New Stromberg 97 jetting help

[donald1950]

i have a new English Stromberg 97 on a stock 1930 model A with factory jetting per Cleve. i know it is running rich with the factory jetting, as I do not need a choke it to start the car. but has poor gas mileage. who would be the best person to contact here on the Barn for better jetting suggestions. i have the choke parts to install on the carburetor. i would just like to get rid of the gasoline smell and get a little better mileage. i know i will need to buy the appropriate jets from a knowledgeable Stromberg vendor. i have been driving the car for 6 months now, also, it has a New Rex automatic timing advance unit installed.

thank you for any and all input and suggestions.

Don

[Flathead]

Do you have an electric fuel pump?

[john in illinois]

I have a stock model A with an English 97 and a 5.5:1 head . Had it for 5 or 6 years. I started with smaller .043 jets and got detonation at cruising speeds. The spark plugs were white and showed signs of detonation.

As mentioned if you have an electric pump pressure over 2.5 lbs could cause flooding and rich running.

I have since used stock .045 jets and the plugs are normal light tan. How do your plugs look?

John

[donald1950]

John, yes i do and it is 2.5 # of pressure. it is not blowing past the inlet valve it is the jetting. tail pipe & plugs a bit sooty...... Don

[Flathead]

Small paper air filter?

[john in illinois]

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Flathead beat me to it,and it is a consideration.

If you have a small paper air cleaner that that can seem like a jet problem.

http://www.modela.org/default.html


Here is a good carb site. He uses a stock carb, but the fundamentals are the same. click on problem solving then air filtration. I use the medium k&n on my A with a Zenith or 97.

John

[Charlie ny]

An elusive culprit possibility.....a leaky power valve. Even new PV's can leak. A leaking
pv allows fuel in the acc pump well to be drawn by vacuum in the venturiis out thru
the 'J' tubes.
Charlie ny

[donald1950]

Flathead, K&N filter.

[donald1950]

Charlie, how do i contact you to talk about power valves and getting several new ones from you? Don

[scicala]

Charlie's (Charlie Schwendler) email is: [email protected]


Phone is (716) 662-9159


Or leave him a personal message on the Barn.


His ID on Ford Barn is Charlie ny


Sal

[Jembow]

Have you emailed Clive at Stromberg, he is very helpful.
[email protected]

[Terry,OH]

What size mains do you have now? What size PV? "you have the choke parts to put on the carburetor" What does that mean??? Are the parts off at this time???

[donald1950]

Jembow & Terry, when i purchased the 97 from Clive he told me it would work fine just as it came out of the box. nothing has been changed so it is as it came with 0.045 inch main jets and a Number 65 power valve. i did purchase the kit of parts to add a choke cable attachment if i might need it. Clive said with this carb on the stock A motor it would not need a choke. it runs rich enough it fires right up and idles from a dead cold ( or at least as cold as it gets in san antonio, and runs fine. the car is a daily driver. the only changes are the 97 with the down draft manifold and a New Rex automatic timing advance device. it has a high speed gear set so it will cruse at 50 mph on the highway. Charlie NY made a suggestion and is sending a new PV so i will go with that.. later this fall the motor will get changed out to a new GM Vortec 3.0 (updated version of the older 153 4 cylinder mid 60s Nova motor) and a 39 Ford syncromesh top loader transmission.

[scicala]

I guess I don't understand the reasoning of making a carburetor richer than needed, just so you don't have to use a choke. If that's what Clive was saying. Sounds like quite the waste of gasoline.


Sal

[flatjack9]

I think I would go with 43 main jets. I also don't get Clive's reasoning.

[donald1950]

Sal, i am not trying to richen the carb i want to lean it somewhat. Charlie is sending me a 68 PV as he thinks the one currently in the carb may be leaking.... i do not drive the car hard enough for the accelerator pump to reach the PV.

[donald1950]

Flatjack9, i think the thinking is that the 200 cu in 4 banger is close to the 221 cu in V8s so every thing should work out pretty close.....

[scicala]

Originally Posted by donald1950

Sal, i am not trying to richen the carb i want to lean it somewhat. Charlie is sending me a 68 PV as he thinks the one currently in the carb may be leaking.... i do not drive the car hard enough for the accelerator pump to reach the PV.

Hi Donald,


I wasn't suggesting that you make the carb richer. I was wondering why Clive would make it rich to avoid using a choke. I agree 100% with what Charlie suggests. Your current 45 main jets should be good, and leaking power valves are a known possibility on 97's.


Sal

[flatjack9]

That was my point in suggesting smaller jets as it seems Clive expects it to be rich with 45's.

[donald1950]

Sal, in browsing a Hemmings article on Stromberg airflow of 97s (155 cfm) and the new 81s (125 cfm) it got me to thinking (and for me that is dangerous as my career was in the telephone industry).

when i use this tire size and gear ratio calculator https://spicerparts.com/calculators/...rpm-calculator
and plug in my 3.55 final gear with 29.5 tires & 55 mph vehicle speed, it gives me about 2250 rpm.

when i use this this CFM calculator,
https://www.widman.biz/English/Calculators/CFM.html
and plugging the 200 cu in motor at 2250 rpm it gives me a recommended cfm of 104 cfm.

so looking at that info, it seems that the new 81 carb at 125 cfm might be a better choice for the 200 cu in model A motor, as the 155 cfm 97 could be over kill on those 200 cu in and allow it to be rich with the out of the box jetting

The model 48 units, rated at 170 cfm, share the same base casting as the 97s but had a larger 1-1/32-inch bore diameter. The 97s got their name because of the 31/32-inch-bore diameter (.97-inch) and were rated at 155 cfm. Model 81s have a 13/16-inch bore diameter (.8125-inch) and were rated at 125 cfm.

don't know if this makes much reality in the real world of carburetor calibration.
i do not think Clive intentionally made it rich so as not to have to use a choke, it just seems to work out that way with that small 200 cu in motor...... Don