How to: Jet flow test?

[RUNNERBUN]

I see a problem with the setup as per post 17 by rockhillwill. The jet is attached to a length of tube which is then lowered into the collection beaker. The jet must be kept in a horizontal position to maintain the 36" or 37 1/4" (whichever you are using) Lowering the jet as shown in the picture will effectively increase the head pressure an will not give an accurate reading. The post by 160B (post 16) and Tom Endys post 20 shows the correct setup for holding the jets at the correct position.

[BlueSunoco]

Or, you could just buy a set of jets from Renner's they are already flow tested and not meaning the annoying FLO that is on TV everytime I turn it on

Now that's progress-ive

[edmondclinton]

Originally Posted by RUNNERBUN

The post by 160B (post 16) and Tom Endys post 20 shows the correct setup.

Even though I don't have a picture I can assure you that my setup is completely accurate as well.

[MVal]

I seem to recall the distance was 1 meter or about 39"--guess I am wrong? Wasn't Zenith a French company?

[edmondclinton]

Originally Posted by MVal

I seem to recall the distance was 1 meter or about 39"--guess I am wrong? Wasn't Zenith a French company?

Yes, you are wrong. The distance is 36 inches.

[Mike V. Florida]

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Originally Posted by edmondclinton

Yes, you are wrong. The distance is 36 inches.

Original Ford jet drawings at the archives specify the flow rates at 37-1/4 inch head, not 36 inch.

[johnbuckley]

So Mike, do you reckon we are mostly running with the jets slightly too rich if we use a 36 inch head test rig, or is it not a significant difference, or have we a consensus that things run best with modern fuels with the jets tested as recommended in most of the modern manuals?

[johnbuckley]

Originally Posted by BlueSunoco

Or, you could just buy a set of jets from Renner's they are already flow tested...

Oh No he can't!OP Bikemaniac lives in Denmark , unfortunately Renners don't ( or at least didn't when I last checked with them) export to Europe.

[RonC]

The zenith company's head used was 37-1/4" however 36" is fine as long as you are using the flow values based on 36" not zeniths values

http://www.fordgarage.com/pages/jetflowrates.htm

[Mitch//pa]

Originally Posted by johnbuckley

Oh No he can't!OP Bikemaniac lives in Denmark , unfortunately Renners don't ( or at least didn't when I last checked with them) export to Europe.

i have a few extra sets of renners jets in stock, i can ship him some if he is interested..

[johnbuckley]

Originally Posted by Mitch//pa

i have a few extra sets of renners jets in stock, i can ship him some if he is interested..

Thanks very kind of you, however let's hope he's got a test rig organised after two pages of Ford barn advice!

[oj]

How do you adjust for the specific gravity of todays' fuels when compared to the original flow data?

[edmondclinton]

Originally Posted by Mike V. Florida

Original Ford jet drawings at the archives specify the flow rates at 37-1/4 inch head, not 36 inch.

My use of the 36" column came from an engineer in MI. named Al Blatter who worked for Bendix designing fuel components and controls for automotive, aircraft, rocket and jet engines. He was advised by some people who were employed at the original Zenith Carburetor plant.

They arrived at their flow figures using new-old-stock jets with a 36 inches head of water pressure. This was in about 1980 or so.

[edmondclinton]

Originally Posted by oj

How do you adjust for the specific gravity of todays' fuels when compared to the original flow data?

According to a conversation that I had with Larry Brumfield about 15 years ago, when I bought one of his heads, he said that gasoline produced back in the day was different and consequently the figures that he used, which were the same as Al Blatter's test with NOS jets, were for a full rich condition and speed. He advised me that I could cut back on the main jet to say 145 cc/min or so and the engine would still run well for normal speeds and economy.

[Tom Endy]

All the literature I have seen in the past 25 years spoke of a 36" high water column. For that reason that is how I built mine. Jet sizing literature calls out a window for each jet. For the cap jet the window is wide, for the main jet, not quite so wide, for the comp and idle jets the window is narrow.

My experience has been that using my 36" water column and resizing the jets to the prescribed window sizes, when installed into a properly restored Zenith they perform as Henry ordered.

