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3.0 rebuild - what LEGAL mods can be made for PCA Clubracing

Let's say I was looking to rebuild a stock SC motor for PCA G or F Prepared. What are the typical things one does to ge the most out of the motor?

I have heard that, from a bolt on p.o.v. that SSIs and richening the mixture help, but are folks boat-tailing, knife-edging, porting & polishing and mooning the cylinders?

Thanks
T
Old 07-07-2005, 01:24 PM
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If you boat tail your case, moon cylinders, knife edge a crank, or port or polish ports your career as a club racer might be short. Nowhere in the CR rules will you find any of these as allowed modifications outside the GT classes. Since the base rule is that what isn't expressly allowed is prohibited, these modifications would seem to fit that rule nicely. And the scrutineers have a nice borescope to snoop inside the case or to take a look at the ports.
Old 07-07-2005, 05:10 PM
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Hiya, Walt.
Good to see you're still verticle.
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Old 07-07-2005, 05:25 PM
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I am not familiar at all with PCA rules but unless you intend to run at high rpm for a sustained amount of time monning and boattailing will be a waist. Port matching, flowing and polishing will be the biggest gain although wont do much without hotter cams and different exhaust but you will get something. Spend your money elsewhere on the car, suspension, tires, brakes, lightweight goodies.
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Old 07-07-2005, 10:08 PM
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What do the rules say??? If you are going to build a race car or a race motor, you should always start with the rules. They will detail exactly what you can or can-not do. Any opinions that are not based on the specific rule book of the intended class are uninformed at best, and will likely wind up wasting you a lot of time and money.

Now if you chose to ignore the rules or feel that for some reason they don't apply to you, that is something else again. Just don't expect to be well received by the other competitors nor the officials if that is the approach that you chose to take.

A brief glance through the PCA rules shows the following rules pertaining to "Stock" engines...

Quote:
As delivered from the factory. No modifications after the air filter or before the exhaust port.
This seems pretty clear. The only opportunity that seems to exist as it is worded beyond swapping out an air filter would be to reshape the exhaust ports and modify the exhaust systems. It's not clear to me that you'll be able to gain much in the exhaust ports without a lot of testing, so basically the intake filter and airbox, and the exhaust system are all free (as long as it meets local sound requirements). Everything else should be per the factory shop manuals.

Quote:
Stock for the year, fuel injection systems must be retained, except carbureters may be substuted for MFI.
If you're running a 3.0SC, this sounds pretty clear. The injection system must stay within the factory specs. I'm certainly not an advocate of replacing MFI's with carb in order to increase HP, but the option exists.

Quote:
Machining for balancing purposes is allowed
Generally, in the SCCA world this means that up to 5 of the 6 connecting rod assemblies may be lightened to match the 6th. This generally means searching through all of the available stock pieces to find the lightest unit to use as the 6th. Everything else is lightened to the lightest tolerance (if in fact lighter is better). Along those lines, if looser is better for certain tolerances, then pieces are selected which will provide the loosest assembly.

Air conditioning systems can be removed.

Oil coolers are free.

Swapping out a flywheel for a different model will bump you up a class to prepared.

Ignition triggers are free as long as the stock distributor and cap are used.

Quote:
Valve springs and retainers are free
Go for light weight or Ti valve spring retainers for a little extra over-rev protection and slightly less engine drag.

That seems pretty clear to me.
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Last edited by jluetjen; 07-08-2005 at 05:37 AM..
Old 07-08-2005, 05:16 AM
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Quote:
Originally posted by Walt Fricke
If you boat tail your case, moon cylinders, knife edge a crank, or port or polish ports your career as a club racer might be short. Nowhere in the CR rules will you find any of these as allowed modifications outside the GT classes. Since the base rule is that what isn't expressly allowed is prohibited, these modifications would seem to fit that rule nicely. And the scrutineers have a nice borescope to snoop inside the case or to take a look at the ports.
WOW! Walt is here! Good to see you posting here!

T- I didn't have a chance to call you back...
Old 07-08-2005, 08:11 AM
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You would never, ever, under any circumstances, regrind your factory cams to the DC15 specs.

