PTS Flowbench Forum

I started building this thing a few months ago. It was a lot more time consuming than I had anticipated, difficult since I'm already so busy. Anyway, I started with a set of 1993 LT1 heads that I have ported. The bench pulls 340cfm at full capacity. At 28" of water I read 288-294cfm screwing around with the R-stat, and letting the motors warm up. The orifice is the 300cfm unit from Bruce. Not sure about the deviations, I imagine the software calibration has something to do with it. The stock intake numbers for LT1 heads from the industry standard SuperFlow benches vary, but generally average as follows:

.1" ----64cfm
.2" ----110-120cfm
.3" ----158-170cfm
.4" ----190-207cfm
.5" ----206-207cfm

Not bad numbers for stock street heads. When ported they can be a lot better, as seen in some of the postings on the web.

http://www.ls1tech.com/forums/lt1-lt4-m ... low-s.html

As seen in the link a set of professionally ported heads will typically flow:

.2" ----138cfm
.3" ----198cfm
.4" ----240cfm
.5" ----260cfm

Generally, this is done on the industry standard SF bench. This is what I got on my PTS bench @28" on my ported heads today:

.2" ----128cfm
.3" ----204cfm
.4" ----238cfm
.5" ----255cfm

Again, stock 1.94 valve. I can't say I'm unhappy. The bench looks like it's in the ballpark. I'm not finished with these heads but I'm sort of hesitant to go further looking at the #s. Just a few more rounds of roughing and smoothing to go. I think I need to do some more configuration tweaking in the Flowsoft also.

At lower lifts the pro heads seem to flow more cfm. I need a velocity probe to get to figure that out. Since I'm too busy to build one I'll probably just buy one from this site.

It will be interesting to see what this bench does when doing exhaust, since they really are the weak spot in these heads. Any pointers would be appreciated. Will try be back at it again tomorrow.

Congradulations on the bench, sound like you need to take a step back and work on your calibration a little, Did you get a calibration plate from Bruce? is this the 300 CFM? what Orifice is in the bench and did it also come from Bruce? Is the bench your design or a PTS bench? Have you leaked checked it? just some things to go over before compairing head flow, kinda need to understand the bench and get to know her Look forward to hearing more.

Rick

Yes, it's a PTS design. No leaks. Orifice by Bruce. I think I need to adjust some #s in the software, density etc. have to be modified. I will consider the calibration plate but I'm tapped right now on other projects.

Only thing you should have to change is the "Discharge Coefficient" (Cd) value.

Brucepts wrote:Only thing you should have to change is the "Discharge Coefficient" (Cd) value.

Haven't messed with it yet. Would that account for the 288-294@28" or do I need to look somewhere else?

Increase your averaging on channel 2 (PT2, CFM) this will slow or stop the rolling numbers set this to your liking. I personally like to have some "rolling".

Do you have a calibration plate? If you do, you need to put that on top of your bench with no head adapter and measure your cfm's compare that to your cfm's on PT2. Change the Cd till cfm reads the same as what the plate is marked for, calibration is done. If you have more ranges of calibration plates you can tweak the numbers even more.

FlowGohst,

I started building this thing a few months ago. It was a lot more time consuming than I had anticipated, difficult since I'm already so busy. Anyway, I started with a set of 1993 LT1 heads that I have ported. The bench pulls 340cfm at full capacity . At 28" of water I read 288-294cfm screwing around with the R-stat, and letting the motors warm up. The orifice is the 300cfm unit from Bruce. Not sure about the deviations, I imagine the software calibration has something to do with it. The stock intake numbers for LT1 heads from the industry standard SuperFlow benches vary, but generally average as follows:

Here goes, if i read your post correctly you have a plate in your bench that is designed to flow 300cfm at 16" Delta P Correct?

You say the bench will pull 340CFM at 28" with a 300CFM Plate Correct?

You do not have a calibration plate I/E a 150CFM at 28" from Bruce Correct?

You are trying to use a set of heads you have as a calibration point Correct?

1. you need an internal plate that will flows about 33% more than your peak intended flow as your internal plate. so you need a 450 cfm or so plate at 16"DP as your internal plate.

2. You must have at least one calibration plate hopfully close to your mid scale of your internal plate.

3. Never Never use a set of heads to try and calibrate. Do you weight the same at home as you do at the Doctors Office Most likely not.

4. Once your bench is calibrated your heads will flow what they flow if you are confidenat in your calibration and test plan then everyone else is wrong even BIG BLUE. But just remember there are alot of veraible in a test setup.

5. A calibration plate from Bruce is little or no money and you cannot properly use a flowbench without a (Standard) calibration plate as most of us check the calibration often.


Rick

Brucepts wrote:Increase your averaging on channel 2 (PT2, CFM) this will slow or stop the rolling numbers set this to your liking. I personally like to have some "rolling".

Do you have a calibration plate? If you do, you need to put that on top of your bench with no head adapter and measure your cfm's compare that to your cfm's on PT2. Change the Cd till cfm reads the same as what the plate is marked for, calibration is done. If you have more ranges of calibration plates you can tweak the numbers even more.

Only other plate I have is a 200cfm plate. I just ordered the pass around plates, I figure that should help get me out of the dark. I will play with the averaging also.

Really appreciate all the input here folks. I'll need more before this is over. Thanks!

1960FL wrote:FlowGohst,
Here goes, if i read your post correctly you have a plate in your bench that is designed to flow 300cfm at 16" Delta P Correct?

I believe the plate is marked 300cfm@28".

You say the bench will pull 340CFM at 28" with a 300CFM Plate Correct?

The bench will pull ~34" at 340cfm. It seems to change with the weather.

You do not have a calibration plate I/E a 150CFM at 28" from Bruce Correct?

No, no calibration plate. I do have a 200cfm plate I haven't used. Perhaps I should try that?

You are trying to use a set of heads you have as a calibration point Correct?

Well, not realistically. I just wanted to see where the shot in the dark would get me. It got me unreliable readings, but at least I got readings, LOL. It's sort of like creating the flux capacitor and not knowing where in time I will land.

1. you need an internal plate that will flows about 33% more than your peak intended flow as your internal plate. so you need a 450 cfm or so plate at 16"DP as your internal plate.

2. You must have at least one calibration plate hopfully close to your mid scale of your internal plate.

3. Never Never use a set of heads to try and calibrate. Do you weight the same at home as you do at the Doctors Office Most likely not.

4. Once your bench is calibrated your heads will flow what they flow if you are confidenat in your calibration and test plan then everyone else is wrong even BIG BLUE. But just remember there are alot of veraible in a test setup.

5. A calibration plate from Bruce is little or no money and you cannot properly use a flowbench without a (Standard) calibration plate as most of us check the calibration often.


Rick

Okay, I'm making moves toward getting calibrated. Will get back to you after I mess around bit. We'll see where I land.

Flowghost,

You say you have a 200 CFM plate at what preasure" 16" ro 28" this could work fine to calibrate.

If it is a 200CFM at 16" DP it will flow 264.8CFM at 28 and .62CD Just call it 265CFM Try to calibrate to this and use it streight on the bench deck without a head adapter sharp edge up on intake mode.

Rick