I really enjoy first generation 59-63 Simplicity riding tractors. They were badged as Simplicity 700,725,Allis Chalmers B1(same as 725) and Wards Garden Mark Squire (same as 725).
These tractors came with a Briggs model 19 or model 19D engine rated at 7 and at 7.25 hp.
They are big block cast iron engines but the 9 thru 16 hp cast iron big block Briggs are bigger engines.
The 9 thru 16 hp are all the same physical size(with one exception for our purposes here,noted at the end of this post)on the outside so even the blower housing sheetmetal will interchange between a 9 and a 16 hp version.
When putting a bigger 9 thru 16 hp cast iron Big block engine into one of these first generation Simplicity riding tractors a lot of people butcher the tractor but you don't have too.
Because the engine is taller the air cleaner sits higher. A lot of people cut that vintage sheet metal (the hood) to clear the air cleaner,but you don't have too.
Going to the other side of the tractor,again the engine is taller and leaving the starter generator in the high mount location causes it to not clear the hood,so again they cut it,but you don't have to.
Moving under the tractor,most think that that you need to cut out that big triangle shaped hole in the frame to clear the 9hp or bigger Briggs,as Simplicity started doing in 64 when they started using the bigger engines,but you don't have to.
On most blocks the oil fill neck won't clear the frame or the side of the hood mount,so they cut up the frame and hood mount,but you don't have to.
I first learned that you could do this swap without hacking up the tractor around 20 years ago on Simpletractors.com from a member there named Rod (can't recall his last name at the minute).
I have owned a few few of the first generation Simplicity riding tractors that have had this swap over the years,some done right,some hacked up.
I did the swap on my 700 a few years ago putting a period correct model 23 in it with without hacking it up.
I done it when the model 19 in it was some worn out that you could wobble the piston in it around by hand and after looking for a good while couldn't find another model 19 in good shape to put back in it.
Now I'm getting ready to do the swap again on a 725 that the model 19 that I pulled out of it is in sad shape.
This time I'm putting a 1971 32000 series cast iron 16 hp big block in it and thought i would document the swap for entertainment, information and maybe to help others and save a tractor from being hacked up.
Basically to make the bigger big block fit:
1:You do away with the half inch spacers that set under the factory model 19 engine that raises it to align the driveshaft. You don't need them. The bigger engines crank height is already a half inch higher.
2:You drill two new motor mount holes just outside the two factory passenger side motor mount holes because the bigger engine has a half inch wider footprint. The driver side motor mount holes are fine as is. The engine will be centered for the driveshaft.
3:There are two bolts on the passenger side frame floor that help hold the front axle assembly to the frame. You will have to remove those the engine pan won't clear them.
4:You will have to enlarge the oil drain pipe/plug hole in the side of the frame. Now that the new(to the tractor) engine is sitting flat on the floor of the tractor frame (instead of on the half inch spacers that the model 19 sat on to raise it slightly),the oil drain pipe out of the engine pan is right on the floor. So you will need to bring the hole in the side of the frame down about a half inch,not quite flush with the floor of the frame.
5: your oil fill neck wont clear the frame or the side of the hood mount. So you will need to screw the neck out of the oil pan and replace it with a flat plug. It does making checking the oil a little more fun but it works.
6:Briggs offered a high mount,mid mount,and low mount starter generator setup over the years.
Simplicity and Allis only used the high mount.
A high mount won't work for this application because it won't clear the hood.
A low mount won't work because the tractor frame interferes with it but a mid mount will work great and is what I will be using this round.
On my last swap I made my own mount setup.
7:Clearing the hood with the air cleaner is a mix and match of carb,air cleaner housings and air cleaner riser tubes trial and error.
☆NOTE: Sometimes the oil drain and fill will be on the wrong side of the pan.
Simply unbolt the pan and turn it 180 degrees (half way around) and bolt it back on.
☆NOTE: There is one big block cast iron Briggs that won't work for this swap and that is the 12 hp version because it has dual counter balancers. So it has one on the PTO side of the engine. The counter balancer won't clear the grill/hood support.
Here are a few pictures to look thru and give you an idea of some of the things that I'm talking about.
