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Carrera 3.0 - which crank and cams to use

Have finished stripping my 3.0 Carrera motor which I will rebuild with 10.5:1 c.r , twin plug heads and 40 Webbers to use in a car with a 901 box for a combination of road and track use.
Firstly the original crank from the motor is .25 undersize and I have no history as to when and "how" it was reground. I have read that many people dont like to use reground 911 cranks. Should I use this crank or a standard 66mm counterweighted crank - my budget does not allow the purchase of another crank. I like the idea of a 2.8 and it might not be a bad idea to limit the torque going through the 901 box.
Secondly, specially if I go the 66mm crank route, would GE80 cams be too peaky on the road - I am used to running smaller 2.2-2.5 motors with S cams on the road - or should I rather go with GE60's?

Robert
Old 06-04-2004, 04:26 PM
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Sounds like you are leaning toward the 66mm crank and I think that's a very nice option, especially considering that crank is probably in better shape.

I don't know the answer to your cam question, though.
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Old 06-04-2004, 06:10 PM
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Have a set of 2.0 rods for the 66mm crank - will this be the safer route to go?

Robert
Old 06-04-2004, 08:00 PM
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Wayne - are you saying that I must use the rods that originally belonged to the crank? 2.7 cranks are very scarce and pricey over here in Australia and even if I did manage to find one at a reasonable price I would then have to use the rods off my crank.

Robert
Old 06-05-2004, 02:09 PM
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The engine Porsche should have built.

ber911 you're in luck. You have the opportunity to build the best small engine Porsche never built a 2.8 short stroke engine (66X95). When they built the 959 they came close (67x95).
The crank and rods are designed with proper ratios, the big valve heads flow great for a 2.8. We built a 9.5 to 1 , twin plug 2.8 with slide valve that makes 315 HP on street gas. It will run 8500 rpm and pulls from 3500 rpm. On this engine we chose RSR sprint cams and believe it or not this car idles and is street derivable with slide valve injection. If you build this project with 46 Webers ( we convert 40 to 46 mm) there is no reason why you shouldn't expect near 300 hp.
We have never built this engine for a customer that wasn't overwhelmed by the result. Like a little puppy they almost pee themselves.
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Old 06-06-2004, 08:00 AM
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Thanks for the info Henry. I am pretty sure that I am going to go the 2.8 route. I assume that from what you found with the motor you described I should be o.k on the street with GE 80 cams - it seems it would be a pity to use cams that wont let the motor rev like it is capable of. Also should I get custom JE pistons made up to give me a 10.5:1 c.r or should I use standard 10.5:1 c.r pistons on a 70.4 crank which would probably give about 9.5:1 on a 66 crank? I am going to twin plug the motor as I have all the parts.

Robert
Old 06-07-2004, 03:02 AM
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If GE 80 cams are what you have , go ahead and use them. Remember this engine wants to spin. If you're not going to spin it, you might as well build a long stroke motor and trundle around like everyone else.
As for pistons, we have done both and actually a third option. We have built custom JE pistons for this application.I believe we have some in stock or if you email me, I'll give you the job number and you can have JE build you some.
We have also used 95 mm 3.0 RSR pistons. You're correct, it makes a little over 9.5 to 1. My favorite conversion was to use 95 mm racing Cosworth piston from Malvern Racing. They are a magnificent piece and the cost is not as high as you might think. This also gives you a CR of 9.5-10.0 to 1 and some very cool bragging rights.
Cosworth F1 stuff, How cool is that?
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Old 06-07-2004, 05:55 AM
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Re: The engine Porsche should have built.

Quote:
Originally posted by Henry Schmidt
It will run 8500 rpm and pulls from 3500 rpm. On this engine we chose RSR sprint cams and believe it or not this car idles and is street derivable with slide valve injection. If you build this project with 46 Webers ( we convert 40 to 46 mm) there is no reason why you shouldn't expect near 300 hp.
Henry,

This motor has intrigued me since I first read about it. Is the slide valve injection the key to the smooth idling and and power? When you say it pulls from 3500 RPM, what would you equate the sub-3500 RPM grunt to (2.2S, 2.7RS, etc.) What would you think about using a TWM ITB EFI system on this motor? Also, do you use stock rods or go with an aftermarket solution like Pauter or Carillo and is there any appreciable difference between using Euro Carrera heads, big port 3.0 or 3.2 Carrera heads?
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Old 08-09-2005, 09:16 AM
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