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Antique Gas Engine Discussion

Stover Cam - Crank Reference Marks


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  #11  
Old 07-13-2018, 12:20:46 AM
EMU EMU is offline
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Cool Re: Stover Cam - Crank Reference Marks

Power of The Past Vol 3 Timing vertical and horizontal engines , if the exhaust valve opens and closes late,loosen the cap screw which holds the large gear in place (cam gear ) and slip the gear out . Turn the gear in the opposite direction the engine runs far enough to set the valve in proper time . Be careful in making this change , for the large gear set a touch to far either way , will make a great difference in the working of the


I understand by Power of the Past Vol 3 detail , that ex valve timing is performed 1st and then 2nd Ignition Timing .


THIS IMAGE SHOWS WHAT I ASSUME TO BE IGNITION MARKS ATTEMPTING TO MESH . WHICH IN THIS POSITION IS JUST AS MAGGIE HAS TRIPPED .
I ASSUME THAT EACH TOOTH ON CAM GEAR CAN BE IN REF AS DEGREES .
IMAGE SHOWS WHAT IS ASSUMED AS SAY 10 DEGREES BEFORE TDC . ? Any way this is what has been noticed . I assume because every thing is working from The Rod , such as Exhaust Valve , Fuel Pump, and Magneto Trip position . That 2 reference marks , in differing positions is playing a major role for timing . Very interesting . Stover 6/8 hp Standard approx 1913 hit / mis , with mag , tank cooled , solid crank gear ( not spoked) .

Last edited by EMU; 07-14-2018 at 05:05:40 AM.
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  #12  
Old 07-13-2018, 09:31:04 AM
EMU EMU is offline
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Default Re: Stover Cam - Crank Reference Marks

Ok. 1 mark on the Cam Gear is for the Angle in degrees just as the Ex Valve Closes .
The other mark is for the trip angle in degrees . I do see a series of 0,s occurring although very faint . These maybe duration . Intervals ..Possibly the duration the Ex Valve is either open or closed . Or interval in between .

Last edited by EMU; 07-14-2018 at 04:59:56 AM.
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Old 07-14-2018, 07:05:44 AM
John Savot John Savot is offline
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Default Re: Stover Cam - Crank Reference Marks

Keep in mind that all valve timing is made in reference to top dead center on the compression stroke. The engine can actually be timed without any marks at all using the valve timing reference chart - which I hope you have been able to find. Forget about ignition timing until after valve timing is correct, existing marks could be wrong.

John
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  #14  
Old 07-14-2018, 07:26:16 AM
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BMiller BMiller is offline
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Photo Re: Stover Cam - Crank Reference Marks

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I post this with thanks to the author -- it's helped me keep my head straight about timing issues.

As John said, forget the marks, set the valve so it operates according to the chart. Then set the ignition.
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Old 07-16-2018, 06:45:23 AM
MotorMike MotorMike is offline
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Default Re: Stover Cam - Crank Reference Marks

Thanks for that chart, I was dealing with this very issue last week on a 2hp Stover K. We couldn't find any timing marks on either gear. This will help get it set up.
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Old 07-17-2018, 05:40:35 AM
EMU EMU is offline
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Default Re: Stover Cam - Crank Reference Marks

Thank You BMiller ,
I searched , google and found the same image . It is self explanatory and shows plainly .

Ref : Stover type DX 8 hp model E . 80 teeth on Cam Gear and 40 teeth on Crank Gear . Radius approx of '' Cam Gear'' approx 130 mm . Calculate Circumference then divide that Value by amount of teeth .
I assume the measurement of the Radius of the Cam Gear should be mid way , of the teeth length . Rather than at the bottom , or the top of the teeth .
Note : I see faint , what possibly looks like 0,s [zero,s ] occurring near the punch marks on the crank gear . If they are or if they are 0 ,s then I assume they are Ex Valve Opening and closing duration intervals . So these marks are needed , then a minor adjustment can be made at the ' clevis' on the Push Rod . The set up for Ex Valve Lever is heavy duty , as there is no ' Nut' at the End of the Lever as seen on later Gas Engines . Therefor the duration adjustment of Ex Valve occurs by adjusting at the Clevis , by removing the The Centre Threaded Bolt at the Rocker Arm at centre Fulcrum point , then loosen the Nut , and spin the Rocker Arm in the direction needed .

Question , what would be the maximum duration ' Gap '. ? . Also Understanding that that ' gap' would be known from ' New ' . ?

I have been taking note , of position of Crank in Relation too Reference of Cam and Crank Markings . It must be understood that when the Factory assembly of the Engine takes place , these reference points , are used ,and obviously there has to be something to go on . I have been taking note of the amount of teeth prior to and after the cam and crank gears mesh . Each Cam Gear tooth can be calculated in a degree . Which calculates to approx. 5 degrees per tooth . Interesting .
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Old 07-17-2018, 06:33:28 AM
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Default Re: Stover Cam - Crank Reference Marks

The "gap" between the rocker and the exhaust valve doesn't matter -- some of them open almost an inch during the compression stroke. What is important is first and last contact of the rocker to the valve stem.
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Old 07-17-2018, 07:01:05 AM
ScooterBob ScooterBob is offline
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Default Re: Stover Cam - Crank Reference Marks

As BMiller stated, the "gap" doesn't matter. If you want to set the pushrod length (duration) first, the duration would be 220 degrees to 230 degrees according to the chart (35 to 40 degrees BBDC, +180, + 5 to 10 ATDC).

Please don't get hung up on any marks, and just set the engine up according to the chart. The factory may have had set up jigs for use on freshly ground cam lobes of known size. Due to wear over the years, things may have changed.
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Old 07-18-2018, 05:19:14 AM
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Default Re: Stover Cam - Crank Reference Marks

Yes, this ' Gap; can also be affected by Wear and Tear of the Ex Valve , also depending whether the valve stem has been shortened .
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