High-Altitude Running

[kpreed]

Hello all,
My 1929 CCPU runs a bit rich at home (9200 Ft.). 90% of my driving will be from home to club outings.(all over 5000 Ft.). I hear of a Denver Head for later Fords, but what other then carb. work will help me?
Thanks.
Patty

[msmaron]

have you adjusted the GAV to start..and are your flow rates on the carb correct?

[kpreed]

Hello,
Yes, the GAV is always used, when on the road it is between 1/8-1/4 turn open and still runs rich any less will make it back-fire. I am thing a smaller jet?

[Jim Brierley]

Higher compression such as the police head or one from Snyder's will be a big improvement in power but you will still need to correct the fuel mixture problem. I would think that if the GAV being closed too much causes backfiring, the jetting must be OK???

[kpreed]

Thank You,
Power is not a big problem, but it can not hurt. I just want it to run not so rich. The Head idea has come up, but with all the cost plus installing it. (my spouse is in a wheelchair now and can not do it) I just need to be sure first.

[msmaron]

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are you sure the flow rate is correct for your jets?

[kpreed]

No, I have no way to know, but it will be the first thing I look in to.

[Patrick L.]

High altitudes will make an engine run rich.. If yours is running too rich, maybe you'll need to re-jet..

[Ron in Quincy]

If you can not close off the GAV then your jet sizes are not correct. I live at 3500' elevation and am able to close off the GAV without any resulting problem. With normal steady driving, by shutting off the GAV will result in better gas mileage. I try to always use original jets; I size them by thousands; I do not flow test my jets. Using a torch tip cleaner set, I mic the smooth ends and come up with the following sizes: .021 for idle jets, .036 and .037 for compensator jets, .037 for main jets, and .038 or .039 for cap jets. The double venturi carbs call for a #18 (.036) compensator jet.
I have been rebuilding carburetors for 30 years, using the above method, and have not had any problems.
Others may disagree with me or have other ways to jet their carbs but this has worked for me.

Ron

[marc hildebrant]

When I first got my Model A, I was living in Longmont CO (5000 ft). I found that the GAV control would work best about 1/8 open after warmed up. Also, I had to be careful to set the spark advance just right.

I did drive the car up to Ward (10,000) feet once. The power was down, but it still ran O.K.

Now that I'm at 1000 ft, it has much more power...but Colorado does have advantages over Minnesota (Berts in Denver and much better weather/views).

Marc

[kpreed]

Thank You all on this, it looks like re-jetting it is in my future.

[Bruce of MN]

When I was a little boy, Dad and I drove up Pike's Peak in his '31 Coupe. He bought it in Colorado Springs and I wouldn't have any idea if it had new jets. It has a Tilly now.

[Paul in Colorado]

You might talk to Steve or Phil at Bert's in Denver. I have two Zenith carburetors rebuilt by Chris Pelican when he was in Denver. They work fine at altitude.