Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

With all the research I've done in the last 24 hours, I am nearly convinced that the governed RPM set by the manufacurer may have much to do with the horse power rating they give them.  The Tecumseh 9hp-11hp Snowking engines all vary greatly in governed RPM, as low as 3,350 up to 3,700 on the 11hp OHV version.  When I see that the Tecumseh 9hp is 318cc's and the 11hp is also 318cc's, where are they getting these horse power ratings from. Making an engine OHV gives you that much more power?

Well, I wasn't able to find the governed operating RPM for my Tec 8hp L-head engine, and given the wide margin of RPM's on their engines, I decided to raise the operating speed of mine to what I felt it should be.  Initially I raised it to 3,600 as it was suggested to me to do, but I felt this was too fast by the way it sounded.  So I then reduced it to 3,400 spiking to 3,430.  Roughly 80-100 RPM's higher than what it was. 

The result of this, I took it out into the street to the 28" high, five foot across snow drifts left on the side of the street from the snowplows.  These drifts are 8" higher than my auger housing.  The sun was out and the snow was nice and moist, perfect for making snowballs.  I raised the throttle to operating RPM, put it in 1st gear and off I sent it into the drift.  The chute started to toss the snow some 40 feet across the road and you could now hear the engine under a load.  The difference this time is that the engine was maintained speed and not a hint of it wanting to stall.  In fact, the tires actually broke loose and I started pushing it into the drift to the point it began tunneling.  The entire time the engine didn't faulter for a second and I actually felt I had a 10 hp engine on this great machine.

What a difference a very small increase in governed engine RPM makes.  At one point on Sunday I was upset with myself for not shelling out the extra money for Toro's top of the line 11 hp OHV version for over $1,600.00.  Well, after how this experiment worked out, now I feel I just saved myself over $400.00 because this snowblower can go through anything now.

and we all know that gas will rot in one of those real fast.

seems that the more different metals you put in a carb the faster it goes sour ,then things get messy.

im still unsure of the horsepower difference,i think its more than just the carb.

im betting there is a bore and stroke change.

ill know tomorrow,soon as i get to the microfiche cards.

hmmm i feel like a secret agent...

later chris 

the 8,8.5,9, 10, 10.5,11L heads all have the same piston... part # 35776a

the 10,11,12,12.5,13 ohv all have the same piston...part #40011

only differences i could find (and i might add i was on my lunch break) was in the carb.

the bowl nut (aka high speed)  part #s 640005 ,640024 ,640012 ,640137. sells for6.56 to 11.46

and main nozzle (aka plastic tube) part # 640005 ,640013.sells for 1.73 to 3.53

all prices are canadian and subject to change without notice bla bla bla ha ha

so it would seem that there is little difference between the engines.

next i went to the service manual and found that the l head engines all have the same bore and stroke but there are 2 different

cubic inch displacements .

didnt get to look for the dislacement info on the ohv engines.

so far its kinda interesting

later chris.

ps i dont know which carb takes which nozzle or bowl nut...i will need engine spec numbers for that.

Marc 

                                                                                                      18 Degrees

Degrees, I'd second that carb. 

I too searched & found out that there WERE different head/piston/connecting rod/carb combinations. That line the Tecumseh rep gave about jetting is HOGWASH. You guys are too quick to "jump on the bandwagon". Chris (Snowshoveller) is the only one besides me that realizes this. On a single cylinder, small cubic inch (15 ci?) OPE engine, you just aren't going to pick up TWO or THREE HORSEPOWER by a jetting change. NO WAY. I've changed jetting on automotive engines & dynoed them - I have found that I never gained more than 10-15hp on a properly carburated engine. These engines were all in excess of 400 cubic inches, mostly Pontiacs (400, 406, 428, 434, 440, 455, 462, 473, 480, 496ci) powerplants. Those "odd numbered" ci displacements are different rod/stroke/piston height/crankshafts to obtain some LARGE displacements, and better rod/stroke ratios for high RPM drag engines (6500 RPM+). These Tecumseh's have about 15 cubic inches, so I want someone to provide me with PROOF that a jetting change can yield 2 or 3 more HP on such a small engine. Its done by changing a COMBINATION of other engine components that will change: compression ratio, head flow, higher CFM carb (CFM=cubic feet per minute, a measurement of airflow). These items will provide a small, believable hp increase. Carb jetting alone on a one-lunged engine will not.

Mods - if you can go back (if possible) to WTB & obtain the thread where I posted my findings, it may shed some light here. I spent quite a bit of time researching this & wish not to "reinvent the wheel".

Nuff said...

Marty