Larger Valves, 3.4

[slick]

Is there enough space in these heads to have them machined for any larger intake and exhaust valves? Getting them machined is no problem, its just whether there's enough room to do it. Also, i know that this would mean more air in and more air out, but how much of a gain would this give?

[god910]

Dude, you already have an extra valve, now you want 2 big valves?? I have NEVER seen flow numbers on the TDC heads, but I don't think you need to worry about outflowing them.

[Aaron]

There is not enough room. The stock valves are already right at the edge and spaced like 1mm apart

[Vegeta]

Ive thought about it but custom valves are gonna be 25-35 each. As for aarons reply, lets prove him wrong like its a hobby.

exhaust valves have 0.314" between them. 0.113" to the edge of combustion chamber. The stock cylinder bore comes to the edge of the CC on the heads so you would really want to bore the block over to help with shrouding. Fortunately this isn't the high flow area of the exhaust valve anyway...but more space is always better.

Intake valves have 0.212" between them. 0.100" between the valve and the edge of the combustion chamber. You can go 1mm over on the valves and have barely any room on the intake side without CC work and an overbore of the block. 1mm is pretty much standard on import oversized valves. Considering the large size the valves though and the cost, this probably isn't gonna be cost effective. It would however help power. I posted stock flow specs on 60V6 so ill post them here.

intake
.050 42
.100 84
.150 135
.200 170
.250 200
.300 227
.350 247
.400 260

exhaust

.050 25
.100 75
.150 110
.200 130
.250 150
.300 165
.350 167
.400 170

I dont know what the flowbench was setup for, 10" or 25" of water. I believe 25 is standard these days but its been a while since I looked that up since my bench isn't running yet.

[Vegeta]

btw, .040 = 1mm.

[Aaron]

When I took them to the shop that is doing my porting, he said that there is now way larger valves could fit. So I'm going off of what he said.

[Vegeta]

You can fit 1mm oversized valves in there but it require more work than simply cutting the seats. You gotta unshroud the CC some and it would only really be of use on an overbore of about .040 on the cylinders as well.

[slick]

So until the block has been bored over, theres really no need to then?

Also, i was thinking that since my heads have been shaved with my higher compression it would help, but until i get another block to work with, its useless then.

[Vegeta]

The shrouding stock isn't that great, so larger valves would hurt more than help possibly. Shaved heads wont make a difference for flow, just compression.

[slick]

Ahh, gotcha. Thanks.