Sport Mod Engine

[strykr]

Hey guys, a local track is starting up a sport mod class and I was wondering what would be a good engine to run. The rules state: OEM block cast iron only. Max cubic inch limit 390. Cast iron crank only no steel, no lightening, no knife edging or reducing of crankshaft circumference. Must have stock appearing rear crank flange. The rods must be of OEM design, IE I-beam rods. The rod length is up to builder. Pistons cast or forged, flat top or dished. No domed or gas ported allowed. No compression ratio is stated. Cam is hydraulic only, no roller, must pull 15 inches of vacuum at 1000 rpm, no 4-7 swaps. Heads must be unaltered OEM heads no vortec. No porting polishing or bowl work, must run stock size valve springs, stock steel stamped rocker arms. Poly locks okay. Any cast or aluminum intake, no porting or intake matching. Carb is a 4412 stock only. No grinding or polishing allowed. All carb components manufactured by Holley only. Distance between top of intake to bottom of carb no more than 1 1/4 inch.

[strykr]

Forgot to mention, I already have a stock bore 350 4 bolt block. 355, 358?

[rubbinsracin]

might take advantage of the cube rule by building a 383 or 377 with some doublehump/camel heads since you cant run vortecs. we run them on our motor and have good success with them with a 2bbl carb. we are at 11.1:1 with flat tops. do you have a compression rule?

[Verdoorn Racing]

I have no experience with hydralic cams and a vacuum rule, but I'd certainly think a 383 (4.000 bore with a 3.75 stroke) would be the best option.

[strykr]

had thought about a 383 but wasn't sure if it would have clearance issues because of the hydraulic cam. I thought a stroker like the 383 needed a small base circle cam. Also would a 500 cfm carb be big enough to run a 10 - 10.5:1 motor this big?

[rubbinsracin]

yeah a 500cfm carb will run that no problem. most of the stock car motors at our track our 406 with around 14-15:1 running a 4412

[strykr]

Just talked to the tech official at the track. He says that there is no max compression ratio. The pistons just have to be a dished or a flat top with 4 valve reliefs. He said that these usually yield around 10 to 11:1 compression depending on the heads. He asked what size engine I was planning on running. I told him that I was still undecided and he suggested the 383 as well. Looks like all your great minds think alike, so 383 it will be. Thanks.