1/2" head studs - block & cylinder deformation

[keltalon]

I've seen more than a few cylinder heads "crush" under the washer when they were either over-torqued .

I had this happen to me one time and since I installed the insert washers never again.

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[99gst_racer]

Well it looks like I might just end up sticking with the 6 bolt L19's after all for this build. But I do have a revised 7 bolt as a spare that I would like to try this mod on, if anyone can give me a part number on a set of these or point me in the right direction of where to get them it would be greatly appreciated!

Send a PM to Turbo23 to order them. There is no single part number kit for them...

 

[SPYDERGSTTUNER]

Send a PM to Turbo23 to order them. There is no single part number kit for them...

I already tried but they advised me against it. I told them I wanted to try in on a 6 bolt since theres really no info on it and he said it wouldn't be worth it on a 6 bolt since 12mm is big enough, which I agree. I also tried to tell them that I have a revised 7 bolt that I would still try this mod on but I still couldnt get a quote on a set.

 

[94awdcoupe]

I agree with jackson machine 100%. doesnt matter how bada__ your studs are . heads are not lifting. heads are flexing. you only have to look at a blown head gasket to see that. they ALWAYS blow right in the middle of two studs. NEVER near a stud. if studs were stretching gaskets would blow anywhere around the circumference. I would ad its actually a bad idea. I had my machine shop measure bore distortion with 11mm studs torqued to 75lbs. he measured nearly .001 (.0009) distortion. he described the distortion as "four bumps near the studs" Does anyone even ask themselves why mitsubishi blocks went from 12mm to 11mm studs? or why VW went from 10mm to 8mm studs on air cooled engines?

a practical solution I found to fight blown head gaskets from head flex. I tried a crapload of things when i was a sloppy tuner. what I found worked best is an oringed head with a felpro gasket. the oring definately holds the fire ring in place during flex. that and I think the gasses have to snake around the rings. tryed oring in block because its easier to find machine shop that can do it, but it doesnt work. it has to be in the head since the head is flexing and the block stays straight.

 

[mercaholik]

That is very useful info, thank you. Is the 2g head less prone to flexing? And would it be hypothetically possible to engineer some type of girdle or bracing system that would apply more force between the studs where the heads are flexing?

 

[94awdcoupe]

I dont think 2g head is stiffer. but i do think evo 8 and especially evo 9 heads are stiffer. they have a different problem that early 4g63 doesnt seem to have. when the heads flex on evo 8/9 they dont blow gaskets. they end up blowing freeze plugs out. i think this is an indication the head is not flexing enough to blow the gasket but enough to over pressurize the water jackets. there isnt room in the head for a girdle of any sort.

side note the evo 8/9 heads also have three times the oil drain back area over early heads. i dont think they benefit from the kiggly regulator like early heads do. the drain back area is seriously restricted on early heads and its very discouraging to see the difference between the two..

 

[mercaholik]

Really that's interesting, I have my 6 bolt head off right now, do you think I should try to open up my oil drain ports? Thanks for the reply, always like learning the differences between the platforms. So maybe the 2g/ evo9 mivec head swapis beneficial in more ways than one.

 

[94awdcoupe]

before you port anything put head back on block and take a look. its really bad. what few holes there are dont even line up with the block that well. I just cleaned up the head return ports on my recent head. but then when I put it on the block and looked at the return path and said "crap that did nothing" the block needs to be opened up to match the ports. not the other way around. the block was already in the car so I couldnt do it. needs to be done before assembly.

 

[mercaholik]

Ok well that's a good time to find this out, my whole engine is completely apart and being specd right now. I think I'll do both even if only a little more the block needs to be hot talked and resurfaced so this should be some what of and improvement over stock. I always like reading your replies, informative and based in fact. Like the discussion about back pressure driving turbines at low, of boost was getting a little out of hand. Corky bell and def full race agree the best exhaust for turbo cars is a 10-15° diffuser mega phone style exhaust proved to be the most efficient. I believe 94awd briefly mentioned it but it seemed to get lost in the shuffle. Well I noticed and from what I've read and seen this is completely true. I think it may be do to the off boost or n,/a to transient boost that maybe giving some kind of better low end feel but it needs to be quantified.