Repowering a late-70's Bolens

Anonymous-0 · May 31, 2013

I have a late 70's Bolens H14XL (I think the model number is 1458) Its a little wimpy for my needs. I have some steep hills and I use it to move boats and trailers around.

It has a 1-cylinder Tecumseh (14hp) that has remarkably low hours. There is nothing wrong with it, but I'm thinking if I just had a wee bit more oomph I could postpone investing in a compact utility.

I'm concerned about overpowering the hydrostatic drive. I'm a hotrodder by trade, so I think in terms of a high-powered stroker in front of a stock tranny. I have access to a Honda GX690 (22hp) V twin. Will I kill it with that much power?

johnw (OR) · May 31, 2013

Shouldn't hurt anything if you are careful. I repowered my H 11XL a number of years ago with a Briggs 16 horse V-Twin made a great mowing and tilling machine no problems except finding tiller parts after 37 yrs.

todd hamilton · May 31, 2013

Drop in a 283, big block probably to heavy for frame

Anonymous-0 · May 31, 2013

Good to know. I thought long and hard about replacing this with a more modern buggy, but its hard to replace a well-made, low-hours, cast-iron tractor with a new Chinese stamped steel thing.

Like I said... hotrodder. I'll take a 1965 Pontiac before I would take a 2005 Pontiac.

I'm concerned about breaking something. Is the main concern fluid temps, or is the main concern actually breaking something? I can add a fluid cooler, but its hard to replace broken parts on an obsolete unit.

Mike (WA) · May 31, 2013

Especially if the '65 is a Catalina 2+2 421 4 speed. Friend bought one in '65, took me for a ride, I've never forgotten it.

Elmers Grassman · Jun 1, 2013

What about building up the 14 horse. maybe a radical cam, bigger carb, stroker rod and piston?

Bret4207 · Jun 1, 2013

(quoted from post at 21:18:04 05/31/13) Good to know. I thought long and hard about replacing this with a more modern buggy, but its hard to replace a well-made, low-hours, cast-iron tractor with a new Chinese stamped steel thing.

Like I said... hotrodder. I'll take a 1965 Pontiac before I would take a 2005 Pontiac.

I'm concerned about breaking something. Is the main concern fluid temps, or is the main concern actually breaking something? I can add a fluid cooler, but its hard to replace broken parts on an obsolete unit.

Are you observing the engine dying down on load? When it happens is the hydro unit warm to the touch? The hydro unit may be able to take a lot more than the engine can put out, but there are limits.

RayP(MI) · Jun 1, 2013

I repowered a JD 140 (hydrostatic - 14hp Kohler) with a Briggs V-TWIN (18hp). No problems dur to swap.

ericlb · Jun 1, 2013

i dont think you'll hurt it, you may need to be a little judicious about running wide open throttle for long periods until you make sure that's no heating up the hydrostatic unit, the bolens is 3 times the tractor you can buy today without moving up to a utility type unit which is why after i wore out my 2 year old rider, i bought a 1949 cub to replace it, im with you on the cars too i have 5, the newest is 30 years old this year i wont ever buy one newer than early 80's and prefer older than that

krm · Jun 1, 2013

I had an HT20 will twin cyclinder Kohler,that would make you a good replacement.

Dean · Jun 1, 2013

I would not unless you can VERIFY that the hydrostatic transmission in your machine was used in higher HP applications.

Hydrostatic transmissions are not tolerant of abuse.

Dean

Dean · Jun 1, 2013

A close friend of mine bought a used 1965 Royal Bobcat GTO with SD 421, tri power and 4.33 rear gear in 1967/8 and still has it.

It's a great torque machine and will get you there in a hurry so long as you are not too interested in top speed.

Dean

Dean · Jun 1, 2013

283 big block???

Dean

todd hamilton · Jun 1, 2013

No I meant don't use a 396 or 454

Curtis Mittong · Jun 1, 2013

Ok, good tip. I'll get some part numbers and see if I can find some specs on it.

Curtis Mittong · Jun 1, 2013

I like how you think. Maybe a tiny little turbo.

curtis73 · Jun 1, 2013

Are you observing the engine dying down on load? When it happens is the hydro unit warm to the touch? The hydro unit may be able to take a lot more than the engine can put out, but there are limits.

