M30 needs a rebuilt?

[Luca318is]

Hi all, I just bought an M30 to put in my 320i, but it isn't in good conditions... the donor car, a 735i e32 had 300k km, i cannot test if it runs, so i removed the head and measure the cylinder bore. I found on the net that the tolerances for the b35 cylinders is from 92.00 to 92.01, it's allowed another 0.01mm in out of round and 0,01 in conicity. My engine has cyl 1 and 6 with 92.045 measuring the bore from left to right and 92.03 measuring from front to rear of the engine. Pistons are clean, only the head is dirt of oil over cyl 1 and 6. Valves are clean too. crosshatching is good until 2cm to the top of the block, where the walls are much more smooth. I'm not experienced with such this measures, so i don't know how bad is this engine, i would like to know if it's better find another or if this one is still in good conditions. anyone can help me?

[Luca318is]

maybe i found a jetronic m30b34, anyone knows if my b35 head fits on the b34 block? that will be great because i will join high compression (10:1) b34 block with big ports of b35 head and motronic injection!

[Luca318is]

some news:
I get to a machine shop and i also asked a tuner and they say my engine is still good also if out of tolerances. So now i bought a new piston ring set, new main bearings (axial crankshaft play was excessive) and a new head gasket set. I will re-hone the block using a 3" and 3/4 flex hone and then put all this new stuff inside... i'm quite curious about what will came out!

[gareth]

at 300,000km, it's barely even run in
mine has the same mileage and the original cross hatch honing marks were still present on all bores, no cam wear, valves all clean and lovely!

incidentally, i skimmed 1mm off the head (M30B35) to increase the compression from 9:1 up to 10:1 and then without any other modifications or rebuilding it made a healthy 220BHP and 323Nm of torque that was without correcting the cam timing either, skimming 1mm retards the cam timing 1°

[e30topless]

hone it, new rings and shells ... should be good for another 300k

[steve_k]

sorry for going of topic slightly but does anybody know how much it would cost to have the bores on a m20b25 honed?

also the cost of a new set of rings & shells for the same lump?

[Luca318is]

i bought the main bearings set for 50$ for the m30 and the rings made by goetze (one of the best brands) for 99$
for honing the engine you only need to buy a flex hone, always on ebay.com you can find them for 50$ shipped, then you need just a drill and in a half hour you will have a perfectly honed engine.

thanks gareth for the info, so i should also lower my head about 1mm to increase compression, right?

[gareth]

I would, it may be worth checking clearances with plasticine first during a dummy build but it worked well on mine

[Luca318is]

ok thanks!