General Head Gasket question

[SupraBo]

I blew my head gasket in my JDM motor. :1zhelp:

I am playing my options here but at the top of my list is to just putting a new HG in.

Now the question I have is what should i do?

I am thinking about a HKS 1.2mm HG. Correct me if I’m wrong but I would think this is the best for my application. I would use ARP head bolts also.

all bolt ons. TT, 3in DP, Intake, 550's/LAFM, welbro. The car is driven purely on the street.

Should I go with a bigger HG? Also I am not going to have the block deck resurfaced. Will this be a problem?

 

[mkIIIman089]

Maybe.

Probably.

 

[SevenMKIII]

You must resurface the head and block to a low enough RA value to suit a MHG. If you don't you'll be in this same boat in your near future.

 

[F_T_F]

when you get the heade machined ask them. HG thickness is a direct correlation to how much material they take off the head when machining it. in a nut shell

 

[skim1040]

The thickness of your headgasket...if you wan't it done well, should depend on how much gets taken off your head.

Which you NEED to get done! Based on how much needs to be taken off your head to smooth it out, you should then find the best match HG.


as for the block, it shouldn't be a huge issue. On our car, since the block is not alluminum, it doesn't warp all too easily so it should be fine unless you had some major overheating issues, otherwise, just make sure its clean/scraped off before you put the new head/gasket on

 

[Burntz]

Dont listen to Skim

You HAVE to at least lap the block, it wont be acceptable for a metal head gasket just how it was.

Best bet is to pull the block and have it machined. My friend matt got away with lapping it while it was in the car. As long as it is within spec. He didnt use a purely metal headgasket though. He used a Cometic multi-layer, which dont require a RA value as low as a pure metal headgasket.

 

[TurboStreetCar]

all MHG's are Multi Layer Steel design, unless your talking about copper head gaskets, but im like 95.3724% sure all HKS, Cometic, Titan Motor sports, ECT. are all MLS. I have a Cometic in my car and i had both the head and block surfaced.

 

[bowsercake]

You can measure the block for warping. Also, since you are getting the head machined you will want a larger HG, probably 2.0mm to keep compression close to stock.

 

[Red '88T]

It may be wise to consider replacing your bearings after a BHG.

 

[TurboWarrior]

Technically you have to machine the head and block. But people have left the block alone and got the hg to seal. So its a risk. Head must be done at least or you are really wasting your time

 

[tte]

Best to pull everything out, get the block n head checked and machined.
Less worries for you.

Cheers,
Roy

 

[jdub]

To do it right, both the block and head need to be re-surfaced to the RA (smoothness) spec for the MHG you choose. The block/head MUST be perfectly flat.

The thickness depends (assuming you want to retain stock compression) on how much material is removed from the block/head. There is .039" per mm...the stock HG is 1.37mm compressed iirc. If you remove .005" each from the block/head, that equals 0.25mm...add to 1.37mm = 1.62mm. That is (or close to it) the thickness a MHG needs to be to retain stock compression.

You also need to match cylinder diameter to the MHG, especially if the block has been bored oversize.