2.7 valve options?

[James Renfroe]

Can 49, 41.5 911 SC valves be made to work in an earlier 2.7 heads that is 46, 40 valves? The valve stem diameters are similar, but the later valves are shorter. I can assume that the 2.7 heads are large enough to accommodate the larger valve seats. I haven’t heard of anyone using larger valves in the 2.7 assuming they were/are available. Thx!

[afterburn 549]

How much shorter are they???

[Tim Walsh]

why change the valves? The stock valves are more than enough to flow plenty of air into just about anything under 2.9L Do a search on valves and jluetjen and you'll get plenty of information on this. If I remember right, it's not the valves that are the restriction, it's the ports.

[James Renfroe]

Both the 930 intake and exhaust valves are about 4mm shorter. I considered the change because the set 930 valves are in better condition (having been remachined) than the valves I removed from my current 2.7 heads. If the new valves would work, I would like have new valve seats installed.

Thx for your imput.

[Henry Schmidt]

It is not possible to put 49mm in and 41.5mm exhaust in a 2.7 head.
The length is not the problem. The problem is that the valves will hit each other. The best we've been able the do is 48mm in and 41.5mm ex. The other problem with running these valves is replacing the seats. I can not explain why but seat replacement in Porsche heads seems to be failure prone. The reason I say that is because the only 911/930 seats I have ever seen fall out were replacement seats.
As for the length you can use a lash cap to bring the valve train back into specs.

[James Renfroe]

Henry,

Thanks much for you highly valued information!!!