Originally Posted by jock
Has anyone had personal experience with running 2v open chamber heads with stock ports and valves.
I am building a 351 Clevo, cam 214 deg @ .050"; .500" lift, stock 2v dual plane manifold, 600 or 750 vac sec carby, currently has 4v exhaust manifolds.
Car is XY sedan, FMX 1800 - 2000 stall, 2.75 gears.
The intention is for a mild usable street car which doesn't guzzle heaps of fuel. I was hoping for about 330 hp.
Do 4v valves make any difference to performance?
Do the heads need to be ported or can I leave them stock?
Thanks for help Jock
I ran factory 2V OC heads on a '71 Ranchero (ute) with an "RV" camshaft of about the same specs as you're describing. However, I ran the factory 2V inlet and a larger Holley 2V carburetor.
The "trick" is to leave it bone stock except as follows: before changing out the valves to good 1-piece valves, (while the old valves are in place) polish the combustion chambers until they glow in the dark. Start off with something like a 120 grit sand paper "flapper" wheel in an electric drill and go like mad. Smooth everything out. (Leave the spark plugs out and the stock valves in!)
Move up to about a 220 grit wheel after everything is throughly gone over with the 120 and do it all over again. (Much easier this time)
When the chambers look like mirrors, take the heads down to the local head shop for reconditioning.
Have them rebuild them with hardened seats in the exhaust and blend the bowl transitions to the ports. Use a good 1-piece valve and springs suited to your camshaft choice. I usually recommend having the head shop convert the heads to screw-in studs and guideplates, but your application probably does not require it. I haven't built a V8 engine without roller rocker arms in so long that I can't remember it.
I don't think that you need more than a 600-650 carburetor. In fact, a spread-bore might be a better choice if you can find one and an inlet manifold to suit.
I would recommend moving to something along the lines of an Edelbrock Performer inlet manifold. The stock manifolds are certainly nothing special. An "air gap" manifold is preferred.