Pure/ Hobby stock Motor

[bartx7001]

This up coming season the track has started allowing Headers. I run a flat top 9.5 to one motor with .390" .410" lift and open chamber head cut down to 70CC. The intake is a stock cast iron gm with a holly 500 CFM 4412. I would like to turn the motor 6600. No stepped headers and 2.5" exhaust. What size header should i buy? Should I get 1 5/8" or 1 3/4" tubes?

I also have two different intake to choose from. I have a 68 327 CI intake with the front oil fill hole. The ports size is smaller than the intake gasket. I also have an egr intake off a 1973 350 CI motor. The intake ports are the same size as the gasket. The 327 intakes plenium is 1/16 deeper than the 350 intake. I have not yet developed a method to measure the runner volume. Any feedback on what intake would be better.

Thank you for the feedback.

[dereksehi]

I would run 1 5/8 headers and use the intake that matches the gasket the best also be sure to block the exhaust crossover in the intake off.

[bartx7001]

I am allowed 3" collectors with reducers for the 2.5" exhaust. Is 1.5 still the best size?
They are four barrel intakes. The 327 intake is casting number 3919803. I will have to look and see what the other casting number is.

[bartx7001]

The other casting number I have is 3987771. What year car do I need to look for to get that "350" intake. I looked at a sbc chart and did not find one.

[ka_jd7and1]

250 intake casting, 76 to 82 pickups.