Flow rate model "A" and "B" Zenith carb.

TDO

TDO

Senior Member
Just when I thought I had the Flo-Rate for the Model A and B carb. I got a surprise when I ordered a set of flow tested jets for my model B Zenith carb. from Dave Renner. I was using the flow chart from the book, Restoring the Model A and B carburetor the "Rex" Reheis way.
So when I got my jets from Dave Renners, I noticed that the flow rate on them was much higher than in Rex's book. So reading below the flow chart , I find that the flow rate was developed by Dave Renner of Renners Corner. So now I'm really confused. So I called Dave and asked him why there was such a large difference then what he had in Rex Reheis book.
He said he developed those flow-rates many a year ago, and since then he and two other guys had been experimenting with different flow-rates. And the ones he uses now work the best. Here are the two flow-rates.
Rex' Reheis chart

main -136-142
cap-372-462
compensator -110-118
idle-43-47
power-110-118

Dave renners new chart that came with my jets.

Flow thru the cap jet is not important as long as it flows more than the comp jet.
main- 153-157
comp -144-148
power -134-138
idle -49-52
These are for a model B carb. If any one has the ones they got with there Model A carb. I would like to no what Dave Renner is now using for there flow.
 
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The difference could be in the way they are tested --the amount of "head" --level of liquid above the jet in the test fixture
 
My preference would be select jets for maximum power in the mid to upper engine rpm range that would not foul the spark plugs.

I do not know what Renner's "works the best" means regarding jet sizing.
 
I think it's all just a get started guide, as
1) bore
2) cam
3) valve size
4) compression ratio
All play a part in how much gas is needed for the different rpms/load on the engine.
But what do I know ?
 
I can't explain why Renner's flow chart may be different from others but I had Renner's Corner rebuild a B carb for me and it runs great. They have been great to work with and I recently had another B carb rebuilt by them. Haven't tested it yet but expect a good running carb from them. I have a 5.9 head, bored out A intake manifold, and a B touring cam if that matters.
 
Chuck Sea/Tac said:
I think it's all just a get started guide, as
1) bore
2) cam
3) valve size
4) compression ratio
All play a part in how much gas is needed for the different rpms/load on the engine.
But what do I know ?
Click to expand...

That's exactly correct, I flow tested mine according to the chart and the engine ran poorly especially at higher RPM, I opened them up until it ran OK, found out at a later date it had an over bore of 90 , the instructions I had were that there maybe further tuning to do, an additional set of jets with added flow rates could be used, this could help overcome the unknown internals, is it possible that Renners upped the flow rate due to Ethanol?.
 
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I installed a set of Renner's jets in my Zenith 2 carburetor and stock cylinder head and I really like them. Dave also includes the flow numbers of the jets so you know what you have. Idles better, smooth transition through the rpm range, more power and better mileage. Not often you get better mileage and more power. I highly recommend Renner's.

Chet
 
If one has several used Model A and/or Model B carburetors, some Zenith, Marvel, Tillotston, etc., some re-built, some not, after trying each, one can experience different amounts of carbon building up on plugs; different MPG; different GAV settings at start up, idle, & on the highway; different carburetor air settings; different pick up, etc., etc.

Then if one has several new jets & several used original jets, one finds the flow rates vary considerably ........ some of the original jet orifices were improperly enlarged with drills, steel wires etc.

Add to this, varying engine conditions in reply #6, one could spend a lifetime tinkering & changing out different carburetor jets & different carburetors.

I remember a noteworthy comment from Mr. Ron Cloat, (Rainmaker Ron), after telling him about my Sears Marvel carburetor that came with my car in 1958. With my brother & I driving to work every day at 45 mph in my Model A, we averaged 28 mpg.

His comment was: "When you ever experience having a real good carburetor on a Model A, don't mess with it ........... just install it & keep it."

Always thought that was some of the most helpful carburetor advice for Model A owners with one or several Model A/B carburetors..
 
Growley Bear (Chet). Can you give us the flow rates that came with your jets from Renner's? Thank You.
 
I bought Zenith 'A' jets from Renner's in March, 2013. Here's the data he sent with the jets (cc/minute):

Jet ..........Target..........Actual

Main.........145-150...........151

Comp........150-155...........155

Idle............48-52..............50
 
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