AmericanMuscle313

iTrader: (5)

What are the pros and cons of a 5 angle vs 3 angle valve job? Why do some after market heads only have 3 angle valve jobs and still flow over 300 cfm while others use a 5 angle?

treyZ28

benifits are marginal for anything short of a full blown racecar.

mrdragster1970

Agreed, we use a radius cutter for max flow, mild stuff, they're both fine.

SStrokerAce

iTrader: (2)

Most good VJ's are usually 4 cuts... all of this depends on the angles and the head and porter working on it.

Ed Wright

iTrader: (1)

I seen guys heads that claim 5 angle valve jobs, and they must be counting the two on the back of the valve. Like Brett said, most use 4 cuts for the intake seats, and most use a radius on the exhaust. I don't think anybody uses a radius intake seat.

1989GTA

When I had my Dart 200 heads ported my porter used radius seats on the exhaust side. Just wondering why they would not work on the intake side.

Maybe some are and not talking. Hehehe.

SStrokerAce

iTrader: (2)

Well they would back flow really well then and that would cause your intake charge to be diluted and really hurt your power..... NOBODY uses them on the intake because they suck. In fact most good VJ's have a hard crisp edge on each angle for best results.

Bret

machinistone

We use a radius on the intake, developed in cooperation with Flowmaster when we worked on their "Blue-Flame" 1000hp pump gas 502 that was in Hot Rod. This cutter has been compared to many 5-angles of our own, and others, it always outflows them. Made 8-12 cfm over Dart Platinums 5-angle job with just re-cutting the seat with our radius. Back to back on the dyno it picks up a little too....I guess you could call it a dual radius cutter because it does have one small lip to discourage the backflow like Bret was talking about.

Ls1Bait

For less of a edge probally. Like stated above 1000 HP

MrDude_1

iTrader: (4)

when you guys are looking at the valve flow, do you look for it to "stick" to the valve, and curl around it, or to "trip" and "tumble" over the surface to go by it??

xfactor_pitbulls

iTrader: (16)

Bret, I think you need to get around some more hardcore airflow specialists. Every "top notch" head porter that I have been around does a hand blend on the valve job. Thus removing the sharp edges, I have done tests first hand after alot of trial and error (with help). A general rule of thumb is that airflow likes a radius over a sharp edge, no matter which way the airflow is flowing around the obstruction. Most people dont blend the VJ simply because they dont know what they are doing, or cant match their work with the back cut on the valve. Sorry to bring the thread back, I just came across it.

SStrokerAce

iTrader: (2)

.................................. yes a hand blend of the bottom cut into the port and the top cut into the chamber is normally needed. Some classes don't allow you to do this so you have to get the VJ perfect, angles, depth, width, to get everything in the right spot so no blending is needed. Some of the guys I work with can take upwards of 4 hours on blending one head. Hell i've seen them do the bottom cut with a hand file rather than a cutter.

What I was referring to is the edges between the top cut and the seat and the seat and first bottom cut. Usually those angles are tight enough that airflow works with them, not huge changes (over 15-20°).

I guess getting a discharge coef over 101cfm/sq in @ .600" on a 3.900" bore with a 243 casting and making 1.9hp per cube under 7000rpm consists of a non "hardcore airflow specialist"...... guess I better start calling up some other head porters then?

(For anyone wondering what that math above works out too.... a AFR 225 (which is 230cc) would have to flow 340+cfm on a 3.900" bore and make 570rwhp on a 347 under 7000rpm.)

Bret

Ed Wright

iTrader: (1)

I guess poor old Carl Foltz just doens't know what he's doing. Pretty sad.

There is more to it than air flow. Gotta manage the fuel also.

66deuce

iTrader: (1)

can you port my next set of heads?i probably couldn't afford it tho,lol.

airflowdevelop

I have never seen a radius or "soft" radius (where you knock the definition off of the transitions) make more power than a properly designed sharp definition seat. It is really easy to get more air with a soft seat, It is not uncommon to have a properly designed valve job be down 20cfm in the mid range, and still make 5-7% more power than a killer flowing soft seat.

It is common practice to blend your bottom and top cuts into the chamber and bowl. This works well on heads that like a back-cut intake vavle, with a nice valve profile, and fat margin.

Blending your bottom and top cuts with a nail head style valve shows little increase.

It is not uncommon for a competition valve job to take 12-14 hours with blending work, this is not the work that your local machine shop is charging $175.00 for.

you can use a radius on the exhaust seat as a cheaper way out.

Ed,
I doubt many in this neck of the woods are familiar with Carl. One thing is for sure though, This isn't his first Rodeo.....IMO, the most respected in the industry.

Dennis