MyE28.com

I'm linking back over to roadfly post, where I posted all the pics.

http://bimmer.roadfly.com/bmw/forums/e24/8371201-1.html

Is that a MLS head gasket? It is very thin. You of course know that the gasket failure point was not open like that when installed. What level of boost were you running for two years?

Here are the pictures so you do not have to go to the Roach -

Here are the basics. 86 635, 5sp. 2 yrs ago installed a Callaway Turbo kit from a 1984 633. Here are the pictures after pulling the head of yesterday. After 21 years, the cross-hatching was still there. The last pic is a close-up of the headgasket for #3. I measured the displacement at 1/8 inch (which explains the white smoke and low coolant light.

First is cylinders 1-3. Notice how clean #3 is!






Now a close-up of #4, which did not fare as well as #3. Look closely at the bottom of the pic. I think the edge of the piston is burned away, I can clearly see lots of the ring. The cylinder wall also had vertical "rubbing" evident.






The gasket is split open, check out just to the left of top center

[quote="Duke M535ti"]Is that a MLS head gasket? It is very thin. You of course know that the gasket failure point was not open like that when installed. What level of boost were you running for two years?

Original Stock gasket installed in April 1986.

Boost levels were 10-15. I'm confident my tuning was "not good."

I installed the system in April 2004, blew the gasket in Aug 2005.

Mike-TurboE24 wrote: Original Stock gasket installed in April 1986.

Boost levels were 10-15. I'm confident my tuning was "not good."

I installed the system in April 2004, blew the gasket in Aug 2005.

WOW, on a stock head gasket for 17 months, which is amazing at that boost level. You need to have the head machined to a RA (roughness average) below 20 and go with a MLS gasket. What are going to do about the piston?

Duke M535ti wrote: WOW, on a stock head gasket for 17 months, which is amazing at that boost level. You need to have the head machined to a RA (roughness average) below 20 and go with a MLS gasket. What are going to do about the piston?

Factory smoothness is well within the requirments for a MLS. No machining is required. Cometic requires a RA of 50 not 20.

I ran my orignal HG for over 20k miles almost the entire time above 15psi. It didn't blow until I upped the boost to beyond 20psi. Made 417rwtq on the dyno prior to failure.

T_C_D wrote:
Factory smoothness is well within the requirments for a MLS. No machining is required. Cometic requires a RA of 50 not 20.

Cometic can get away with a 50 or lower due to a thicker layer of viton rubber on the gasket. The industry standard for a MLS gasket used with a aluminum head and iron block is 20 or lower. The factory smoothness can exceed a RA of 50. Todd you found this with some of the OEM heads in your shop. A SAFE/NO SHIT head preperation will have a RA of 20 or below. Why do it to a "just within" the specs job?

I ran my orignal HG for over 20k miles almost the entire time above 15psi. It didn't blow until I upped the boost to beyond 20psi. Made 417rwtq on the dyno prior to failure.

So........see above.

Click HERE for PLENTY of data on how to prep a head for the MLS use.

Here is my head with a 16 RA -

Duke M535ti wrote:

T_C_D wrote:
Factory smoothness is well within the requirments for a MLS. No machining is required. Cometic requires a RA of 50 not 20.

Cometic can get away with a 50 or lower due to a thicker layer of rubber on the gasket. The industry standard for a MLS gasket used with a aluminum head and iron block is 20 or lower. The factory smoothness can exceed a RA of 50. Todd you found this with some of the OEM heads in your shop. A SAFE/NO SHIT head preperation will have a RA of 20 or below. Why do it to a "just within" the specs job?

I ran my orignal HG for over 20k miles almost the entire time above 15psi. It didn't blow until I upped the boost to beyond 20psi. Made 417rwtq on the dyno prior to failure.

So........see above.

Click HERE for PLENTY of data on how to prep a head for the MLS use.

Cometic requires RA 50. Period! I do not understand how you know more about their product than they do? Reading a couple of articles on the internet doesn't make you more iinformed about their products than Cometic.

