Advice on 1987 Carrera Build

[Fly911]

After five years of going nowhere, I'm starting to rebuild my 3.2L Carrera. Rennsport in Sealy, Tx will do the job.

When I started the project, I was going to build a street legal track car. With very aggressive modifications. But things have changed, and I will build a Street car with modifications for the track.

I would like some expert advice, and general opinions about cam shafts and air intake choice. I'm building on the original matching # 930 block, and have already purchased everything:

997 GT3 crank shaft, cross drilled, knife edged and balanced
997 GT3 Pankl titanium rods, balanced to +/- 0.1 gram
997 GT3 intermediate shaft and cam gears
LNE 102mm "Nickies" cylinders
JE 102mm light weight pistons
Jenvey 48mm ITB's
Elgin race cams 324 degrees inlet and 318 degrees exhaust (can't remember lobe angle or lift)
Valve rockers machined for cams
Fabspeed RSR headers
997 GT3 titanium muffler
Twin plug heads, ported and polished, with 993 RSR valves, titanium retainers
Canems ECU with 2xBosh coil packs
G50 with GT LSD and shorter 3-4-5 gear

The car has already 930 brakes and full coil over suspension.

So the race cams will make this engine too aggressive for the street.

I'm also looking at getting a 964 aluminum intake with a bored out 993 TB and some other mods.

So my question is; with the engine being 3.746cc (Porsche calls it a 3.8L), what are the most aggressive cams I can have with a single TB plenum (and potentially a MoTec ECU)?

Will a RSR cam with 280/264 duration and 109 degrees lobe angle separation be too aggressive with a single TB, and reversion issues?

Would a DC44 with 264/254 duration and 112 degrees lobe separation work?

I know that for the standard 3.2L with Motronic, the 993SS (248/234-114) works, and is probably the most aggressive for an otherwise unmodified ECU and intake.

If I keep the ITB's, what would be a good (spirited) street cam (and occasional track use) be?

I look forward to hear the experts chime in!

[Jeff Alton]

What is the recommendations of the shop you are trusting to complete the work? Do they have thoughts on the parts you purchased for them to work with?

[Fly911]

Jeff Alton, Rennsport in Sealy Texas is doing the work. They are building anything from 911 race engines to 997 GT3 4.0L to 356, 914, 944, 928, etc, etc. Basically all kinds of air cooled and water cooled Porsches. Typically they are building pure race engines (like my original approach) and mildly modified street engines. My new approach is a very aggressive street engine. I would like the opinions and recommendations from people that have experience with cam shaft selections for aggressive street cars. With ITB's and with single TB plenums.

[targa72e]

Hi Fly911,
Plenty of info on big cams and ITB's, that setup generally works.

Winders on this fourm had a 3.6 built with DC43 cams with a common plenum. It was a race motor and would not idle under 2000 rpm.

911 3.6L Race/Track Engine For Sale

You might reach out to him for his experience.

john

[Fly911]

Thanks Targa72e.

The DC43 cams have a lobe separation angle of 102 degrees, that is probably the main reason for the 2000rpm idle. With that lobe separation angle you will have reversion om lower idle speed.

The DC44 cams have a similar duration, but have a 112 degrees lobe separation angle, very close to the 113 degrees of the standard SC/Carrera cams.

But the open valve overlap (that causes reversion) isn't only determined by the lobe separation angle, but also the duration.

And again, my questions to the experts here are:
Will a DC44 work with a single TB plenum with reasonable idle speed (900-1000rpm)?
And if not, what would be the next step down that would work?

[targa72e]

HI Fly
From other post his were DC43 112 lobe centers
3.8 RSR Camshafts in a 964 3.6

john

[jpnovak]

Warren runs a great shop. Ask for his recommendations.

I would not go with common plenum. These have known air flow restrictions and you would have a cam and rpm capacity that would exceed the flow of the 964 intake. Stay with the ITBs.


regarding cam overlap. most ECUs (including CANEMS and Motec) can be tuned with either alpha-n )TPS) or speed density (MAP sensor) load calculation. Some even allow for a blend of the two. You can run just about any cam you want as long as your tuner understands how to account for the difference.