Does anyone know how the PCA checks camshafts?
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Old 07-08-2005, 09:55 AM
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Walt, welcome to the board. Your experience is greatly appreciated here.

Michael
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Old 07-08-2005, 12:34 PM
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Quote:
Originally posted by camgrinder


Does anyone know how the PCA checks camshafts?
The old fashioned way. We used a degree wheel and a dial guage to check the lift and duration.
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Old 07-09-2005, 07:35 PM
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Basically, you can't do anything. The whole point of a stock rebuild is that it keeps the costs low.

I am sure there are people who cheat, but it's silly to cheat when the only incentive you have is your name in the record and a plaque that's identical to everyone else's.

John, you may not remove the air conditioning system. If you are racing an '88 Carrera in F, which was exported to the USA with air conditioning, you have to have the compressor and all the crap installed. You may cut the belt.
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Old 07-11-2005, 01:07 PM
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Oops. You're right John. The system must remain, but the belt can be removed. It's the air injection system that may be removed per para. 1G.
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Old 07-11-2005, 03:55 PM
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John (Cramer),
What about documented option delete cars? I have a 78 SC coupe that was delivered with one option (right hand outside mirror). I'm toying with making it a PCA stock class car - it may seem like a foolish question, but since I can't imagine any race organization asking you to put AC back on a track car that wasn't delivered with AC, I'll ask it. Why, when some cars were delivered without AC, would PCA require those that were to keep AC onboard when racing?
Thanks
Phil Van Buskirk
Old 07-12-2005, 12:52 PM
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Phil

Air conditioning was an option on SCs and earlier 911s back to whenever it was first offered, but it wasn't part of the base car. So you can run as an SC without any of the air conditioning equipment, whether your car came from the factory with it or not.

All the Carrera 3.2s (sold as US cars anyway) had air conditioning as part of the base car. So they all have to have all of the AC parts installed if running in the stock classes. Doesn't have to work, and yes you don't have to have a belt driving an unengaged compressor. But the stuff has to be there.

However, if you are worried there is one sure way to deal with rules interpretation questions: send a letter or e-mail to Lance Weeks (see PCA club racing pages on their website), who is the keeper of the rules. If you send a 40 page open ended what if letter, don't expect much of a reply, but if you focus on a single issue you ought to get one. I wouldn't bother him with this AC question for an SC, but at some point you may have a question whose answer is less well known (or on which you are hearing divergent views).

Walt Fricke
Old 07-12-2005, 01:09 PM
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Quote:
Basically, you can't do anything. The whole point of a stock rebuild is that it keeps the costs low.
I'm with you but I can't help wondering what goes into these $20,000 rebuilds that I keep hearing about.

Of course no one on this board would actually own up to doing any of these things, but I'm 100% convinced that there are a lot of 'stock' motors in PCA club racing.

I may be putting a 3.0 into my 74 to run as a SC in F so just wanted to know what should be done so as not to be at a disadvantage.

T
Old 07-12-2005, 01:16 PM
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Thanks Walt! I appreciate the info and the tip on Lance. I have a 70 E track car but since I own this option delete SC it also seems like a fun way to go - would have to sell the E though which would be hard to do - the SC will most likely end up a street rod I guess.
Phil
Old 07-12-2005, 02:15 PM
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Walt is exactly correct.

Tristan, the scrutineers have really been cracking down lately on "building" a car to specifications. If you want to run as an SC, your car must be a duplicate of an SC IN ALL RESPECTS (except, of course, the modifications expressly permitted by the rules).

The biggest issue that I see is tire width. SC's have flared rear fenders, whereas the '74 is a narrowbody. So you would have to flare using factory material to run as an SC in G-stock, and make all the other required changes to make the car identical to an SC, with documentation thereof. Probably not that hard to do given the similarity of the cars.

The real issue is, if you want to run in F Prepared-- you basically have to do everything in the Prepared rule book, including slotting the suspension for greater camber, big brakes, 3.8 RSR spoiler, flare the fenders to accomodate the widest rims permitted by the rules, etc., if you want to be competitive with the F-stock Carreras. By the time you got done doing that, you could probably buy an F car.
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Old 07-14-2005, 12:38 PM
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