Re: Tight lash camshaft questions
Posted: Mon Sep 09, 2019 10:23 pm
Bill i think you are correct in what you said. ^^^^^^^ Mark H.
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Mike, thanks for sharing so much useful information.CamKing wrote: ↑Mon Sep 09, 2019 12:46 pmWe use a .012" Lash ramp on most of our roller profiles, so Hot Lash would be .012" x Rocker Ratio.
We chose .012", because if you go down to a .010" ramp, with an Aluminum block and Aluminum heads, the lash growth from cold to hot, would be more then the Hot Lash setting.
We have a series of rollers with .010" ramps, but we recommend them for iron block engines.
We have made roller cams with lash ramps as small as .004", but they're for restricted classes, and have to run with iron blocks and heads.
No. The ramps are matched to each cam.David Redszus wrote: ↑Tue Sep 10, 2019 1:47 pm Do you use the same ramp slope for all cams? What slope do you use, if you feel comfortable sharing that info.
Bill,
The 097 is nothing like the 30/30. The 097 was something like 228/230@.050, about .400” lift. The 30/30 was 254@.050, .485 lift
A constant velocity ramp would consist of a slope (rise over run) for a certain number of degrees.Stan Weiss wrote: ↑Tue Sep 10, 2019 11:19 pmBill,
I don't see why trying the lash looser would be any different between a tight and loose lash cams. Now if you want to try a tighter lash setting then you would probable have to set the valves hot on the dyno.
Stan
David,David Redszus wrote: ↑Wed Sep 11, 2019 1:47 amA constant velocity ramp would consist of a slope (rise over run) for a certain number of degrees.Stan Weiss wrote: ↑Tue Sep 10, 2019 11:19 pmBill,
I don't see why trying the lash looser would be any different between a tight and loose lash cams. Now if you want to try a tighter lash setting then you would probable have to set the valves hot on the dyno.
Stan
If the lash is set to a value greater than the ramp height, the follower will crash into the flank of the cam producing a substantial increase in valve acceleration and very often rocker breakage.
Knowing the ramp height and duration in degrees allows one to adjust seat to seat valve timing.
While cams for mechanical lifters may have a ramp duration of 30 deg or more, cams for hydraulic lifters have very limited ramp duration, if any at all.
StanStan Weiss wrote: ↑Wed Sep 11, 2019 9:01 amDavid,David Redszus wrote: ↑Wed Sep 11, 2019 1:47 amA constant velocity ramp would consist of a slope (rise over run) for a certain number of degrees.Stan Weiss wrote: ↑Tue Sep 10, 2019 11:19 pm
Bill,
I don't see why trying the lash looser would be any different between a tight and loose lash cams. Now if you want to try a tighter lash setting then you would probable have to set the valves hot on the dyno.
Stan
If the lash is set to a value greater than the ramp height, the follower will crash into the flank of the cam producing a substantial increase in valve acceleration and very often rocker breakage.
Knowing the ramp height and duration in degrees allows one to adjust seat to seat valve timing.
While cams for mechanical lifters may have a ramp duration of 30 deg or more, cams for hydraulic lifters have very limited ramp duration, if any at all.
How does any of that change between a tight and loose lash cam and being able to do lash loops?
Stan
A lobe designed for say 0.012" lash will have a far shorter ramp than one meant for 0.030", thus a narrower range between running off the end of the ramp as per David's post and encountering zero/negative cold lash. (Speaking of which, I read of a well-known West coast Porsche specialist that was running a series of lash loops on an air-cooled engine. Power was improving with each lash reduction, but after they broke for lunch the engine wouldn't start... )Stan Weiss wrote: ↑Tue Sep 10, 2019 11:19 pmBill,
I don't see why trying the lash looser would be any different between a tight and loose lash cams. Now if you want to try a tighter lash setting then you would probable have to set the valves hot on the dyno.
Stan
Reviewing about a dozen Cam Dr files for various camshaft types, some consistencies seem to appear which can be easily confirmed.MadBill wrote: ↑Wed Sep 11, 2019 9:18 pmA lobe designed for say 0.012" lash will have a far shorter ramp than one meant for 0.030", thus a narrower range between running off the end of the ramp as per David's post and encountering zero/negative cold lash. (Speaking of which, I read of a well-known West coast Porsche specialist that was running a series of lash loops on an air-cooled engine. Power was improving with each lash reduction, but after they broke for lunch the engine wouldn't start... )Stan Weiss wrote: ↑Tue Sep 10, 2019 11:19 pmBill,
I don't see why trying the lash looser would be any different between a tight and loose lash cams. Now if you want to try a tighter lash setting then you would probable have to set the valves hot on the dyno.
Stan
Actually, it would change 4 degrees, because you would be changing each side 2 degrees.David Redszus wrote: ↑Thu Sep 12, 2019 12:22 pm A ramp height of .020" over 40 deg would produce a slope of 2 deg/.001". That is to say a change in lash of .001" would result in a duration change of 2 deg.
Bill,MadBill wrote: ↑Wed Sep 11, 2019 9:18 pmA lobe designed for say 0.012" lash will have a far shorter ramp than one meant for 0.030", thus a narrower range between running off the end of the ramp as per David's post and encountering zero/negative cold lash. (Speaking of which, I read of a well-known West coast Porsche specialist that was running a series of lash loops on an air-cooled engine. Power was improving with each lash reduction, but after they broke for lunch the engine wouldn't start... )Stan Weiss wrote: ↑Tue Sep 10, 2019 11:19 pmBill,
I don't see why trying the lash looser would be any different between a tight and loose lash cams. Now if you want to try a tighter lash setting then you would probable have to set the valves hot on the dyno.
Stan