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Old 11-21-2020, 08:28 AM
PamRichardson PamRichardson is offline
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Default Restrictor for Holley 600

All --

Whether or not the restrictor rule is passed by the BOD, I have been preparing for it. My engine builder has found a source for it, but he must order 5 of them at a time. I only need one, so, if you are interested in one, PM me and I will get it worked for you. The cost will be approximately $30+shipping.

Pam
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Old 11-21-2020, 11:48 AM
PbFoot PbFoot is offline
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Thanks Pam. I would be interested, but the proposed rule does not say what the hole size will be for a particular spec line, just what the max will be.

"The max diameter of the holes is 39.0 mm. unless specified in the individual carís specification line."

BTW, from my research 39 mm is a very odd size for a Holley restrictor plate.
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Old 11-21-2020, 12:49 PM
PamRichardson PamRichardson is offline
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Default Restrictor

I'm guessing that the one specified in the rule change is for all the carb cars at this point, since no carb car spec lines were listed in the rule change. I don't even want to think about the future of all this, but, I'd say that March 1, if the BOD passes this rule, the one that I'm getting will be required.

Pam
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Old 11-22-2020, 01:26 PM
MarkMuddiman MarkMuddiman is offline
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Restrictors make sense if there's a master plan to equalize a wide range of carbureted engines. It provides a way to allow any carb, getting rid of the ridiculous details on the booster and throttle plate screws. It also allows the weight penalties for >311 cid to be reduced or disappear.

But, forcing what is essentially a zero restriction on the current FP 4776 carb is needless hassle.
First, round up instead of down from the 4776 throttle bore to 40mm.
Then, use "may" instead of "must".
If and when, in whatever future, there's a need to restrict the 4776 for a particular car, put that in the spec line(s).
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  #5  
Old 11-22-2020, 03:02 PM
Scott Sanda Scott Sanda is offline
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I don't know shit about carbs, with the exception of side draft webers from my GT3 days.

However, My TA2 car used a flat plate restrictor, and several years ago they changed it to this:

https://allstarperformance.com/adjus...-1in-all26060/

I run a ford, so it uses a 4BBL carb style intake, specifically a edelbrock Victor Jr although it is fuel injected.

It seems to me that if there MUST be a restrictor, it should be this piece, since it uses simple drop in components that can easily be changed to adjust for whatever you need.

Just food for though, and a lot simpler than everyone making their own, or having a bunch of different ID diameter.

And, as Mark points out, you can then eliminate the entire section on measuring all the little crap in the carb, since this will control the flow regardless of what is above it.

Scott
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  #6  
Old 12-01-2020, 12:51 PM
Tim White Tim White is offline
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Where does one even find an 1/8" thick restrictor plate? As far as I can tell it will have to be machined, wtf.
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  #7  
Old 12-01-2020, 01:53 PM
jimwheeler jimwheeler is offline
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Yes. You would have to have them made and be certain that they are smaller than the mandated size, so that there is no chance of a tech failure. Then, when they decide it isn't small enough, you will have to have another one made, etc.
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  #8  
Old 12-01-2020, 06:31 PM
PamRichardson PamRichardson is offline
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Default restrictor plate, easy

Tim and Jim --

Just go to ebay and type in "restrictor plate for Holley 4150" and there are a bunch of old NASCAR ones for $15 plus shipping. None will have the 39 mm hole, but, will all be less than 1.5 inches (~39 mm), so you can order them and drill them out at your local machine shop or engine builder.

I have ordered one and shipped it right to my local fab guy. When ready, it will go out to the engine builder who has one of my engines that needs to go to the dyno.

What is really important is sending in a letter to the CRB with your opinion on this. Jim is right. Once the rule is in place, the CRB can make a change on the hole size within a month. Then you will need to go back to the dyno to figure out what jet sizes you need, because our carb engines don't have a computer to automatically adjust the air/fuel mix. That becomes a huge issue for ALL carb cars.

I talked to my carb person who worked on these with the NASCAR teams and he said for the carb cars it was a total disaster because the NASCAR teams figured out ways to get around the restrictor plate and, because of what I said before about dynos.


Pam
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Old 12-02-2020, 01:35 PM
jimwheeler jimwheeler is offline
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Letters to the CRB are not as critical as letters to the BoD. This is already out of the CRB and is on the BoD agenda for next month. The CRB sent this as a Recommendation, without asking any of us. Send the letter to the BoD.

BOD@scca.com
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  #10  
Old 12-02-2020, 03:26 PM
Ted Johnson Ted Johnson is offline
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Default Future

Am curious if they are taking this approach due to the now obsolete/unavailable edelbrock heads?

If someone wants to build a fp car right now what do they do? Head unavailable? Build an iron head motor?

If they open up the rules for any head with valve restrictions I bet the restrictor plate idea may not seem like such a bad idea.
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