I've been thinking about my future M30 TCD build and I need some opinions on headgaskets. My plan is to run 15 lbs maximum, mostly 10 daily, with headstuds, non intercooled. I know a MLS is recommended but with all the problems Duke had and reading other threads I'm leary of a MLS. Differing opinions on the proper gasket surface, sealant to use (copper spray or hylomar), and torquing (hot, cold, after run in, etc.) have me wondering. I heard of people using the stock gasket with success, but it seems every engine has it's own particulars.
I know a stock gasket can be used but is limited because of it not being meant for FI. I thought a gasket from a 745 could be used but on real oem's site the 745 gasket has the same number as the regular M30 gasket. Is this right?
Any thoughts or can someone put my mind at ease on the MLS issue?
Thanks.
headgaskets
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Kyle in NO
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MLS head gaskets are the standard of the automotive industry now. Although many manufactures made cylinder head design changes along with their move to the use of the MLS gasket, very few people have a complaint with the gaskets. Which doesn’t mean I would use a MLS head gasket only that I think they are good.
To answer one question, yes the m106 and m30 gaskets are the same, which is one reason many 745 owners have popped the gaskets after cranking up the boost and not addressing fuel.
Vance
What would you use instead, oring head and copper gasket? I think the Alpina Bi-turbo gasket uses a cutting ring.M635CSi wrote:Which doesn’t mean I would use a MLS head gasket only that I think they are good.
Vance
You can use a M1 gasket which is a cutting ring design. $400+
A MLS gasket will be fine. Make sure that the head and block are prepared properly for it. The RA should be below a 20 on the head and block. Even though Cometic recommends a 50 RA or lower, the majority of information on MLS gaskets and aluminum head on iron blocks is 20 or lower.
Use ARP studs. Do the initial torque with the ARP molly to 80 lbs. Run the engine to full operating temp, let cool overnight retorque. Retorque again in one week, month or until nuts do not move when retorquing. Always retorque when engine is overnight cold.
I removed rivets from MLS gasket and sprayed Hylomar between each layer when I placed them on the block. I just did a leak down test on my engine. I used 100 psi with no more than 4 psi drop in any cylinder.
Lots more info here - Clicky
A MLS gasket will be fine. Make sure that the head and block are prepared properly for it. The RA should be below a 20 on the head and block. Even though Cometic recommends a 50 RA or lower, the majority of information on MLS gaskets and aluminum head on iron blocks is 20 or lower.
Use ARP studs. Do the initial torque with the ARP molly to 80 lbs. Run the engine to full operating temp, let cool overnight retorque. Retorque again in one week, month or until nuts do not move when retorquing. Always retorque when engine is overnight cold.
I removed rivets from MLS gasket and sprayed Hylomar between each layer when I placed them on the block. I just did a leak down test on my engine. I used 100 psi with no more than 4 psi drop in any cylinder.
Lots more info here - Clicky
I agree. Another reason is the stock gasket was on its way out and/or the engine was out of tune.vance wrote:To answer one question, yes the m106 and m30 gaskets are the same, which is one reason many 745 owners have popped the gaskets after cranking up the boost and not addressing fuel.
M635CSi wrote:Which doesn’t mean I would use a MLS head gasket only that I think they are good.
That would depend entirely on the budget. For low boost (8>10 psig) running with or without an intercooler I'd belly up to the BMW counter and buy a stock head gasket and head bolts. Next level up in boost I'd use an MLS gasket with BMW hardware. At the next level of boost or budget (with or without intercooler) I'd use the MLS gasket with studs. After that, I'd internally cool the engine and use a solid copper head gasket with studs. At the highest level budget I'd use internal engine cooling, a solid copper head gasket and an o-ring prepped block and head utilizing Wills Rings clamped with studs. In all cases, I'd use a relatively thin head gasket.vance wrote:What would you use instead, oring head and copper gasket? I think the Alpina Bi-turbo gasket uses a cutting ring.
Vance
This isn't intended as a suggestion to anyone but it is, after a lot of thought and experience, what I would do with my own engine.
Thanks for the info guys. The only issues now are what to seal it with, and finding a good shop in the Dallas area to surface the head & block to the proper finish.
The surface finish seems to be critical for a MLS.
I was thinking of running 10lbs and just sticking with the stock gasket. Then I'd start getting greedy and begin turning it up. So I figured I'd build it for everything short of 20lbs and a Megasquirt.
The surface finish seems to be critical for a MLS.
I was thinking of running 10lbs and just sticking with the stock gasket. Then I'd start getting greedy and begin turning it up. So I figured I'd build it for everything short of 20lbs and a Megasquirt.
I have a stock gasket and head studs on 9-10 psi non-intercooled and have had no issues with it over the last 3 years. Knock on wood of course.
The stock surfaces are generally appropriate for MLS. It seems to be when you get things skimmed or resurfaced that you need to be careful about the final RA.
Jeremy
The stock surfaces are generally appropriate for MLS. It seems to be when you get things skimmed or resurfaced that you need to be careful about the final RA.
Jeremy
The factory surface is usually between a 45-55 RA. Here again, less than 20 RA is recommended. BMW did not intend the OEM surface of the head and block for use with a MLS gasket. But yes, generally it will work but increases the risk of failure.Jeremy wrote:The stock surfaces are generally appropriate for MLS. It seems to be when you get things skimmed or resurfaced that you need to be careful about the final RA.
