Help with Production Limited Prep rules

Tom,

Yep, that's a turned down stem.

Also, see how there are only two angles on the valve head? A backcut would add one or perhaps two more shallower angles where the valve seat surface meets the back of the valve. Right now there's a pretty sharp lip there, and it can disrupt the airflow. Making a couple of angles leading into the valve seat surface keeps the flow attached and increases airflow significantly.

MC

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Mark Coffin
#14 GP BSI Racing/Airborn Coatings/The Shop VW
Scirocco
Zephyr Race Coaching and Consulting
http://pages.prodigy.net/Scirocco14gp
 
Cool. More angles smooth the curve, creating better flow. Applied calculus. So I assume you can back-cut and turn down a stem. But you would have to bench flow the setup to see if/how it improves.

Thanks again. Time to go home.

Tom
 
Mark, 2 comments.

#1 You web link doesn't work.

#2 I don't think that "back cutting the head" is allowed in Limited Prep, but would be legal in Full prep. Just my $0.02 worth.

As far as reducing the diameter of the valve, between the valve and where it contacts the guide, that's in the grey area.

When we (VW's) get into the top 3 @ the run-offs, and start to get torn down, I don't think it's a problem until then.

When impound says "I want 1 intake valve, 1 exhaust valve, cam, 1 rod and piston" will questions start to be asked.

Good luck this year @ Mid-Ohio. I heard that your looking into a 1.6 motor (finally). Let me kow, I've still got all kids of 1.6 stuff in my shed.

I do agree that there are all kinds of loop-holes in the Limited Prep classifications.

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Tim Linerud
San Francisco Region SCCA
#95 GP Wabbit
http://linerud.myvnc.com/racing/index.html

[This message has been edited by racer_tim (edited August 27, 2004).]
 
It's a grey area, but I think the valves in question are legal. It depends on whether you consider the LP rules regarding IT cylinder HEAD prep as meaning the the bare, cast head, or the complete assembly. Since everything that Mark is talking about refers to the valve and not the valve seat, and since valves are in fact free as long as the base diameter is the same as stock, then it should be legal.

For that matter, I would think that a set of purchased 'Rimflow' valves would be cheaper than modifying a set of stock valves to achieve the same effect. One possible outcome of a protest would be a determination that it is a poorly written rule, and the result would stand but the rule would change/clarify the following year, similar to what Sargis went thru with the carb spacer rule.

[This message has been edited by Greg Gauper (edited August 27, 2004).]
 
For what it's worth, I agree with Mark about "any valve", as long as it's (1) ferrous; and (2) has the stock head diameter. I also agree that back cutting the head and turning the stem are allowed.

Maybe this will make it more clear. Mark also mentioned cutting a couple of additional angles into the valve. That would be legal. But, cutting additional, matching angles into the valve seat would not be legal, because the valve seat is part of the head.

I think part of the difficulty in understanding this concept is because IT folks are used to thinking in terms of hull assemblies, primarily with regards to update/backdate. That same concept of a "complete assembly" really doesn't exist in Production.

Thus, in IT, a "head" includes the head casting, valves, guides, keepers, seals, springs, rockers (if any), tappets (if any), cam (if it's there), etc. But in Production, a "head" is just that -- the head casting.

You have to look at it in terms of the full prep rules. In full prep, the head can be ported, it can be milled to any compression ratio, and any valve seat angles may be used. In limited prep, the porting is limited to IT specs and the valve seats are limited to stock (as in IT). The specs specifically permit milling to achieve the compression ratio, just like in full prep.

I believe this is what they intended -- an easy way to limit the full prep specs as far as porting and valve seats are concerned. The valves, keepers, valve springs and tappets/shims are separately referenced in the specs, so they must not be part of the head.

Finally, there is this phrase in the PCS section about what you can do do a head: "On engines which are restricted to Improved Touring cylinder head preparation, the cylinder head and/or valve train may be machined for clearance to install an alternate camshaft, and adjustable cam gears are allowed." I emphasized the phrase "and/or" to point out that the PCS considers the head and the valve train to be separate items. I believe that closes the case.


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...Don

[This message has been edited by hornerdon (edited August 27, 2004).]
 