That "rubber" is Viton.

The stock unsurfaced head that I installed on the race car's engine was 35-40.

Stock smoothness is way below RA 50 so resurfacing an otherwise good stock cyl head is a waste of money. I have proven this at least 20 times over.

I sell Cometic gaskets and they require RA 50. Period! Reading a couple of articles on the internet doesn't make you more iinformed about their products than Cometic

Whatever Todd, you keep doing what you are doing and that’s your choice.

Its not a "couple of articles", I referenced five and there are many more. So what if someone does not use a Cometic gasket?

I will continue to inform people what the industry standard is for a MLS application. This is also recommended and required by competent machinists, i.e - Paul Burke.

That is what a BMW Forum of information is for.

Try to stop losing your cool whenever I pass researched, verified and accurate information to fellow board members.

Peace

Duke M535ti wrote:

I sell Cometic gaskets and they require RA 50. Period!

Whatever Todd, you keep doing what you are doing and that’s your choice.

I will continue to inform people what the industry standard is for a MLS application. This is also recommended and required by competent machinists, i.e - Paul Burke.

That is what a BMW Forum of information is for.

Try to stop losing your cool whenever I pass researched, verified and accurate information to fellow board members.

Peace

Who says you are qualified to inform the board what the industry standard is?

I am not losing my cool just commenting what I believe is true so that BMW members can draw their on conclusions.

T_C_D wrote:Who says you are qualified to inform the board what the industry standard is?

I am not losing my cool just commenting what I believe is true so that BMW members can draw their on conclusions.

Nobody, I have BTDT with substandard head preparation and the consequences of that work though................and indeed, board members have drawn their own conclusions.

Duke M535ti wrote: Nobody, I have BTDT with substandard head preparation and the consequences of that work though

I agree and that is a totally different subject. BTW, thanks to you our new machine shop is wonderful. Sent a head out this week that was RA 20 or better. Cheaper than the old place too. Local as well. Feel better?

T_C_D wrote:I agree and that is a totally different subject. BTW, thanks to you our new machine shop is wonderful. Sent a head out this week that was RA 20 or better. Cheaper than the old place too. Local as well. Feel better?

Yes, I do feel better.

I am just sorry that you and I had to pay the price in hide, time and money for us to figure out this issue though.

However, I am very happy that you are now turning out a first rate product and service for your customers.

Duke M535ti wrote: Yes, I do feel better.

I am just sorry that you and I had to pay the price in hide, time and money for us to figure out this issue though.

However, I am very happy that you are now turning out a first rate product and service for your customers.

We had a machine shop improperly resurface a cylinder head one time! Don't get crazy on me. Remember that same machine shop resurfaced the head onthe Buzz Bomb which is still putting down 300rwhp, 303.5 to be exact and has never had a leak.

You were just the unfortunate result of his poor work on one occasion.

T_C_D wrote:You were just the unfortunate result of his poor work on one occasion.

OK - I'll let you have the last word on this. Peace Bro.

Mine's at 40, Cometic MLS, 18+psi backed down to 15 for about 6k mi. with no issues. That being said, I'll probably blow the damn thing tomorrow. It's been a while since I toasted something so I'm probably due

I wonder if it has something to do with warm up. If you take it easy, the head wouldnt be expanding much faster than the block. On the other hand, if you got on it too soon, it would be expanding relatively quickly, causing a maximum amount of mating surface scrubbing. Hmm.

wow. you two... (Duke and Todd) you're just funny. Anyway...

How much for a cometic hg for an '86 535i??? I had one that i put on my '92 325i with ARP head studs. But it got repo'd before i could drive it!

and i don't think i'll have the money to machine my head. wish i did though. i'm doing some suspension upgrades and figuring out a fuel leak, then i have to fix the a/c and some interior parts. then i'll be saving for a TCD s2 kit...

I've been on here saying that since I was 15 but i still swear it's true. haha.