Valve clearance on Briggs 8 hp - Snowblower Forum : Snow Blower Forums
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post #1 of 11 Old 02-27-2016, 04:36 PM Thread Starter
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Valve clearance on Briggs 8 hp

Greetings friends...I was thinking of repowering a 1978 Toro 8 26 , but decided to tear into the Briggs first to see what was up. It had extemely low compression, when pulled over by hand and 40 lbs spinning over with the starter. When I got inside, I checked the valve clearance.....nothing. The cylinder walls were perfect and no slop in the piston. What is the optimal valve clearance? Thanks in advance
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post #2 of 11 Old 02-27-2016, 04:38 PM
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What engine model?

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27", B&S 305cc 13.5 ft/lb Torque 9.5 hp
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post #3 of 11 Old 02-27-2016, 04:51 PM
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I believe an 8HP Briggs uses 0.008" on the intake and 0.012" on the exhaust.

If the valve clearance has closed up considerably (or is gone to zero) you probably have valve seat recession and/or valve face wear issues. When you get the valves out of it do a thorough inspection of everything to make sure it's worth saving. Also check the valve guide clearance. You might consider at least lapping the valves with some fine compound prior to setting the gap though if the seat or face is too far gone this may be pointless.

Keep in mind that a compression test on an engine equipped with a compression release is going to give suspect results. If you can spin the engine backwards for the test you'll learn a bit more. A leakdown tester would tell you even more. This is moot, however, if you've already established that the valve clearances are nil.
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post #4 of 11 Old 02-27-2016, 04:58 PM Thread Starter
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Thanks again guys...the model number is 190402. I'll lap them and grind the stems ....and check the guides of course....but I'm not going to get really fussy LOL.
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post #5 of 11 Old 02-27-2016, 05:13 PM
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Quote:
Originally Posted by cranman View Post
Thanks again guys...the model number is 190402. I'll lap them and grind the stems ....and check the guides of course....but I'm not going to get really fussy LOL.
Make sure you have at least a little bit of a gap before lapping them

Once you have them lapped then go ahead and set the final gap.
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post #6 of 11 Old 02-27-2016, 05:44 PM
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+1 ^ I like to set the gap on the max-spec...then lap them to the middle of the spec range.

from the 270962 Briggs Service manual:
Intake: 0.005" - 0.007"
Exhaust: 0.009" - 0.011"

Briggs seems to be pretty conservative on the valve-guide clearance; a little movement is OK. They make an insertion tool (#19151) for checking.

EDIT: Link to the service manual


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Last edited by classiccat; 02-27-2016 at 05:46 PM.
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post #7 of 11 Old 02-27-2016, 05:49 PM
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Just double checked those numbers. Looks like the intake is 0.005-0.007" and the exhaust is 0.009-0.011" for the 190000 series Briggs engine.

EDIT: classiccat beat me to the correction.
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post #8 of 11 Old 02-27-2016, 06:28 PM
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Quote:
Originally Posted by Blackfin View Post
Keep in mind that a compression test on an engine equipped with a compression release is going to give suspect results. If you can spin the engine backwards for the test you'll learn a bit more.
Turn the engine over backwards by hand. When you reach the compression stroke the flywheel should rebound sharply. If so there is adequate compression to start the engine.
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post #9 of 11 Old 02-27-2016, 06:30 PM Thread Starter
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Much appreciated for the info....I'm fortunate to have an automotive valve grinding machine to grind new faces and grind the stems....the seat look OK...I did check the guides, and the intake is fairly snug, but the exhaust is loosey goosey. Anyway of replacing the exhaust guide?....it appears to be a bushing from the valve seat....
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post #10 of 11 Old 02-27-2016, 07:27 PM
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Quote:
Originally Posted by cranman View Post
Much appreciated for the info....I'm fortunate to have an automotive valve grinding machine to grind new faces and grind the stems....the seat look OK...I did check the guides, and the intake is fairly snug, but the exhaust is loosey goosey. Anyway of replacing the exhaust guide?....it appears to be a bushing from the valve seat....
Alice's Briggs exhaust valve is a little wobbly...but surprisingly in-spec.


I do plan on replacing the bushing this summer.


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