Most jets found in old Zeniths and the ones that come from many of the suppliers are not sized accordingly and should be re-sized if you expect a good running Zenith.

Tom Endy

[edmondclinton]

Originally Posted by RonC

The zenith company's head used was 37-1/4" however 36" is fine as long as you are using the flow values based on 36" not zeniths values

http://www.fordgarage.com/pages/jetflowrates.htm

The link that you show here, i.e., Vince Falter's, says that it was Ford's measurement that used 37-1/4 inches not necessarily the Zenith Company's.


According to the link:

"FORD measured the flow rates with a head pressure of 37 1/4 inches of water pressure but nearly all recent articles and specifications use 36 inch head pressure of water as the reference. I don't know why the difference but it is something to be aware of."



And according to me, if one made two different columns or one column with enough length to work with 2 test ports it would be an easy test to see what effect another 1 1/4 inch of head pressure would have on the flow rates using the exact same jets.

And by the way and of course no one has said otherwise even though those on this site will sometimes argue with him but Vince Falter is no dummy. He is, or was, an engineer for General Motors.

[edmondclinton]

Originally Posted by Tom Endy

All the literature I have seen in the past 25 years spoke of a 36" high water column. For that reason that is how I built mine. Jet sizing literature calls out a window for each jet. For the cap jet the window is wide, for the main jet, not quite so wide, for the comp and idle jets the window is narrow.

My experience has been that using my 36" water column and resizing the jets to the prescribed window sizes, when installed into a properly restored Zenith they perform as Henry ordered.

Most jets found in old Zeniths and the ones that come from many of the suppliers are not sized accordingly and should be re-sized if you expect a good running Zenith.

Tom Endy

The stream coming from a jet being tested should be a solid circular cross section about 2 or 3 inches long before it breaks up. If the stream is fuzzy and not circular, the jet probably has a nick, if it's an original jet, or a machining burr on the entrance to the jet, if it's a repo.

The entrance shape to the jet was carefully designed by the manufacturer to obtain the correct flow. However, two jets of the same size (diameter) can flow quite differently. In fact, if one jet has a smooth streamlined entrance shape and the other has a sharp cornered entrance, the latter may only flow about 60% or so of the smooth jet flow rate. The design is not important to us as long as we can get the correct flow range.

[RonC]

Originally Posted by edmondclinton

The link that you show here, i.e., Vince Falter's, says that it was Ford's measurement that used 37-1/4 inches not necessarily the Zenith Company's.


According to the link:

"FORD measured the flow rates with a head pressure of 37 1/4 inches of water pressure but nearly all recent articles and specifications use 36 inch head pressure of water as the reference. I don't know why the difference but it is something to be aware of."



And according to me, if one made two different columns or one column with enough length to work with 2 test ports it would be an easy test to see what effect another 1 1/4 inch of head pressure would have on the flow rates using the exact same jets.

And by the way and of course no one has said otherwise even though those on this site will sometimes argue with him but Vince Falter is no dummy. He is, or was, an engineer for General Motors.

Ed the flow rate is affected by the head or pressure of water at the jet outlet. Water has a weight (62.4 pounds per cubic feet) and the more depth of water the more weight. So yes if you change the amount of water (head) over the jet outlet the flow rate will change. The difference in rates based 36 or 37 1/4 is listed on Vince's site. You can calculate the exact flow rate one can expect based on the head used and jet outlet size and shape. I'm sure Ford calculated what they wanted for rates for their engine and instructed zenith to manufacture according to their specs. It doesn't matter what head you use in inches as long as you are using the expected flow rates derived from that head. Al Blatter tested flow rates of nos jets at a head of 36 inches based on his experience. He could have used any other head just his flow rates would be different. You need to stick to whatever head was used for water ever rate information you are comparing to.

[Mike V. Florida]

if you push the water past the outlet, I would think there would be added pressure to the outlet as opposed to water supplied from a different pipe and flows over the the tube with the outlet?

[RonC]

Originally Posted by Mike V. Florida

if you push the water past the outlet, I would think there would be added pressure to the outlet as opposed to water supplied from a different pipe and flows over the the tube with the outlet?

The pictures I have seen show Zenith flow testing the jets with a flow tester that has a tank of liquid above with the level controlled by a float