HKS 3mm Head Gasket?

[Rennat]

Im debating between the 3MM and the 2MM HKS Bead gasket... i think the only person who sells a 3mm (at least shows it on there site) is 935motorsports.

If your using one, where did you get it from? and do you like it? did you blow it apart?

 

[jdub]

That's gonna depend on how much material that been removed from the block & head decks. The type piston (compression wise) you are going to use and how much boost you plan on putting through the motor. You have to keep in mind HG thickness affects cylinder quench area in addition to compression.

 

[Rennat]

they didnt shave that much off, if i wanted to keep relatively the OEM compression, then the 2mm gasket would be better. but, im running probe pistons. so im not sure if they have higher or lower compression.

i dont mind if its lower compression, in the LONGGG run im shooting for either a to4b turbo with 500ish... OR a ct-26 57trim or 60trim and just maxing that out. either will give me more than enough power for my street car.

 

[gofastgeorge]

but, im running probe pistons. so im not sure if they have higher or lower compression.

Contact who ever sells the probe pistons,
they will be able to tell you if the probes are the same as the stock.

And 'not much' isn't much of a measurement to go by.
.010" cut on the head, and .010 on the block
ends up being a half a milimeter.
So you really should know what was really cut off
before deciding on a gasket.

 

[jdub]

Rennat - this is not really something you want to "guess" at

 

[Rennat]

haha... yeah, i see your point. and i'll call somebody at probe later on today...


and they cut 7 thousandths off the head. and i for the block it was under 10 thousandths... i cant remember right now.

so for grins and giggles... they cut 17 thousandths off, what gasket should i be running then? 1.2mm? 2mm? 3mm? (im only going to be using the HKS gaskets)

 

[jdub]

It's higher math...addition :biglaugh:

There's .039" in 1mm

Stock HG thickness is 1.37mm compressed

Increase MHG thickness by the amount removed from the block and head.

 

[HommerSimpson]

spend the extra and get a stopper 2mm

 

[Rennat]

hommer your a funny man to preach spending money... lol

stopper or bead. they both do a damn good job from what i've read. and i could afford the stopper, but i would rather buy a new oil pump and a head gasket rather than just buying one...

and i guess i'll just get the 2mm as that will make it a tiny bit bigger, and lower the compression just a tiny bit also.

 

[HommerSimpson]

hommer your a funny man to preach spending money... lol

stopper or bead. they both do a damn good job from what i've read. and i could afford the stopper, but i would rather buy a new oil pump and a head gasket rather than just buying one...

and i guess i'll just get the 2mm as that will make it a tiny bit bigger, and lower the compression just a tiny bit also.

Hey now.... Im great at spending other peoples money....
lol
but yea if money was no object :{

 

[Rennat]

LOL.

between buying eagle rods, probe pistons, southbend clutch, divorced downpipe, gasket set, and my ultra JDM TRD oil cap. AND my $1200 machine shop bill... a $300 head gasket hits my wallet pretty hard right about now... i actually borrowed the money from my dad to pay the machine shop... so im paying him back ( as im supposedly working right now with him)

im gonna go search around for head gaskets though... i found a few sites that had good prices on them, but id rather support a vendor on here.

 

[BJ91T]

I m actually glad this thread came up, I purchased a motor from a local guy that was already assembled. It had a 3mm MHG in it and He claims he did that just to run High boost. I have a 57 trim going on this motor and would like to get it back to stock comp ratio so I can make more power at lower boost on a CT. How can I measure the block and head to see how much was removed. The head is off but the block has main caps etc already in.


Thanks In advance
BJ

 

[jdub]

Stock head thickness = 116mm deck to cam cover sealing surface
Block height = 198.5mm between main bearing saddle and deck

 

[BJ91T]

OK so since the main caps are installed is there another way to check



Thanks
BJ

 

[Zumtizzle]

haha... yeah, i see your point. and i'll call somebody at probe later on today...

Probe is wrong. Their Books say -17CC dish, when this is clearly a -20cc DISH.

Use an Online compression calculator, no matter what you do now, you won't have the exact 8.4:1 Compression, remember that.

 

[Zumtizzle]

http://www.csgnetwork.com/compcalc.html

I've played around with that one before and it was pretty accurate, i had the equations written down somewhere.............

Edit: Heres the equation, if you need help with the math let me know it's pretty simple. Please Excuse my Dear Aunt Sally.

Basic measurements (Formulas used below)
Bore Diameter = 83.5mm
Stroke = 91mm
Bore Radius = 41.75mm
Piston Volume = 19cc
Deck Clearance = -2.8cc
Combustion Chamber Volume = 37.5cc
2.0mm x 84mm Head Gasket Volume = 11.08cc

Cylinder Volume
Bore size = 83.5mm
Stroke = 91mm
Bore Radius = 41.75mm
Volume of Cylinder = (pi*radius*radius*height)/1000
(3.1416*41.75*41.75*91)/1000 = 498.316cc
Total Bottom End Capacity = (498.316cc*6 = 2989.896cc)

Gasket Volume
Gasket thickness = 2.00mm
Bore size = 84mm
Volume of head gasket = (pi*radius*radius*height)/1000
(3.1416*42*42*2)/1000 = 11.08cc

Deck Clearance
Piston height = 0.5mm
Bore Size = 83.5mm
Volume of Exposed Piston = (pi*radius*radius*height)/1000
(3.1416*41.75*41.75*0.5)/1000 = 2.74cc

Compression Ratio
CR = Compression Ratio
D = Displacement
PV = Piston Volume
DC = Deck Clearance Volume
G = Gasket Volume
CC = Combustion Chamber Volume

CR = (D + PV + DC + G + CC) / (PV + DC + G + CC)
8.685:1 = (498.316cc+19cc-2.74cc+11.08cc+37.5cc)/(19cc-2.74cc+11.08cc+37.5cc) = (563.156)/(64.84)

 

[jdub]

OK so since the main caps are installed is there another way to check

Thanks
BJ

Not that I'm aware of.

If the probe's are a 20cc dis, CR will be lower than advertised.

 

[Zumtizzle]

Not that I'm aware of.

If the probe's are a 20cc dis, CR will be lower than advertised.

Yea..........Doward Measured them.

I haven't had a chance to measure them, but even the box says -17.5 cc's on the side.

 

[BJ91T]

ok thanks Jdub I am gonna go see if i can get some measurements I will post my results here.

 

[jdub]

and i guess i'll just get the 2mm as that will make it a tiny bit bigger, and lower the compression just a tiny bit also.

Zum - I've got a feeling he doesn't really want to do the math...looking like a "best guess" will do

A 2mm MHG will lower compression in addition to the -20cc "unadvertised" dish.