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Hello I have a Briggs Stratton 18.5 hp ohv so I looked up the Valve Clearance it’s .003/.005 intake and .005/.007 exhaust Not sure about the numbers for example intake is .003/.005 what one am I supposed to use the .003 or the .005 Simple enough to do I’m just not sure about what one to use Thanks for any info you can give me

Personally I always shoot for the middle. If I end up a thousand off I’m still fine.

When I run into that I just grab the .005 and set both of them. Clearances are subjective. One persons .005 would be another .004 or .006 depending on how much drag they create on the gauge.

I always shot for the minimum on the Intake valve which is the most critical for Conpression Release action, mid on Exhaust

Walt Conner

Thanks to everyone. You all are a huge help because of financial difficulties I have to fix things myself and this forum makes it possible for me. Thanks again

As for me on OHV engines say if the value are .003-.005. I set to lowest end by using the following. Get a .003 gauge to pass but not the .004. I use the method on other specs too. Right the opposite on L-head (side valve) say if max clearance is .011 then set where a .011 passes but not the .012.

StarTech said:

As for me on OHV engines say if the value are .003-.005. I set to lowest end by using the following. Get a .003 gauge to pass but not the .004. I use the method on other specs too. Right the opposite on L-head (side valve) say if max clearance is .011 then set where a .011 passes but not the .012.

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Thank you

I did the adjustment last night and it starts much better. Thanks so much to everyone

Not sure about yours but my B&S has a cam that holds the exhaust valve open at low speeds (a decompressor). If the valve clearances are too big this doesn't work correctly and the engine can be hard to turn over. You get the impression its a faulty starter or battery. Adjusting the valve clearance correctly can really makes a big difference to this.

The quoted specs are a range .003 being the minimum and .005 being the maximum clearance. I usually go for the lower clearance of .003; normal wear will increase the tolerance over time

I always go middle of the spec, but for motorcycles or anything with a shim-under-bucket valvetrain design, the valves will tighten with wear. On some OPE engines, this is opposite.

Correction needed, normal wear will cause the clearance to become less, not more. This is most commonly due to valve stem stretch.

Rivets said:

Correction needed, normal wear will cause the clearance to become less, not more. This is most commonly due to valve stem stretch.

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So why do you have to readjust the clearance? I have never had to increase the clearance when readjusting during routine maintenance. If the valve seats and/or valve sealing surface is worn it could cause the clearance to become less.

Jane said:

Hello I have a Briggs Stratton 18.5 hp ohv so I looked up the Valve Clearance it’s .003/.005 intake and .005/.007 exhaust Not sure about the numbers for example intake is .003/.005 what one am I supposed to use the .003 or the .005 Simple enough to do I’m just not sure about what one to use Thanks for any info you can give me

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I can't believe how dumb some people are. It's anywhere between 3 and 5 thou.

On L- head engines valve clearance will normally become less. On OHV engines the valve clearance will normally become more, due to rocker arm locks coming loose allowing the change, not wear.
Boot, I will gladly answer questions like this everyday of the week. It shows me that this person is reading the manual and trying to learn the right way to do the job. YOUR COMMENT IS WAY OUT OF LINE. Better to ask a dumb question than make a stupid mistake.

bootface said:

I can't believe how dumb some people are. It's anywhere between 3 and 5 thou.

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Look not everyone are well verse on equipment terms or specs. I imagine you didn't know how to do the paperwork after you went to bathroom yourself when you started not wearing diapers.

Even college educated people don't know everything nor a tech that been working on equipment for over 40 yrs knows everything. We all need help from time to time; although, most my questions are way above most here or on other forums. Sometime even the OEM can't answer them and have get back to me.

BTW we all have things we are good and bad at. So don't complain about someone asking about they don't know. I rather have someone asking then screwing up because they didn't.

bootface said:

I can't believe how dumb some people are. It's anywhere between 3 and 5 thou.

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I can’t believe how rude some people are.

Jane said:

Hello I have a Briggs Stratton 18.5 hp ohv so I looked up the Valve Clearance it’s .003/.005 intake and .005/.007 exhaust Not sure about the numbers for example intake is .003/.005 what one am I supposed to use the .003 or the .005 Simple enough to do I’m just not sure about what one to use Thanks for any info you can give me

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I kinda thought intake and exhaust valve settings are different for each and is why the two specs.

