Dart shp short block- street recommendation?

[mep]

Looking for advice for a Dart SHP-based 400 short block. Will be used on street in a 57 Belair hardtop. Local shop said stay away from 434/427 with this block, stay with 415 or 421 motor. Overheating should not be problem: have Griffin aluminum crossflow with dual electric fans and temp switch. Beefed 700R4 and 9" with 3.50 posi. 770 Holley Street Avenger on Motown single plane. Cam is Comp Cam middle Thumpr, 235/240 @ .050, 522/509 lift hydraulic roller. Power band peak under 6000. Looking for torque, top end not that critical. Which way to go? Thanks. Mep

[cepx111]

Actually the 415 or 421 will be plenty enough for the street, I'd shy away from anything bigger than that for street use.

[mep]

Thanks. I'll probably go with the 421. Mep

[zipper06]

The only difference i see, is that i would go with a duel plane manifold, the single plane manifolds tend to be flat below 3,000 rpm and don't produce as much torque in the lower rpm range. the 421 will be plenty for a street engine.

JMO

Zip.

[mep]

Thanks, Zip. I was previously running this intake on the street on my 355 with 10.5 comp. It actually ran very well down low, although I suspect you are right in that a dual plane makes more torque down low. The intake and heads are already port-matched so I will probably stay with the combo. Thanks again. Mep

[oldandtired]

The only difference i see, is that i would go with a duel plane manifold, the single plane manifolds tend to be flat below 3,000 rpm and don't produce as much torque in the lower rpm range. the 421 will be plenty for a street engine.

JMO

Zip.

x2, heavy car needs the dual plane.
Dave