Like Jeremy said, if you have the head or block surfaced, make sure the end result will be the proper RA.
i use the mls gasket and arp studs and i have had one blown headgasket. however, when the headgasket blew, i had a dodgy tune trying to get straightened out and a an even more dodgy tuner who wanted to make as much power possible and really wasn't watching for the signs. Sicne then, the head has been resurfaced and put back together and i was at the tuner's today for tuning (my normal tuner, not the one who messed up the head). the car runs perfectly with 15 psi and have had no problems with the mls gasket since the reinstall.
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Steve Haygood
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Thats great. Has the wastegate been modified? If it is running the stock boost, it should run for many more miles with no problems. The OEM HG can take 7-8 psi for a long time. When you get above 12 psi, thats when the OEM gasket has a much shorter life.Steve Haygood wrote:I've got a 745 at the shop now that has upwards of 200k on it with high boost levels run,stock gasket and stock head bolts, never had a problem, John says just make sure you give it enough fuel. Just an observation,not a recommendation.
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rundatrack
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What about o-ringing the block?Duke M535ti wrote:Thats great. Has the wastegate been modified? If it is running the stock boost, it should run for many more miles with no problems. The OEM HG can take 7-8 psi for a long time. When you get above 12 psi, thats when the OEM gasket has a much shorter life.Steve Haygood wrote:I've got a 745 at the shop now that has upwards of 200k on it with high boost levels run,stock gasket and stock head bolts, never had a problem, John says just make sure you give it enough fuel. Just an observation,not a recommendation.
Define, "much shorter". RussC had very good luck with a stock headgasket running around 15psi intercooled if my memories are correct. I'm fairly certain it lasted over 100k miles. I suppose that is much shorter than stock on a stock motor, but not entirely unacceptable IMHO.Duke M535ti wrote:Thats great. Has the wastegate been modified? If it is running the stock boost, it should run for many more miles with no problems. The OEM HG can take 7-8 psi for a long time. When you get above 12 psi, thats when the OEM gasket has a much shorter life.
Also note that the 745i, even running "high boost" only makes around 300 rwhp, perhaps a bit more. Power levels are what determine stress on the headgasket so long as the motor is running with a proper tune, not boost pressure. The BMW headgasket appears to be capable of holding on under the stress of at least 325-350 whp with reasonable longevity based on what I've seen.
Jeremy
100K is great on the stock HG. Although I do not know the history of Russ's car, I bet that is did not have 15 psi of boost for that 100K miles.Jeremy wrote: Define, "much shorter". RussC had very good luck with a stock headgasket running around 15psi intercooled if my memories are correct. I'm fairly certain it lasted over 100k miles. I suppose that is much shorter than stock on a stock motor, but not entirely unacceptable IMHO.
Much shorter is, half the life expectancy that the component was designed for. In my opinion.
That is a possibility. Zane had his block and head O-ringed with a solid copper gasket. It saw 25+ psi for six years before he over boosted (38 psi) and blew the gasket. The other option is a cutting ring gasket. Zane is working on a custom composite gasket, he does not like the MLS gaskets at all, I am waiting for his results on the gaskets manufacture to see abut getting one for my application.rundatrack wrote:What about o-ringing the block?
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rundatrack
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dont know if you shuld also do welded coolant channels as well duke...
That with the o-ring should keep everything in its place
Only thing that would move it is bad tuning.....well with the o-ringing you would probably completely destroy the bottom end before the hg pushed out....
I will let you know after I complete my build how it goes..
That with the o-ring should keep everything in its place
Only thing that would move it is bad tuning.....well with the o-ringing you would probably completely destroy the bottom end before the hg pushed out....
I will let you know after I complete my build how it goes..
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Steve Haygood
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Wow, a lot of info here, thanks.
As seeing how BMW used the same gasket on the 745 as the M30 I think I could run the stocker with studs. People have obviously had success with this setup. Plus on a stock HG I wouldn't have to worry about the critical RA. Really would like to do a air to air IC, but I've read space is limited.
Are stock head bolts TTY or the standard "torque to xx lbs." type? It would seem studs would retain the load better on a stock gasket for that extra security.
A stock gasket seems like it could handle the occasional boost oops. I had a Buick GN with 240k on it. While playing around with the homemade boost controller going up a hill I was just in time to see the gauge bury itself past 30 psi. Sounded like a freaken diesel. Was the comp ratio like, 40:1? Didn't blow the HGs but it never ran the same after that.
As seeing how BMW used the same gasket on the 745 as the M30 I think I could run the stocker with studs. People have obviously had success with this setup. Plus on a stock HG I wouldn't have to worry about the critical RA. Really would like to do a air to air IC, but I've read space is limited.
Are stock head bolts TTY or the standard "torque to xx lbs." type? It would seem studs would retain the load better on a stock gasket for that extra security.
A stock gasket seems like it could handle the occasional boost oops. I had a Buick GN with 240k on it. While playing around with the homemade boost controller going up a hill I was just in time to see the gauge bury itself past 30 psi. Sounded like a freaken diesel. Was the comp ratio like, 40:1? Didn't blow the HGs but it never ran the same after that.