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Correct Turbo head


m6smitten

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So I blew a head gasket today while driving the car pretty hard. I guess it's good excuse to pull the head and take care of some other things ie valve guides and seals.

I have looked around the FAQ and have seen threads about the correct Turbo head being the E12; mine is stamped 121T  with * 80 * under. Curious what you've all seen/heard. Is E12 the five series head? I'll be sure to check the specs once I get it pulled. I am thinking the motor was rebuilt because the vin on the block has X4290896X stamped on it. Perhaps a later rebuild meant they installed an alternate head. Always fun "discovering" the history of these cars.

Also, please let me know if there is a Turbo head out there for purchase.

Edited by m6smitten
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The 2002 turbo head is cast with 121TI. However, the combustion chambers are machined out into a hemispherical shape to lower the compression ratio. The exhaust manifold studs were made bigger and of better materials. If you can’t find an original you can always make a regular 121 or 121 TI head work by taking it by a machine shop specializing in aluminum heads.


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Mine is a 121T. The combustion chamber is an E12 style that is machined out and has the larger studs on the exhaust side.

 

The "80" should be within a circle with "dots" going clockwise to delineate the month it was cast. Mine is January, because the engine is / was a replacement long block about that time. The records show that the original "had lost compression" and it was less expensive to buy a long block than to rebuild it......IIRC about 850 GBP.

 

When I took mine apart, I made a cast of the volume, if you want to scan it for the profile, but basically it is hemispherical; handy too for calculating the chamber volume if you haven't already done that.

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If you lost a head gasket it is possible it had a “cutter ring” style gasket ( the factory used them when the cars were new, also in the Ti & Tii) DO NOT replace the gasket without resurfacing the head if it did, and I recommend you use a commetic MLS gasket when you put it back together, just make sure the head and block are clean and mirror smooth. 

1970 1602 (purchased 12/1974)

1974 2002 Turbo

1988 M5

1986 Euro 325iC

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Well, yes and no.

 

Yes, they came with a cutting ring head gasket, and yes it is advisable to skim the head before using another.

 

However, when I rebuilt my motor in the '80's they were NLA, so i used a non cutting ring gasket, thinking I would be replacing that soon. It worked fine for tens of thousands of miles of vigorous driving, many thousands on the track at DE events.

 

So, will a non-cutting ring gasket work? Yes. Is it optimal or the proper procedure? No.

 

I have several of the OE cutting ring gaskets, but am interested in where you get the Commetic MLS and what Part Number it is.

 

Thanks!

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I used the Reinz standard head gaskets for my race engines for many years (185-225 hp 12.0-13.5:1 compression ratios) but about 7-8 years ago I started having head gasket problems.  I'm not sure what changed but I went to the Cometic MLS gaskets and have not had any trouble since.  I buy them directly from Cometic but you can get them from Ireland Engineering, Korman, and Probably VAC. They make them in different thickness and also bores.  the Cometc part number is C4293-051 then you specify your bore (the 051 denotes a 0.051" thick gasket).  The head and block need to be virtually mirror smooth and I recommend painting the gasket with Copper Coat.  I also have a stash of cutter ring gaskets but don't plan on ever using them.

I did take a turbo engine apart a few years ago that some idiot had kept blowing head gaskets and kept replacing them with cutter ring gaskets without surfacing the head.  There were witness marks from at least 6 cutter rings and they could not figure out why new gaskets did not hold.  They had also cracked the block around 7 0f the 10 head bolt holes (I'm sure because they used a air gun to run the bolts down without removing the oil from the holes first)   

1970 1602 (purchased 12/1974)

1974 2002 Turbo

1988 M5

1986 Euro 325iC

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First, I want to stand corrected on the head. the combustion chamber is not an E12, but a 121Ti machined out to the domed shape.

 

I will look up the Cometic MLS, thanks for the tip.

 

I too have seen those ( and friends to be un-named) who have not cleaned out the bolt holes, nor meticulous in their measurements when rebuilding an engine. Sad, because they just want the end result without taking the time to do it right.

 

Thanks,

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  • 2 months later...

Im sure it would make a difference in off boost performance. You will have to be careful about ignition timing and octane. I would also use a modern MLS head gasket and not the stock cutter ring gaskets. 

1970 1602 (purchased 12/1974)

1974 2002 Turbo

1988 M5

1986 Euro 325iC

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