August West

I'm in the midst of having the top end of my engine rebuilt to take care of oil leaks and to upgrade performance. My cams are being redone by Dema Elgin to his Super C2 cams profile. I will have the Fabspeed cat bypass and already have a g-pipe in place of the secondary muffler. I also have a K&N airfilter and the Fabspeed airbox cover. I have the Steve Wong chip but am also willing to dynotune/reflash ECU as well

I asked my mechanic about upgrading the valves to 993 valves and he mentioned as another option the Euro RS valves. He also mentioned titanium retainers.

Do any of you guys have an opinion one way or another as to which valves to use? What are the differences?

Thanks!

ALEX P

I've been going through exactly the same valve questions myself!

Maybe the link below could help answer a few questions.

https://rennlist.com/forums/964-foru...rebuild-3.html

Bill Verburg

All of the 993 valve stems are thinner than 964, so to use 993 valves all the guides must be replaced w/ 993 sized versions
964 including euro RS use ~8.9mm/stems, 49mm/42.5mm, intakes are sodium cooled

'94-95 993 use ~7.9mm stems, 49mm/42.5mm, sodium cooled intakes

'96 -98 993 use ~7.9mm stems, 50mm/43.5mm, sodium cooled intakes

993RS use ~7.9mm stems, 51.5mm/43.5mm, sodium cooled intakes& exhausts

the 993 heads also have bigger ports.

there are also aftermarket ss or Ti valves that can be used.

lots of guys build early 993 heads w/ the 993RS valves w/ good results, I don't know how much benefit bigger valves would give w/ the smaller port 964 heads

hockenheimr

Bill is the only difference between the early and late 993 heads the extra 1mm on the valves?

Bill Verburg

As far as I know, yes.
993 non vram valves are 43/39, vram are 50/43.5 these are sodium filled on the intakes, RS is 51.5/43.5 sodium filed on intake and Exhaust

all 993 valves have 8mm stems

The port size is 43/39 for all 993 except the RS/Cup and RSR which are 46/42

all 964 are 41.5/38 w/ 49/42.5 valves intakes are sodium filed
all 964 valves have 9mm stems

9146GUY

Not trying to hijack this thread but I have a set of 993 105 409 42 51.5 Intake Valves and 993 105 419 43 43.5 Exhaust Valves.
Both sets are new OEM.
These are the RS valves. They are left over from a project. 90.00 ea
PM if any interest
Thanks
Steve

prschmn

Unless you have money to burn I wouldn't recommend changing the valves. There's plenty of flow capacity with stock heads-ports. Most important for maximizing is a quality valve job. Ti
retainers are nice and shiney but alll they are really good for on a more or less stock engine is allowing slightly less seat pressure. Biggest impediment to flow is factory exhaust so I'd say spend your money there.

hockenheimr

I already have the late 993 heads and they have a valve job already done on them and the intake ports look to be ported slightly. I need sport springs and titanium retainers since I plan to move up the rpm band. While I am there, for a few extra dollars I am thinking it would be better to have the 993 RS 51.5mm intake valves.

prschmn

Your seats will have to be recut then of course.
Might want to ask Dema his take on it.

hockenheimr

Are the seats large enough? I was told the 95 heads only have 51.5mm seats.

Steve Weiner-Rennsport Systems

If you want the RS intake valves, you will need to install the larger RS seats as well. Its an expensive undertaking with little benefits unless many other things are upgraded at the same time.

prschmn

Yup-you need new seats-what I should have said in the first place.
Spend your money on a good exhaust.

hockenheimr

Thanks guys I just cancelled that plan.