Fly911

Steve Weiner and all!

Iīm about to build a high rev engine based on my 1987 3.2L Carrera with a standard 930 case. I have purchased the following "goodies":

-997 GT3R Crank (new), cross drilled, knive edged and ballanced
-997 GT3R oil pump (new)
-997 GT3 Pankl titanium rods (used 50 hrs in a 3.8 RS)
-997 GT3 intermediate shaft
-Fabspeed equal lenght headers and race muffler (from my 993)
-993 Air intake manifold and air filter (from my sold 993)

Iīm planning on either Jenvey ITBīs and RSR cams, or use the 993 intake with RSR 3.8 cams.
I will use LNE 102mm pistons/cylinders with leight weight JE pistons, wrist pin offset to match the titanium rods, and light weight wrist pin.
The original 3.2L heads, ported and polished and ceramic coated, twin plugged
-Dual coil pack or 12 plug distributor (please advice)
-Boat tailing the case
-Titanium valves (?) and retainers (!)
-LWF and clutch

My question to Steve and the others, what or where would the weak point be if I want 8000-8500rpm?
And how much Hp/Tq difference (and rpm range) would it be between the 993 intake manifold (50mm ID) and the Jenvey ITBīs (51mm ID)? Rocker arms? Could I use the original ones?

I look forward for some interesting answers!

Steve Weiner-Rennsport Systems

JMHO,...

You'll never see 8K RPM using that intake manifold,....

3.2 heads on a 3.6 or larger engine can be a liability when trying to get big power unless they receive a lot of work.

BTDT, and its all done by 7K; it was never designed for high RPM power and all the ITB's will do is provide excellent throttle response.

Further, there are MUCH better exhaust systems that will help, not hinder your quest for higher RPM performance.

Lastly, Ti rods are life-limited parts and thats why you got them with 50 hours. For street use where one rarely sees 6600, one sometimes gets away with such things for awhile, however operation over 7500 is discouraged unless they are replaced. The consequences are frighteningly expensive.

Like many things, there is a LOT more to this than meets the eye. If you do this right with a realistic budget, you will have the time of your life,...

Fly911

Steve

Thank you for your inputs. So what is your suggestion here? Modify a 993 engine instead? What is the limiting factor on the 993 intake? Or is it just the heads that limit rpm and power? Any suggestions for head work and valve sizes?

As far as rpm and weak parts, what other parts than the Ti rods would break or wear out first? Can I use the original rocker arms?

I have been playing with the idea of forced induction using a Rotrex compressor. Would that help the 993 intake to breathe better?

Iīm a little surprised about the Ti rods; I have seen GT3īs with 50k miles and thousands of high rpm track miles, and they are still running fine! What is the problem with the Ti rods? Will they break, stretch, bend or get deformed in some way? Please clarify!

Thank you!

Steve Weiner-Rennsport Systems

Are you building a race or street engine?

Personally, I'd use a 3.6 and your GT-3 crank, GT-3RSR oil pump, etc to start with. Heads, intake & exhaust are the biggest limiting factors, depending on what power level you are trying to achieve.

I'm not a fan of supercharging unless an engine is specifically configured for forced induction and that would mean using TT heads which are a different alloy.

Ti is a fatigue limited part in this application. Engines that never see 7K never stress these things compared to Cup & RSR engines that see 8K RPM to 9K multiple times each & every lap. Street GT-3's are limited to around 8K and rarely "live" there, like a race engine does. Timed-out Cup parts are not good candidates for engines that will be operated in the same RPM range.

I'd be installing new Pauter or Carillo rods of the same length.

Fly911

Thank you Steve!

Do you have any suggestions for cam shafts? What would the "wildest" cams be for the 993 intake, using an ECU that can to a certain extent compensate for rough idle and reversion? Would RSR 3.8 cams work? And for the ITBīs, RSR 3.0 cams?

You also mentioned in an earlier post that you know of exhaust systems that are "MUCH" better than the Fabspeed headers, please clarify. I thought the Fabspeen ones were pretty good...

The car will be a track/DE toy, not a pure race or competition car, but drivable on the street. I donīt mind rough idle and a jerky car at low speeds, and on my week end rides Iīm using ear protection...

Thanks again!

KaiB

Steve is a bit of a gentleman, so I will comment here.

You really want to get in touch with him about the newest of the Rothsport header/muffler systems. Trust me when I tell you that this setup can make a world of difference.

Pricy, but the absolute best for your build. Why spend all that money and time on getting fuel into the chambers - and not want to get it out with a system designed to do the job properly.

Steve Weiner-Rennsport Systems

You are quite welcome.

Without an ITB system of some kind, RS cams are the limit. Single-throttle, common plenum manifolds will not tolerate cams with much duration or LC's closer than 114 deg.

With an ITB system, you could use 993 RSR cams for effect. I would not use the old 3.0 RSR Sprint cams in any street application due to serious drivability issues. You MUST have good close-ratio gears for any of these,.......

I'm no fan of Fabspeed stuff at all. While I won't comment further, you can always call me for details.

Fly911

Thanks again Steve!

Iīm offshore Brazil right now, and I canīt make phone calls. But I will be back in Houston in a couple of weeks.