More hp out of a 930/10...

atelier14 · 12:52 AM

Hello,

I have a newly rebuilt 930/10 Euro 204hp SC engine and because smog laws are not an issue on historic cars here in Europe I have put some newly rebuilt Weber 40 IDAs and 1 5/8 headers on it. The CR is 9,8:1 with the standard CIS pistons and its equipped with 911 E-cams and single ignition. It still has the small 34/35mm SC heads.

It currently has 210hp with this configuration and I want to try to get perhaps driveable 230-240 hp out of it during a winter top end rebuilt on heads and perhaps P&Cs. The car is light at 2100 lbs and will see 70% fast road and 30% track use.

Some questions do arise:

What do you think I should add beside a DC40 cam? Would porting to perhaps 38-39mm intake diameter make sense with the standard displacement, the 40 IDAs and the DC 40? Would perhaps adding 98mm P&Cs make sense with the 40 IDAs (do not want to switch to 46mm PMOs etc).

Many thanks,
Christian

Flat6pac · 09-23-2009, 04:13 AM

The 40s will be too small, theyre usually too small for 8.5 3 liter
Bruce

atelier14 · 09-23-2009, 05:48 AM

Bruce,

I do not think the 40 IDAs are generally to small for 3.0L displacement - it will mostly depend on the cam profile and ports.

During the dyno session of the 3.0L SC-engine with E-cams mentioned above, we made nearly the same top end hp with 34mm and 36mm venturis. Finally we did choose 34mm for a better low end response and torque.

So there seems to be room for a DC 30/40 cam, porting and (perhaps) 98mm P&Cs.

Cheers,
Christian

atelier14 · 09-23-2009, 10:20 AM

Any further input to recommended top end changes of my 930/10 for my hp goal would be very much appreciated!

Many thanks,
Christian

Shaun @ Tru6 · 09-23-2009, 03:37 PM

Christian, if you end up wanting to sell your set of P/C, please let me know.

Eagledriver · 09-23-2009, 04:15 PM

I don't know how you can get cams like those to work with the CIS pistons. The pistons should hit the valves. As Bruce said the Weber 40's are too small for that engine to make it's full potential. It will drive nicer with 40's but you are leaving at least 10 HP on the table. The intake ports need to be opened up. You can get 230-245 HP depending on exhaust with 46mm carbs, 39mm ports and stock SC cams.

-Andy

atelier14 · 09:50 AM

The engine currently runs CIS pistons with CNCed notches to clear the valves with the E-cams.

Thanks,
Christian

beepbeep · 09-24-2009, 10:02 PM

Have you tried to play with ignition advance?

If you want substantially more power, I believe twin-plug, higher C/R JE pistons and more radical cams would be in order. Also, a dyno session and proper mappable ignition system would be of great help. Twin EDIS-6 and Megasquirt II could manage the ignition and you could keep the carbs.

CliffBrown · 09-25-2009, 10:30 AM

Quote:

Originally Posted by atelier14

The engine currently runs CIS pistons with CNCed notches to clear the valves with the E-cams.

Thanks,
Christian

I think notching the pistons results in a larger combustion chamber.

How did you keep the compression ratio from getting reduced after notching the pistons?

atelier14 · 09-28-2009, 12:12 AM

We measured the CR on one head and came out with 9,8:1 CR with slightly reduced deck height - The notches are not very deep.

I would not like to upgrade to 46mm PMOs. So it seems the general suggestion is to stay with 95mm P&Cs with the 40IDAs and do some porting to 38/39mm to the intakes and perhaps a DC30 cam?