308s vs Magnums

[racingsnake440]

On a 9.5:1 compression 360 with a comp cams 268 and 340 exhaust manifolds, any idea how much power unported magnum heads would be worth over unported 308s.

thanks

 

[MoparMan_1]

Not much as long as the compression ratio remains the same. It sounds like you are planning a pretty mild build.

The differences in the 308 and Magnum heads are mainly in the combustion chamber size and stock rocker arm ratio. The Magnums will flow slightly better stock and do have a more efficient combustion chamber.

 

[6t8 Dart]

I am planning a fairly mild/econo build of a 360 for my Dart; I talked to a machine shop owner I have known for years and posed the same question about the heads- the magnum is a better head, but the involved adaptation of the magnum head to the '92-down block is more trouble than it is worth in this application. Money-wise (at this performance level or lack thereof in some eyes), I was told to have my 308s' gasket matched, just cleaned up abit, and a good rebuild (multi-angle valve job, heads milled, MP springs w/ dampers, etc; standard fair stuff). Then I'll be on par w/ the magnum head for less money :salut:

 

[D-mailman]

6T8Dart, you are on the right track. Looks like you are building a mild motor (torque). Bowl port and blend, good 3 angle valve seats and don't forget to do a light mill cut on the decks, and back cut the valves 30 degrees. You will have a better than stock Magnum piece and for so much less money and hassel. Good luck, Terry.

 

[moper]

I think if you have a set of both, I'd run Magnums. You'll need new pushrods and lifters, which are off the shelf parts. You should be buying new ones of both anyway. You'll neeed to have the holes for the intake drilled for the std LA intakes, or buy Magnum or combo intakes. Everything else is the same. If you're careful, you can even use LA style valve covers to hide them. The exh port is better in stock form , along with the better chamber, and higher velocity intake port/vavle. The biggest issue is having a set of Magnums that arent cracked. If you are planning to go faster on the same heads later, then I'd run 308s built with Heads' ideas.

 

[racingsnake440]

Why not do the same modifications to the Magnums and have a better head yet?