Be nice to know the cam specs, lift, duration, LSA.

If you have the heads off Bore notch the block while you are at it.

I'll see if I can find the cam specs.

Bore notch? Not sure what that is? Boring the block for valve clearance?

bore notch is basically opening up the bore a little right where the intake airstream goes past valve and runs into the cyl wall. DON"T cut down anywhere near the top ring...stainless valves are not inconel, but should hold up to marine use. they are a little heavy, but few people rev much past 6k.

Grinding out the block to unshroud the valves. You can use the head gasket as the template. Also do not go to deep.

I see. Thanks

How fast is your current set up with pp heads?
On my 781 heads i didnt increase valve size. I changed so many diff things i gained 10mph but i changed heads,cam, intake manifold, domed pistons, who the hell knows. if im in dead calm water i can push the 24 pantera to 70 with 23plus rpm approx 5100
I never dynoed motor but ppl have guessed approx 420ish

* I had to put stiffer sprigs in 781 heads bc i changed cam to approx .6 lift and bob mandera recommend it plus i got morel lifters, with the 781 you have to change to adjustable rockers, you cant use gm non adjust setup

70 sounds good. As for my speed I'm not sure as I don't have a gps in te boat. Had a little hand held once and saw low 60's. I have a 23 mirage plus that I'm seeing a bit over 5000 rpm's. I just ordered a 25p mirage plus today because I was told not to spin over 4800 with my bottom end.

I did get a set of crane gold roller rockers to go with the 781 heads.

I'm hoping for a nice improvement. We'll see...

Nice good luck with the build I have stock bottom end

Bring up and old thread here but how did it turn out? I am looking at putting a set of 781's on my 454 this winter along with a new cam and intake. Did you go with larger valves?