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post #1 of 24 (permalink) Old Mar 30th, 07, 8:31 AM Thread Starter
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cam lope

What causes a cam to have the loping sound. If I were looking for a cam that sounded like that, which of the cam specs would I look at to get that sound.
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post #2 of 24 (permalink) Old Mar 30th, 07, 8:34 AM
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Re: cam lope

Overlap. Duration and lsa have alot to do with this.
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post #3 of 24 (permalink) Old Mar 30th, 07, 10:10 AM
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Re: cam lope

yep, If you want to understand cam stuff better take a look at The Comp Cams website. On their site, they have an "articles" section. Once your in the articles section you can read an abundance of info on how a cam works and all of its characteristics such as duration, LSA, overlap, seat timing, lift, area under the curve, etc. I would think duration has a lot to do with the "lope lope" of a cam. Most general performance street cams are usually ground on a 110lsa.
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post #4 of 24 (permalink) Old Mar 30th, 07, 11:53 AM
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Re: cam lope

"Cam Lope" is caused more by uneven cyl/cyl fuel distribution than the cam grind. If you were to put an 097 cam in 2 barrel 283, it would lope like crazy; in a fuel injected car, it idled smooth. What lope really means is that your engine could run better if you had a better intake manifold. When I hear an engine that lopes, I hear an engine that needs tuning.

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post #5 of 24 (permalink) Old Mar 30th, 07, 12:09 PM
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Re: cam lope

FYI, if you are looking for the sound more than performance, Comp Cams has their new Thumpr line of cams designed specifically for that purpose. Generally speaking it is true that lope does not equal power or performance. You can have a lopey cam thats a dog in a given combo, and a smoother cam that kicks a$$ in a given combo.

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post #6 of 24 (permalink) Old Mar 30th, 07, 12:28 PM
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Re: cam lope

Quote:
Originally Posted by kirkwoodken View Post
"Cam Lope" is caused more by uneven cyl/cyl fuel distribution than the cam grind. When I hear an engine that lopes, I hear an engine that needs tuning.
so your SB with a 250@ .050 cam has NO lope? & all pro drag cars need tuning?

sorry kirk, gotta call BS on that

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post #7 of 24 (permalink) Old Mar 30th, 07, 12:34 PM
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Re: cam lope

Quote:
Originally Posted by dreis454 View Post
so your SB with a 250@ .050 cam has NO lope? & all pro drag cars need tuning?

sorry kirk, gotta call BS on that
I agree. Could you explain that a little further? In certain specific situations this may be true, but not as a blanket statement. JMHO.

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Last edited by jbird; Mar 30th, 07 at 1:22 PM.
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post #8 of 24 (permalink) Old Mar 30th, 07, 2:45 PM
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Re: cam lope

One more for the EFI and lope = needs tuning. Not true at all.

Go to the LSX world, they are mostly EFI and still lope like a SOB w/ a big cam. Some are putting down 430rwhp SAE cam only from a 346.

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post #9 of 24 (permalink) Old Mar 30th, 07, 3:10 PM
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Re: cam lope

I agree with the general consensus. What about fuel injected dragsters that run like crap until the engines are taken up to 3,000 RPM? It's the big camshafts that do that. Long duration camshafts are made and intended for not only more power, but for higher RPM operation. They move the throttle response and the available power further up the RPM scale than shorter duration camshafts do.

So with that extra power delivered by the longer duration cam, there is a trade-off. Because idle and low RPM operation in general is compromised. it's a sacrifice that's made for increased high RPM power. The longer duration cams cause rougher idle characteristics, but Lobe separation angle (LSA) is more specifically the cause. The tighter LSA cams (such as 108, and 110 LSA) will tend to cause choppier idle quality, but they will also cause the power band to be a little narrower. So the power will begin later and end sooner within the RPM scale with the tighter LSA's. However, that narrower power band will also come on stronger and will be more intense than with wider LSA cams.

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post #10 of 24 (permalink) Old Mar 30th, 07, 5:27 PM
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Re: cam lope

You can also pick up a lot of sound by using a cam with an early opening exhaust valve. You lose a little low end TQ because you let cylinder pressure out early...but it will help the *thump* part without going crazy with overlap and it's poor manners.

Plus compression always helps sound..the more the better!!

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post #11 of 24 (permalink) Old Mar 30th, 07, 5:34 PM
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Re: cam lope

Its worth agreeing with kirkwoodken in the fact that EFI in most cases will mellow out a lope a bit, as it can constantly fine tune the fuel mapping and ignition at idle and change in an instant with the dab of throttle. BUT, i do not agree at all that lope is more to do with that, than the cam. The cam certainly makes the lope.

Its also worth noting that lope is amplified when your talking big cam, and little engine. A 236/244@.050 on a 110 will be pretty mild in a 400 SBC, but that same cam in a 283 will be rough.
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post #12 of 24 (permalink) Old Mar 30th, 07, 5:44 PM
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Re: cam lope

Slightly OT, but exhaust configuration has a bit to do with it, as well, correct? Straight duals will sound more lopey than duals with a crossover due to the pressure equalization with a crossover.

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post #13 of 24 (permalink) Old Mar 30th, 07, 6:15 PM
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Re: cam lope

Early timing events both produce that sound. A well advanced cam will produce that rolling lopey sound from the early intake valve opening. Early exhaust opening produces a very distinct sound due to exhaust valve opening at peak cylinder pressures.
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post #14 of 24 (permalink) Old Mar 30th, 07, 8:48 PM
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Re: cam lope

Quote:
Originally Posted by 540Hotrod View Post
You can also pick up a lot of sound by using a cam with an early opening exhaust valve. You lose a little low end TQ because you let cylinder pressure out early...but it will help the *thump* part without going crazy with overlap and it's poor manners.

Plus compression always helps sound..the more the better!!

JIM
Ditto, absolutely!

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post #15 of 24 (permalink) Old Mar 30th, 07, 9:46 PM
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Re: cam lope

Quote:
Originally Posted by 540Hotrod View Post
You can also pick up a lot of sound by using a cam with an early opening exhaust valve. You lose a little low end TQ because you let cylinder pressure out early...but it will help the *thump* part without going crazy with overlap and it's poor manners.

Plus compression always helps sound..the more the better!!

JIM
OK, so if one cam has ex. open at 64.5* BBDC, and another opens at 67* BBDC,
the lower one, 64.5, is the earlier opening??

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