Can I use 2 1.4 MHG at the same time?

[CarlosPTR210]

Hi guys,

I'll rebuild an other 7M engine, this time will be real, with JE forged pistons and eagle rod's, all ARP studs and new oil pump.


I have a HKS MTG of 1.4mm, but I want to install a 3mm mgh to run 18psi, I was thinking if I can use 2 mhg of 1.4, will be shipper that buy a 2.0 and sell my 1.4mm

What do you think?

 

[JustAnotherVictim]

You're kidding right?

 

[AF1JZ]

Correct me if I'm wrong, but are you saying you want to use 2 mhg's on one head?

 

[tte]

You must be joking...You cannot do that...

Just go buy the thicker head gasket if you need it.
Do it right the first time and save yourself lots of stress later.

Cheers,
Roy

 

[CarlosPTR210]

I don’t remember where I read that some one use 2 gasket, that’s why I prefer to ask first :aigo: .

So is not the correct way right!, UPS! :3d_frown:

Thanks guys :icon_bigg .

 

[Junior]

this is one of those "works in theory, might even survive a couple of passes in a drag car, but in the real world is a really bad idea" things.

 

[ToyoHabu]

In the 1jz the exhaust union piece employed two gaskets from the factory, so in some applications its not unheard of. Some head gaskets i have seen are stacks of thin metal. I think it will screw with the required torque and that might cause too much crushing of the copper. I wouldn't risk the unknown get a correct thickness part and forget about it.

 

[staticpat]

If it was a flat piece of metal torqued really tight I guess in theory it would work. But don't the mhgs have rings around the cylinders and passages? There's no way they would seat right.

If you can afford all those other high end parts, why would you skimp on something so simple?

 

[cjsupra90]

Not saying to go ahead and do it, but I do know of a local Turbo'd 2jz-ge SC300 that is running two stock OEM 2jz-gte MLS and running 25psi and has been for more then 2yrs now and the car is a daily driver at that. I have heard of this befor amongest other 2jz-ge guys and other engines as well.

So, in both theory and reality, it does work, do it at your own risk if you want to try it.

 

[MRSUPRA]

Why?? As long as your head and block are not shaved a lot, you could probably run 18psi with a 1.4mm headgasket.

 

[MKIIINA]

i dont think it would be a good idea really. you are talking about different metals with different expansion rates to start off with. you need to have a pretty tight RA on the head and block for things to seal correctly and i think adding more layers (which you cannot estimate on the MHGs) is just asking for more trouble. you can get 3mm hgs all together so why try and put 2 hgs together for something that it wasnt designed to do?

 

[JustAnotherVictim]

Just because you can doesn't always make it a good idea.

 

[starscream5000]

Very rarely do you need a 2mm HG because of material taken off, let alone a 3mm. If so, that would probably be one of the last times that head/block combo would be used. Most people get the 2mm MHG to be able to increase boost a little, or they want the 2mm stopper (like me) for sealing purposes. I'd say get the 2mm stopper and be happy . Boost is just a resistance of air to flow through a given object (in this case, the engine). I'd rather make xxx HP at 15 lbs. boost than 25 lbs. making the same HP... Do you just want to say that you're running big boost or what? If I was you, I'd rather worry about fuel needs with a thinner gasket then pushing a lot pressure through the engine on a thicker one .

 

[boltz]

could possibly be done with composite gaskets for sealing the liquid passages more reliably, but MLS MHG multi stack is bad idea.

If you took the gaskets rivets appart and combined the gaskets properly you might get away with it.

Example, remove rivets from 2 gaskets, re stack as follows

thin
thick
thin
thick
thin

The thick piece always has a thin layer on either side. However i doubt this would work with a stopper gasket, so only the bead style coulddo this.

After you re stack them use some brass rivets and set them in with a hammer.

I in no way think you should try this, and i am only going by what i see my gredy MLS bead gasket to look like.

 

[hellraiser456]

wow..imagine having 2 BHG's at the same time!!!! that would be a bad day.

sorry had to say it

 

[bwest]

instead of just buying a 3mm hg to run mad crazy boost (and have a motor that runs like shit when its off boost) why don't you figure out what compression ratio that 3mm gasket will give (and if you really want to get into it, the dynamic ratio while boosting). That way you at least have an idea why your 7m runs like garbage with a 3mm gasket.

some places to start:
http://www.angelfire.com/fl/procrastination/motor.html
http://www.csgnetwork.com/compcalc.html
http://www.rbracing-rsr.com/compstaticcalc.html
http://www.race-cars.net/calculators/compression_calculator.html
http://www.turbofast.com.au/Tfcomp.html
http://www.rosspistons.com/calculator.php

if you really want to get motivated, here is a dynamic calc:
http://www.wallaceracing.com/dynamic-cr.php
http://www.rbracing-rsr.com/comprAdvHD.htm
http://www.kb-silvolite.com/calc.php?action=comp

now you can make a decision. if your measurements are wrong, then it really doesn't matter anyway. shit in, shit out....

 

[JustAnotherVictim]

It would also depend on the compression ratio from his pistons. Say if he used n/a pistons there wouldn't be as much of a difference from stock, but with stock compression turbo pistons the ratio will be really low.

 

[shaeff]

my first question, why do you have a goal of 18psi when your motor isn't even built yet? do you even have a turbo yet? if not, how and WHY would you decide that 18psi is the amount that you want to boost.

this just doesn't add up. build a motor PROPERLY, get a good turbo, and boost it within it's range of efficiency. don't just imagine this fictitious engine that you want to build and come up with a magic number like 18psi.

-shaeff

 

[bwest]

It would also depend on the compression ratio from his pistons. Say if he used n/a pistons there wouldn't be as much of a difference from stock, but with stock compression turbo pistons the ratio will be really low.

In all the calcs there is a place for piston dish volume. Each brand of piston is different. That is how to take that into consideration... There is much more that just piston dome volume that figures in comp ratio.

anyone replaced the stock valves with dished-faced ferrea's? this will impact CC volume as well as many other things. The above calcs are great for that.

 

[JustAnotherVictim]

In all the calcs there is a place for piston dish volume. Each brand of piston is different. That is how to take that into consideration... There is much more that just piston dome volume that figures in comp ratio.

That's what I was referring too.