Head Gasket thickness selection

[IJ.]

20 thou isn't going to make much of a difference to the CR or gasket used, the "stock" bore MHG's are already oversize in the hole.

Stoppers are only available in the 86mm bore but are overkill for 99% of 7M builds.

 

[Needboost]

20 thou isn't going to make much of a difference to the CR or gasket used, the "stock" bore MHG's are already oversize in the hole.

Stoppers are only available in the 86mm bore but are overkill for 99% of 7M builds.

are the cometic 1.9mm headgasket any good or the titan 2.0mm

 

[IJ.]

Cometic make the gaskets for Titan, don't start stressing over a .1 difference in the real would unless you're building a class race engine it's going to make 0 difference.

 

[Needboost]

Cometic make the gaskets for Titan, don't start stressing over a .1 difference in the real would unless you're building a class race engine it's going to make 0 difference.

well i was really wondering about how good they are i saw where the hks stopper 2.0 is almost 400 dollars where the titan and cometic are around 180 wondering what the real big difference was

 

[IJ.]

1 extra layer that's rolled/folded on the Stopper, as I said up there the Stopper is overkill and will still blow if something goes "wrong".. none of the HG's for a 7M is bullet proof some just take more abuse before letting go, the danger here is if there are other weak links in the chain they will fail before the HG.

 

[Needboost]

1 extra layer that's rolled/folded on the Stopper, as I said up there the Stopper is overkill and will still blow if something goes "wrong".. none of the HG's for a 7M is bullet proof some just take more abuse before letting go, the danger here is if there are other weak links in the chain they will fail before the HG.

ok well i guess i may go with the titain 2.0mm gasket since you said cometic makes the gaskets for titan and that 2.0mm is the size that i would need thank you for the help

 

[IJ.]

No probs, shop for Price/Availability they're all much the same there are no "Bad MHG's" for a 7M that I'm aware of.

 

[Skeezix]

OK so I decided to bury the needle on the car, twice, bad fuckin idea. Now I'm back to another build (took out #6 rod and main) and am thinking of going MHG this time. The Top Line OEM replacement never blew (with ARP studs). But when I had the motor done six months ago we had the head planed a bit and the block resurfaced, now don't know exactly how much was taken off. Read this entire thread and could not find where you measure the block. The main saddle, now are we talking measure from where the cap meets the block,or where the bearing would sit in the journal? Seems like measuring from the journal may be difficult but I don't have/never used verniers. Help would be appreciated as I don't want my car in the garage all summer again.

 

[Skeezix]

Also my block has already been bored 40 over would I need to jump up to the 86mm bore gasket or is the 84mm just enough seeing as how stock is 83mm and 40 over is 1mm?

 

[D.J.T.]

Read this entire thread and could not find where you measure the block.

Odd, i found all the HG info i needed in this thread back in OCT 2010.

You measure it from the top of the block to the center of the bottom where the main bearing sits.

 

[Skeezix]

Yeah could've missed it, that is where I figured to measure from thanks for the help!

 

[JJBToyotaSupra]

Trying to figure out my compression ratio using this calculator: http://www.csgnetwork.com/compcalc.html but when i enter all the stock values i get 8.7:1. Isnt stock 8.4:1? Anyone else have this issue?

Also, im changing the HG on my GTE. Just got a stock size fel-pro composite HG because i didnt wanna take out the engine. The machine shop said they took .040" off my head, so now im not sure what to do. I understand the concept of adding what was taken off to the gasket to maintain compression and squish/quench but im wondering would i be able to get away with a stock gasket with that much taken off the head and just running stock boost stock engine? Would my compression be too high and damage the engine or would my valves hit the pistons? Toss the head in the garbage an get a new one? Appreciate any input, im afraid to put it together now lol.

 

[IJ.]

Remember -19cc on the piston dish.

 

[JJBToyotaSupra]

Yes sir. These are my number:

1 = Inches 2 = Millimeters: 2
Enter Cylinder Bore Size: 83
Enter Piston Stroke Length: 90.98
Enter Head Gasket Bore Diameter: 84
Enter Compressed Head Gasket Thickness: 1.37
Enter Combustion Chamber Volume In CCs: 40
Enter Piston Dome Volume In CCs Negative For Dished Pistons (Use '-'): -19
Enter Piston Deck Clearance Negative If ABOVE Deck (Use '-') : -.5

Gives me a C/R of 8.7:1 am i doing something wrong or is that calculator a little off?

Also IJ, in your opinion would it be ok to run my head with .040" machined off on my stock HG on stock boost? I just need my car driving again, wont be driven very hard. Planning to rebuild it all next year.

 

[IJ.]

Pistons in a 7M are 20 thou out of the holes at TDC, from memory CC volume is 49cc but it's been awhile since I was hands on with one.

You'll have to listen carefully for any sign of detonation and maybe pull some base timing out of it if you hear some.

 

[JJBToyotaSupra]

Thanks alot for the help!

 

[IJ.]

Bang 49cc into the calculator and see what it says.

 

[mcammarn]

so i took my block in to machine shop to get rebuild, and they didnt have to take nothing off from the block. they said it was good still.
for the head, they took off 6 thousands. (.006)

so from what ive been reading in the 14 pages,lol, is that i wont need a mhg since the block didnt get resurfaced?
and my end hp goal is roughly 350.
what thickness of hg do i need then if i go with compsite or mgh?
thanks

 

[IJ.]

Stock will do it 6 thou is nothing to be concerned about.

 

[mcammarn]

Stock will do it 6 thou is nothing to be concerned about.

will stock be good to run around 350hp? like fel pro, oem toyota. theres a hg in the gasket kit i got its from ITM.
im just dont want to end up pulling a head off from bhg.