Valve adjustment
- Martin Benade
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Re: Valve adjustment
I did it once on my race engine; somewhere around .018" Cold was .oo4" and .006".Wes Bender wrote: ↑Tue Aug 02, 2022 2:18 pm Or setting the valves on the old Chevy sixes through the engine side cover while they were running. I've still got a set of feeler gauges in my junk box that were dinged pretty good doing that. If we take up a collection to cover the burns, maybe we can convince Vic to get us some actual numbers on the hot valve clearances.
For those commenting on checking hot clearance on Brit stuff, as I recall, their valve covers are on TOP!
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Re: Valve adjustment
Why did they close up so much? I thought they went the other way, allowing you to set them cold at 0 clearance.
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Re: Valve adjustment
Close up? .018" is way looser than .004" or .006"Martin Benade wrote: ↑Wed Aug 03, 2022 9:28 am Why did they close up so much? I thought they went the other way, allowing you to set them cold at 0 clearance.
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Re: Valve adjustment
I misread, thought you’d set them to .018. It no longer sounds impossible.
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- Wes Bender
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Re: Valve adjustment
I would assume (dangerous, but a bad habit that I've got) that the increase in gap of .012 - .014+/- would probably vary with the amount of heat, rather than being a percentage of the initial gaps. I was asking tongue-in-cheek, but that's really good info, Vic. It makes one wonder why anyone would ever set their valve clearances wider, especially on a street engine.
Some days it's just not worth chewing through the restraints.....
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Re: Valve adjustment
Just a datapoint... My friend Dr John Witner, Moto Guzzi Factory development engineer, worked with a dyno equipped with a device that measured the valve gap while the engine was running. He was testing pushrods made of various materials to see if material types changed the power output. Yes, he confirmed that the material type does matter. Aluminum pushrods make the least amount of power, and he tried many types of aluminum. Guzzi was using aluminum cylinders combined with aluminum pushrods and he wanted to change to steel pushrods for the power improvement but ultimately Guzzi stayed with aluminum because it was feared that customers would not accept a standard cold setting of .000". I believe that when using a .000" cold setting with steel pushrods and aluminum cylinders that the hot running clearance is in the low 20s, not too different than the aluminum pushrods with a conventional gap setting. On race engines with Nickies I use tapered steel pushrods set at .000" cold. My street cars with Nickies have aluminum pushrods with conventional cold gaps.
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- C J Murray
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Re: Valve adjustment
I use Manton pushrods and they have some interesting tech stuff on their website. Links below. There is much more when you search their site. In the past 10 years I have had 2 major engine failures in the race cars where the pushrods should have been bent but they never did bend. Strong!
http://mantonpushrods.com/pushrod-info/tool-steel/
http://mantonpushrods.com/tech-info/facts/
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Re: Valve adjustment
Interesting info, Cliff. Thanks. I think my engine will be o.k. with the chromemoly push rods since I'll keep it under 12,000 rpm and is not even close in horsepower!
Mike
Mike
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- Al Zim
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Re: Valve adjustment
If you switch to steel cylinders (I did a LOOONG time ago) the aluminum push rods on my 1963 S-90 caused all the exhaust valves to burn. I was a lot more inexperienced 45 years ago. Pushrods ( steel) from engines of the early 60's have a wooden dowel in them to control the oil flow (bad idea) they tended to continually shed ( small) amounts of wood into the oil. Neither the magnet or the screen can catch the wood.
HOW DO YOU DETERMINE THAT YOU HAVE THE CORRECT CLEARANCE? With the feeler gauge properly positioned between the valve and the rocker you should just be able to turn the push rod (it needs to have resistance or it is too loose)
MORE BAD NEWS: Rocker arms wear on the tip after 65+ years an indent becomes apparent. Send them out have them resurfaced then the valve setting will be correct.
ROCKER ARM ADJUSTING SCREWS: They get abused because more than 15 foot pounds of torque is used to tighten the nut. You have to take the rocker arms off extend the adjusting towards the push rod. Cut the bottom off the adjusting nut with a cut off wheel ( a hack saw will not work the metal is too hard) purchase a new adjuster and lock washer and practice 15 foot pounds of torque. After the adjuster cup end is cut off the adjuster will have to be screwed out backwards.
HOW DO YOU DETERMINE THAT YOU HAVE THE CORRECT CLEARANCE? With the feeler gauge properly positioned between the valve and the rocker you should just be able to turn the push rod (it needs to have resistance or it is too loose)
MORE BAD NEWS: Rocker arms wear on the tip after 65+ years an indent becomes apparent. Send them out have them resurfaced then the valve setting will be correct.
ROCKER ARM ADJUSTING SCREWS: They get abused because more than 15 foot pounds of torque is used to tighten the nut. You have to take the rocker arms off extend the adjusting towards the push rod. Cut the bottom off the adjusting nut with a cut off wheel ( a hack saw will not work the metal is too hard) purchase a new adjuster and lock washer and practice 15 foot pounds of torque. After the adjuster cup end is cut off the adjuster will have to be screwed out backwards.
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