M30 valves in M10?

[kronus]

Has anyone heard of this working? I have some M30 valves and an M10 head, and they seem to fit fine when mocked up, but I'm not sure if the shaft lengths are the same.

Dimensions on M10 valves: 46x8 intake, 38x8 exhaust
Dimensions on M30 valves: 47x8 intake, 38x8 exhaust

So if I'm reading this right and the lengths work out, M30 valves are an easy way to get +1 valve size in M10s.

[LJ851]

I just measured a pair of M10 valves and they are approx 104mm long.

[kronus]

Thanks! I'll try to get mine measured and update this thread.

As a note, the valves I have are M30B35 valves from a '88 635. IIRC the B35 valves are bigger than older M30 valves.

[SkiFree]

but I'm not sure if the shaft lengths are the same.
.

The lengths are different. Just had two of them in my hand not 5 minutes ago.

[kronus]

[SkiFree]

Sorry...... was like, should I or shouldn't I.

Sent you a potentially good PM.

[kronus]

As an aside, how much extra flow do +1 valves add, anyway?

I'm sure it can be math'd out to a fairly generic formula, but I am at work..

[SkiFree]

As an aside, how much extra flow do +1 valves add, anyway?

I'm sure it can be math'd out to a fairly generic formula, but I am at work..

I don't have the numbers in front of me. Generally speaking it's not worth doing unless you're going with a cam well over 300'.

EDIT: UNLESS your going turbo, then it is beneficial to go oversize on the exhaust.

[SA E30]

I don't see why you couldn't shorten the M30 valve shafts and new grooves retaining grooves into them.

[kronus]

For completeness's sake, M30 valve lengths are 108mm intake, 109mm exhaust.

[SA E30]

I'm really keen to give this a shot. I have to pull the cyl head off my m10 that is almost ready to go into the car. To open up the ports on the cyl head. So might as well try get this done.

[SkiFree]

I don't see why you couldn't shorten the M30 valve shafts and new grooves retaining grooves into them.

Technically you could, but to me its not worth the risk vs cost balance. Again, I would not do the +1mm on the intake side.

I can maybe understand in South Africa where shipping can be a killer.