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Author Topic:   Restrictor plates
Blackgold
Dirt Full Roller

Total posts: 71
posted November 24, 2003 05:57 PM  
we run a track that limits carb size to a 2bbl with no larger than 1 11/16 inch throttle bore. Most run the large Rochesters and they are to be stock in appearance and measurements. Some are wanting to run 4bbls. Quadrajets or 600 cfm vac. Holleys. I would like to know what size restrictor plate holes would limit these 4bbls to an air flow comparable to the 2bbls. What are your tracks doing? I think the airflow is a good way to equalize the different cube engines and keep the HP somewhat equal
Thanks, Black Gold

zeroracing
Dirt Forum Champ
Total posts: 1875
posted November 24, 2003 06:32 PM  
i would either consider restrictor plate, or i would consider a spec 4412 holley carb, and a spec ignition(like stock hei). the holley carbs should have to pass a tech like make a few templates to go off. the plate would be a good idea like a 2 barrel can run anything as long as it fits the bore, but a four barrel must run a plate. but you will constantly have to take off the plate in order to ensure people are not boring it out or anything. also a cam rule may be effective, or a head rule, or even a 305 rule with stock heads, that would cut hp to a good level, and make a pretty level field.

Blackgold
Dirt Full Roller

Total posts: 71
posted November 24, 2003 09:43 PM  
WE're allowed any engine. Most common are 327 to 406. Have to run stock heads.Most common are the double humps. Stock cast in and out, no center dumps. Any compression, any cam. With the 2bbls we've run 327, 355, 406. They all ran fairly equal, just had different rpm and torque qualities. The smaller engines were weaker on starts and restarts, but came on strong down the straights. The 406 was real strong on starts and fell off at the higher rpms. Had to run a completely different gear to fit each engine. My calculations look like four 1.2 inch holes in a restrictor plate might flow about the same as the 2bbl. Supposed to be an entry level low cost class, and some of the guys think that the Qjets would be cheaper than the big Roch. 2bbl. We're also required to run 70 series DOT tires on 7" rims to hold speeds down.

24s52
Dirt Maniac

Total posts: 122
posted November 25, 2003 08:05 AM  
I agree with the Holley 4412 idea. I have run it on several different engines with much success. Granted it was only a cruiser car, but a Pontiac 301, Buick 307, Olds 307, Olds 350, Ford 351w...All worked well and produced a win for us. Easy to jet, easy to tune. And I don't think the size of the tires will slow you down much if you get the set-up of the chassis and tires right.

racer17j
Dirt Forum Champ
Total posts: 5390
posted November 26, 2003 05:44 PM  
wow racers17j, your younger than me, for soom reason thought you were older.

Blackgold
Dirt Full Roller

Total posts: 71
posted December 04, 2003 09:27 PM  
Still would like to know what size holes a restrictor plate would have to have to limit flow to equal that of the stock Rochesters.
Thanks, Ed

Blackgold
Dirt Full Roller

Total posts: 71
posted December 04, 2003 09:30 PM  
Still would like to know what size holes a 4 BBl restrictor plate would have to have to limit flow to equal that of the stock Rochesters.
Thanks, Ed

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