Air cleaner "Auto Therm" unit

[GMCDAC]

Did any of the later V-6 GMC's use the Auto Therm valve on the air cleaner snout? Although not on a V-6, I need to replace one and since a lot of folks on this forum tend to lean toward restoration, I thought maybe someone here has done it without bending the heck out of the air cleaner snout! I know the unit can be bought at a decent price but I sure can't find how people replace them.

If this is too far from the purpose of this forum please delete.

Thanks, DAC

[bigblockv6]

Yes, 1968 and 1969 305E and 351E V6 1/2 ton trucks did have the Auto Therm unit, even the carburetors for those particular models were ported for that as well.

[GMCDAC]

Originally Posted by bigblockv6

Yes, 1968 and 1969 305E and 351E V6 1/2 ton trucks did have the Auto Therm unit, even the carburetors for those particular models were ported for that as well.

Thanks for the fast reply Pete! Do you know how to change the darn thing out without butchering up the air cleaner? I can't figure out how to bend the tab back into place once the new one is installed. I can get the tab "unbent" but you still gotta put it back together---LOL!

Thanks---DAC

[bigblockv6]

It's all about bending that tab, just use a flat blat screwdriver to bend it. When you replace it use a vise grip or C clamp as long as one will fit in to hold down the unit so you can bend the tab back to it's proper position.

[GMCDAC]

Originally Posted by bigblockv6

Yes, 1968 and 1969 305E and 351E V6 1/2 ton trucks did have the Auto Therm unit, even the carburetors for those particular models were ported for that as well.

Originally Posted by bigblockv6

It's all about bending that tab, just use a flat blat screwdriver to bend it. When you replace it use a vise grip or C clamp as long as one will fit in to hold down the unit so you can bend the tab back to it's proper position.

Ha ok that's what I was afraid of----I better go to Harbor Freight and see if I can find an oddball long-armed clamp of some sort to bend that darn tab back into position. The unit still works with a vacuum gun on my '72 GMC and it doesn't need it due to headers but even though I have owned that truck since 1979 someone had drilled a bunch of holes in the filter can part before we bought it. I'm hoping to keep the '70 air cleaner assembly on the '70. I want that valve to work though!

DAC

[TJ's GMC]

Be sure to post pictures of the finished product and maybe even some of how you did it!

[GMCDAC]

Originally Posted by TJ's GMC

Be sure to post pictures of the finished product and maybe even some of how you did it!

Ok TJ I did get started on it today--Mondays are my day off, but I had other chores to do also. Since I'm on an almost non-existant budget I decided to pull the good one and swap it to the one for the '70, which gave me a little practice in removal and it came out without destroying the snout!

I had to go into town for a roll of welding wire so I stopped at Tractor Supply since it was on the way for a long reach clamp. Much closer than Harbor Freight.

I got the flat bill and the long reach locking pliers at TSC (pic1) for $9.99 in a combo deal so I wouldn't be out much if it didn't work.

Pic 2-7 show how I had to cut the clamp up to fit into the air cleaner snout and get to the position to press on the tab for installation.

Pic 8 is looking up the snout to where the clamp has to reach in pic 9.

Pic 10 is bending up the tab and bracket to remove the good one.

Please pay no attention to the engines in the pics-----

[GMCDAC]

Four more pics. I had to bend the retainer quite a ways to get the good one out-pic1.

The good one and the bad one-pic2.

Pic 3 and 4 show the stroke of the diaphragm from closed to open.

That's where I'm at right now. I will try to get the swap done after work tomorrow. I hope this may help anyone that wants to do this repair on their later V-6 engines.

DAC

[TJ's GMC]

Thanks for the pictures! Wanting those for future reference for anyone who may have the same issue.

[GMCDAC]

I got the good one swapped last night. The retainer kinked a bit but I slid that thin knife blade under it and tapped on it with a plastic hammer to work that out. It was much easier to do the clamping with it secured to the engine. The clamp I built would not hit the tab right until I pulled vacuum on the valve, closing it. Then the tab pressed into shape easily.

DAC