Allis Chalmers “B” overhaul

[Reddog556]

Allis B bored to 30 thousands oversized what should the bottom jet in the carburetor be changed to?

 

[old]

Allis B bored to 30 thousands oversized what should the bottom jet in the carburetor be changed to?

So are you saying you bored out the sleeves in a wet sleeve engine?? If you did you may have problems with it very soon due to the sleeves being ti thin

 

[Reddog556]

Thanks for your comment, was told at purchase that the engine was bored 30 over, wasn’t aware that it was a sleeved engine? Just trying to figure out why it seems to be starving for fuel no matter how the carburetor is adjusted?

 

[DrAllis]

If the internal main jet is truly too small (assuming everything else carb related is correct) you can correct how it runs by giving it some partial choke, correct ?? I've only had to do this one time, but I have an extensive drill bit assortment ( sizes A thru Z and 1 thru 80) and determined what size the main jet currently was...and then drilled it out by hand the next size until the problem was corrected.

 

[Reddog556]

Yes you are correct a little choke does improve how it runs, but never liked using the partial choke. I do have numbered drills so I will open the main jet up. I added a needle valve for finer adjustment but it didn’t improve performance at maximum opening. So it probably is starving for fuel. Thanks for your wisdom on this matter.

 

[Dick L]

Allis B bored to 30 thousands oversized what should the bottom jet in the carburetor be changed to?

If your not going to increase the RPM's it will run fine as is. Your answers had not been on when I saw this post.

It most likely just had the 3 3/8" kit put in. I did this to all the B's and they ran fine without changing the orifice size until I changed springs on the governor. When changing springs I put in an orifice from a C carburetor and changed the venturi from a C. Those things need to be in you thoughts when bringing up the RPM's

 

[Dick L]

For the most part of changing things more than a little is a cut and try deal with very small changes working up to where it runs.
If you check my post to the link to my C pulling I had everything balanced and used a cot spring and ran like an auto engine. with a 4 inch stroke. It had Small block Chevy valves and a Crane ground cam shaft. I used a standard C carburetor with many hours of tinkering to get it to run smooth.
Several Pulls I went to the engine had to be factory to the eye

 

[DrAllis]

I never suggested using "partial choke" as a fix, but only to verify the lean mixture problem.

 

[olddavid]

Leaking intake manifold gasket?

 

[Reddog556]

Leaking intake manifold gasket?

Hmmm I will check with oil around the manifold thanks

 

[Reddog556]

I never suggested using "partial choke" as a fix, but only to verify the lean mixture problem.

Agreed thanks

 

[Reddog556]

For the most part of changing things more than a little is a cut and try deal with very small changes working up to where it runs.
If you check my post to the link to my C pulling I had everything balanced and used a cot spring and ran like an auto engine. with a 4 inch stroke. It had Small block Chevy valves and a Crane ground cam shaft. I used a standard C carburetor with many hours of tinkering to get it to run smooth.
Several Pulls I went to the engine had to be factory to the eye

Thank you for all of this information just trying to get it to run smooth and strong.

 

[old]

Hmmm I will check with oil around the manifold thanks

If the carb is stock if I remember right the only adjustment it has is the idle screw which will not do anything for it running and working.

 

[Watthour]

Might also want to verify float level.