MSD bench mods

[JRM]

What I was thinking of doing was to set the bench up so it will constantly flow 600 cfm instead of it having adjustments.
I was thinkng this would leave me with less headaches on calibration. Or is this idea going in the wrong direction.

[larrycavan]

[Mouse]

[84-1074663779]

JRM, I don't think it will be possible.

If 600 CFM is roughly say, 7.65 inches of water with a four inch orifice, then 60 CFM would be only 76.5 thou water rise up the same tube. How do you plan to see that ?

If you wanted to see the difference between 60CFM and 61CFM that is only just over a thou difference in water height, not really feasible I think.

[JRM]

Tom V do you have the hole sizes for the superflow 600?

Whats really getting me confused with the MSD bench design is I copied what they said with the orifice plate holes. Needless to say I did come up with diferent flow numbers, But where im getting confused is the pie shaped cut they say is 960 CFM. The opening is 4" x 5 1/2" . If I turn on all my vacc motors with no restriction I still pull 8" on the virt manometer and according to the incline meter im only at 95%. SO i know something is messed up.
What I really want to do is get a plate made or purchased with only 4 settings max. 200cfm ,400cfm , 600cfm ,800cfm and know that the hole sizes are exact.
I would make the plate myself but the boring bar I have only goes down to 2 5/8" so making smaller holes is only do-abol via hole saw and I dont think I can get a clean enough cut.

[bruce]

JRM, You can't grind a smaller cutter to use as a boring bar? Use a piece of HSS and grind it into a smaller boring bit so you can machine the smaller holes.

[larrycavan]

JRM

Why you wouldn't want to include at least two holes of lower flow rates like 50cfm and 100cfm?

[84-1074663779]

There ar a lot of different ways to go about this, but so far my best attempt has been to build a rotating turret mechanism into which the individual orifice holes can be fitted.

Each orifice can be turned exactly to size in the lathe and fitted into the turret. It then becomes possible to quickly swap sizes or move things around to get suitable ranges without dismantling everything to do it.

It is also handy if the same orifices can be fitted to the test hole with an adapter, so orifices can be flowed against each other.

[JRM]

unfortunatly I havent purchased a lathe yet. or a virt. mill havent found any that I can afford. The boring bar I have is for boring engine blocks and the head of the bar is 2 1/2" in dia. once i put the cutter in the smallest I can get it is 2 5/8".

I wasnt really concerned with the smaller flow number is because most of the cyl heads I do flow above 200 cfm in the higher valve lift range. And same goes for the carb bodies and throttle bodies my customers want flow checked

I have thought about using my valve and guide machines reamers to enlarge a pre drilled hole but the largest reamer i have is .500/ (1/2")

[bruce]

Ok I've pondered this all day today and just have to ask . . . why would you not be concerned with flow in the lower lift ranges?

Even when I work on carbs I flow at various throttle blade openings and watch fuel signal strength in the idle, transition and highspeed circuits.

Just something that made me say "humm" so I had to ask . . .

[JRM]

Ask away.
When it comes to carb bodies all my customers ask is what is the total cfm. I agree with you on the checking of booster signal and all, but I have yet to have anyone ask me to do it. Most of the guys/gals around here get AED or BG to do their carbs.
As much as I am a Holley man Id rather let them go elsewhere for their Holley carb mods. I hear their complaining alot on how much they spent yadda and it still isn't right. Then they pay me to tune it in. Now if they would only realise a bigger jet is not always better lol.
My secondary plan will be build another small bench just for low cfm work but for now that is a way back burner thing, i need to fix/finish the current bench if i can get it all to make sence in my head.

[Mouse]

If you used a 4" measuring orifice, I estimate a FlowPerformance FP1 processor would give you a resolution of about 2cfm at around 100cfm flow. At around 150cfm, the resolution would be about 1.5cfm. At about 200cfm, a 1cfm resolution, 300cfm at about .7cfm res, about .6cfm res @ 400cfm and at 500cfm about .5cfm resolution. These numbers could be very conservative, and better resolution may be possible.

[Mouse]

Well, I got to thinking about the orifice thing and couldn't resist connecting an FP1 to my flow bench to measure the differential pressure across an orifice to see how the resolution would be at low flow rates through a larger size orifice. Was I surprised!

Using the manometer mode of the FP1, I connected the FP1 aux serial port to a laptop running a spreadsheet. The manometer readings were converted to realtime cfm readings by the spread sheet using this simple equation for standard air density flow rates and .62 Cf :

13.55 * orifice diameter^2 * square root depression

I used a 2.710" diameter sharp edge orifice which will flow 526cfm @ 28"wc. Here are my results:

depression Reading Should be
"H2O CFM CFM
.021 14.70 14.42
.023 15.16 15.09
.030 17.38 17.23
.032 17.86 17.80
.059 24.16 24.17
.062 24.93 24.78
.091 30.08 30.02
.103 32.06 31.93
.105 32.32 32.24
.200 44.53 44.50
.201 44.71 44.61

I'll have to make a 4" orifice and see how well it does.

John

[Mouse]

I made a 4.010" sharp edge orifice to see what kind of resolution I could get with the Flow Performance FP1 processor for possible use in a single orifice flow bench. I used the same setup and equation as in the post above. Here is a sampling of the lower flow results:

Depression Reading Should be
"H2O CFM CFM
.009 21.1 20.7
.010 22 21.8
.013 25.3 24.8
.028 36.8 36.46
.050 49.05 48.72
.051 49.25 49.20
.059 53.2 52.92
.060 53.4 53.37
.061 53.9 53.81
.072 58.7 58.46
.075 60 59.7
.079 61.4 61.23
.095 67.2 67.15
.096 67.8 67.5
.106 71.1 70.93
.107 71.2 71.26
.108 71.8 71.6

John

[JRM]

John
Am I reading correctly the results you posted look fairly accurate. So is my thoughts of a single hole bench viable if you just use the electronic setup?