<font face=\"Verdana, Arial\" size=\"2\">Don't blame US for ugly rumors that get started when you make veiled statements like that. </font>
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Mark,

How exactly was it 'veiled'? All I said was that it was an l-p HP (probably shouldn't have mentioned the class) car w/ converted brakes. Who's car it was, or what kind of car it was, were not germane to the question at hand. So, if you want to speculate as to who's car it was, or what kind of car it was, that's totally on you.

Don,

If you're back cutting the valve, you're putting more angles on it than are listed in the FSM, I'm not sure how this is legal. Also, the passage of the PCS you cite refers to maching for the purposes of installing an alternate camshaft. So, they've restricted just what type of machining that you can do. You can't justify machining on a part of the valve that has no contact whatsoever w/ the cam/tappet/lifter/etc., when it says you're only allowed to machine what is necessary to clear the alternate cam.

Mark,

You make a good case, and I guess it comes down to what the interpretation of the head is. Is it the bare casting or the whole assembly?

<font face=\"Verdana, Arial\" size=\"2\">Be sure to thank Bill for sharing your story.</font>
Click to expand...

Kiss my ass Drew! If you, or any other driver, have a problem w/ getting called to tech to investigate a potentially illegal component, that's your problem. I mentioned something that I saw that I questioned the legality of, and decided to not be specific about the car/driver. And from what others have posted here, the majority opinion is that it's illegal. I'm not sure why you wouldn't want something like this to be out in the open. But however you feel about it, save your strong-arm comments for someone else!

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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608
 
<font face=\"Verdana, Arial\" size=\"2\">If you're back cutting the valve, you're putting more angles on it than are listed in the FSM, I'm not sure how this is legal.</font>
Click to expand...
Well, of course, I'm falling very strongly into the camp that in Production, the head is the casting, so the valve is not part of the head. And, the rules say "any" valve that is ferrous and has the same head diameter, so I say you can make whatever cuts you want on a valve, as long as you don't reduce the head diameter.

<font face=\"Verdana, Arial\" size=\"2\">Also, the passage of the PCS you cite refers to maching for the purposes of installing an alternate camshaft.</font>
Click to expand...
You're correct, but that has nothing to do with the reason I cited it. I cited it because that rule clearly separates the head (casting only) from the valve train (valves, springs, keepers, tappets, lifters, rockers or what have you). If they considered the valve train to be pat of the head, they would not have had to say "and/or" in the rule; simply saying "head" would have been enough. My point is that if the head and valve train are considered separate entities in the cited rule, then they are different entities in all other rules, including what you can do to a valve.


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...Don
 
You make valid points Don. I'm still trying to understand the folks that justify the valves but not the brakes.

But this is just one more reason why the various CS sections need some major overhaul.

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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608
 
Bill, on the spec line under Brakes Alter.: With thE word "None" typed IMHU the word None means there are no alternate brakes. Meaning you SHALL use the brakes that came from the original manfacture. If there is nothing type under Brakes Alter.: you refer back to the PCS. If there are words typed under Brakes Alter.: that state specific brake types or sizes then you are allowed to use brakes to those written specs.

Look on page PCS-101 & you will find alL three items that I mentioned above.

Have Fun
wink.gif

David

PS: List a specific car manufacture & model & lets talk through it's brakes.
 
David,

I understand where you're comming from, but how about the case where only alternate front brakes are listed? Or where alternate rears are listed, but they are drums? Here's an example:

FP Triumph Spitfire (either Mk III or Mk IV)

Std. Brakes (F)9.0" disc ®7.0" drum
Alt. Brakes (F)9.7" disc ®8.0" drum, May use GT6 caliper as alt. front caliper

By your logic, this car would only be allowed to use either 7" or 8" rear drum brakes. Do you think Steve Sargis is running rear drum brakes? Ask Drew or his dad if they're still running rear drums (they have GP Spits, but they show the same alt. 9.7" disc and 8.0" drum).

I can see valid points on both sides of this arguement. The PCS clearly states that cars w/ rear drums may convert to discs. Nothing to differentiate a limited prep car from a full prep car, unlike the restricted suspension vs. unrestricted suspension.

