35fountain

My old heads 781 casting had 2.19 + 1.88 stainless valves..They sprung a water leak in #5 exhaust port..

The new set of 781's have 2.06 + 1.72 stainless with harden seats..Will there be a drop in horse power due to the valve sizes..The machine shop said it may increase the torque with better fuel mileage..
The cam is a 553 lift 236 [email protected] and LBA 114..
502 bbc

jeffswav

That is the stock valve size, I had mine opened up to 2.19/1.88. A good machine shop can do this for you, make sure they are bowl blended otherwise you will kill the flow.

CSCinc

A friend of mine jus put a set of pro comp alum. heads on his 502. He had a head go bad and i think bought these for 1495 w/ stainless valves. Its a thought.........

ezstriper

someone added those size valves to your original heads...you will see a degrease in H/P how much ?? depending on the rest of the engine..

35fountain

I was told that if they grind too much from the bowl area and seats , it will get to close to the water jacket and could cause problems.. Maybe thats what happened to my original heads..They were primarily used in fresh water...I think i'll leave them along this time.. 2.19 vs 2.06..13000 ths..So instead of doing 80 mph I'll do 78 ??

HaxbySpeed

It is pretty common on 781's to cut too deep when putting in bigger exhaust seats. There are different seats you can use and a good machinist can usually do it, but every casting is different. I usually just up the intake to 2.19 and spend a little time cleaning up the bowls. I don't think you will lose any power.