Gav

Mcb12

Mcb12

Member
I have been playing with the Gas Adjustment Valve tuning for a cooler running engine. I have noticed that opening the valve seems to help run cooler at higher speeds. That I expected. But, when idling if the GAV is open at all the car runs ruff, As soon as a close it it smooths out. I though that the GAV should have no effect on idle, is there something wrong in the carb?
 
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the model A likes to idle low.. make sure your not set to high..
dont use your hand lever to idle the car... set it with the idle stop/ curb idle screw
 
That makes sense Mitch, I am adjusting the idle with the throttle and it is pulling fuel through CAP jet rather than idle jet. I will give that a try. Thank you.
 
Still seems strange though, doesn't it?
Our "A" will idle fine with the GAV cracked some, the same setting we drive it at. Even a fast idle is fine, or any speed for that matter.

Mcb12, do you have an air filter and if so which one?
 
MrTube said:
Still seems strange though, doesn't it?
Our "A" will idle fine with the GAV cracked some, the same setting we drive it at. Even a fast idle is fine, or any speed for that matter.

Mcb12, do you have an air filter and if so which one?
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what are you running for a carb and jets?
 
Mitch//pa said:
if its running good leave it alone
every carb has there little differences of where the settings are happy at.
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Mitch, you sure got that right. I've owned over twenty Model A's since 1961, and played with many more, and I can testify there is no standard setting for the carb.
 
I just looked at my recently purchased set of Renner's jets and none of them are numbered. However, all are measured for flow. Two look like reproduction. Two looker original but not numbered.
 
I am thinking the original poster must have a big problem if he is seeing a temperature change on a gauge from running lean, I would think a severe loss of power would be evident first along with engine damage, - you can be close with jet sizes and still have a clean running - idling engine, I buy forever4s statement.
 
forever4 said:
I have found that virtually all original jets are fine, as is. It is repro jets and non-original ones you need to be concerned about. Many carbs have been 'rebuilt' over the years with dubious replacement jets.

All Renner does is take original jets and measure them and tell you what they flow. He does not modify any jets to my knowledge. He just sells you a set of original jets that he measured and that are within the range that he has deemed acceptable.

You can get the same running results pretty much by using any set of original numbered jets in good condition.

Model A Ford Garage ~ Carburetor Jet Sizes & Flow Rates
Model A Ford Garage ~ Carburetor Jet Sizes & Flow Rates on Ford Garage

p.s. I will buy your extra original numbers jets in good condition.
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most i received from them were recalibrated
 
I started this thread because I had read that the GAV should not affect Idle, yet it does in my car, even when I have the idle as low as it will go without stalling the engine. But, I have also read an article on Carbs (Model A Basics site) that the GAV does little to affect gas flow once higher RPM are reached, in fact it states that you should use the GAV to lean the mix for fuel economy. Am I missing something here. In my 31 the GAV has a tremendous effect on fuel mixture at all speeds. I may have a separate issue with overheating but the the fuel mixture is still perplexing to me. My plugs look great is there another way to determent if and when I am running lean or rich, behond the obvious, backfire.......
 
The GAV affects engine running at all speeds in my car. I read somewhere to turn the GAV richer for starting and warmup, which I do with definite effect. (Standard Zenith with Hi-Boy air cleaner)

John
 
Mcb12 said:
I started this thread because I had read that the GAV should not affect Idle, yet it does in my car, even when I have the idle as low as it will go without stalling the engine. But, I have also read an article on Carbs (Model A Basics site) that the GAV does little to affect gas flow once higher RPM are reached, in fact it states that you should use the GAV to lean the mix for fuel economy. Am I missing something here. In my 31 the GAV has a tremendous effect on fuel mixture at all speeds. I may have a separate issue with overheating but the the fuel mixture is still perplexing to me. My plugs look great is there another way to determent if and when I am running lean or rich, behond the obvious, backfire.......
Click to expand...
"MAYBE" your float level is HIGHER than the tip of your GAV nozzle & it's "dribbling"? "Maybe" add a washer or 2, under your float valve, to lower your fuel level.
Bill W.
 
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