flow test questions

[Art Bjornestad]

I am not too sure about what a flow test tells you. What figures are you expecting to see and what steps do you take if they aren't correct?

[Jim/GA]

If you are talking about flow testing your jets out of your Zenith carburetor, it tells you if the jet's internal diameter (that controls how much fuel goes through) is the right size.

The test procedure has you measure the volume of water you collect passing through the jets in a prescribed amount of time. People have measured a lot of jets out of a lot of carbs that run well and come up with recommendations of what the volume of water should be during a test for each of the jets in the Zenith carb. (Each jets has its own range of numbers that you try to be within.) So those are the figures you expect to see.

If you do not, you can try different jets (keep measuring jets until you find one that yields the number you are looking for) or you can attempt to adjust the inside diameter larger or smaller to get the volume you are looking for.

Hope this helps.

[Dave in MN]

Originally Posted by Art Bjornestad

I am not too sure about what a flow test tells you. What figures are you expecting to see and what steps do you take if they aren't correct?

I assume you are questioning carb jets. If you want to fine tune your zenith carb, I suggest you order a booklet written by Steve Pargeter. You will find "ZENITH MODEL "A" CARBURETOR RESTORATION GUIDELINES" sold by most of the national parts vendors. This booklet clearly explains the process. Good Day! Dave in MN

[Ron in Quincy]

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What I'm about to say will certainly create discussion but it's what I've done for years when rebuilding in excess of 2,000 carburetors including the early double venturi.

I have measured the smooth tip of a Torch Tip Cleaner and marked them in thousands so I end up with one at .021, .018, .019, .036, .037,.038, and .039.

I prefer to use original jets as some of the new ones available are junk.

I use a magnifiing glass to inspect the orfis of the jets to be sure they are not damaged. Jets don't wear out, just get dirty. It's amaizing the varitey of jet sizes that exist with original marked jets; example # 19 in most cases will measure .037 but you will also find some at .038 and .039. The compensator jet in the double venturi carburetor usually measures .036 and the later #19 usually measures .037. I always use a .021 Idle jet, some of the remakes will measure .022 to .024, way to big !!!.

I have arrived with a combination of jet sizes that seem to work well for me, run well, don't leak even when the gas shutoff is left on. I have never flow tested even one jet, sold numerous carburetors and garanteed the people their money back if not satified. The sold carburetors have helped to supported my "A" hobby over the years.

By the way, due to the hardness of the new jet gaskets, I use a tooth pick and put a small coating of Aviation Gasket Cement on them before installing the jets; I also use the same on the threads of the choke driver housing as the threads are below the bowl fuel level.

Again, this is only my opinion, so don't be upset with me.

Ron