I have a set of stock "781" heads and want to know what the reccomended largest valves (diameter)I can have installed.

2.25" intake is possible, but normally 2.19" will do.

1.90" is possible on the exhaust too, but again 1.88" will also do.

Personally, I wouldn't go farther than 2.19/1.88 for risk of hitting a water passage.

Not that I am an expert but I thought I remembered reading in Scoggy dicken or whatever the 781's can have up to a 2.30" intake valve?

Merlin ovals can go 2.30"/1.90" or 2.25"/1.94" so can -781's/-049's do the same???

I figure the latter should be about right if they can..

I kinda like the big exhaust valves to lessen pumping losses....

pdq67

I wouldn't go past 2.19/1.88. Just ask BB Mike about what happens when you get into a water passage. :eek:

My 049's have 2.25/1.88 with no problems

My Chevelle Page (http://home.swbell.net/kenladd/Home.html)

3830 lbs
All Steel with full interior
10.25 1/4 mile @ 130 MPH

Bump......

I kinda like the big exhaust valves to lessen pumping losses....

pdq67
=
Huh?? :confused:

With the ports in these heads 2.19x1.88 or with more work 2.25x1.88
Either will do almost nothing but hurt you if you don't get the port correct for the valve in question as well as unshroud the chamber accordingly.

http://www.chevelles.com/forums/showthread.php?t=158951

Some talk about valve size on this thread too. I must have been really bored that night, I normally dont like to type that much.

My 781s have 2.300 I and 1.880 E without any problems.

Pete