M40 - 16valve head??

Mon Aug 10, 2015 9:26 pm

I'm sure someone has asked this before but can you fit a M42 head to a M40 block? Want to build a 16valve 1.6 if possible. Can't just use a 1.8 as it'd be for competition use.

Failing that is it possible to destroke an is to 1600cc?

please note there's going to be machine work anyway so if it can be machined to work that'll do.

Thanks
ThosO

Mon Aug 17, 2015 12:05 pm

its entirely possible to fit a b16 crank to an m42, the issue arises with the timing chain on the m42 vs the belt set up on the m40.

Thu Aug 20, 2015 3:35 pm

Double check the bore sizes but the blocks are the same I know that much. So theoretically you could fit the M40b16 internals to an M42 block to take advantage of the head. You'd need to make sure the nose of the b16 crank can accept the chain pulley from the M42. What competition is it you're entering?

Thu Sep 17, 2015 8:53 pm

Thanks guys. Bore sizes are the same at 84mm. I thought I read before that there was a slight differences with oil galleries in the block or something to that effect. That was about 5 years ago so I'm slightly fuzzy on the details.

Looking to do rallying here in Ireland rix. Motorsport Ireland regulations mean that I've to complete 3 rallies in a class up to 1650cc. Hoping to build either an e30 coupe or e36 compact and ideally I'd like to keep it BMW powered. Only problem is the vauxhall and toyota boys are pushing a reliable 180bhp from their 1600's.

Thu Sep 17, 2015 9:42 pm

ThosO wrote: Looking to do rallying here in Ireland rix. Motorsport Ireland regulations mean that I've to complete 3 rallies in a class up to 1650cc.

And after the 3 rallies you can run over 1650cc? In which case I'd build an E30 or E36 with a 1.6 M40/M43 and run it as is for the 3 rallies and treat them as experience builders. Then bang a bigger engine in once the restriction of 1650cc is lifted.

Thu Sep 17, 2015 10:01 pm

Yes after 3 rallies you can go up to 3000cc (4 valves per cylinder) with the likes of an e36. Having said that there's a lot of very very competitive drivers in class 13 (up to 2050cc 4 v.p.c.) and class 14 (2050cc+ 4v.p.c.) these are the guys with 60-70K euro mk2 escorts and more skill and experience than myself so I'd prefer to stay more competitive in class 11r (up to 1650cc 4v.p.c. rwd). At least for a year or two to learn my trade and develop the suspension and the rest of the car.

Also this all depends on money, the 3 rallies have to be done within a certain time period and a slip up on the stages could put it back for a while as I'm not making big money.

Fri Nov 06, 2015 8:55 am

I am no expert so please feel free to put me straight.
What about using a m43b16 crank it runs a chain ?