2.25 valves too big for 454
 

I got an extra set of 188 rectangle port heads cheap. I was going to resell them with some other parts, and while checking them out they got Manley valves in them and 2.25 intake. Is that too big for a 454? May go 30over and do a 4.25 stroke. I have a stock set of 188 with the 2.19 valves.

They be just fine

The 454 will run fine with the2.25 intake valve the only concern would be contact with the piston,on stock trw style piston the valve pocket on the piston is small and sometimes the valve can get close,if you bore and use a je,manley or a aftermarket piston the pocket is much bigger and you have plenty of clearance,just needs to be checked

My 468's have a 2.25 intake in them. They made 800HP with 6lbs of boost. I hardly think if I went to a 2.19 valve, I'd see a power gain. Alot of the valve shrouding is within the chamber walls of the head. A decent bore notch on the cylinder doesn't hurt either.

The 454 420HP, and 454 450HP merc engines, had 2.25 intakes. The 454 365's, 370's, had 2.19's.

Only thing to watch is PTV clearance with certain pistons.

I run 2.30"s in my bore notched 454's.
I'd run the 2.25"s if you have them.

MT. I thought the 365 and 420 used same Pistons. I have the 365.

Based on the valve dia. alone, in those heads there will be no performance difference between the 2.25 and the 2.19. The throat will remain the same (size of the hole in the head). The benefit of the 2.25 valve can be in the valve job itself, so unless you know someone who can do a good valve job with the right angles, there will be no benefit over the 2.19. If you do go with the 4.25 stroke then the 2.25 with some bowl work would be a good upgrade and that way, take advantage of the larger valve.