Engine rev limit

[Oversteer]

hi!

I was just wondering what is the real limit of a standard M42 (E30 in my case), in terms of revs... It cuts around 6,5k but I believe it can take more, even in standard form, considering the forged crank and rods...

[swiss318is]

dont... the hydrolifters will destroy your valves and even the head... above approx. 7000revs
above this revs the hydros will get filled with oil more then normal and it can be that the valves touches the pistons... the springs are also not strong enough
change to solid lifters and stronger springs then you can rev up to 8 or 9000

it can go well without changing anything, it CAN... but it is only a matter of time

[Fergus1980]

Many people over here in Ireland and England use chips from a very reputable company. It raises the rev limit to 7200 rpm and no failures have ever been reported.

[Febi Guibo]

M42s can rev to 7000 rpms (heck, mine revs to 8000 rpms )

if you're super concerned about valve float, new beehive springs, M44 valves, and M50 lifters will do the trick.

The harmonic balancer issue of yonder also turned out to be a non-issue...

[swiss318is]

yes i am a bit concerned!! because i saw fully destroyed heads after reving too high! but maybe it was about 8000revs. anyway... i am going to change my hydros with solid ones! i hate removing the head... for things like that

[haledj]

M42s can rev to 7000 rpms (heck, mine revs to 8000 rpms )

if you're super concerned about valve float, new beehive springs, M44 valves, and M50 lifters will do the trick.

Why m44 valves? I thought ours were lighter.

[Febi Guibo]

M44 is a teeny bit lighter, narrower stem etc.

[sheepdog]

For short bursts, yes you can pass 7k. Above 7k, power drops dramatically anyhow so there is no point unless you change the cam, at which point everything changes.

Keeping it there for even short periods on a stock bottom end though is not recommended as it has been deemed not built to take it. Forget the lifters, the oiling system is not good enough for the lower end bearings at those revs.

[1991318is]

For short bursts, yes you can pass 7k. Above 7k, power drops dramatically anyhow so there is no point unless you change the cam, at which point everything changes.

Keeping it there for even short periods on a stock bottom end though is not recommended as it has been deemed not built to take it. Forget the lifters, the oiling system is not good enough for the lower end bearings at those revs.

HAHA, learned that the hard way, kept up w/ some e36's I shouldn't have, but my number 2 rod bearing was laying in the bottom of the case when I came out of a few corners.

[Oversteer]

So, 7K is the limit, right?

[sheepdog]

So, 7K is the limit, right?

Yes, and with stock cams useless to exceed.

[swiss318is]

yep! except you want to turn the inside of the engine to the outside!

[conlethryan]

i chipped my car a year and a half ago and it revs to seven thousand no problem and it hits it allot

[Boyracer]

It's hard to give definite rev limit for stock lifters, springs or bottom end but 7000 sounds bit too low. There is always some safety margin built into the engine to allow for springs loosing their stiffness with age or occasional misshift.

Higher rev limit can be beneficial on stock engine even if it does not increase power. On my favourite track there is two places where I need to upshift for few seconds, then almost immediately downshift before entering a turn. That is 4 pretty useless gearshifts which could be avoided if I could stay on lower gear for few hundred revs longer

[Oversteer]

Higher rev limit can be beneficial on stock engine even if it does not increase power. On my favourite track there is two places where I need to upshift for few seconds, then almost immediately downshift before entering a turn. That is 4 pretty useless gearshifts which could be avoided if I could stay on lower gear for few hundred revs longer

I know what you mean!;)

i chipped my car a year and a half ago and it revs to seven thousand no problem and it hits it allot

What chip are you using? I mean brand...