how much boost and hp CAN a stock hg take anyway

[GrimJack]

NICE! Now there's some good news.

What fuel pump and injectors are you using?

 

[aye mate]

Grim:I know hes got 550's and a Lex.

 

[MK3Brent]

Walbro and legitimate RC 550's, with flow sheet.
I plan on dynoing soon with my new T66... and if the clutch holds I'll put 400 some on it.

 

[JDM 1JZ]

nice, i guess my path is chosen of what hg to use, thanks for the imput and help guys!

 

[Nick M]

I'll throw some info into the mix here.

DSMs run a 2L 4 cylinder turbocharged engine with stock headgaskets to well over 500hp at the wheels with no problems.

Not to nitpick your fine post, but I dont agree that DSM's have no problems. I have seen more of those blow the headgasket, including naturally aspirated, than the 7M.

well i dont like reason number one to be honest because just cause something says its not to be done doesnt mean anything

:nuts: So you think Toyota just wanted to waste paper and ink?

 

[JDM 1JZ]

no its just simply stating that just because something doenst say something it doesnt mean its not a good idea or will help. if toyota told u to jump off a bridge would u follow

 

[GrimJack]

Hmmm... I know lots of DSM guys here, and they very rarely have head gasket problems. They blow up trannies, crack pistons, tear apart blocks... but I've seen them running well over 500 whp without blowing head gaskets.

The local guys don't even consider a MHG until they are nearing 600 whp.

My roommate built his DSM engine - completely, we're talking forged pistons, Ti head bits, billet rods, brand new cams, full port and polish, the works - and he still put it all together with a composite gasket.

Now I'm sure that they still have problems, I'm just saying that they guys here seem to avoid them.

 

[bigaaron]

I'll throw some info into the mix here.
My personal opinion is that the stock head gasket should be fine to at least 700rwhp - as long as the tuning is done correctly.

You can't be serious. There is no way you are going to EVER see 700hp on a stock 7m headgasket without instant hg failure. The headgasket would deform around the cylinders before you ever created enough cylinder pressure to make that kind of power.
And don't use copper spray designed specifically for headgaskets on your mhg, use "brake quiet" designed for squealing brakes...
Sometimes I wonder...

 

[JDM 1JZ]

And don't use copper spray designed specifically for headgaskets on your mhg, use "brake quiet" designed for squealing brakes...
Sometimes I wonder...

huh?

 

[bigaaron]

I was being sarcastic. Brake quiet is for brakes. Permatex copper spray coating is for headgaskets.

More sarcasm:
Spray brake quiet on your stock hg, torque those stock bolts to 100ft/lbs, slap your t88 turbo on there and make 700hp at 40psi!
Make sure to add a 200 shot of nitrous to help with spool, that stock hg can take it with the proper tuning.:icon_bigg :biglaugh: :icon_bigg :biglaugh: :icon_bigg :biglaugh: :icon_bigg :biglaugh:

 

[JDM 1JZ]

oh, fuck i read it wrong haha, good shit my bad

i do think the stock hg can support atleast 500, done right, tuned right blah blah

 

[bigaaron]

You can drive 200mph on R rated tires, are you going to try it? The 7m stock headgasket is a poorly engineered piece of crap. Period.

 

[JDM 1JZ]

yeha but just because you've had bad luck with htem doesnt mean eveyrone else who posted in this thread hasnt, plenty of people have had luck

 

[bigaaron]

yeha but just because you've had bad luck with htem doesnt mean eveyrone else who posted in this thread hasnt, plenty of people have had luck

I dont want to base my engine's lifespan on luck. I fixed all those bhg's in the pic, plus more. If you have been around 7m's for a while you will eventually think the same way as me. Oh yeah, I have two more jobs lined up to fix bhg's as we speak.

 

[JDM 1JZ]

i dont understand what makes the 7m hg so much weaker then any other car, theres a bunch of local guys with dsms that are fine, 2 of them are making over 600awhp, theres a local mk4 guy making 900 and some odd hp 9 second street car, nos the whole 10 yards, comepltely stock ass motor, i just dont get it

 

[Mr.PFloyd]

i dont understand what makes the 7m hg so much weaker then any other car, theres a bunch of local guys with dsms that are fine, 2 of them are making over 600awhp, theres a local mk4 guy making 900 and some odd hp 9 second street car, nos the whole 10 yards, comepltely stock ass motor, i just dont get it

prbably metal hg's. ours are stockceramic.

 

[JDM 1JZ]

well i know the dsm guys are jsut running junk felpro's, and the supra guy hasnt even touched his motor, as far as the bottom end or the head or anything bone stock motor

 

[bigaaron]

i dont understand what makes the 7m hg so much weaker then any other car, theres a bunch of local guys with dsms that are fine, 2 of them are making over 600awhp, theres a local mk4 guy making 900 and some odd hp 9 second street car, nos the whole 10 yards, comepltely stock ass motor, i just dont get it

The mk4 has a METAL stock headgasket, Toyota changed to metal headgaskets after they had lots of problems in the late 80's, early 90's with headgaskets on several models of engines, not just the 7m. Here is a 1jz hg next to a 7m hg:

See how much more surface area the gasket covers around the cylinders.
See how they moved the coolant passages between the cylinders so the hg has more sealing surface and the gasket can't deform. Look at how meaty the jz hg is, it is almost impossible to make it deform. I still love the 7m. If it didn't have any problems then what fun would it be to fix? I love 7m's for the challenge. I know what is wrong with it and I know how to build one that IS reliable, and part of the formula is a MHG!

Just look at the 7m headgasket
1: it is way to thin in many places.
2: there is not enough clamping force to keep the gasket from deforming
3: there are more holes in the hg then there are coolant passages in the block which leads to errosion of the block and head over time.

Obviously the hg was designed for the engine, not vice versa, so I guess the engine design was the real problem that causes the hg to blow.
I will admit it.

Also notice the arrow in the 1jz hg, that is some funny shit! I guess people put lots of headgaskets on backwards LOL

 

[NDBoost]

holy hell never knew the 1J HG is that beefy. that things meaty! i wish the 7M was like that

 

[GrimJack]

bigaaron, I'm not saying people should build motors with composite gaskets and head for 700whp. Realistically, a MHG and the prepwork for one isn't that much of a cost to consider when you are going for that level of performance, and the extra insurance is well worth it.

What I *am* saying is that the 7M gasket, in my opinion, fails 99.9% of the time for one of two reasons - insufficient torque on the head bolts from the factory, or bad tuning resulting in detonation.

As for the brake quiet spray, someone has to try it. Might as well be me, if it doesn't work, I don't mind tearing down my engine to replace it. If it does work, it's a very nice trick to save a lot of time, effort, and money when swapping in a MHG. As for whether it actuallly works or not, ask me in another 5 years.

I'd seriously like to see someone put together an engine with a stock head gasket, arp head studs, and a proper standalone ECU and some good tuning and see what the stock gasket it good to. I don't think it will ever happen, but that is the only way to determine what power levels the stock unit is good for.