mark kibort

maybe i misunderstood the rules. I thought they are factoring in the displacement to the formula, and the only thing that is fixed is the 16 valve or 32 valve classification and 90 or 100 HP index.

8 valve???

mk

mark kibort

(3000/(6.0*90))*100=555 GT3

so, a 6 liter 2 valve hybrid would have 555 points, or GT3 at 3000lbs.

if this is the weight as the car comes off the track, its about 50lbs heavier than when both mark and i did speed GT world challenge. a very manageable weight. For GT3, if you could get a big bore 6 liter, using a stock GTS crank rods and custom 968 pistons with a coating , you would be golden! probably be a ripper!!!

Dennis K

I dunno. If sub-1:34 at 2004-era Laguna is required to win GT4 at Laguna, you're going need a lot of hp (500 rwhp?) in a 3042 lb car.

I took that chart from the PCA website: http://www.pca.org/clubrace/docs/200...Calculator.pdf

But as far as I can tell, your calculation is correct. For a 3000 lb. GT3 car, it comes down to whether you believe a 6.0L 16V or a 5.4L 32V will make more power. (90 vs. 100 hp/L)

atb

I get it now (finally), the displacement in the lower charts is just for a quick reference, its not part of the classing, the PI is determined by using the top chart which references only engine configuration and the number of valves per head or whether air/water cooled.

BC

The radiacal cams needed, as well as the lifters, are more available with the 2V configuration. Also its cheaper when you blow it up (and it will, sometimes, at 8500 rpm).

I think that this may be a good plan. But I would go with a stroker and lightweight everything, keeping as much torque as possible, since its still a 3k pound car that needs to get going.

BC

Wait - do these classes allow aftermarket EFI? Because if they don't this entire process is useless to talk about a wicked 5L 2V

mark kibort

im not convinced the 4valve heads are that much better, than the euro stuff and a little more cam. I guess proof is in with scots car. 5 liter Ljet with a 1.2" x 4" opening, puts out near 300hp, while the holbert engine has made as much as 335 but recently more like 310 to 315rwhp.

I would think that a 6 liter bottom end would yeild some big gains.

to your point, it would be a simple engine to do the big work on . an aftermarket ECU would be the key to take advantage of the 6 liter and the engine management without that crummy Ljet system to strangle the inlet with.

Mk

Jim bailey - 928 International

The engine must be an OEM Porsche...modifications are unrestricted but must run on gasoline.

BC

The 2V heads can use Ford Springs, Chevy Valves, or custom valves, and the cam has no gear on it - making reproducing them into bit bump-sticks easier - though you are still limited to the size of the bearings in the carrier - though - in thinking about it, you could increase the size of the bearings in the carrier with a sort of align hone I guess.

BC

OEM porsche, sure, but what about valves, springs, etc.

Gasoline? Or do you mean "Fuel available at a pump"

Because if they allow ethanol you could do like 13:1 compression or higher.

mark kibort

Is that block only, as anderson's motor is not too much porsche anymore?

where do they draw the line of what an OEM porsche engine really is?

mk

John Veninger

The basic "requirements" for the GT class is a Porsche block, Porsche transmission case and leave the floor pan alone from shock tower to shock tower. Almost anything else is "free".

The PI index is not ideal, but gives way to a few new ideas on how to compete with a 928 in PCA racing.

Jim bailey - 928 International

Rules say "gasoline"... the wheelbase is supposed to be the same and body is to be recognizable as a production Porsche based body ... But as John said pretty much anything goes as far as engine modifications on a Porsche block. so pistons crank rods valves cams engine management induction are all FREE ! as far as the rules are concerned . The ONLY limit is what you wish to spend.