With the proper springs , valveing and intake what is the highest rpm the M70 could sustain? I cant help but wonder espcially sine its so well balenced?
guesses anyone?

How big is the budget?

The revs are limited by the camshaft drive design rather than the valve train. 6400 is pretty much as far as I would like to go, and I wouldn't sustain that for long either.

8Tech, the S70 in the 850CSI can rev higher than the M70 in the 850i.

Stock the M70 can only rev to 6K RPM so it is not a high reving motor and personally IMO it is fine stock. Now if you could some how get two M50 heads to fit on a M70 than it could rev to 6,500RPM, that is what I am talking about!:D

if that is what you are talking about, be sure to Bring your wallet. Topic has been beaten to death on just about every forum out there.

*actually the "redline" for an M70 is around 5700-5800rpm. You want higher revs, buy a 4-banger.

:)

Some of the highest reving big horsepower big blocks (2000-2500 HP) were of chain drive design (SOHC FORD). They are not the limiting factor. Ramp design, valve lift (cam lobe) and valve train (roller lifters/cam followers) along with spring pressures dictate alot and valve float will kill it all. RPMs cost lots o dinero....make power down low where its useable and exploit the torque curve............

if that is what you are talking about, be sure to Bring your wallet. Topic has been beaten to death on just about every forum out there.

*actually the "redline" for an M70 is around 5700-5800rpm. You want higher revs, buy a 4-banger.

:)

I was going by what Alldata said "Max engine speed is 6,000rpm."

wow, 6000rpm wats that enigine sound like at those speeds

..like 2 inline 6's running at 6000 rpm.... :)
(sorry, couldn't resist)

Some of the highest reving big horsepower big blocks (2000-2500 HP) were of chain drive design (SOHC FORD). They are not the limiting factor. Ramp design, valve lift (cam lobe) and valve train (roller lifters/cam followers) along with spring pressures dictate alot and valve float will kill it all. RPMs cost lots o dinero....make power down low where its useable and exploit the torque curve............

Like my other dream car the 87 Ford Cosworth RS500 (moonestone blue) YB 2.0 DOHC motor (belt driven though) using a T4 turbo making well over 500 bhp, I think it was a stage iv motor with 8 fuel injectors and one big intercooler...

wow, 6000rpm wats that enigine sound like at those speeds

The orginial Transporter gives a good example of sound when he is driving the reverse in the opening chase. To me sounds like an airplane motor screaming.

..like 2 inline 6's running at 6000 rpm.... :)
(sorry, couldn't resist)

Man, you and Rod both.:rofl:

Actually the S70 motor has a stock redline of 6400 rpm in 1st and 2nd gears, 6200 in 3rd, 6100 in 4th, and 6000 in 5th and 6th.
In fact, with the speed limiter engaged, you can only get about 5150 rpm in 6th.
It IS the design of the chain drive that limits the rpm because the chain attempts to centrifuge outwards, putting excess loading on the guides and tensioner. The chain runs are too long. If you used a titanium chain then you could increase the rpm threshold.
Irrespective of cam design, valvetrain weight or spring pressures, all the normal things that affect rpm threshold, these will not help in this instance.

8Tech.

Switch from chain to Gilmer belts and go for it.............

The Rs cosworths are very quick as standard, the 4x4 was a ver popular car in the early nineties. The turbo charged 4 pot sounds quite rough however is an excellent rally engine.