When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I discovered that by adding too much spacer thickness under my carb I ended up with the hood pushing a little on the rim of the stock air cleaner assembly. It didn't dawn on me right away what this may be doing to my carb.
Here is the main problem when the air cleaner assembly gets pushed down by the hood.
The air cleaner bolt that has the wing nut on it to hold the top on goes in here.
After it passes through the air horn it screws into the main body here.
With the hood pushing down on the rim of the air cleaner box it is using the edge of the carb and the air cleaner box as a levering system attempting to pull the bolt out of the main body of the carb. This causes the main body to warp up around the bolt and also the airhorn since it is on top of the main body.
Soon enough I was getting some erratic behavior from the carb and could not seem to get it jetted just right.
I decided to take the carb off and check it out.
This is what I found.
Air horn warped .035"
Main body warped .080"
This wouldn't be a big problem if both were warped together and still mated well, but not the case. A thick gasket could probably make the issue better but I decided I wanted to try to flatten it out.
On the air horn initially I started sanding it on a piece of sand paper taped to some glass. It didn't take me long to see that to remove .035" of material was going to take lots of time and in the end was going to make the air horn thinner making it easier to warp again in the future.
So I decided to make a straightening rig of some sort. After a short search on the internet I had a pretty good idea of how it should look.
I started with some 3/8" plate steel and drilled holes for the primary venturies since they protrude above the level of the main body of the carb. Then holes or 1/4-20 bolts to bolt the thing down to the carb body.
Not knowing if this would just warp to the shape of the carb I added some stringers for strength to keep it flat.
Then enlarged the holes on the carb side of the plate to ensure I was going to clear the primary nozzles. Didn't relish the though of breaking them.
The hole in the middle is threaded to accept a bolt to un-warp the air horn. I used 60 in/lbs of torque and heated it in the oven to 170*f while attached to the plate and allowed it to cool. After it reached full temp I re-torqed the air horn and then again before I let it cool. Once cool I removed it from the plate.
Results after flattening the air horn.
Then I bolted the main body to the plate with the backing plate that I also made.
Here is a pic of both pieces.
Alignment of the primary nozzles is important so as to not damage them. I would have drilled the holes bigger but did not have anything larger than a 1/2" drill on hand.
I used a similar procedure to un-warp the main body. First heated it in the oven to 170*f then bolted it to the plate. Torqed this one to 150 in/lbs (about the limit of the 1/4-20 nuts) then put back in the oven for one hour. Re-torqed it once every thing was up to temp again and then a third time when done heating. Then let it all cool back to room temp.
Results of the main body un-warping was good. Not perfect but within .010" or so at the edge.
I'm not sure how much a business charges to do this service, but at least now I can do it anytime it needs to be done in the future.
I did see that the un-warping rig, if you could get it, is in the neighborhood of $600.
Wow! Thx for sharing. I had read of the de-warping tool and wondered if easy to build for oneself. And for some reason i was thinking stainless steel. Guess because of higher melting temp. But now that i see de-warping at only 170* it wouldnt make a difference. That and SS has some springy tendencies.
So 170* is all thats needed? Good to know. I was thinking more like 400*. What a mess that would have made. Now if u let it slowly cool the metal becomes what they call "annealed". And if u rapid cool the metal its called a quench. I recall in welding class quenching with both oil and water for different case hardening (sorry cant recall which does what now). But oil u can heat to a temp for "quenching". In this case u could heat the whole rig in oil to 170* and slow cool or just oil quench at a lower temp then 170* (or even below freezing). I only mention this because im sure the carb will see close 170* with the hood closed and im wondering if some quenching would "toughen" the carb somewhat?
Lars had a great pic of a carb with overtorqued mounting bolts and the entire carb body became so distorted the carb was unrepairable.
Wow! Thx for sharing. I had read of the de-warping tool and wondered if easy to build for oneself. And for some reason i was thinking stainless steel. Guess because of higher melting temp. But now that i see de-warping at only 170* it wouldnt make a difference. That and SS has some springy tendencies.
So 170* is all thats needed? Good to know. I was thinking more like 400*. What a mess that would have made. Now if u let it slowly cool the metal becomes what they call "annealed". And if u rapid cool the metal its called a quench. I recall in welding class quenching with both oil and water for different case hardening (sorry cant recall which does what now). But oil u can heat to a temp for "quenching". In this case u could heat the whole rig in oil to 170* and slow cool or just oil quench at a lower temp then 170* (or even below freezing). I only mention this because im sure the carb will see close 170* with the hood closed and im wondering if some quenching would "toughen" the carb somewhat?
Lars had a great pic of a carb with overtorqued mounting bolts and the entire carb body became so distorted the carb was unrepairable.
I let it cool slowly in the oven. I didn't want to make the metal brittle in any way. I figure better soft and warpable than brittle and capable of cracking and that basically simulated the same conditions it sees during use.
As long as I don't allow the hood to touch the air cleaner assembly and don't over torque the mounting bolts I'm guessing it should remain fairly straight for some time.
It went the last 37 years pretty well.
It was warped a little when I did the carb overhaul a couple years ago, but not so bad that a little sanding on the air horn and a thick gasket couldn't fix it.
I do not doubt it took you 5 hours. When I am making special tools a fixtures...the DEVIL is in the details.
DUB
Agreed. If I were to build another one it would only take half that time.
One of the challenges was cutting 3/8" plate steel without a band saw. Much angle grinder work.
"I used 60 in/lbs of torque and heated it in the oven to 170*f while attached to the plate and allowed it to cool. After it reached full temp I re-torqed the air horn and then again before I let it cool. Once cool I removed it from the plate."
Hope you're still in this forum. This is a good write-up, but I'm a little fuzzy on the torquing/heating/cooling process. Could you please give me more details? Such as how much time between full temp re-torques?
"I used 60 in/lbs of torque and heated it in the oven to 170*f while attached to the plate and allowed it to cool. After it reached full temp I re-torqed the air horn and then again before I let it cool. Once cool I removed it from the plate."
Hope you're still in this forum. This is a good write-up, but I'm a little fuzzy on the torquing/heating/cooling process. Could you please give me more details? Such as how much time between full temp re-torques?
09-22-2014, 03:33 PM
Home made Q-jet un-warping tool
I like this a _lot_. Reminds me of the barker de-warping tool.
Now if u let it slowly cool the metal becomes what they call "annealed". And if u rapid cool the metal its called a quench. I recall in welding class quenching with both oil and water for different case hardening (sorry cant recall which does what now). But oil u can heat to a temp for "quenching". In this case u could heat the whole rig in oil to 170* and slow cool or just oil quench at a lower temp then 170* (or even below freezing). I only mention this because im sure the carb will see close 170* with the hood closed and im wondering if some quenching would "toughen" the carb somewhat?
