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Turbo M10 Advice


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Hey guys,


My 2002 has blown a head gasket, I have not done a compression test yet, but I am losing coolant (no water in the oil though). I have been looking for a rebuilt m10 for sale, since its usually cheaper than to rebuild it my self.


I came across a guy selling a rebuilt m10b18 that he planned for a turbo build for his E30, but scope creep and all led him to buy a m20.


The engine has new stock pistons, bearings, oil pump, gaskets, fresh head with a regrind 290' cam.

The engine has the stock 318i inlet manifold with a m30 throttle body (why?), a custom built exhaust manifold and a unknown turbo (to me) he used for mock-up.


Engine never ran, and is fully assembled in his car at the moment. He is willing to pop the head off so I can inspect the internals.


Since the engine is mostly stock, I thought I could get it to run without a turbo with Megasquirt or something similar, and then when I want I can swop it into a different chassis and do a turbo build.


He wants about $550 for everything including a Getrag 240 gearbox, lightened flywheel, clutch, etc.


I have many questions, but lets start slow.


-Should I trust an engine that has not run yet, even if I can see the internals?

-I would like about 200bhp from the turbo'd engine, can stock m10b18 internals handle this reliably?


Please feel free to raise and concerns that I have overlooked.





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Since he was building this engine for a turbo application, he should have installed some pretty low compression pistons. (Factory 2002 Turbos had 6.9:1 pistons)  Since an M10's CR is primarily determined by the pistons, and not by milling the head, you should find out the pistons' CR--if they're really low, without a turbo you're not gonna be able to take advantage of the hotter cam and the EFI system.  


BTW, have you done a compression test on your current engine?  If you have two adjacent cylinders with low compression, it's probably a blown head gasket, but if it's just one, you may have a cyl head coolant passage that's eroded into the combustion chamber--not uncommon on M10 heads.  It's usually the one that's directly over an exhaust port--localized coolant boiling after engine shutdown gradually erodes the aluminum until the passage meets the edge of the combustion chamber.  A good machine shop can weld up the passage and resurface the head, or just find another head.  Cheaper and much easier than another engine.



Edited by mike
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If the engine is legit, that is a very very very good deal.  A set of stock pistons runs more than that these days.


With the 1.8i head, the stock E21/E30 pistons are good for a modern turbo setup- you should be able to run

about 1 bar of boost, and you'll still have decent off- boost response.  It's how I'd do it, if I was going 1.8l.

And yes, that should put you comfortably into the 200bhp range, with some expectation of durability.


The M30 throttle body is because the 1.8 TB is pretty small.  The M30 is pretty big- but it's not too hard to find

something in- between, if you need later.


I think it sounds like a gamble- but the stakes are very low, at that price, and you'll have a lot of fun parts to play with.


I'd buy it first, then pull the head off what you have- as Mike says, you MAY be able to put  a head gasket on, and 

go.  They DO sometimes simply fail from old age, especially the aftermarket ones.


buy it buy it buy it!!!





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Low compression pistons are only needed for very high boost applications. Modern engine management systems allow stock (if not higher) compression ratios safely. For a street car a high compression turbo motor feels fantastic; less lag and a broader power band. With modern engines 10:1 and 14psi of boost is not uncommon.

If the motor spins okay and everything checks out its a good deal. Tune the engine without the turbo. You may find it's powerful enough for your purposes. You can always turbo later, and it's safer to set up EFI without the added risk of boost.

M30 TB was likely used as the stock 1.8 TB is restrictive, especially in turbo charged cars. I would switch it out for one from an m20; the m30TB will not feel very progressive as it is far too big for a non turbo car

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Thanks for all the advice so far.

My current engine has 180k+ kilometres on the clock. So I think my engine might need a rebuild anyway. But if a gasket can fix my problems, i'd be very happy.

I think I am going to have a look at the engine that is for sale and see if the rebuild looks good, if so, I will definitely buy it. He told me that the turbo needs a new compressor wheel though, and that the head is from a 316i, but the bottom end is from a 1.8.

Are the 1.6 and 1.8 heads the same? I can't seem to find much information on the two.



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Search for the HSV turbo thread on r3vlimited or e30tech. This guy built an e30 318i drag car that made over 350 hp on a stock engine with an MLS headgasket and head studs. You should do both of those on whatever engine you turbo. I'd take the deal, even if there's something wrong with the engine the parts alone seem worth it. Then continue with your plan of megasquirt before turbo.

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