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Old 08-23-2012, 04:57 PM   #1
c125bob
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Default GAV + Advance Spark = Hot ?

Still learning how to drive this thing ! Got the new water pump on, fixed the brakes, and while testing brake adjustments I ran hot. I know I have to much water in the radiator but it was steaming and spitting. Close to home so no big deal to coast her back to the barn. So........ I need some help with spark advance and GAV setting.

Since I was jumping on the brakes pretty hard on a dirt road to check lock up and skid marks I had the GAV open more than usual, a little extra throttle and the spark higher than I normally run it. For some reason when stabbing the brakes the engine wants to die.

The radiator is "supposedly" rodded and cleaned recently, haven't had the car a month yet so I don't know for sure. I have driven it 10-20 miles without running hot on a hotter day. Today she was boiling.

Somebody please talk me through the proper GAV and spark advance settings for normal driving. Also, can these to cause the engine to get hot if not properly managed?

Thanks,'
Bob
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Old 08-23-2012, 05:08 PM   #2
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Default Re: GAV + Advance Spark = Hot ?

This link will take you to the owners manual, check out page 8 for spark and GAV adjustments.
http://www.motormayhem.net/mode-a-fo...owners-manual/

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Old 08-23-2012, 05:15 PM   #3
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Default Re: GAV + Advance Spark = Hot ?

Yep, it sure can cause it to run on the warm side. The gav should be set so, when the engine is warmed up, that it runs nice and smooth. If the engine is loping, then it is usually to far open. Needs to be turned to the right some to see when it will run smooth. If you run the engine with the spark advance lever in the upward position, it will most definitely make the engine run hot. Normal advance, if the engine is timed right would be about 2/3 of the way down, at about 40 to 55 miles per hour. The engine wanting to die when putting on the brakes could be electrical short in the brake switch, or most likely the fuel level in the carb. is to low or to high.
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Old 08-23-2012, 05:32 PM   #4
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Default Re: GAV + Advance Spark = Hot ?

I noticed the amp meter discharged when brakes are applied. I need to check the wiring for shorts. I was surprised at the car running hot, it never has before. I guess the prolonged idle, wrong advance, higher idle with throttle and incorrect GAV setting could cause it. I hope that's all it is anyway ! Lots to remember when driving these old dolls ! Thanks for the advice.
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Old 08-23-2012, 06:09 PM   #5
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Default Re: GAV + Advance Spark = Hot ?

The amp meter will show discharge when brakes applied, like the headlights, signal lights(if you've got them) until idle comes up. JMO
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Old 08-23-2012, 06:32 PM   #6
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Default Re: GAV + Advance Spark = Hot ?

Retart your spark and see if it still wants to die when you put on the brakes . I had the same problem and the cause was my timing was to far advanced .
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Old 08-23-2012, 08:23 PM   #7
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Default Re: GAV + Advance Spark = Hot ?

I have animated part of the owners manual, it might answer some of your questions.
http://modelabasics.com/Starting%20&%20Driving.htm

Your timing might be slightly off causing your overheating.

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Old 08-23-2012, 08:38 PM   #8
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Default Re: GAV + Advance Spark = Hot ?

Thanks Paul, I sent that to my iphone so I'll have it next time I drive the A. I just need to get used to it I guess. I've put about 60 miles on it so far and haven't had a problem with heating up till today. I had messed with the GAV and timing as well as a few long idles while adjusting the brakes. I hope it was just the "perfect storm" of me messing things up and not a cooling system problem. The old pump was pouring water, had a scored shaft so I replaced it. I searched and read a ton of posts on cooling system issue tonight.

I'll leave the water level a little lower tomorrow and see how it goes. I had it nearly full and I'm sure it was pushing out water. It was coming out the overflow as well as spitting and steaming around the quail cap. Bear with me, I appreciate the help folks !!
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Old 08-24-2012, 06:40 AM   #9
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Default Re: GAV + Advance Spark = Hot ?

Ammeter discharge,, it should with brakes applied [switch]..
GAV,, Zenith- cold, 1/2 turn open.. warm, closed
GAV,, Tillotson-cold 1/2-1.0 open.. warm, 1/4-1/2 open
Spark.. retard,up, 10:00- start.. run,, lower speeds, 9:00 [1/2].. Higher speeds,, 9:30[2/3]
Engine quitting on decel,, idle speed, idle mixture, float setting
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Old 08-24-2012, 06:58 AM   #10
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Default Re: GAV + Advance Spark = Hot ?

