I have an early set of race w2 heads. They appear to be the early factory ported versions
(1977). I am getting them flowed currently with factory 2.02 and then plan on getting new intake valves.
What is the potential gain by adding a 2.05 or 2.08 valve and corresponding work to take advantage of the bigger valve. I am trying to decide if it’s worth the effort. Thanks

I’d like to add that this is gonna be a pump gas 408 with a .580-.600 lift solid.

I easily got 308 cfm out of my econo W2 heads with a 2.02 valve. I would have loved going to a 2.08 valve BUT I was only running a racer brown .520 lift solid cam and the heads were set up for 3/8 valves and I didn’t want to spend the money to upgrade them. Luckily I didn’t because they cracked. That 408 engine ran 9.80’s on BP93 pump gas at 2840 pounds.

I would look at a 2.05 valve for the intake and a 1.500-1.550 exhaust and use a known good 50* seat on both sides.

Without sonic testing I wouldn't use a 2.08 and a 50* seat. Plus, you'll get the bowl so big you'll have to make the port square to get enough area to feed the valve.

The 1.600 exhaust is a bit big, unless someone has blown the bowl out on that. Then you are stuck.

I'd flow the intake at 28 inches and then again at as high as the bench can go and look at the numbers. They are what they are.

Flow the exhaust and port as little as you can to make the port quite. What it flows is what it flows.

M


Boy do I agree with cranking the bench up. I’ve bumped my depression up to 40 inches when I’m leaning on something searching for more flow. I’m glad I don’t charge myself

I am still wondering what I could gain in flow and would it be upper lifts where it wouldn’t matter? I don’t want to go through the trouble to gain 5cfm. Anybody?

It’s unlikely there would be big gains by doing nothing other than changing the valve sizes.

Even with a 2.02 valve they can have turbulence issues unless someone has profiled the short side radius.
If they are only marginally hanging on in the high lifts now, a bigger valve will probably just induce turbulence(or have it occur at a lower lift).

As with just about everything flow related....... there’s only one way to know the answers to your questions....... about your heads.

I stopped worrying about a port that has turbulence issues a long time ago. Obviously you do what you can to eliminate or control it, but I don't select cam lift by where the port goes turbulent.

I can make that happen at .250 lift.

The best you can do for them is fit the short turn, clean up the guide and get the valve job correct. The rest will take care of itself.

Ok lets try this again. If you go to a bigger valve size and to not touch the port its a waste of money. It would be like peeing into a bigger funnel with the same outlet. bigger valve take a bigger throat. Throat size is APPROXIMATELY 89-91% of the intake valve size, slightly bigger on the exhaust. This increases the velocity speed at the venturi. Sizing must be done to see gains. To little no gain, get greedy and you TRASH the head. As far as turbulence that is mostly cured by poor shaping and lack of required area and should be addressed. 28 inches of depression is the industry standard but last I've heard nobody is sure exactly how high the depression is in a running race engine but it is suspected to be MUCH higher.

Shady dell thought going to a larger valve on our ported W2s would only be worth a small handful of horsepower. They flow 320 with the 2.02 valve.

This is excellent.

Viperblue72, IMO, it is a lot of work for only a little gain. It would probably be a positive move. The larger valve has (of course) a larger radius area for a larger curtain for more air and fuel flow. While it is marginal on one hand, it is the old case of moving faster Incrementally.

The other thing about a stroker is, it is hard (or impossible by others opinions & standards) to get enough head on top of a stroker.