CWatters said:

Not sure about yours but my B&S has a cam that holds the exhaust valve open at low speeds (a decompressor). If the valve clearances are too big this doesn't work correctly and the engine can be hard to turn over. You get the impression its a faulty starter or battery. Adjusting the valve clearance correctly can really makes a big difference to this.

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Thank You

CWatters said:

Not sure about yours but my B&S has a cam that holds the exhaust valve open at low speeds (a decompressor). If the valve clearances are too big this doesn't work correctly and the engine can be hard to turn over. You get the impression its a faulty starter or battery. Adjusting the valve clearance correctly can really makes a big difference to this.

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In the Briggs 310000 series the ACR is on the intake as the head is a cross flow design and the intake is closest to the ACR on the camshaft. Matter of fact the 210000 (if I remember correctly), 280000, 310000, and 280000 series all use the same camshaft and head design.

Rivets said:

Personally I always shoot for the middle. If I end up a thousand off I’m still fine.

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I was going to post the same advice.

Mowers are not the same quality as car engines or even a motorcycle for that matter .
They are the cheapest engine it is possible to make
Because OHV systems tend to increase the valve lash with use you set them on the tight end of the spec so they remain in spec for longer.
The often you adjust them the better
Side valve engines burn the valve seats so the clearance gets smaller over time thus you set them at the loose end of the spec particularly as it is a ardious task on most mower engines .
The only reason to have any valve lash is to account for expansion so when the engine gets hot the valves are not held open .
As for exact measurements don't beat yourself up over it.
I was at a bike show where the CSIRO had a stand as they were on a recruiting drive
The stand had a set of ignition points ( it was a long time ago ) which were connected to a measuring device accurate to within 0.00001"
Any one who set the points to exactly .030" got a prize and you could use their feelers or your own.
By the end of the show not a prize had been awarded and I got a copy of the results which showed no one got to within 0.0005" of exactly 0.030"
They also had a variety of measuring tools there to check the measurement of peoples feeler gauges and again very few .030" gauges were in fact 0.030" from one end to the other

Roymg said:

I kinda thought intake and exhaust valve settings are different for each and is why the two specs.

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It varies. On some engines the Exhast spec is the same as the Intake.

awkerper said:

I was going to post the same advice.

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when assembling a engine when the engine is cold you should use the lower clearance number if engine is hot you use the higher clearance number exhaust is usually two thousands more clearance

Jane said:

Hello I have a Briggs Stratton 18.5 hp ohv so I looked up the Valve Clearance it’s .003/.005 intake and .005/.007 exhaust Not sure about the numbers for example intake is .003/.005 what one am I supposed to use the .003 or the .005 Simple enough to do I’m just not sure about what one to use Thanks for any info you can give me

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.003/.005 means it is a go and no go setting. It means that a .003 will go but a .005 will not. In other words .004. The same goes for .005/,007 - meaning .006.

In a manual written for engineers it would be 0.004" +/- 0.001"

You are working with .003s one way or the other don't worry about it because you will never get it perfect.

wevertx said:

.003/.005 means it is a go and no go setting. It means that a .003 will go but a .005 will not. In other words .004. The same goes for .005/,007 - meaning .006.

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It means anything in the .003 to .005 range is acceptable. .0050 is acceptable. Anything greater than .00500001 is not. It does not matter if it is presented with upper and lower limits or with a bilateral tolerance. i.e. .004 +/- .001. Using feeler gauge is a skill. You have to develop a feel. Some may get the .005 gauge to pass. while another will say it does not go. Feeler gauge is a no-go type of measurement. No -go measurement tools tell you a range in which the feature in question falls. It does not give the actual dimension.

With that said, if you are right on the edge of the limit you have to make a judgement call to adjust it or not. I think folks covered this well earlier.

Maybe that is why they call it feeler gauge.?

Actually it means anything over 0.0055" is not acceptable
+ or - 1/2 the final digit
As the final digit is a thou then that will be + or - 1/2 a thou
It is a bit problem when Americanizing a UK drawing
The drawing will show 3 1/4" which is 3.1/4" +/- 1/16"
Americans transpose that to 3.125 " which implies that the size has to be accurate +/- 1/2 thou