The engine just labors when going up hills or cutting high grass. I rebuilt the carb when I pulled it out of moth balls, changed the oil, etc. It runs flawlessly, just underpowered. I watched the governor while my friend was mowing uphill. As soon as it starts up the hill the governor pegs. Additional input just bogs down the engine.

I'm not talking like near-dying type bogging down, just that its clear it has reached its limit. I verified top RPM with a tach to make sure it was at the proper RPM. I'm pretty sure its making all 14 hp, I think its just a bit underpowered for PA hills and a 48" deck.

I haven't actually laid my hand on the hydro pump after long use, but the hydro fluid on the dipstick is just very warm. I know that isn't a quantitative diagnosis, but I was pleased at how not-hot it was.

(by the way, this is the OP, Curtis Mittong. I just discovered the "modern view" and had to log in)

RN · Jun 1, 2013

The Tec 14hp isn"t made anymore- the company isn"t around either. If this is the basic flathead engine- look for a LP gas head for higher compression, was common to use the Tecumseh in industrial warehouse applications with the LP. Next step is basic cleanup around the intake maniflods and exhaust- match manifold to port, trim gasket as needed, file a bit at the matching ends- this applies to the OHV models also. A bit of relieving port work around valve guides using old "area rule" practice, lengthen and open exhaust pipe a step if practical before muffler will get a little reduced exhaust pressure and maybe slight extraction effect at operating speed. Minimal parts expense, some labor for a winters keep busy work and a extra 100 rpm, 1 hp at load with no adverse reliabily issues.
If you really need the extra hill climbing capability, check out the mounting patterns on Vtwin Honda"s, Kohlers, late Briggs and get the working RPM match- 3200, 3600, 2800- whatever you need to set governor at to match your tranny final gearing. I managed to fit a $25.00 garage sale XBolens 12/14hp OHV Tecumseh into a old Simplicity 700 frame. RN

Brian Jasper co. Ia · Jun 1, 2013

You could power the hydro with a 454 Chevy and not hurt it. The only way the hydro would be damaged is if you increased the hydraulic pressure relief valve setting.
You could look on line at Small Engine Warehouse on evilbay for repower options.

ss55 · Jun 1, 2013

If the Bolens is in good condition you may be time and money ahead to buy the correct size of tractor that you need and then sell the nice Bolens privately to offset some of the cost.

curtis73 · Jun 2, 2013

look for a LP gas head for higher compression, was common to use the Tecumseh in industrial warehouse applications with the LP. Next step is basic cleanup around the intake maniflods and exhaust- match manifold to port, trim gasket as needed, file a bit at the matching ends- this applies to the OHV models also. A bit of relieving port work around valve guides using old "area rule" practice, lengthen and open exhaust pipe a step if practical before muffler will get a little reduced exhaust pressure and maybe slight extraction effect at operating speed. Minimal parts expense, some labor for a winters keep busy work and a extra 100 rpm, 1 hp at load with no adverse reliabily issues.

This appeals to me big time... custom work, hard-core tech, and hot rod mentality. I'm all about hotrodding what you have, but an extra 1-2 hp won't cut it in this case.

If you really need the extra hill climbing capability, check out the mounting patterns on Vtwin Honda"s, Kohlers, late Briggs and get the working RPM match- 3200, 3600, 2800- whatever you need to set governor at to match your tranny final gearing. I managed to fit a $25.00 garage sale XBolens 12/14hp OHV Tecumseh into a old Simplicity 700 frame. RN

I have noticed over the years that they have remarkably universal mounting patterns... which makes sense, much like SAE bellhousing patterns in heavy trucks. The engine I'm looking at is a Honda GX690 Vtwin.

Bret4207 · Jun 2, 2013

The only problem with hot rodding is longevity. The more you demand of an engine/drive train the shorter the life, as a general rule. It's a lawn mower. Greasing the arbor and spindles can make a difference. More HP is nice, but over loading the drive train or deck system leads to it's own issues. Finding a nice balance point is the key. 1 or 2 HP might be a big difference. HP then as opposed to HP now are 2 different birds.

Those old Bolens were HEAVY. That's where part of your HP goes. But I wouldn't give that up. A system designed for 14 hp...I wouldn't put much more than an additional 5 in it. I think the drive train with the hydro will be okay as long as you don't horse it. The mower system might eat a lot of belts and bearing though.

Repowering a late-70's Bolens

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