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leaded fuel


simple_stan

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These older engine were built when the only fuel was leaded. Do they have hardened valve seats? My 8N was built with hardened seats, so it wasn't new technology. Sould I add a leaded supplement to the fuel?

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Well for one thing you don't have any build up on the valve. There was an article years ago by Briggs that they like no-lead for that reason. Never read anything on pinging with low compression engines.

Every so often my 89 Merc would ping on slow speeds in OD.

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When I went to a Briggs school, they emphisized low octane because, who cares if the lawn mower engine pings. I never thought to ask about the older engines at that time.

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Everyone should care if their engine pings! Pinging is an errant flame front in the combustion chamber. Prolonged pinging or it's even worse version - outright detonation - can/will lead to damage to spark plugs, pistons, rings and performance.

Briggs doesn't care about octane because the old flat head engines only have about 6.5:1 compression, and are able to safely run on about 77 octane. Typical pump gas is 86 octane at the lowest in America.

An OHV Briggs is somewhere between 7 and 7.5:1 I believe. They usually need the 87 octane - I don't think they are rated to run on as low of octane as an old flat head.

However, a modified flat head - one with changes to increase compression or advance timing - that ups the need for octane in a hurry. Been there, done that, lucky I didn't break a piston... Tim

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I must be missing something or have lead a sheltered life as I have never heard nor do I know what a samll engine sounds like when it pings, and I have run hundreds of small engines?...Just me I guess!

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I must be missing something too. I run unleaded, of course, but always run the 93 octane, have been for years, around 40 of them. I have never had a problem with anything that is inside the engine, except that the innards are always clean. Even the oil remains like new, even without a filter. I have a ZZ Briggs on a garden tractor that gets well used all gardening season, the 65 Landlord with a 10 HP cast iron, and am working on a sister to the ZZ, only she'll be a few years younger than her older brother. I don't work on my engines, usually full choke, pull the rope a couple of times til gas runs out of the carb (on the ZZ), half choke and he is up and running. I start it rich, adjust to whatever I am doing, whether plowing or cultivating. The Landlord is a simple full choke til the engine turns over a couple of times, and we are off to the field. I am a firm believer in high octane for all...ALL small engines, including a 1 3/4 HP Hercules I have been showing for years, chai9nsaws, weed whackers, blowers, etc.

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