Help with Production Limited Prep rules

Yes Don, I'd say you've got it. I also spoke w/ a friend of mine who's on the PAC, and he pretty much concured w/ my analysis. BTW, his opinion is that you cannot turn-down or back-cut the valves, as Mark suggests (in a limited-prep car).

Kirk,

You actually don't have to do that. Send the $250 to Topeka, and they'll tell you if it's legal or not.

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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608
 
Originally posted by Bill Miller:
BTW, his opinion is that you cannot turn-down or back-cut the valves, as Mark suggests (in a limited-prep car).
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Well, I guess if I was still building a car, I'd just have to buy some valves that already have a smaller stem and a different profile on the back of the head. My justification is actually in the limited prep spec line. First, the note talks about the head. Then, the manifold. Then, as an obviously separate issue, it sets the limits for valves, keepers, springs and pushrods -- they have to be ferrous. Other restrictions on head size are also in the spec line in another column. Then it calls out stock rocker arms and other components, which it wouldn't have to do if they were considered part of the head. And, of course, the cam is obviously considered a separate compenent and not part of the head, even with an overhead cam engine. Otherwise, the entire cam would have to stay stock except for the increased lift.

As I said, all this is in the Spec Line, so there are no questions about precedence like with the brakes. I'm absoultely convinced that you can take any valve and modify it any way you want, as long as the head diameter ends up as specified, and it is of ferrous material (no titanium). And, of course, as long as it still fits...
biggrin.gif



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...Don
 
<font face=\"Verdana, Arial\" size=\"2\">Well, I guess if I was still building a car, I'd just have to buy some valves that already have a smaller stem and a different profile on the back of the head. </font>
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Don,

Please tell me how it matters if you modify the valves yourself, or if buy 'pre-modified' valves?

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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608
 
That was an attempt at deadpan humor. You reported that your contact did not favor back cutting nor reducing the size of the stem, so I figured if the valve was already made that way, he wouldn't mind....I was just being a smart aleck...

Most of the PAC members are full prep folks who struggle with the limited prep stuff. Tim is the only limited prep guy on the committee and he takes a much more cautious and conservative approach than most. And, of course, no one on the CRB, nor most tech inspectors, nor the announcers at the Runoffs, have a clue.


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...Don

[This message has been edited by hornerdon (edited August 31, 2004).]
 
Actually, Brian Culbertson is also on the PAC.

I see the loop holes here. In LP on the car classification line, it says "Cylinder head prep to IP specs except that the head may be milled to achieve max. comp. ratio." and "Valves, keepers, springs, and tappets/shims to be ferrous-no titanium alloys."

IT Head prep is different than valve prep. So, I can see that back cutting the vales would be OK since it is not part of the "head"



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Tim Linerud
San Francisco Region SCCA
#95 GP Wabbit
http://linerud.myvnc.com/racing/index.html
 
Oops, I missed Brian. But, he can be as conservative as you, Tim. Not that that is a bad thing -- we need folks to keep limited prep from going down the same road as full prep.

In this case, I think the loophole was deliberate. I remember a discussion about this on the old volkswagenracer board, in which someone asked about using 7mm guides and valve stems instead of 8mm, if I remember the numbers correctly. Basil responded that the 7mm guides would be illegal, but threw very strong hints about accomplishing much the same thing in other ways -- such as the cutting of the valve stem where it doesn't go through the guide. Basil was on the CRB at the time and can be considered the father of the 2nd generation limited prep rules.

Basil threw in plenty of wiggle room in the limited prep rules, once telling me that no one would be really successful with a limited prep program until they had tested out at least 6 different cam configurations. This is because the cam rules are kind of impossible -- no one has ever designed a decent cam without also increasing the valve size, porting and using a different intake manifold...


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...Don
 
I agree Don. It was the 7mm vs 8mm valve and guide thing. I also don't think that the LP cars would be very competitive for a while, simply because the rest of the "status quo" who have been racing older british cars for years, and have spend THOUSAND's of $$$'s on them, wouldn't want to be blown away by a hot IT car (LP car).

I see both sides to this point. We need LP in order to keep participation at a decent rate, because not everybody can afford to buy and run a Huffaker Midget. But we don't want to piss the old guard that has been the backbone of SCCA for so many years.

The entire "stock box but internals are free" I see as the biggest PITA. We won't get any competitive adjustments until we spend $10k for a dog box with custom gears, ratio's.

This is EXACTLY why production got to where it is, and they are doing the same thing to LP.

I'd like to see other competitive adjustments instead of loosing weight. If LP was designed to keep the costs down, then why should we have to go with figerglass parts and Lexan in order to get the car down to min weight? I'd rather see other standard parts, like letting the "G" grind cam on the LP VW 1.8 motor. We would spend tons LESS development $$$'s with off the shelf cams.

Oh well, I'm only 1 voice in the wilderness, and sometimes I can't see the forest from the trees.

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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 31, 2004).]
 
Originally posted by racer_tim:
Oh well, I'm only 1 voice in the wilderness, and sometimes I can't see the forest from the trees.
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Tim,
You aren't the only one, you just live to far away to hear the discussions that go on at our house.
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Lesley Albin
Over The Limit Racing
Blazen Golden Retrievers
 
Although Tim is a small bore LP guy I will remind you that Tony Rivera, John Brake and myself are all LP racers also.
 
As I posted on the prod site, perhaps the rule would be more clear if the 'powers that be' deleted the words "IT head prep" from the rule and just keep the "no porting/polishing, port matched to 1" depth only, head may be milled ANY amount to achieve desired compression" and leave it at that.

[This message has been edited by Greg Gauper (edited August 31, 2004).]
 
Originally posted by eprodrx7:
Although Tim is a small bore LP guy I will remind you that Tony Rivera, John Brake and myself are all LP racers also.
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Yes, John, I thought of that when I said what I said, but this discussion has been about 2nd generation LP, which applied primarily to F, G & HP. There's Limited Prep (the first batch of EP cars), then there's Limited Prep (the EP Miatas), then there's Limited Prep (the Caterham), and then there's Limited Prep (the second generation). You're Limited Prep (first batch), and that's a different can of worms.

I stick by my statement that the majority of the PAC struggles with 2nd generation Limited Prep. I can accept that you are in the minority that struggles less. Follow any discussion on Limited Prep, however, and no matter who is responding, the predominant attitude is confusion.



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...Don
 
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