Tight lash camshaft questions
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Re: Tight lash camshaft questions
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.
Do you use the same ramp slope for all cams? What slope do you use, if you feel comfortable sharing that info.
Re: Tight lash camshaft questions
About 15 year ago I had a tight lash cam reground on a new stock core for a vintage GMC 302 inline powered 37 Chevy PU street truck I had...It was done by the late Lazer Cams owner supposedly to get as much duration as possible from a regrind..It was .005 and .007 hot lash I believe ,stock was about .012 and .016 with long ramps..It was faster than the other vintage lumps........
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Re: Tight lash camshaft questions
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.
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Re: Tight lash camshaft questions
Nope...they were called "30-30" 's for a reason.
The valve noise was enough to drive off most street racers...if it's that loud it must be fast.
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Re: Tight lash camshaft questions
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
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Re: Tight lash camshaft questions
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
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Re: Tight lash camshaft questions
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
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.
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Re: Tight lash camshaft questions
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.
How does any of that change between a tight and loose lash cam and being able to do lash loops?
Stan
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Re: Tight lash camshaft questions
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
How would you define a tight and loose lash cam?
Re: Tight lash camshaft questions
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
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Re: Tight lash camshaft questions
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
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. Valve train flex and compliance not being considered here.
The same ramp slope could apply no matter what the actual ramp height might be. Or the slope might be steeper or more shallow. I feel much more comfortable knowing the actual ramp height and slope for the cam; actually it is the valve position that must be considered, not the only the cam.
If lash is set larger than the maximum ramp height, we have a problem waiting for us. The impact of excessively large lash settings becomes more severe as the engine rpms increase due to the emergence of valve acceleration spikes.
It is not uncommon, upon CamDr measurement, to find significant variance in duration from valve to valve. Some compensation can be accomplished by setting each valve lash to a different value. In total angle area, it may make little difference, but it does have an affect on overlap and event locations.
Re: Tight lash camshaft questions
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.
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Re: Tight lash camshaft questions
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
I knew someone years ago that happened to. Luckily his was water cooled and he was able to run some hot water into it and was off and running again.
Stan
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Re: Tight lash camshaft questions
Still not sure what the lash ramp height has to do with lash loops.
I don't know what style lash ramp is being used now, but I have not seen many constant velocity ones lately, although they do make the calculations very easy. For illustration this is a 40 degree 0.020" constant velocity and constant acceleration ramp one side.
Stan
I don't know what style lash ramp is being used now, but I have not seen many constant velocity ones lately, although they do make the calculations very easy. For illustration this is a 40 degree 0.020" constant velocity and constant acceleration ramp one side.
Stan
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