The Ford Barn

Ford_Freddie · 03-25-2016, 04:53 AM

I have to remove the frozen GAV assembly on my Zenith carburetor. So I take a welding torch and apply heat to it. Then I have to dunk the carburetor into a pot of cold water. But isn't that dangerous for the casting? I'm afraid of cracking it. Thank you in advance.

Dollar Bill · 03-25-2016, 05:41 AM

When you say welding torch, I assume oxy/acety with a brazing tip.

Brass begins to soften about 1500F - You only want to heat it to about 500 degrees.

Brass and cast iron expand at different rates - Simply heating the carb housing should be enough movement to break it loose. First try without quenching.

Benson · 03-25-2016, 06:59 AM

MAPP gas is much better for heating brass as it is hotter than Propane and not so hot that it melts the brass.

O A will melt brass choke and throttle shafts in a heartbeat and then it is VERY hard to remove the shaft from the casting as the shaft is no longer round.

Small shaft screws can be heated if slot is still in good shape, Once slot is damaged then it takes a lot more work to get them apart.

On Cap and Main jets use caution so that you do not melt the jet even with MAPP gas or Propane. Then it is drill and PITA (one word is pain) time.

For secondary wells and GAV seats you must use O A on casting around the part ... heat area to dull cherry red, cool a little then dunk it.

Better to let casting cool a little before dunking.

Tom Wesenberg · 03-25-2016, 08:44 AM

I heat the carb with my propane torch then dunk it in cold water. It never hurt the casting.

Ford_Freddie · 03-25-2016, 09:14 AM

Thank you all. I will try it with my propane torch.

Benson · 03-25-2016, 09:25 AM

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Maybe I have just been unlucky with dunking in cold water but I have seen 200 or 300 castings that are cracked, so I let them cool first.

Ford_Freddie · 03-25-2016, 09:58 AM

Unfortunately the brass hex of the GAV housing is completely damaged. So I have to use the propane torch.

captndan · 03-25-2016, 02:12 PM

Where can you still buy MAPP gas?

Tom Wesenberg · 03-25-2016, 02:19 PM

Fleet Farm sells MAPP gas in small steel bottles, but it's about $10, while the same propane bottle is $4.

ian Simpson · 03-25-2016, 02:30 PM

True MAPP gas is not available. See https://en.wikipedia.org/wiki/MAPP_gas

Rich in Tucson · 03-26-2016, 12:01 AM

I am still nursing a small true MAPP gas cylinder that I bought in 1991 or so for HOT, NOW! with the push of a button but have acquired and use very small acetylene/oxygen tips when I have the time for their proper set up and use.

03-25-2016, 04:53 AM	#1
Ford_Freddie Member Join Date: Mar 2014 Location: Rosenheim/Germany Posts: 39	Removal of the frozen GAV assembly I have to remove the frozen GAV assembly on my Zenith carburetor. So I take a welding torch and apply heat to it. Then I have to dunk the carburetor into a pot of cold water. But isn't that dangerous for the casting? I'm afraid of cracking it. Thank you in advance.

03-25-2016, 05:41 AM	#2
Dollar Bill Senior Member Join Date: Oct 2014 Location: Keystone Heights, FL Posts: 647	Re: Removal of the frozen GAV assembly When you say welding torch, I assume oxy/acety with a brazing tip. Brass begins to soften about 1500F - You only want to heat it to about 500 degrees. Brass and cast iron expand at different rates - Simply heating the carb housing should be enough movement to break it loose. First try without quenching. __________________ I Love Anything That Turns Money Into Noise

03-25-2016, 06:59 AM	#3
Benson Senior Member Join Date: May 2010 Posts: 2,594	Re: Removal of the frozen GAV assembly MAPP gas is much better for heating brass as it is hotter than Propane and not so hot that it melts the brass. O A will melt brass choke and throttle shafts in a heartbeat and then it is VERY hard to remove the shaft from the casting as the shaft is no longer round. Small shaft screws can be heated if slot is still in good shape, Once slot is damaged then it takes a lot more work to get them apart. On Cap and Main jets use caution so that you do not melt the jet even with MAPP gas or Propane. Then it is drill and PITA (one word is pain) time. For secondary wells and GAV seats you must use O A on casting around the part ... heat area to dull cherry red, cool a little then dunk it. Better to let casting cool a little before dunking. Last edited by Benson; 03-25-2016 at 07:07 AM.

03-25-2016, 08:44 AM	#4
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Removal of the frozen GAV assembly I heat the carb with my propane torch then dunk it in cold water. It never hurt the casting.

03-25-2016, 09:14 AM	#5
Ford_Freddie Member Join Date: Mar 2014 Location: Rosenheim/Germany Posts: 39	Re: Removal of the frozen GAV assembly Thank you all. I will try it with my propane torch.

03-25-2016, 09:25 AM	#6
Benson Senior Member Join Date: May 2010 Posts: 2,594	Re: Removal of the frozen GAV assembly Sponsored Links (Register now to hide all advertisements) Maybe I have just been unlucky with dunking in cold water but I have seen 200 or 300 castings that are cracked, so I let them cool first. Last edited by Benson; 03-25-2016 at 09:32 AM.

03-25-2016, 09:58 AM	#7
Ford_Freddie Member Join Date: Mar 2014 Location: Rosenheim/Germany Posts: 39	Re: Removal of the frozen GAV assembly Unfortunately the brass hex of the GAV housing is completely damaged. So I have to use the propane torch.

03-25-2016, 02:12 PM	#8
captndan Senior Member Join Date: Nov 2015 Location: Tennessee Posts: 714	Re: Removal of the frozen GAV assembly Where can you still buy MAPP gas?

03-25-2016, 02:19 PM	#9
Tom Wesenberg Senior Member Join Date: May 2010 Location: Mpls, MN Posts: 27,582	Re: Removal of the frozen GAV assembly Fleet Farm sells MAPP gas in small steel bottles, but it's about $10, while the same propane bottle is $4.

03-25-2016, 02:30 PM	#10
ian Simpson Senior Member Join Date: Apr 2014 Posts: 709	Re: Removal of the frozen GAV assembly True MAPP gas is not available. See https://en.wikipedia.org/wiki/MAPP_gas

03-26-2016, 12:01 AM	#11
Rich in Tucson Senior Member Join Date: May 2010 Location: Tucson, Arizona Posts: 374	Re: Removal of the frozen GAV assembly I am still nursing a small true MAPP gas cylinder that I bought in 1991 or so for HOT, NOW! with the push of a button but have acquired and use very small acetylene/oxygen tips when I have the time for their proper set up and use.