The Ford Barn

Kpar · 11-05-2015, 07:11 PM

Some time back I installed a new Stromberg 97 to the 33. I thought all was working ok but the color of the plugs & comparison with the mates 33 (Lawrie) confirmed a rich mix.
Installed an A/F meter and test run with the standard #45 Jets.
Results were in the10 to 11 with the odd 12.
Changed to #44 results low 12 to high12
Changed to #43 results high 12 to low 13
Changed to #42 results High 13 to a low 14
Will run with this for a while and then maybe try #41 jets and test again.
All tests done at different cruising speeds.
It will be interesting on "How Low Can We Go" before loss in performance.
Hopefully hit the magic 14.7
Kpar

Ross F-1 · 11-05-2015, 08:22 PM

What does it drop to when you stomp on it and the power valve is flowing?

I've found that the idle mix screws have a fair amount of influence up to about 50 mph (this is on Holleys and Rochesters). A very small reduction at idle can affect cruise by as much as .5 AFR.

FWIW, I had mine totally dialed in at high altitude (5300'), and on a trip back east to ~600', I got up into the low 17's. It worried me so I bumped up two jet sizes, which put me back in the low-to-mid 14's. But while it was running lean, it ran great, very responsive. But interestingly, no real difference in mpg.

Charlie ny · 11-05-2015, 09:06 PM

Kpar,
I believe the power valve is leaking...trust me even brand new ones leak.
I have a little device to check PV's before I use them.
Charlie ny

Lawrie · 11-05-2015, 09:36 PM

Any chance of a picture of it.
Lawrie

G.M. · 11-06-2015, 09:31 AM

I used an exhaust gas tester when I tested several sets of adjustable
main jets. By testing a number of times and cleaning the plugs each
time it tells you how to "read" the plugs better. G.M.

Kahuna · 11-06-2015, 10:32 AM

Sponsored Links (Register now to hide all advertisements)

This may be of some help to some:
Interesting reading/very informative

http://www.dragstuff.com/techarticle...ead-plugs.html

Ol' Ron · 11-06-2015, 11:00 AM

One thing you have to consider when tuning an engine is the affects that ignition timing has on the FA reading, especially in the lean mode. A lean mixture requires more ignition lead for the slower burning mixture. Having more advance in cruse can increase the AF number. Biggest problem with stock ignitions systems is: This can't be done with the present distributor design and is a good reason the GM distributor is better. It can be tuned for this. I may have a solution for this in the future.

Kpar · 11-06-2015, 05:02 PM

Quote:

Originally Posted by Charlie ny

Kpar,
I believe the power valve is leaking...trust me even brand new ones leak.
I have a little device to check PV's before I use them.
Charlie ny

Charlie NY, What you're saying is the jet sizes we are down to should be producing a better AF reading ?. And yes as Lawrie said a photo of your test gadget would be great.
Kpar

11-05-2015, 07:11 PM	#1
Kpar Senior Member Join Date: Feb 2012 Location: Gladstone QLD Australia Posts: 324	Air/Fuel Readings Some time back I installed a new Stromberg 97 to the 33. I thought all was working ok but the color of the plugs & comparison with the mates 33 (Lawrie) confirmed a rich mix. Installed an A/F meter and test run with the standard #45 Jets. Results were in the10 to 11 with the odd 12. Changed to #44 results low 12 to high12 Changed to #43 results high 12 to low 13 Changed to #42 results High 13 to a low 14 Will run with this for a while and then maybe try #41 jets and test again. All tests done at different cruising speeds. It will be interesting on "How Low Can We Go" before loss in performance. Hopefully hit the magic 14.7 Kpar

11-05-2015, 08:22 PM	#2
Ross F-1 Senior Member Join Date: Nov 2010 Location: NM Posts: 2,443	Re: Air/Fuel Readings What does it drop to when you stomp on it and the power valve is flowing? I've found that the idle mix screws have a fair amount of influence up to about 50 mph (this is on Holleys and Rochesters). A very small reduction at idle can affect cruise by as much as .5 AFR. FWIW, I had mine totally dialed in at high altitude (5300'), and on a trip back east to ~600', I got up into the low 17's. It worried me so I bumped up two jet sizes, which put me back in the low-to-mid 14's. But while it was running lean, it ran great, very responsive. But interestingly, no real difference in mpg. __________________ '52 F-1, EAB flathead

11-05-2015, 09:06 PM	#3
Charlie ny BANNED Join Date: May 2010 Posts: 3,019	Re: Air/Fuel Readings Kpar, I believe the power valve is leaking...trust me even brand new ones leak. I have a little device to check PV's before I use them. Charlie ny

11-06-2015, 09:31 AM	#5
G.M. Senior Member Join Date: May 2010 Location: Florida and Penna. Posts: 4,471	Re: Air/Fuel Readings I used an exhaust gas tester when I tested several sets of adjustable main jets. By testing a number of times and cleaning the plugs each time it tells you how to "read" the plugs better. G.M. __________________ www.fordcollector.com

11-06-2015, 10:32 AM	#6
Kahuna Senior Member Join Date: May 2010 Location: NorCal Posts: 2,617	Re: Air/Fuel Readings Sponsored Links (Register now to hide all advertisements) This may be of some help to some: Interesting reading/very informative http://www.dragstuff.com/techarticle...ead-plugs.html

11-05-2015, 09:36 PM	#4
Lawrie Senior Member Join Date: May 2010 Location: Qld, Australia Posts: 4,529	Re: Air/Fuel Readings Any chance of a picture of it. Lawrie

11-06-2015, 11:00 AM	#7
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,985	Re: Air/Fuel Readings One thing you have to consider when tuning an engine is the affects that ignition timing has on the FA reading, especially in the lean mode. A lean mixture requires more ignition lead for the slower burning mixture. Having more advance in cruse can increase the AF number. Biggest problem with stock ignitions systems is: This can't be done with the present distributor design and is a good reason the GM distributor is better. It can be tuned for this. I may have a solution for this in the future.