D Bull gears

[Old case Mike]

Hey mEL I’m going to be running a DO for pulling I have 4
inch pistons at the top of the sleeves. 5505 head will be used
I’m wondering what would be the better bull gears 38 or 31?
I believe it has 31 in it. I will be using 16.9 or 18.4 26 inch tires
this tractor is just getting started for pulling I haven’t pulled it
yet thanks for any info I can use either 5576 or 5505 head I
checked both chambers 5505 has 190cc and 5576 has 240cc
right now 5576 head is on tractor I’m will be cleaning up
intake and head with mild port work most everything else will
be stock for now thanks ol case mike

 

[mEl]

(quoted from post at 16:30:43 12/26/20) Hey mEL I m going to be running a DO for pulling I have 4
inch pistons at the top of the sleeves. 5505 head will be used
I m wondering what would be the better bull gears 38 or 31?
I believe it has 31 in it. I will be using 16.9 or 18.4 26 inch tires
this tractor is just getting started for pulling I haven t pulled it
yet thanks for any info I can use either 5576 or 5505 head I
checked both chambers 5505 has 190cc and 5576 has 240cc
right now 5576 head is on tractor I m will be cleaning up
intake and head with mild port work most everything else will
be stock for now thanks ol case mike

OCM

A 4 inch DO with the big tires will be marginal with 31 tooth sprockets, We use them but in much higher HP than your engine is capable of. The best head for flow is the 5576 but the compression suffers. Porting is good but most gain will be underneath the valve seats, take the guides down to the port floor, that will get a major bunch of Cast Iron out of the flow path. We take .100 off the head safely, that will help a lot. You should be looking for a 400-700-800 carb, that carb is so much superior to the Zenith you would not know it was the same tractor even stock. Talking to my son he thinks that .100 may get you close to the 190 with much better flow, better than 1/2 the valve is shrowded by the combustion chamber walls. That head was able to feed our 470 CID engine at good rpm, a lot faster than you will be running. Keep me posted, don't get me wrong, there is nothing wrong with a 4 inch engine in good shape, If you were building from the floor up, I would have you set it up with no head gasket, there is another .080" that your head would drop. I will help you along as I can and there are others who have worked with that engine as well. Those engines like more valve lift but that is another problem if you are not doing a cam right now.

 

[TractorTucker]

If you decide to not use the 31 tooth sprockets I would be interested in buying them.

 

[TractorTucker]

How do you connect the 400 carb to the air
cleaner? I thought the newer carbs had a
machined shoulder for a rubber pipe to go
to the air cleaner instead of the bolt
holes for connecting it to the air
cleaner?

 

[mEl]

(reply to post at 19:36:00 12/26/20)

he 400-700-800 MS carbs have the exact pattern and dimensions as the DC Zenith later series went to a hose type inlet. the worst I have ever had to do is loosen the whole air cleaner so it can slightly shift . If you remember there was a casting that bolted to the carb which came up and back to the air cleaner inlet hose at the air cleaner.