To me, saying "factory spec at all 4 wheels" is no different than listing the explicit stock sizes. If anything, it saved people the time of looking up the brake sizes for all of those cars. And by the same token, leaving the alt. brake section blank is the same as saying "None". I don't necessarily see where either of those has bearing on the line that says all cars w/ rear drum brakes may convert to rear discs. Like I said, I'd be willing to chip in towards getting an official ruling on this one.

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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608
 
C'mon Kirk, you know you want to! Get that A3 classifieed as an l-p FP car and you're on your way!!! The lure of the dark side is strong!!!
biggrin.gif


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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608
 
No doubt the limited prep brake rules are open to some interpretation. I think the confusion starts because historically, all prod cars, including full prep, have been required to run factory spec at all 4 wheels with 2 exceptions: (1) if there are specific alternates listed on the spec line; and (2) they are all allowed to convert rear drums to rear discs within parameters.

So, for the limited prep cars to have "factory spec @ all 4 wheels" listed in the brake section of the spec line, the reaction could well be, "Ho hum, yeah, duh, what else is new?" But, here's the rub, and I think the controlling factor. For all Prod cars, the brake requirements are spelled out in the PCS. The alternates are in the spec line, and override the PCS. But, in addition, the limited prep cars have a specific limitation in the spec line that no full prep car has: factory spec @ all 4 wheels. Because the spec line overrides the PCS, the rear disc rule is overridden.

Follow this sequence:

* In the PCS, the brake rules are pretty well spelled out -- original calipers, alternate disc/drum material but with original sizes, rear drums can be replaced with discs, etc.

* In the Spec lines, certain cars are given specific alternates such as larger sizes for rotors/drums. This overrides the PCS.

* In the Spec lines, limited prep cars are restricted to "factory spec @ all 4 wheels". This overrides the entire brake section of the PCS.

In fact, if one wanted to question the wording of the limited prep restrictions, it would be interesting to ask, where does the brake system at each wheel stop? Does the "factory spec" include the pads? The brake lines? THAT would be an interesting protest -- slam a competitor for running a racing pad or a SS brake line!

So far, there's been pretty much a gentlemen's agreement that "factory spec" means IT level preparation on the brakes. In fact, the only limited prep car I've heard of running rear disc replacements is the report you made -- although, several people have threatened to test the rule.

Remember, it's even more limiting for the Spridgets -- some of them have to run with the tiny front drums they came with!
 
Originally posted by Knestis:
This is great - as a reminder why I would never go play the Production game. Eek.
Click to expand...

Aw, c'mon K. Unless you've been totally corrupted by the "do it this way" mindset of most educators, for a guy as smart as you the Mind Game of Prod rules is part of the fun! The rules were deliberately tilted so creative thinking is rewarded.

It goes both ways. In the case of the brake discussion, it turns out that the rules are probably more restrictive than initially apparent. But, in the case of the valves, it turns out that thinking outside of the box, and carefully comparing various parts of the rules, results in some pretty neat tricks that the average competitor may never imagine from an initial reading.

That's the very definition of Production. If you want everyone to wear dark suits and white shirts, race SRF...




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...Don
 
Originally posted by Bill Miller:
Ask Drew or his dad if they're still running rear drums (they have GP Spits, but they show the same alt. 9.7" disc and 8.0" drum).
Click to expand...

Yep, on both counts. Although alot of guys have gone to the disc setup with their full prep cars - I just haven't gotten around to it YET. My only point about the other issue you have with me Bill is that if you see or hear something about someone's car that's in the grey area, it may not be the best idea to post it on a public forum.





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#42 GP Spitfire
Member 289368
 
In the Spec lines, certain cars are given specific alternates such as larger sizes for rotors/drums. This overrides the PCS.
Click to expand...

Don,

I'll throw this out again. Based on your logic above, a full-prep GP or FP Spitfire would only be allowed to run 7" or 8" rear drum brakes. Ask Sargis or Allen if they're running rear drums or their cars.

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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608
 
Originally posted by Drew Aldred:
Yep, on both counts. Although alot of guys have gone to the disc setup with their full prep cars - I just haven't gotten around to it YET. My only point about the other issue you have with me Bill is that if you see or hear something about someone's car that's in the grey area, it may not be the best idea to post it on a public forum.
Click to expand...


