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Hi all,

Here is a dump of information in hopes someone is bored and/or helpful enough to base an analysis on any of it.

The manual for my beloved old family mower says the spark plugs should be changed every season. After 30 seasons, I think it's time. I'd like another 30 on this old nag.

It's a Sears Craftsman LT1000, Model 917.271920 with a Briggs & Stratton engine. I have purchased the new plugs from Sears parts direct but they won't provide me with any technical information on the engine.

I don't want to strip the threads on the cylinder heads, and I don't want loose plugs. I called Champion (plug manufacturer). Their rep told me they recommend seating the plugs at 18-22 ft-lb for aluminum cylinder heads, 26-30 for cast iron. He said that even the "hand-tighten-then-fraction-of-a-turn" recommendations would be different depending on the head material. In any event, I am too dumb and clumsy and not handy with machines to turn 1/16th of a turn, or whatever, reliably. So I got a torque wrench and I'm trying to figure out which value range is correct.

I don't know what the cylinder heads are made of. The part of the cylinder that has the model number stamped on it was rusty enough that I had to scrub it with vinegar and a wire brush to read it. But, I don't know what that tells me about the cylinder *heads*. And, aluminum corrodes a little, right? (It wasn't green "rust", though, so if I had to guess I would say that particular part is iron.)

Craftsman won't talk to me because my mower is a Sears Craftsman "exclusive" product that they don't support.

Sears won't give me this tidbit of information because they want me to buy a service contract and have them install my plugs. I got transferred to 3 different tech reps who cut me off when I said I didn't have a service contract, and they transferred me back to the people that kept saying only the tech reps had the information.

I haven't figured out a way to contact Briggs & Stratton as a consumer with a non-B&S branded product containing a B&S engine. Their "engine locator" has no documents for this engine.

My engine model number is as follows:

MODEL: 407777

TYPE: 0167-E1

CODE: 020518YG

I don't know why the emissions compliance label would help, but just in case, it says:

FAMILY: YBSXS.7242VF (and then a bunch of spaces, and then) 274844

Any help would be greatly appreciated! Thanks all.

I've never torqued a spark plug. just get it good and snug with your favorite 3/8 drive ratchet.
Of course Cast iron should be Magnetic and aluminum won't be...

"Cast iron should be Magnetic and aluminum won't be"

holy crap let me go write another 1000 word post because i don't have a brain.

THANKS! by which I mean thanks x 1,000,000 !!

Add to that, the torque should be different depending upon what type of plug you are using , the thread size & thread length.
For parallel threaded plugs with a crush washer it makes no difference what the head is made of because all you need to do is crush the washer to make an air tight seal
Hand tight + 1/4 turn has always worked for me regardless of everything
And that is holding athe plug wrench by the shaft till it stops turning then a 1/4 turn with the arm of the wrench.

OTOH the old addage is continue tightening till it goes loose then back off 1/2 turn .

18-21.6 ft-lbs for the 14mm Champion QC12YC (Briggs PN 691043) plugs or hand tight plus 1/2-2/3 turn (note this is hand tight not wrench tight).

Many plug manufacturers specify ON A NEW PLUG ONLY, tight and 1/4 turn. Once the crush ring is crushed that spec changes. Keep a small magnet around if you need to know whether something is ferrous or another generally non-magnetic metal like aluminum. However even aluminum will allow electric eddies which give it magnetic properties like in an aluminum disk motor - think of your electric meter.