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Old 05-28-2008, 11:41 AM   #8
charliew
Scooby Specialist
 
Member#: 125304
Join Date: Sep 2006
Location: Crawford, TX.
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The flow bench is "homemade" but it uses 12 120 vac motors in two seperate chambers and uses Audie Tech. Flow Quick controls and software. It is adjustable to way over 28 inches at less than 2 inches of orfice. It is calibrated with a 2 inch orfice and can be set on: actual cfm, 10 inches, 28 inches, cmm 710mm, cmm 255mm and actual cmm. It also has a high cfm and low cfm setting. I also bought a Flow Quick variable speed control to control the 6 120 vac. motors that we use on lower flowing settings, (300 cfm or less). When we need 600 cfm we turn on the extra 6 motors and open their compartment and a 4 inch duct to test the higher flowing stuff. When you go to the next increment on valve lift you readjust the 28 inches on the magnehelic gauge to give a accurate reading at each lift. At .050 intake lift you will be running the vac. motors real low as there is not much air flow needed but you still want 28 inches of h20 on the magnehelic to be accurate. The magnehelic gauge goes up to 50 inches of water and 15 psi on pressure.
Audie Tech Flow Quick is used by lots of flow testers and is considered very accurate. You are really doing a before and after comparison on your flow testing. I'm not sure about comparing flow results to other benches it's sorta like comparing dynos.
I built my own mainly to get a useable tester that I could cost justify and to make one that didn't take up so much space. It's on casters to be moved around, it also needs two 50/60 amp 220vac circuits to run the vac. motors. I still spent over 1000.00 on parts
Our head adapter uses a 4 inch bore with a 4 inch stroke to test the subie heads with a modified tgv for the intake and a short exhaust fitting to test the exhaust. We use a fixture that has two 1 inch travel dial indicators to set the individual valve openings at each .050 inch lift increments.
I found this formula on Autospeed for cfm = hp.(.43x max port flow at your cam's lift (in cfm at 10 inches) x number of cylinders = peak HP) There is a formula for 10" to 28" conversion but it's not handy.
For street motors the average flow improvement is whats important because the street car spends most of it's time in the lower rpm range. High flow numbers are great on race cars at high rpm's. A 20% improvement at low lift would be magic on the subie head but would also wreak havoc if it's not already on boost. Too big of ports at low rpms would kill the velocity and hurt na chamber filling.
I don't think any head can be ported and only a improvement realized. In my limited experience you loose a little low lift flow as you increase higher lift flow.
As wittmer 25 told me " it is the average improvement across the lift range that counts as the real improvement"

In short don't buy a race head for the street.

If I remember correctly we left the small ledge of overhang at the exhaust port to header to stop reversion. I think we did the same thing on the intake ports to the tgvs.

I thought I would add that we also used a Phase II sonic checker to see if there where any thin areas in the ports. We didn't find any thin areas to worry about with the amount of porting we wanted.

I have since got a good assortment of Kwik Way valve seat cutters and a Gizmo valve resurfacer to play with as I have time. I will say the exhaust seats are very hard and cutting them out to a mm bigger is a little time consuming. The intake seats are easy.

I'm still not convinced a 5 angle valve job is better than a hand contoured seat area.

On the oil pan to pickup clearance on wittmer 25's motor we ended up with about 7/16 clearance. We actually lowered the pan to get the clearance to keep from modding the pickup's length. We did add a additional brace to the pickup.
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Last edited by charliew; 01-11-2010 at 09:56 AM. Reason: adding new tools to list
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