Lean mixture? This can also cause a hotter run. If you downshift 3> 2 does the exhaust POP? If so, you are probably running lean.
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Old 08-24-2012, 12:23 PM   #11
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Default Re: GAV + Advance Spark = Hot ?

Yes, it would pop when slowing with engine speed on down shift. It pretty much quit doing that when I turned up the GAV. I'm know I was running it lean at high idle with retarded spark when it overheated. I think I have a small exhaust leak that could cause what's left of an occassional pop.

I'm learning and I appreciate those that have helped me. Jim Johnston has helped me alot among others. I always felt like I was a decent mechanic and had a good feel for engines etc. This Model A has shown me things I've never thought of !!! Thanks again folks. Great forum.
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Old 08-24-2012, 12:44 PM   #12
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Default Re: GAV + Advance Spark = Hot ?

Not meaning you. Many that have no mechanical experience think that because they can see the spark plugs and the carburetor, that the model A is simple, untill the first problem happens.
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Old 08-24-2012, 12:55 PM   #13
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Default Re: GAV + Advance Spark = Hot ?

The brake light switch could be the problem. Mine shorted and the amp meter discharged about twenty amps. I have a fuse on the starter and on the generator out put now. Some of the reproduction brake light switches are not high quality.

Retarded spark and lean fuel mixture will make an engine run hot.

Just went to Deadwood SD (three miles away) and looked at all of the shinny street rods. Kool deadwood nights is this weekend. This starting to be a big event. I am thinking of wiping down the "A" and heading back down to Deadwood. They actually carry all kinds of waxes and polishing stuff in their trunks in special trays and little travel bags. I carry some tools in a cardboard box.

The model "A" was not running real good for a while but straightened out on the way home. There are some high dollar cars at the event but I do not think I would trade cars with the people.
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Old 08-24-2012, 01:40 PM   #14
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Default Re: GAV + Advance Spark = Hot ?

In my "not so vast" experience, the Model A people are FAR nicer than the hot rod people. My wife calls the hot rod car show types, "car snobs". You know the types- Constantly yelling out into the crowd "Don't touch!" and seen any weekend re-polishing the finish of their cars with increasingly finer materials, concluding with a final buff using the inside of a cat's ear.
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Old 08-24-2012, 05:05 PM   #15
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Default Re: GAV + Advance Spark = Hot ?

Paul you are so right. Everybody I've met in my short A Model experience has been very nice. I have a cardboard box with tools in my trunk as well. I guess I fall into the category of folks thinking they knew all they needed to know about engines and cars. It didn't take long for this car to set me straight ! It's a whole new ball game for me and I love it.

Took the A out for a "run hot" test drive today, set the GAV and advance as it should be and had no problems. It was nice having a little more brakes and being able to relax and enjoy the ride. I think we have bonded !
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Old 08-25-2012, 08:02 AM   #16
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Default Re: GAV + Advance Spark = Hot ?

Ooopps,, I really need to proof-read.. I meant 8:30[2/3]
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Old 08-25-2012, 10:20 AM   #17
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Default Re: GAV + Advance Spark = Hot ?

Got it Patrick and thanks again. Just got back from a 25 mile ride up and down hills, running fairly hard, some higher RPMs and no problem. I think I have "the zone" figured out on spark advance and GAV. It's a good feeling to make a trip without a problem.
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Old 08-25-2012, 10:47 AM   #18
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Default Re: GAV + Advance Spark = Hot ?

you might want to check to see if there is a vacuum leak. A small leak will cause carburetor popping and can be overcome by opening the GAV, but then the engine will be running rich at speed. Dying at stops also can indicate a vacuum leak. Areas to check are a loose throttle butterfly shaft, leaking vacuum wiper motor, warped (very common) or cracked manifold, loose vacuum fittings. A vacuum gauge will indicate whether or not there is a leak. A vacuum gauge will also indicate if the timing is too late. Too rich or too lean will contribute to overheating. Late timing will contribute to overheating. If your brakes are dragging, they will contribute to overheating too.
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Old 08-25-2012, 11:03 AM   #19
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Default Re: GAV + Advance Spark = Hot ?

Good info....I suspect a slight exhaust manifold leak. Had a major leak at clamp between manifold and muffler pipe. I fixed all that but it was kicking up a fuss before I did. It has to be wound up tight and gearing down to pop and then it's just a little if advance is high. I'll keep an eye on it and see how is does. Wiper (vacumn) works as it should carb seems tight and right. I'll watch it though.
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