M42 Questions

Post Tue Sep 30, 2008 11:46 am

Hi there just after a little info on the M42 engine. I understand that the crank and rods are steel items, what sort of power are these good for? What are the pistons made of? Are they squeeze cast? What do the standard heads flow like? And lastly what CR do they run?

I am currently looking a getting a 318is as a second car and am thinking about turboing or supercharging to make it a little more lively.

Many thanks
Mark

Post Tue Sep 30, 2008 12:06 pm

Not sure about all the construction but stock CR is 10.1:1

I hear stock they're good for max 7200rpm. I'm putting, as at least one other has, an eaton m45 supercharger from a mini cooper on mine (recently rebuilt) and that should be good for 200odd brake at 7000. All on stock internals

Here's my thread if you want to follow it. Will be nice to see what you do to yours too.

http://www.e30zone.net/modules.php?name ... 01#1195601

Post Tue Sep 30, 2008 12:07 pm

Cheers mate just reading through appletrees one, too much info in there though!

Post Tue Sep 30, 2008 12:22 pm

Anyone know anything about the material used for the pistons?

Post Tue Sep 30, 2008 1:44 pm

MarkT wrote:Cheers mate just reading through appletrees one, too much info in there though!

Yeah - that project is awesome but the thread is a beast to read and digest. I've asked him to do a write up on it for the wiki, a condensed version of the thread and all relevant info but not heard back from him yet. Probably too busy burning out some tyres

Matt- are you reading this? - Where's my Wiki article?!?!?!

Post Tue Sep 30, 2008 5:44 pm

I know the crank is forged but I don't think the rods and pistons are, custom pistons (more to lower the CR than anything) with stock internals should be able to take a fair bit of boost, you could decompress by using a thicker steel headgasket though. Without decompressing the M42 should be able to take about 8-9psi without much issues as long as it's mapped properly, this could net you upto about 230bhp ish?

Post Tue Sep 30, 2008 6:42 pm

The crank and rods are forged in the M42. Not sure on the pistons.

Post Wed Oct 01, 2008 8:28 am

Cheers guys.

Thinking that a small bowl can poss be machined out of the top of the piston (depending on material) and using a thicker 2mm cometic type head gasket.

Post Wed Oct 01, 2008 9:40 am

Would be much better off spending circa £400 with TEP in the States and getting a nice set of forged pistons in whatever CR you want, giving you a nice forged bottom end. - I worked out that 8:1 compression with a GT28RS ball-bearing turbo and efficient FMIC could give a solid 250rwhp. Plenty!

Machining your own pistons might result in hot spotting, bad detonation etc, and if you're putting extra ponies down the bores it may be worth doing it properly.

Post Wed Oct 01, 2008 2:37 pm

I know what your saying mate. But unfortunately on a tight budget as I've just bought a house. Might just end up with a thicker head gasket.

These things with me are more enginering exercises.

Post Fri Oct 03, 2008 12:34 pm

Yes yes i'am reading this just been on my hols for 2 weeks ans now i'am bk i'am feeling alittle jet lagged.

I'll sort it

Post Fri Oct 03, 2008 6:07 pm

appletree wrote:Yes yes i'am reading this just been on my hols for 2 weeks ans now i'am bk i'am feeling alittle jet lagged.

I'll sort it

Just been on holiday and still complaining

No worries though dude. Whenever you get some time is cool.

sorry for the thread hi-jack... I dunno... mods today