M43 Frankenstein build.

[ivanrcks95 3]

Hello everyone, dont know exactly where to put this but thought ill start here. I am currently thinking of doing a M42 head conversion on my M43 motor, this is a build that i have seen done before and its mainly done to gain the benefits of a twin cam on a block with superior oil squirters and knock sensors. I am just curious to find out whether anyone in NZ has done it before? If so ill be keen to have a chat and learn a few things. Current ideal situation is to take my M43 apart, find a M42 head, skim and port and polish the head as well as install some 256 cams, bolt it up to the M43 block, after this is where it gets a bit confusing as the thread ive followed supercharged theirs so they made a custom intake, i know i can use the factory ECU and sensors from the M43 just fine, but can the M43 intake set up bolt up to the M42 head just fine? Or will some changes need to be done in order for this to work? Or do i just run the M42 intake manifold and re route all the sensor wiring to that? Any help and advice will be appreciated. 

[Hellrot 325Ti 0]

In my opinion it's not worth the hassle, money and time involved. But I'd be a hypocrite saying that because I want to put an M47 crank in an M42 with some high-compression pistons, itb's and long duration cams and drop it all in a 318Ti Rally Car... Lol. Good luck with your endeavour though, keep me posted on how it goes!  

[ivanrcks95 3]

yeah I've been told this before haha but I've got a 2.8 swapped 316 back home that's getting a turbo and I'm kinda bored of 6 bangers haha, as of right now I know I need the crank sprocket from the m42, chain, tensioner and chain guides, the lower intake has to be m42 and upper has to be m43, exhaust from a 318is, the ecu and everything electrical stays the same, should all bolt up and run instantly, although finding a m42 head/good enough motor to part out for cheap is proving difficult.

[gjm 3258]

The pistons used in the M42 are slightly different to those in the M43. I don't know if the difference is significant enough to preclude using the 16v head on an M43.

[eliongater 718]

Wouldn't it be easier to build a m42/m44 hybrid?

[ivanrcks95 3]

as stated above the m43s have better oil squirters than the m44 and m42 as well as better knock sensors, m42s have better heads due to not being limited by emissions like the m44s were, so m43 block and m42 head is the best combo to use, from what I have read this is a bolt on build, should not require any custom work or odd parts, but will see. 

[ivanrcks95 3]

As for pistons, shouldnt really matter, compression ratios/bore/stroke is identical between the 2 motors. Only thing ive heard is early m42s had the 6mm stem lengths while later ones had 7mm i think, cant remember of the top of my head.

 

[aja540i 1906]

From what I have seen you wont be able to skim much, if anything, off the head before a valve kisses a piston, unles you cut bigger reliefs for them. The M42 has knock sensors and unless you are going forced induction the oil squirters shouldnt be necessary, why not just drop the M42 straight in? I have match ported and polished mine, there is a bit of room for improvement there, but the cams will make the biggest difference. I also made custom headers as the factory ones are a bit too small for my liking, and they always crack at number 4 pipe where it meets the flange. The 6mm /7mm valve stems diameters dont seem to make too much difference, but the 6mm ones leave a tiny bit more room for porting. Also, the valves are sodium filled so dont cut them in half! (Sodium can explode on contact with water)

Good luck

[ivanrcks95 3]

The simple answer to not dropping a m42 is simply because this hasnt really been done before, its kinda what ive always liked to do, the b28 in my car back home is a twin vannoss unit from a 728i, with full miller performance forged internals, AEM infinity ecu, VAC bearings, Volvo injectors from their 2.4L line of motors, married to a Schwitzer S2B turbo, all in a 1992 SA 316i why? Because no one else has done it haha, so i would like to do the same here. As for why i keep stating the oil squirters and knock sensors, is because this is going to be a track car, and ive heard enough stories of running bearings in the m4x line of motors as soon as you take them on track, so if i can reduce that risk by using the m43 block then good. I will look into the clearances between pistons and valves once i have the head on me, hopefully everything clears even with cams. Would start a build thread once i have all the parts in place, if all goes well it should be good referencing point for others who want to do a similar build.

[thorburn 121]

what does running bearings have to do with oil squirters and knock sensors?
+1 for what andrew has said. M42. Keep it simple
 

Good luck