Whats a good flow bench cost ?

A really good flow bench is $8000 - $10,000 brand new I would guess. Yes you can buy a smaller, used one which would be less. I did see one a while back where you plug your shop vac into it. Very simple and inexpensive. My guess is it wasn't very accurate.

Good cylinder head port work makes anything run better. More air allow more fuel which = more power. That's been the same since the advent of the internal combustion engine.

Marty,

You recently ported a 301 diesel head for another member on the forum who was impressed with the change in performance. Do you recall what flow numbers you ended up with and which size valves?? I just use someone who knows how to do that kind of works numbers for comparisons sake. I have ground a few of these, but only ever flow tested one years ago. The numbers were so depressing after all of the work (in comparison to the competitors heads)that I vowed not to flow test an OEM head again.

Doug, this member may chime in and tell the difference in a before and after 301 diesel head and what a nice port and polish will do for a turbo diesel engine. If I understood him correctly he used the same fuel system and turbo. The only change was Marty's work and he was very happy with the results.

Typically on a high swirl port there is a limet on valve lift, the 301 has a high swirl. The 5.9 cummins is another example. Once you pass the point the air gets turbulant arounf the valve and things go bad. Unless you make some serious changes the port gets "angry" or noisy.. Good quality airflow is worth more than poor quality airflow. When testing a part it gives a sound, you can tell if things are "happy" or not, I'm sorry for the vague explination, but it's one of those deals where you can tell if things are going to work or not by the sound.

Anyways, the 301 head can take a larger valve but the real choke point is in the valve bowl, the port is small and has a high swirl factor. Throw a big valve in it, the flat face of the head and you have a bad combination of a small port, a big curtain area and a poor discharge coefficient. You get a mix in air velocity and pressure.    With a smaller valve and less work the numbers aren't good from these heads, bult numbers aren't everything, things are more uniform.

I took a junk head and treid stock valves in one cylinder, larger valves in another, some in between valves in one cylinder and some other trial work with the "in between" valves in a cylinder. This gave me a decent direction as to what worked and what didn't and what more to do on the finished head.

To be honest on Carls head I put a valve in smack dab in the middle for size, I took 426 valves and cut them down, did some bowl hogging and a decent valve job. No real rocket science, no big impressive numbers. But hopefully good quality "happy" airflow through the operating range.....there's some things that are best left unknown, the flow numbers on a 301 are one of those things. You'll just be disappointed if you know.

I don't rember the numbers, I just know ther aren't impressive. I know of other engines with un-impressive parts, but they seam to wind up better off on average than some of these guys with the latest "trick of the week".

Edited by wi50 - 04 Feb 2014 at 2:20am

The flowbench is pulling a constant depression once set when testing the air speed for a given valve lift is consistent in a sense, at least each area stays consistent during that given test.

But as we all know the airspeed varies when the engine is running and the valve going through it's cycle... So where does a guy draw the line and make the compromise?. I'd give up some flow numbers through the range of valve motion for better quality airflow.

The "area under the curve" will be more in the end, even if the tests give better numbers but things just don't sound right it's not going to work as well as it would to make the compromise and run a little smaller valve.


Finally a little intelligent conversation on the subject, you guys gotta check out YT mag.  I put up some pictures of my Moline head project and guess who's making a fuss.

I did look at the thread on YT. Much nicer on here without that stuff. The Moline heads beautiful though. I typed this at faster than the speed of sound through a venturi.

Using intake valves for an exhaust valve won't work in the sense of life expectancy. I knew an old AC dealer years ago that had the cylinder head off of a 220 tractor three times for burned exhaust valves and in the end, the problem was they were using 301 intake valves by mistake for 426 exhaust valves, which was the cause of failure after failure after failure.

thanks for the info. when I had my 262 apart the intake and exhaust valve were very close to the same size don't remember exact sizes can u tell me valve sizes for 426 301 and 262? intake and exhaust

Paul graves web site tractor sport has a flow bench message board. Most the turbo guys like to test close to the psi they run. Most small benches don't have that capability. What shows big increases in cfm at 28 inches of water can be detrimental to cfm readings at 105 inches of water. Bossmans on another pulling forum covering this identical subject.

Ihateillinoisnazis wrote: Hey Pankey. Your big airflow post got deleted on YT... Think there's a reason for that? Go spam some other board. Maybe you can preach at Paul graves website since you have such a hard on for him. Or did you already get booted from there? Go home troll you're drunk. Where's the Gleason?

Edited by Butch(OH) - 06 Feb 2014 at 7:52am

Enjoying Marty's dissertation on "bigger is not always better".  I concur that the "quality" of airflow is primary, "quantity" is secondary.  If you can get both - that's just doubly better.

Question for wi50 or anybody else with the knowledge. The 426 and 301 both have notches on the intakes to induce swirl, technically its not fully machined like the exhaust. My question is do you fully grind the rest of that material out? It looks to me otherwise it would shroud the valve.

Yup, that's what I was referring to wi50, THANX. Removing intake and grinding away.