Small Engines (Lawn Mowers, etc.)/tecumseh cylinder wall
QUESTION: Hi, i have a 1977 ariens model 924026 serial number 020931 with a 8 hp Tecumseh engine hm80-155128c ser-6302D.I'm thinking of rebuilding the engine however i was told not to mess with it if it has an aluminum cylinder. Without taking the head off, would you know if this engine has a iron cylinder or an aluminum one.
ANSWER: Cast iron models have different model numbers. Refer to this link:
HM model info at this URL:
Odds are you have an aluminum cylinder with an HM model series.
It will be cheaper to replace the whole engine than to rebuild. Labor costs, cylinder boring, and parts will cost over half the price of a new engine. We stopped rebuilding in the 1990's due to increased labor and parts costs.
Email the company below to see if they have a replacement engine:
According to your engine's crankshaft part number you have a 1 inch diameter crankshaft. This is the same crank used on the older 10 hp engines.
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QUESTION: thanks, nothing seriously wrong with the engine except its age, would of done the work myself to refresh the engine but if it has an aluminum cylinder i will let it be. The only thing you could tell me is that if i set my idle to low can it cause carbon build-up and therefore at what rpm should the idle be to prevent this?
ANSWER: Today's fuels do not produce much carbon but since the engine is old I'm betting there is carbon build up from years ago. Some might burn off and you could remove the head and clean the carbon but you would have to replace the head gasket and re-torque the head bolts.
The idle speed should be around 1800 RPM. Too low of idle would not really contribute to carbon build up as the engine will be running at operating temp regardless of idle or high speed. High speed loading, such as when you are blowing snow, will put extra stress on the engine but not enough to cause the engine operating temp to get too hot.
If the blower is in good shape I'd still price a new engine or at least know what you need. You can find snow blower engines on sale in the spring and summer.
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QUESTION: thanks again. before i decide to change the engine , what numbers should i be getting if i take a compression test(it has compression release) or for a leak down test? Secondly, is a 7hp (has 8hp) good enough for my blower (24 inch). My local hardware store has a rato (honda clone) on sale this week for half price at $125 here in Canada. They come on sale like you said but only sell 6hp and 7hp.
thanks Eric for this great service.
1) Compression varies on small 4 cycle engines due to compression release. We see a lot with between 40-50 PSI when we check them.
a) The Briggs and Stratton leak down tester has a small range but does not give an specs. The main things the leak down tester checks is valves, head gasket and rings. If you Google cylinder leak down test you will find various specs...here is an excerpt from one article.
A brand new street engine might measure from 5% to 8% depending on the engine, manufacturer, and degree of break in. A street engine that measures 10% to 20% per cylinder, although indicating some wear, if there is consistency between cylinders and if all of the air is leaking past the rings into the crankcase indicates a reasonable street engine for daily driving that does not need any immediate work. Any readings 30% or higher indicates a severe engine problem.
2) Depending on how much snow you get a new 7 hp would probably be fine but like most guys more power is always better...but for $125 it is hard to pass up that bargain. You could probably increase the engine RPM slightly to get a little more power but the engine will wear out faster as well...it's a trade off.