For the car?

It's a sleeper so I can't divulge too much. It's a hydraulic roller, single plane, 750 carb, turbo 400 built by myself, 4.56 12 bolt posi, all N/A.....no gas.

As for peanut port heads....they are considered open chamber heads also, but to get the actual volume they need to be measured. But....they are VERY close in size to the 781's. Everything I can find is stating within 5cc. I'd machine .010 off the 781's to have a clean mating surface and bolt them up.

You missed the point, in your car you have low gears and a 3 speed,

I realize that, but those peanut port heads start to choke the engine off around 4500 RPM's.

at 650 done the 781s are good buy. at 500 a set plus work, you would not be able to justify not spending a little more for alum. Inconel valves handle the extreme heat of sustained full throttle use only a boat or airplane will see. but if engine spends it's life at 4k or lower, stainless valves will live. you can not justify ever spending money on peanut heads unless they are in a 34 hatteras.

^^^Well said^^^

Ran 781 on a 454 and a large cam and efi setup. Ran well and strong.

Anyone ever run the 820 castings? They have similar ports to the 781 and 049, but a smaller combustion chamber - generally around 112-114 cc, versus the 119 cc of the 781/049. This can help out if you are trying to bump up compression a little bit on a flat top engine.

You are also going to to need special head gaskets and pay close attention to cooling ports if going on a Gen V/VI block I strongly recommend the Cometic. You are going to need new rocker arms and possibly pushrods depending on set up height. Compare accessory bolt holes cause some may need tapped to 7/16. You will need to get new valve covers or modify the drip rail inside your original ones and may need to run a double gasket. If your pushrods are the right length make sure guide plates are matched to your diameter as the stock are 5/16 and alot of the 781 heads ran a 3/8 pushrod.

I have the 781's on my engines..twin 509's dyno'd at 495 HP. with edelbrock air gap dual plane manifolds and crane flat tappet cams 236 [email protected] 551 lift 100 over on the valve length ferrol valves
my machine shop did not go with 219/188 valves sizes. They went a bit smaller because of the water jacket too close to the exhaust ports.. Running 1 piece push rods and comp cams stamp steel rockers with roller tips and stock chrome valve covers with drip rails.

Thats the issue many face on the budget flat top engine upgrade for peanut port, other than buying a set of aftermarket heads with a 100 or 110cc chamber. the valve sizes on the peanut and oval are the same and the gen 5 peanuts often still have some meat on the exhaust seat .
with some ambition and some fresh carbides they can be reworked to make good power but its a sloppy messy proposition.