Cam "lope" question?
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Race Director
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From: Indianapolis IN
Cam "lope" question?
This may be an unanswerable question but here goes,
At what point does a cam begin to lope? I have read that, for vacuum puposes, it is not recommended to have more than .225 Intake at .050.
With that said and using a Hyd-Roller cam, would a .225 have any lope or just a smooth idle?
At what point does a cam begin to lope? I have read that, for vacuum puposes, it is not recommended to have more than .225 Intake at .050.
With that said and using a Hyd-Roller cam, would a .225 have any lope or just a smooth idle?
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Re: Cam "lope" question? (ld85)
You can tune something around 225 int/exh to have a smooth idle, you could probably go a little bit bigger and not have very much lope at all.
Safety Car
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From: Fountain Hills AZ
Re: Cam "lope" question? (ld85)
With everything being equal, more duration will usually result in more lope but there's no majic line where lope will occur or not occur. Slightly more duration will give slightly more lope. A lot more duration will give a lot more lope. There are a lot of other factors like timing, fuel mixture, displacement, head port volume, etc., that will affect lope also. One engine may have a very noticeable lope with 220º and another may have none with 225º.
Lope is usually the result of lower intake velocities caused by longer duration and which prevent the fuel/air from mixing well or not keeping the fuel suspended in the air and also from exhaust gasses flowing into back into the combustion chamber. In the latter case, the lower intake air velocities offer less resistance to exhaust reversion and also, because both the intake and exhaust valves are open together for longer periods, there's more opportunity for this to occur.
Lope is usually the result of lower intake velocities caused by longer duration and which prevent the fuel/air from mixing well or not keeping the fuel suspended in the air and also from exhaust gasses flowing into back into the combustion chamber. In the latter case, the lower intake air velocities offer less resistance to exhaust reversion and also, because both the intake and exhaust valves are open together for longer periods, there's more opportunity for this to occur.
Race Director
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From: The Top of Utah
Re: Cam "lope" question? (Vetterodder)
...also, because both the intake and exhaust valves are open together for longer periods...
RACE ON!!!
Drifting
Joined: Nov 1999
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From: St. Peters MO
Re: Cam "lope" question? (CFI-EFI)
HOWEVER, for a given amount of duration, the overlap is decreased by increasing the amount of lobe separation.
In some cases, a "lope" is a desired property. In a cruising type car, not an all out race car and not a daily driver. (Street Rods for example :thumbs: )
Or, can you alter cam timing enough with a mild cam to "induce" a lope at idle?
Thanks,
Tom
Pro
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Re: Cam "lope" question? (NASCAR314)
Yup! Some people buy cams with short duration and very tight lobe separation like 106 or 104, so they get that lopey sound without killing their low end performance too much. I would never personally choose a cam for its sound. If you're gonna build the motor to sound fast, build it to be fast!
You can't induce a lope by advancing or retarding a cam. It has to have the valve overlap ground into it. You could slightly increase overlap by increasing the rocker ratio, but it would only make a very small difference.
[Modified by L79vette, 4:21 AM 4/10/2003]
You can't induce a lope by advancing or retarding a cam. It has to have the valve overlap ground into it. You could slightly increase overlap by increasing the rocker ratio, but it would only make a very small difference.
[Modified by L79vette, 4:21 AM 4/10/2003]
Race Director
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From: The Top of Utah
Re: Cam "lope" question? (ld85)
In am effort to make a "healthy" cam more streetable, copious amounts of spark advance, can help. If you want it to sound "nasty" try retarding the timing. It won't run like it should, but it will sound mean. Personally, I'd rather sound stock and run otherwise, than the opposite. Either way, good luck, and...
RACE ON!!!
RACE ON!!!
