360 and X heads?

[68Valiant]

ok, i have a 360 motor, basically stock, with the exception of a mystery cam that the power band starts a 2000 rpm ( i think it's a MP 484 cam). I can get a set of rebuilt 340 X heads, with heavy valve springs that will support up to .500 lift, they have been cut for 2.08 intake, 1.60 exhaust valves. Will these perform better than my 587 casting 360 heads that are on the motor now? Will this raise or drop my compression at all? i was thinking of using MP thin head gaskets to boost up compression a little bit. Does this sound good? would it be worth doing in other words? the motor will have a 670 cfm holley street avenger carb on a edelbrock LD340 intake manifold and have 340 exhaust manifolds if that helps. Thanks for any input.

[freak007]

this sounds like a very solid setup,as far as compression goes,most 360s had the same head CC,so unless you have changed something on the engine(pistons,head gasket or heads shaved)the compression should stay the same...

[68Valiant]

Anyone? please help me out here!

[Stoga]

One question about the heads, they've been recut for larger valves, but has the bowls under the seats been opened up? They won't breath much better than the original size valves if the work under the valve seat hasn't been done. Also 2.08?
Thats a big block valve size, IIRC small block valve stems are different, you may want to check for valve length and other things before you just stick those heads on your engine. The main advantage the original X heads had was a 2.02 intake versus the 1.88 intake valve used on most 360 heads. The main value in X heads is for folks restoring a 340 car who need an original casting, thought I think in unported form, the X head is a bit better breathing than the later heads, just not hugely so. I'd look at those heads a little closer, 2.08 doesn't sound right, and would definetly have problems with being shrouded by the stock combusion chamber. Maybe they just mismeasured the intake size.

[rumblefish360]

They do have 2.08 sizes for small block heads. Some shops will grind them down to fit. If the head is modified, it'll depend on the level of work on each head. Valve size isn't as important as the work and flow capablitys of the port work in the head.
2.02 vs. 2.08 isn't that much when compared to the 1.88's. Thats a big jump. However I feel that 2.08 is really pushing the street issue.

[moparmikey]

Hey 68 Valiant! Got any pics of your car? I have one also. It's great to see them although few and far between as they are. Make great race cars. I've been told they are the stiffest of the A bodies. Mine is Kickass yellow, 470 BB, 10.51@126. Email me.

[68Valiant]

pics of all my cars are at http://photos.streetracing.org/moparmuscle

whoa i have never seen a yellow 68 valiant before, let me see pics of yours! Thanks for all the respsonses.