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.

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

Even if its THIRTY cubic inches, a jetting change will NOT yield 2 or 3 hp...

Marty

Even if its THIRTY cubic inches, a jetting change will NOT yield 2 or 3 hp...

Nobody has said it would.  To keep confusion, if any, to a minimum, I was correcting the 15 cu. in. in your post to exactly what engine sizes are in question. 

Let me know and I will go get it and copy it here....

C

This is a quote from a friend who deals with Tecumseh engines.  He too has been trying to get a few questions answered for me and spoke with a Tecumseh rep yeserday.  Below is what he was told by a different tech than I spoke with.  

Richie this is straight from Tecumseh engineers. There is no difference between a 8 thru 11 hp Tecumseh snowblower carb . The difference is in the intakes and valves. But there is no difference in the carbs. Don.

Everything is the same on an 8-10, including carburetor, jetting, head, crank, exhaust valve, intake valve, cam shaft.  The difference is that the piston and connecting rod are different.  I was also told from a mechanic that works on these engines that the Tecumseh 11 hp OHV engine uses a new cheaper type of carburetor.  So, is it really worth the extra money for a 10 hp L-head, that is up to the buyer.  Is it worth the extra money for the 11 hp OHV engine, I'd always prefer an OHV over an L-head.  Just depends on how deep your pockets are.