Farm Equipment - allis model b max rpm

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allis model b max rpm

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Category: Allis Chalmers
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=7360
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Topic: allis model b max rpm

Posted By: boom
Subject: allis model b max rpm
Date Posted: 29 Jan 2010 at 5:56pm

I have a 39-40 i think model b in the process of rebuilding it and wanted to tweak some little things on it and wanted to know what the max rpm one could turn one of these old tractors before they blow. and what weak points they have on them. i cant find any info. on these anywheres.

thanks,

boom

Replies:

Posted By: Brian Jasper co. Ia
Date Posted: 29 Jan 2010 at 7:18pm

The weak spot might be that the connecting rods are not pressure lubed. They are squirted by holes in the cam as they turn. Seems like the no load high idle is 2100 with a rated load speed of 1650 for a CA which has the same basic engine. For reliability, I wouldn't recommend speeding it up above the 1650 load speed.

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"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford

Posted By: mlpankey
Date Posted: 29 Jan 2010 at 7:24pm

We have installed the d15 series two gov spring on them and not blown them . youre valve springs and points should keep you from blowing it . points usually bounce and cause a miss the weak valve springs usually let the valves float keeping the rpms down.

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people if they don't already know it you can't tell them. quote yogi berra

Posted By: boom
Date Posted: 30 Jan 2010 at 10:28am

ok thanks alot

Posted By: Dick L
Date Posted: 30 Jan 2010 at 11:19am

To get the maxim RPM.s, in my opinion and experience, you would need to go to a pressurized oil system to the rods thru the mains. You would need to have the engine balanced by an engine shop that has the proper equipment. Line boring the mains and reconditioning the rods would be more than necessary. You would have to put a larger venturi as well as a larger main jet.

On a well balanced engine with changes above you could get 4000 RPM's and above.

Doing so will loose lugging power. Also doing so would most likely cause the governor to fly apart in prolonged high RPM's which would mean that the governor should be removed.
You would then have a racing engine not a tractor engine. You would not have a pulling engine that would have a lot of extra horse power. You could pull a light load like a bat but when the load started to increase like on a transfer sled the RPM's would drop quickly and with the larger venturi you would fall flat fast and the little B that was at factory RPM's would clean your clock.

Posted By: boom
Date Posted: 30 Jan 2010 at 1:18pm

Oh i thought if it turned a little higher rpms its produce a little more torque. ok so my goal is to get as much power as i can out of it not rpms then.

Posted By: mlpankey
Date Posted: 30 Jan 2010 at 1:40pm

hp are torque values on a dyno are the same at 5250 rpm. To get to that rpm takes balancing everything as Dick mentioned and alot stiffer than factory valve springs a cam shaft with more than factory lift . A d15 series 2 gov spirng works well . Governor springs do more than just set high idle they also try to maintan a full load rpm. In the d15 case that is higher than the b full load rpms. Same thing with the 175 spring vs the d17 and combine spring they all control at the same high idle give or take a few rpms but one seperates itself from the other two at full load rpms. ps if at cranking speed the carb. will suck the palm of youre hand up to it and youre engine dont lug its something besides the carb for its none to big to recieve adequate signal from the engine .

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people if they don't already know it you can't tell them. quote yogi berra

Posted By: Dick L
Date Posted: 30 Jan 2010 at 2:43pm

The higher rpm.s will add some horse power as long as you can maintain those rpm's. When the load drops the rpm's the horse power drops as well. Horse power that can be maintained under load is added by adding compression thru larger pistons, longer stroke or both.
If you pull a B at a tractor pull you will most likely be pulling with a speed limit in what is called an antique class and traction would be what your main focus should be. Larger pistons and 150 thousands off the head would be of help also. That would help you to maintain the extra rpm's you could get from a stronger governor spring.

Maxim RPM's was the question and the short answer would have been (lots of money)

Posted By: mlpankey
Date Posted: 30 Jan 2010 at 5:49pm

if it dont make a horsepower more if the rpms allow you to drop a gear to maintain the speed rule youre mechanical advantage is better. another words say you can run 3 mile an hour at 2200 rpms in first and youre competitor runs 3 mile an hour in second at 1500 rpms and both engines make the same ponies same gearing .my money would be on the first gear tractor.

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people if they don't already know it you can't tell them. quote yogi berra

Posted By: boom
Date Posted: 30 Jan 2010 at 6:31pm

ok so ill have the head milled down a little. now heres the stupid question, what would one use for larger pistions? a newer aftermarket pistion for a automoble probly wont fit im guessing?

Posted By: Dick L
Date Posted: 30 Jan 2010 at 6:50pm

Just buy the 3 7/16 standard over bore kit.

2200 rpm in first gear will blow the horn with the B at 3 mph with 11-2 24's
You can run the 2200 with the C at 3 mph almost.

Posted By: mlpankey
Date Posted: 30 Jan 2010 at 6:55pm

the c would be the one to build then. a ford 170 had a 3.5 bore with a 1.58 comp.height it might work maybe dick will post wither it will. be a.062 bore over the 3 7/16 bore

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people if they don't already know it you can't tell them. quote yogi berra

Posted By: Dick L
Date Posted: 30 Jan 2010 at 7:30pm

You just have to hold tight until you have tire slippage before you open it up.
I always on all my tractors started pulling at a bout 1/2 throttle and opened it up a little at a time as the weight box came up and would be wide open just before the tractor was at full load. Then it would lug, start to die down or start to spin.

Posted By: mlpankey
Date Posted: 30 Jan 2010 at 7:42pm

a buick 215 v8 also had a 3.5 bore and a 1.843 comp.height chevy 251 ran a 3.437 bore 1.978 compression height. the 251 would be the equivelent in bore as the over bore kit dick mentioned the comp. height may be a issue.

235 chevy 3 9/16 bore 2.06 comp height

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people if they don't already know it you can't tell them. quote yogi berra

Posted By: mlpankey
Date Posted: 30 Jan 2010 at 7:57pm

bumb

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people if they don't already know it you can't tell them. quote yogi berra