Do you get for changing to oversize valves, if you're not going to a larger cam?

That is going with 1.7 and 1.44 valves, without signficant modification to the head or ports.

Roughly, what kind of horsepower change?

Not alot, my experience says that you'll get more benefits when you do multiple things for your slant.

What carb do you have?

Milling the head is the single BIGGEST gain on a slant head.
Frank

_________________
Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

Agreed, night and day after milling .100 off the head on my old motor.
I run the valves your talking about i can't really tell you what gain from them specifically because when i installed the valves i built the whole motor, rather than piece by piece testing.

Kev

_________________

If you want to see the benefit of the bigger valves you really need to work the bowl area under the valves. It's not tough to do if you have the tools. If you can't do the work yourself or afford to have someone else do it I would skip the oversize valves. Regardless I would get the compression ratio up to about 8.5:1 with a stock cam. I would use new exhaust valves and hard exhaust seats especially if you're serious about running on propane.

_________________
Joshua

Thanks for the input, guys. I didn't figure the gains to be huge, but the stainless valves are the same price for a set of 12 as the machine shop wants just to replace the exhausts now. So, for not that much more, I can have all new valves. So, the cost isn't any big factor.

I'm definitely going to get the head milled down, and going to super six manifold and EFI or Propane (havent' finished nailing it down yet). I don't have the tools to do the head myself, as far as porting goes. I don't suppose a die grinder and bits is that expensive, I just have no experience or familiarity with any of it.

When you get the head done ask for a "bowl Hog".

I put Chev valves in my head (!.72/1.50) When I took it to the machine shop I asked for a bowl hog to match the SBC valves. They are Chevy guys so they just machined out the bowls (under the seats) to a stock car standard(yes....blueprint slant bowl to sbc small valve spec). This cost very little, required little work on my part, and gave me a bowl that would work with my valves. Dudes were somewhat amused by the ports beyond the bowls.....but they are Chevy guys.......

_________________
Yeah....Im the one who destroyed this rare, vintage automobile.....