cohare

I guess I should have said "safely". I have always said I would love for my 993 to rev to 8k (or higher!). I am assuming there is no easy way to do it but, lets discuss..

I have read the entire thread on the 9M heads and they sound awesome but, its sounds like they are more torque than revs. Has any one experimented with new cams, valve springs, lifters to get some more revs? (even a few hundred?)

Call me crazy but, I just love a high reving motor.

BobbyT

Be sure to post the pictures of your engine after you rev it to 8k...

Steve Weiner-Rennsport Systems

Great subject!

993 engines are limited by 3 main things:

1) Camshaft profiles dictated by emission compliance and compatibility with factory, single-throttle intake systems.

2) Intake manifold flow capacity.

3) Connecting rods and bearings.

Other components such as piston weights, valves, valve springs, retainers, exhaust, etc also play supporting roles.

JMHO, but you REALLY do not want to spin one of these engines to 7K without aftermarket rods and bearings. Beyond that, one really needs to do some extensive modifications to the oiling system for reliability.

Rev limiters are changed in software, however I will not raise this when I reprogram the DME unless I know the rods, valve springs and retainers all have been upgraded. To do otherwise would be irresponsible for the owner.

Hoep this helps,

cohare

^^^steve very informative, exactly what I suspected. I was hoping it was simpler like cams, valve springs but, considering I have not heard anyone do this I figured it was highly cost prohibative and it appears that is the case.

Again hypothetically, if one were to do rods, bearings, cams, valve springs, etc how high would the motor be able to rev? Sounds like this would be a 25k+ undertaking huh?

cohare

I said "safely".. I guess I should have said with out grenading the motor..

Steve Weiner-Rennsport Systems

Stock heads, intake and exhaust systems pretty much restrict HP to about 7K. RS cams simply bolster the existing RPM range,... . $25K is acccurte.

With an ITB or slide-valve system, the right cams, better heads, lighter pistons, all the above mods (plus the oiling mods), and an appropriate exhaust setup, you're good to 8200+. All that takes is a bunch of $$$$$,.... I know of one 3.9 litre race engine making 460BHP+, but that was quite expensive to do.

bobesser

Crank is good to 8200?

Bob

cohare

Now that you say that, I know of a race engine making similar power on the east coast, I know it started as a 3.6 not sure if its still is, slide valve system, etc. That engine cost a lot more than 25k to move it from an already strong 350-375 NA to ~450+ its making now.

The only way i would consider doing anything close to this is if I already had to do a top end rebuild.

Steve Weiner-Rennsport Systems

Well,..with the proper mods & GT-3R oil pump, yes. A 964 (thats what the RSR used) or GT-3 crank is really preferable, but the latter requires different rods and rear pulley arrangement.

NeufCentOnze

May be that is too simple, but why not buy a GT3 car or retrofit a GT3 engine instead?
996 GT3s are sort of affordable nowadays. Buying one is something I seriously have in mind and just waiting to save enough.
Chris

Marco8

My thought too, 996 GT3 simpliest and overall least expensive way to have a Porsche that revs to 8K!

Bill Verburg

Geoffrey Ring and Colin Belton build these 425hp 993 engines that will rev to 8k


As Steve says start w/ a GT3 crank and oil pump in a 993 block, build up from there, not cheap

matt777

Somehow I think I would prefer that engine or some variation of it over a 996 or 997 GT3.

Bill Verburg

+1

Stealth 993

That's interesting. I thought the rev limit was more a function of the valve springs & rockers. Funny that the lower end needs so much work. Given all this work, is there any power up there?

So it is the weight of the parts (rods, pistons, etc) or the strength? Stock, I thought the parts were really strong & well balanced?

Balance, cryo, shot-peen the crank, Pauter (or better rods), JE or some other forged piston? Do the GT3 TI rods work in a 993?

I would be totally happy with our rev limit, if we had a better power band.