undercut valve cfm and right tools?

thanks was wondering about that, how much more flow do you think a stainless undercut manley valve is worth?

10%+ at low lift or there-bouts. Was on my 351C 2V heads.
[addsig]

CKelly
The 10% gain at low lift. Low lift being .500 and lower?
And is that checked on Flow Bench?
Not doubting you just amazed at the increase. Makes the price of undercut valves more attractive.
We don't have access to a flow bench around home.
Any idea the increase you get going to larger valves?
Knowing there is a lot of factors involved. Just thougth maybe you might have an idea.

10% IS SOLID, if this is true than I'M SOLD on some undercut valves, too bad you cant shave the valve stems down yourself........

Low is between .100 and about .350. I don't have the exact figures, but it was a noticable increase.

mine were 40% difference between undercut and straigh-stemmed "cheap" valves. The "good" ones were Titanium 1.94/1.60 that I had cut down from 2.02's, then ground a little on them to gain a few more CFM on a test head. All said, we were able to get 225 CFM out of a pair of D5TE 351w heads. Too bad I don't have 'em anymore...BUT I do have the valves and everything else on my Mustang street car, but I didn't go through the time/work/money to port them to their fullest. I just ground on 'em until "they looked good" and put the valves in and said heckwithit--that's good enough.

Car don't run too bad, though I have to keep an eye on RPM as it tends to climb way too fast in 1st gear with no limiter. It's still making decent power at 7000--and it's a mild motor that shouldn't go more than 6000 according to the cam guy.

When I say we ground on the valves, I mean we ground different/weird angles to the face and head. Not just your run-of-the mill single 45* cut....there's 9 different angles there and looks more like a radius than a single angle. The seats are 5 angle---was easier to cut it that way[img]/phpBB/images/smiles/icon_spin.gif[/img]

You'd be surprised how much you can get out of just grinding the valves, but it takes a bunch of work/time (read: $$$) to get 'em there. An ex super stock engine builder was telling me about doing some of that stuff on AMC iron heads, and I tried it on the Ford heads....and it worked basically the same way. If I would have paid someone to do the grinding on the valves, I would have about $500 JUST in the valves themselves, not counting the cost of the valves--which Ti valves ain't cheap anyway, but they were old sprint car parts that I got in trade for some labor. That's the beauty of doing it yourself. You know what works and what doesn't.

mind disclosing any of your valve secrets[img]/phpBB/images/smiles/icon_smile.gif[/img] so i can tell my head guy how and where to cut the angles??[img]/phpBB/images/smiles/icon_spin.gif[/img]

Sorry, I'm sworn to secrecy on that one.

the procedures have been commonplace in sprint cars and other forms of limited-circle trackers for years. Even starting to hear more about it in stock and super stock classes NHRA/IHRA stuff. In fact, my machinest owns a "E-mod" roundy-rounder....2 barrell carb on a iron manifold (can be alky, though), 15" of vacuum minimum, etc etc. Tough rules...but still is squeezing about 480 HP out of 355 inches. They'll let Fords run cleveland heads, but no 4V heads and no porting. One guy is running a aluminum block, painted with a special iron-based paint that a magnet will stick to so that when they check it, it'll check out fine....at least 'til someone tears him down[img]/phpBB/images/smiles/icon_lol.gif[/img]. These guys MAKE ways to get every last bit of power. Same guy also figured out a way to get a SBC crank down to around 40 lbs, lighten the rods up to about 520g, pistons are 370g, pins are 75g....on and on. Hollow camshaft and all...I don't know how that works (never seen it) but nevertheless, it works for them.

in the famous words of Forest, "that's all I have to say about that"