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Restrictor plate and 2bbl carb

4K views 3 replies 2 participants last post by  BadMonkey 
#1 ·
Has any one had to use restrictor plates. I race on a 1/2 mile dirt track and they have new rules, any flat tappet cam-no rollers or solid cams. No vacuum or idle rpm rule but now they are getting some restrictor plates that we will have to run. I don't know what size they are yeat.
351w 4412 holly stock 2bbl intake, stock exhaust manifolds, manual trans, run in second gear, 8.8 rear axle 3.55 gear the final is about 6000 car is 3500 lbs with driver. rpm range 2200 t0 6000.
any one have any advice on how to build power with restrictor plates and 2bbl carbs?
 
#3 ·
you need lots of compression to help in the power dept.A 2 bbl lowers the density of the air fuel charge lowering cylinder pressure and the way to get some back is with compression.You can run much higher on a restricted engine with the same fuel vs an open engine with a 4bbl.It kinda works like this a 12.5 to 1 engine will idle fine and run with no load with 87 octane but put a load on it and it will detonate itself to pieces.Same principle with the 2bbl you just can't get enough mix in to create pressures high enough to detonate assuming race fuel.Most good 2bbl. engines are in the 14 to 16 to 1 range.You just can't nail it in high gear at low speeds have to be coming out of the corner about 3000 to 3500.Cam it to run between 3500 and 6000 and gear accordingly.It is ok to run out of steam halfway down the chute you generally want to be 500 to 700 rpm past peak hp when you lift to set for the corner.Remember the race that pays is the one from turn 4 to the flag stand it is the one you want to win.
 
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