the measurement for me but i feel like i have made a misake some where

i added the stock head+block+headgasket size to get my total of 315.87mm
then dded the after machine work of head and block then subtracted the amount 313.918
to get 1.952

head
before- 116mm
after 4.560in = 115.824 mm

block
before-198.5mm
after- 7.799in= 198.094mm

stock headgasket. 1.37mm

before- 315.87mm
after machine work- 313.98

315.87mm-313.98mm= 1.952mm
 

Needboost

New Member
Authorized Seller
Joined
Mar 2, 2009
Messages
312
Likes
0
Location
danville, virginia
2mm will do it fine if your math is correct.
with the cylinders being bored .20 over what difference does that make on compression and do i have to get a certain kind of gasket since the block was bored. sorry for the ignorance on this just trying to get everything correct for the first build and learn in the process thank you.