I'm just starting on the 16 hp swap into the 725 and did a little mock up this evening.
I plan to document the swap as I go.
These tractors came with a Briggs model 19 or model 19D engine rated at 7 and at 7.25 hp.
They are big block cast iron engines but the 9 thru 16 hp cast iron big block Briggs are bigger engines.
The 9 thru 16 hp are all the same physical size(with one exception for our purposes here,noted at the end of this post)on the outside so even the blower housing sheetmetal will interchange between a 9 and a 16 hp version.
When putting a bigger 9 thru 16 hp cast iron Big block engine into one of these first generation Simplicity riding tractors a lot of people butcher the tractor but you don't have too.
Because the engine is taller the air cleaner sits higher. A lot of people cut that vintage sheet metal (the hood) to clear the air cleaner,but you don't have too.
Going to the other side of the tractor,again the engine is taller and leaving the starter generator in the high mount location causes it to not clear the hood,so again they cut it,but you don't have to.
Moving under the tractor,most think that that you need to cut out that big triangle shaped hole in the frame to clear the 9hp or bigger Briggs,as Simplicity started doing in 64 when they started using the bigger engines,but you don't have to.
On most blocks the oil fill neck won't clear the frame or the side of the hood mount,so they cut up the frame and hood mount,but you don't have to.
I first learned that you could do this swap without hacking up the tractor around 20 years ago on Simpletractors.com from a member there named Rod (can't recall his last name at the minute).
I have owned a few few of the first generation Simplicity riding tractors that have had this swap over the years,some done right,some hacked up.
I did the swap on my 700 a few years ago putting a period correct model 23 in it with without hacking it up.
I done it when the model 19 in it was some worn out that you could wobble the piston in it around by hand and after looking for a good while couldn't find another model 19 in good shape to put back in it.
Now I'm getting ready to do the swap again on a 725 that the model 19 that I pulled out of it is in sad shape.
This time I'm putting a 1971 32000 series cast iron 16 hp big block in it and thought i would document the swap for entertainment, information and maybe to help others and save a tractor from being hacked up.
Basically to make the bigger big block fit:
1:You do away with the half inch spacers that set under the factory model 19 engine that raises it to align the driveshaft. You don't need them. The bigger engines crank height is already a half inch higher.
2:You drill two new motor mount holes just outside the two factory passenger side motor mount holes because the bigger engine has a half inch wider footprint. The driver side motor mount holes are fine as is. The engine will be centered for the driveshaft.
3:There are two bolts on the passenger side frame floor that help hold the front axle assembly to the frame. You will have to remove those the engine pan won't clear them.
4:You will have to enlarge the oil drain pipe/plug hole in the side of the frame. Now that the new(to the tractor) engine is sitting flat on the floor of the tractor frame (instead of on the half inch spacers that the model 19 sat on to raise it slightly),the oil drain pipe out of the engine pan is right on the floor. So you will need to bring the hole in the side of the frame down about a half inch,not quite flush with the floor of the frame.
5: your oil fill neck wont clear the frame or the side of the hood mount. So you will need to screw the neck out of the oil pan and replace it with a flat plug. It does making checking the oil a little more fun but it works.
6:Briggs offered a high mount,mid mount,and low mount starter generator setup over the years.
Simplicity and Allis only used the high mount.
A high mount won't work for this application because it won't clear the hood.
A low mount won't work because the tractor frame interferes with it but a mid mount will work great and is what I will be using this round.
On my last swap I made my own mount setup.
7:Clearing the hood with the air cleaner is a mix and match of carb,air cleaner housings and air cleaner riser tubes trial and error.
☆NOTE: Sometimes the oil drain and fill will be on the wrong side of the pan.
Simply unbolt the pan and turn it 180 degrees (half way around) and bolt it back on.
☆NOTE: There is one big block cast iron Briggs that won't work for this swap and that is the 12 hp version because it has dual counter balancers. So it has one on the PTO side of the engine. The counter balancer won't clear the grill/hood support.
Here are a few pictures to look thru and give you an idea of some of the things that I'm talking about.
I'm just starting on the 16 hp swap into the 725 and did a little mock up this evening.
I plan to document the swap as I go.
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