Identify Sportster Cams?

Classic short-frame models

Identify Sportster Cams?

Postby wallaman » Sun Nov 05, 2017 9:41 am

New to the forum but have "lurked" for a bit. Working on a '59 XLCH and was going through a box of cams and found these. They look a bit longer duration than P cams, and have what look like degree markings on all the gears. Does anyone recognize them or know anything about them? Any help appreciated.
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Re: Identify Sportster Cams?

Postby Yard Dog » Sun Nov 05, 2017 9:59 am

look like Sifton minus minus.

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Re: Identify Sportster Cams?

Postby ambike » Sun Nov 05, 2017 10:40 am

Right.
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Re: Identify Sportster Cams?

Postby wallaman » Sun Nov 05, 2017 11:03 am

Wow, that was quick! Info appreciated. So what are they good for (street, drag, etc.)? If they are good street cams, what "needs" go with them for best performance? Stationary mag or adjustable? Carb, etc.?
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Re: Identify Sportster Cams?

Postby wallaman » Sun Nov 05, 2017 12:09 pm

So now that you folks have pointed me in the right direction I did a little more research, I think this set of cams is mixed. The intakes are "minus-minus" but the exhausts are a milder grind (still Sifton). From what I found, an exhaust "minus-minus" has a duration of 257° and these appear to have a duration of 242° and open later and close earlier based on the degree markings on the gears. Any thoughts as to why someone would mix them, better street performance with a stock sized motor?
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Re: Identify Sportster Cams?

Postby wz507 » Sun Nov 05, 2017 1:34 pm

This link should be useful to answer your questions.

http://victorylibrary.com/tech/XLcam-c.htm

From the data table at the link and the opening/closing stamped on the cams it appears you have “minus” intakes and “H” exhaust lobes, as the data in the table match perfectly with the stampings on your cams (IN 33, 55: EX 42,20), and the EX duration is exactly what you quoted (242 deg). Only if both IN and EX were “minus” would you have a “minus-minus” set. Your set is a “minus-H”. This would be a drag racing IN lobe and is a pretty hot set of cams as you can see from the data table. Coupling the “minus” IN lobe with the considerably shorter duration “H” EX lobe would reduce overlap, thereby taming the system down a bit and significantly reducing tendencies toward reversion (stuttering/blubbering that occurs with straight pipes before the engine is in phase [on the cam]).
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Re: Identify Sportster Cams?

Postby wallaman » Sun Nov 05, 2017 2:15 pm

WZ507,
Appreciate the reply. Checked out the link, and it is helpful with specs and identification. What I am really trying to understand is what sort of street performance one would expect with this combination, and what, if anything else one might need to do to get a good running street motor with them. My motor is stock bore and stroke with 9:1 pistons. I found a set of heads on my shelves that were ported by Jerry Branch years ago and never run. Valves are slightly larger than stock. I will be running a high pipe with a stock muffler and had been planning on running a stock set of "P" cams. I have a stock Linkert for it, but also have a Branch Mikuni with his manifold as an alternative. I don't need a hot rod - a nice performing bike is the goal, maybe with a bit more pep than stock. Just because I found these cams certainly doesn't mean I need to run them. Any thoughts here?
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Re: Identify Sportster Cams?

Postby EKHKHK56 » Sun Nov 05, 2017 3:30 pm

I don't know these particular cams as I'm primarily a K guy. However any additional over lap over stock will cut down compression. Which lowers vacumn also, and etc. Rougher running idle and low end power loss are typical unless you bring the compression back up. Cams are the icing on the cake. They need to be chosen to match the rest of the engine and to determine operating rpm. Cam for the conditions! Don't put high rpm screamer cams in a 5" low end torquer motor, etc. Match the cams to the rest of the motor build and desired rpm operating range. Any added duration cuts vacumn, added lift does not signifiicantly change it. Strong vacumn is necessary for smooth idle and cruise, proper carburetion throughout rpm range. 21 lbs vacumn ideal. Less than 15 and smooth idle impossible.
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Re: Identify Sportster Cams?

Postby Ferrous_Head » Sun Nov 05, 2017 4:15 pm

The minus minus intakes are good for street ridden strokers. They don't have a very high lift but long duration. This means the inlet closes pretty late. The late closing inlet drops the compression ratio down to a point that makes it possible to kick start the engine.
They wouldn't be first choice on a stock stroke engine. They are going to drop the compression down a lot which in turn effects low end torque.
"I know only too well the evil that I propose, but my inclinations get the better of me."
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Re: Identify Sportster Cams?

Postby wz507 » Mon Nov 06, 2017 3:35 pm

wallaman wrote:WZ507,
Appreciate the reply. Checked out the link, and it is helpful with specs and identification. What I am really trying to understand is what sort of street performance one would expect with this combination, and what, if anything else one might need to do to get a good running street motor with them. My motor is stock bore and stroke with 9:1 pistons. I found a set of heads on my shelves that were ported by Jerry Branch years ago and never run. Valves are slightly larger than stock. I will be running a high pipe with a stock muffler and had been planning on running a stock set of "P" cams. I have a stock Linkert for it, but also have a Branch Mikuni with his manifold as an alternative. I don't need a hot rod - a nice performing bike is the goal, maybe with a bit more pep than stock. Just because I found these cams certainly doesn't mean I need to run them. Any thoughts here?

It is my opinion that the subject Sifton cams require a different exhaust system, higher compression and more engine size to realize their full potential. If it were mine I'd stick with your plan to run the stock "P" cams which should compliment the entire set-up well. For the engine specifications you provided I like the 2 into 1 high pipe with the stock muffler that will have plenty of yank from right off idle to whatever you care to wind it to with the "P" cams. And if the Branch heads do in fact pass more air and have properly sized ports it will certainly have a "bit more pep than stock".
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