Well there you go Drew. I posted exactly what the PCS says about the Spit brakes. By the logic that people are using here against l-p cars, the Spits aren't allowed to use rear discs eitehr. But others have, and you are planning on converting to rear discs. Something that I'm sure you and the others (as do I) feel is perfectly w/in the rules.

I can imagine the mindset that's going on. Something to the effect of
<font face=\"Verdana, Arial\" size=\"2\">Oh, it's a limited prep car, they couldn't possibly have meant to allow that.</font>
Click to expand...

And they may well not have intended to allow it, but I'm inclined to agree that the rules, as currently written, do provide for it. At the very least, as I stated above, you can make a good case either way. Although, I do beleive the case for allowing it is stronger, given the current rules.

As far as mentioning it here (or anywhere else for that matter), why not? My only fault was A) mentioning the class, and possibly B) mentioning the race. It was only after people began speculating and germinating rumors that it was Johannes Kraus, that I said it wasn't a VW. I never did say who it was, or what kind of car it was. Again, because I didn't feel it germane to the discussion at hand.

If anything, some of the comments here have shown that it's pointless to discuss gray areas of the rules on an internet forum.

And I still want to know how you figure I'm the bad guy for asking about this. Do you consider one driver that protests another the bad guy? Do you consider the tech official who DQ's a competitor because of an illegal part, the bad guy? Would you rather see someone get to impound at the Runoffs, only to be tossed because of something that may have been clarified sooner?


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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608
 
Originally posted by Bill Miller:
Don,

I'll throw this out again. Based on your logic above, a full-prep GP or FP Spitfire would only be allowed to run 7" or 8" rear drum brakes. Ask Sargis or Allen if they're running rear drums or their cars.
Click to expand...

OK. I spent some time with the PCS, and I see where you're coming from.

The PCS allows rear disc conversions if you have rear drums. I think we all agree about that.

The Spec lines override the PCS. We all know that.

The Spec lines for limited prep cars, in the column ""Brakes Std." calls out "Factory Spec @ all 4 wheels". Because the Spec Line overrides the PCS, rear disc conversions are not allowed.

The Spec Lines for ALL full prep cars call out specific dimensions for "Brakes Std."; these happen to be the factory specs, and are defined for all 4 wheels. While the method of listing is different, this is saying exactly the same thing as "Factory spec @ all 4 wheels". The difference is that they got lazy with limited prep cars and make the owners and tech guys look up the factory specs, instead of listing them.

However, because the factory spec dimensions are listed in the Spec line, they override the PCS, so NO one can convert to rear discs, unless they have something listed in the "alternate" column.

"WAIT A DARN MINUTE!" all the full prep guys scream. "The 'Brakes Std.' column is just a description of what is standard, and doesn't override the PCS! We can convert to rear discs!"

OK, reply the limited prep guys, "if the 'Brakes Std.' column does not override the PCS, then the 'Factory spec @ all 4 wheels' statement does not overide the PCS, because it's in the Brakes Std. column. We can convert to rear discs, too!"

Am I finally catching on to what you are saying?


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...Don

[This message has been edited by hornerdon (edited August 30, 2004).]
 
Hey - I like a good academic argument as much as or more than the next guy but I really don't like the idea that I need to spend racing budget, put a part on the car, then wait for a protest before I have a real understanding of the "truth." That's a different world than is arguing on the 'net and one for which I'm not ready.

Kirk the Wimp
 
Kirk, the only reason I converted by ITB VW GTI was for the opportunity to race Nationals. I also choose to run in other than IT groups because there tends to much less body contacts when you run with more expensive cars.

I'm not knocking IT, those were just 2 of my reasons to convert. Oh year, slicks are way more fun than DOT tires.

Small more here in San Francisco runs with SRF's @ Thunderhill and Sears Point, and because of the sound requirements, we still run with with Big Bore @ Laguna Seca.

Heck, the only body contact I've had was when we run with the SS and T cars.

It's just another "playground" with different people bitching about different technical things.

Same ol' SCCA stuff




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Tim Linerud
San Francisco Region SCCA
#95 GP Wabbit
http://linerud.myvnc.com/racing/index.html
 
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