contact

I occasionaly see backcut valves, especially
for ***** stuff.

if so,why is it not more popular?

sofakingdom

iTrader: (1)

Some of us consider it part of our standard procedure.

Can't say too much about "popular" though, that's not my specialty. Putting fart pipes on 90 HP 4-cylinder cars is "popular". Building motors that extrtact as much power as possible from their parts however, costs money; whereas slapping big stickers of Asian- or European-appearing words across windshields, or cutting the stock springs on an economy comapct car without changing the shocks so that the car bounces uncontrollably on every little bump, are cheap. That might have something to do with this "popular" thing, but I don't really know too much about it except to laugh at it when I see it.

Damon

The valves on factory-stock Vortec heads are backcut. GM built millions of them. Popular enough, don't you think? Racers have been doing it to valves for decades. Also, many aftermarket perormance valves are already backcut when you buy them.

Sonix

iTrader: (1)

vizard tested some flow #'s, then backcut the valves, picked up something like 7cfm.... I did it by hand on my intakes, exhaust is kinda harder to do, but I mananged, however the valve stems turned out to be shot, so I just used new ones, untouched.

1989GTATransAm

iTrader: (3)

It's quite popular. You must be traveling in the wrong circles.

contact

consider Manley and Ferrea.

Backcut, 30 degree backangle, tulip-shaped...,in those styles,
their offerings are either scarce or none, for the SBC.
if anything, only for exhaust.

where would I look to see whvt GM Vortec stuff is available?
anybody got part numbers?
any backcuts, featured in GMPP?

what do companies like Dart, Brodix, AFR, etc,
supply with their heads?

thanks for any comments.

Apeiron

What? Scarce? Do a search on Summit for Manley intake valves for the SBC and you'll get pages of valves.

Streetiron85

Last time I had a valve job done, the machinist charged me $1 per valve for a back cut.
It isn't a big deal at all. I've seen some articles where they showed how to DIY with an electric drill and a grinding wheel.
It does make a noticable improvement in the performance.

Sonix

iTrader: (1)

I made a post on how I did mine, if you're looking for a DIY solution. Search for it.

But if you have to buy new valves anyway, pre-back-cut ones would probably be the same price as normal ones so...

contact

let me restate the question.

are 30 degree back angle valves,
any better than nailheads?

30 degree, for the SBC, are unusual

sofakingdom

iTrader: (1)

Yes, they are.

No, they are not the least bit "unusual"; they're just not in the catalog that way.

You don't generally buy them like that. It's something you do yourself (or your machinist).

That doesn't mean it's not "popular".

rx7speed

your stereotyping again

vorgath

Actually I've never seen people with imports cutting their springs, no offense to those who have imports, but from what I've seen, most go should I say RUN and buy aftermarket springs, and make sure they get the sticker to put on their car too *l*.


Speaking of which though, valves, back cut etc ... how can one "test" or examine titanium valves to see whether one can still use them ? I have several sets in the garage, however I believe all of the sets are exhaust valves, while I have Manley 2.02 intake ones (not titanium).

Sonix

iTrader: (1)

use your micrometer and measure wear on the stem. Over .001" wear won't seal much and you'll get lots of burned oil. Roll the stems on a piece of glass, like you would with a pushrod, to check for straightness.
That's pretty much it, to see if they're too worn for use. Or did you mean specifically for titanium valves?

Matthew91-Z28

There is a great article in carcraft this month regarding 30* angle back cuts. I dont feel like regurgitating the entire article, but the conclusion was improved flow. They didnt guess at improves hp and tq, but flow was increased 4-10% at at all measured lifts. Generally $64 to do an angle job on all 16.