I have the factory 083 heads with a simple gasket matching on the intake side. Will upgrading the valves to 2.02/1.6 make any noticable difference. I don't have any porting experience and I don't want to ruin the so that's wht only a gasket matching was performed. So, will the larger valves alone help??

 

The greatest gains are realized by cleaning up the bowl area (the port right under the valve) and short side radius. Gasket matching doesn't help nearly as much.

Unless the bowl and short side radius are cleaned up, larger valves aren't going the help much at all.

 

Get an old head to practice on. It's not that hard.

 

But what if only the valves were changed? Will I see a difference? How much extra cfm would the heads improve? I will try porting but I have to finnd an extra set of heads first. THanks!

 

only putting in the big valves would probably hurt flow actually.

 

How's that possible?

 

If you just cut for the valves you will create alot of shrouding and you will have a very noticeable ridge going into the ports that will create alot of turbulance when they cut for the larger valves.

 

'zactly.

Picture a 1.94" valve getting 100% of flow around the circumference. Then put in a larger valve, now it's "closed" on the side of the wall, so you get a larger circumference, but 40% is blocked by the wall = net loss.
That's an exaggeration, but that's how it can work.

I wouldn't be too caught up in valve size, that's what the folks used to brag about in the '60s with old "double hump" heads and whatnot. Now it's more about the bowl area, and the angles on the back of the valves. Back cut, radius/chamfer front face, etc.

 

I agree the stock valve size can be made to be very efficient with some cleaup work. Look at this thread and you can see how far he got with the stock valve diameter. Check out his flow numbers in part 3 since those have the stock valves with the 3 angle valve job. He doesnt even cut for larger valves til part 4 and states this requires alot more work.

Here is a comparison between the 1.94 valves and the 2.02. He even states by working on the short side radius he could have gained even more flow to get it up to 100%.
1.94 1.5 valves flow

.1 63.8 41.4
.2 120.6 88.2
.3 178.9 124.1
.4 215.2 154.3
.5 240.1 171.8
.6 241 180

2.02 1.6 valves


1 72.4 47.6
.2 135.1 101.0
.3 201.3 140.2
.4 237.8 171.1
.5 264.6 187.6
.6 266.1 192.6


https://www.thirdgen.org/forums/tpi/...d-project.html

 

I'll see if I can find an extra set and start grinding.