The carb rebuild was going great until....

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

NCNole

NCNole

10 Year
Joined
Feb 20, 2013
Threads
58
Messages
647
Location
Florida Keys
So, the secondary slow jet will NOT come out. It screws in to the top of the bottom portion of the carb and I have tried to turn it and it won't budge. If I put too much pressure it starts to bugger it up. PB blaster does nothing. Any idea on how to get this out and also, can I buy a new one anywhere? If it would have come out, the take apart would be done now. Rats.
 
go buy some of that canned air for blowing out a computer keyboard.....invert the can when you use it and the liquid will drip out and cause instant cold....try to freeze the part you want to remove ........might work.......you can get frostbite it you get much of the stuff on you.......can freeze off a wart too
good luck
 
The thermal expansion rate for aluminum is bigger than that for brass. Because the two metals are in thermal contact there is no way to cool only the jet. You want heat, not cold.
 
I should have known the physicist would know the answer! :) Thanks guys-I dipped it with it in there to hopefully eat what's holding it but will try heat if needed.
 
Good luck! These individual carb parts are tough to find. I have the carb out of a 74 sitting on the shelf. Not sure what the differences would be but if you need something let me know. Maybe it will work. These things can be a real PITA. Maybe try contacting Jim C if you need anything.
 
Rice said:
The thermal expansion rate for aluminum is bigger than that for brass. Because the two metals are in thermal contact there is no way to cool only the jet. You want heat, not cold.
Click to expand...

If the thermal expansion rate is greater for aluminum than brass, then wouldn't it be the inverse for cooling and therefore, not make a difference if you used heat or cold? they are going to contract at different rates as well. I'm intrigued.
 
Stumpalama said:
If the thermal expansion rate is greater for aluminum than brass, then wouldn't it be the inverse for cooling and therefore, not make a difference if you used heat or cold? they are going to contract at different rates as well. I'm intrigued.
Click to expand...

Heating means the aluminum will expand more than the brass; Cooling means the aluminum will contract more than the brass.
 
Stumpalama said:
And the jet is brass so cooling should make getting the brass jet out easier, no?
Click to expand...

No. Whatever change in temperature takes places has a larger effect on the aluminum. Thus, heat it, aluminum expands more than the brass, so brass jet is now looser. Cool it, the aluminum contracts MORE than the brass and now the jet is tighter than it was before. It would work if there were some way to ONLY cool the brass, but there is not.
 
Sorry to further hijack this thread...isn't the goal to create that increase/decrease is size to break bonds between the 2 pieces? The increase/decrease due to temps is cursory and back to ambient pretty quickly if I understand my basic physics. Heat/cool expands/contracts the pieces, which do so at different rates, breaking any bonds due to corrosion/rust/etc, this rate difference is a desirable thing IMHO...
 
The aluminum contracts, but that doesn't make the hole smaller, it makes it larger and the threads contract as well and creates a gap between the brass and aluminum threads.
 
Stumpalama said:
The aluminum contracts, but that doesn't make the hole smaller, it makes it larger and the threads contract as well and creates a gap between the brass and aluminum threads.
Click to expand...

Negative. If an aluminum bar is cooled all dimensions of the bar contract, that includes the diameter of a hole drilled in the center.

Edit ... Sorry for the hijack, Joanna. Do what the frick you want with the thing. I'm out.
 
Last edited:
Don't drop out of the conversation. I am merely asking a question that is germane to the OP's question. I think it a a legit question regarding the threaded holes in an aluminum block would get slightly larger as the aluminum cooled and contracted. I could be thinking absolutely opposite of what actuallywould occur.
My thought was a hole drilled in an aluminum block
 
when all else fails...use a bagger hammer
 
Stumpalama said:
I think it a a legit question regarding the threaded holes in an aluminum block would get slightly larger as the aluminum cooled and contracted. I could be thinking absolutely opposite of what actuallywould occur.
My thought was a hole drilled in an aluminum block
Click to expand...

I am not sure of your logic here that contraction would make a hole larger.

If you drilled a hole in an aluminum block, then cooled it enough that the dimensions contracted by 1%, every linear dimension would reduce by that 1% - length, width, and depth. The total volume of the block would decrease, and since mass is conserved, density goes up.

Think of the cylinder bores in the engine block. They are larger in diameter when the engine is at operating temperature than who you start it after 24 hours in 20 degree weather.

Back to the OP, heat or cold can help with that jet ....

My $0.02, 30 years after thermodamnatics in E school ....



Misspellings courtesy of autocorrect from my iPad using IH8MUD Forum
 
Last edited:
Not much to add here other than to try heat. Make sure you use a screwdriver that fits snugly into the slot. Too small and you'll waggle it out. Once you do that it's a slippery slope to ugliness. The last one I rebuilt had some spares in the holders. Does yours? Do you know what size jet you need? Surely somebody here has got what you need.


...via IH8MUD app
 
roadstr6 said:
Make sure you use a screwdriver that fits snugly into the slot. Too small and you'll waggle it out.
Click to expand...

Good point. The precision ground bits in a decent gun smithing screwdriver set might be just the ticket here



Misspellings courtesy of autocorrect from my iPad using IH8MUD Forum
 
Holy moly....actually I asked Pinhead and he said I was fine leaving it in, just dip and spray it out and if it isn't clogged, good to go. Carb is done and hopefully will be running great when I put it back on tomorrow!
 
Got it. I was trying to rectify the whole mass contracting and compressing the hole (essentially vs. contracting from every surface... if that makes any sense. It has been many moons since studying thermo.
 
You must log in or register to reply here.

Share this page

Back
Top Bottom