Cam Spec. Questions

Gear Case (cams, idlers, cam cover)
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Hauula Pan
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Cam Spec. Questions

#1

Post by Hauula Pan »

I have not been able to find an answer in the knowledge base & hope someone can help. I have 3 questions I'm hoping to get answers for. 1st. Can anyone provide the specs. for the stock FL & FLH cams? "ie" Lift, Duration, Timing. 2nd. I've noticed in the after market catalogs that you can buy just a cam or a, "cam & pinion set", is there a reason you would need to buy the set? shouldn't all the cams have drive gears that would mate properly with my existing pinion? or are they selling the sets just so you don't run a new cam with a worn pinion gear? and 3rd. I'm a bit confused about the specs. themselves. My Andrews #1 just lists Lift as .450, Duration as 232, and Timing as 16/36 and in the catalog most cams are listed with similar specs. one # for lift, one # for duration & two #'s for timing. However they show the stock FL with Two sets of numbers for duration & timing which has me confused. They show Lift as .412 duration as 220/244 for front & 232/244 for rear I don't understand why there are two numbers, "ie" 220/244 and 232/244 as opposed to the single 232 shown for the #1 they also do this with the timing. they show front as -6/46 and 44/20 front and 14/38 and 44/20 rear where the #1 cam only has one set of #'s 16/36 can someone explain the extra numbers for me? Thanks for any help you guys can provide.



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Re: Cam Spec. Questions

#2

Post by ingram »

1st and 3rd question - You have the stock specs. The reason for the two sets of numbers is that the intake cam profile is different on the front and rear cylinders.

2nd question - The reason for the kit is that the gears are matched so that the mesh between the gears is correct. Not too tight and not too loose. This helps the gears to run quieter.

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Re: Cam Spec. Questions

#3

Post by Hauula Pan »

I have the specs. for the FL cam but not the FLH does anyone know what they are for the FLH cam?

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Re: Cam Spec. Questions

#4

Post by 1950Panhead »

FL duration 220 lift .412"
FLH duration 256 lift .450"
Rear cylinder duration longer then front.
Jerry

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Re: Cam Spec. Questions

#5

Post by Hauula Pan »

So am I correct to read my FL cam profile numbers to mean the cam has a Lift of .412 on all lobes and the 220/244 Front duration means the intake is 220 and the exhaust is 244 and the other set of 232/244 means the rear intake is 232 and exhaust is 244 and the Timing numbers -6/46 & 44/20 Front and 14/38 and 44/20 Rear are the opening & closing degrees for each intake & exhaust lobe??? & that would also mean that when you only see one set of numbers like .450 lift & 256 duration they are only giving you partial specs. & not including the actual duration for each lobe????? If that is correct what lobe or lobes would they be most likely referring to with the single duration number???

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Re: Cam Spec. Questions

#6

Post by ingram »

Hauula Pan wrote:So am I correct to read my FL cam profile numbers to mean the cam has a Lift of .412 on all lobes and the 220/244 Front duration means the intake is 220 and the exhaust is 244 and the other set of 232/244 means the rear intake is 232 and exhaust is 244 and the Timing numbers -6/46 & 44/20 Front and 14/38 and 44/20 Rear are the opening & closing degrees for each intake & exhaust lobe??? & that would also mean that when you only see one set of numbers like .450 lift & 256 duration they are only giving you partial specs. & not including the actual duration for each lobe????? If that is correct what lobe or lobes would they be most likely referring to with the single duration number???
Your analysis of the numbers is correct. The only reason there are two sets of numbers is because the front and rear cylinders have a different intake cam profile. The exhaust cam profile is the same on both cylinders.

On most camshafts, the intake and exhaust cam timing will be the same on both cylinders. The intake and exhaust timing specs on these camshafts are only listed once, since they are the same on both cylinders. One set of specs will be for the intake and one set of specs will be for the exhaust. Hope this make sense. :)

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Re: Cam Spec. Questions

#7

Post by Cotten »

Ingram!

To me they are just the 'bumpstick', and I'm easily confused.
Do I understand this thread that the OEM cams have the different duration of the intake lobes, but aftermarket cams are "symmetrical"?

That would be disturbing, and I hope I have misunderstood.

....Cotten

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Re: Cam Spec. Questions

#8

Post by ingram »

Cotten wrote:Ingram!

To me they are just the 'bumpstick', and I'm easily confused.
Do I understand this thread that the OEM cams have the different duration of the intake lobes, but aftermarket cams are "symmetrical"?

That would be disturbing, and I hope I have misunderstood.

....Cotten
Sorry Cotten, sometimes when I am trying to make something sound simple, I end up making it more confusing. :? It's especially easy to do when talking about camshafts.

The OEM camshafts for the Shovelhead engine were made this way. The front cylinder had one intake profile and the rear cylinder had a different intake profile. The exhaust profile on both the front and rear cylinders is the same. That's why the specs were confusing to "Hauula Pan". That's what I was trying to explain.

The aftermarket cams have the same specs on both the front and rear cylinders. "Symmetrical" actually means something else when talking about camshafts. It means the opening and the closing side of one lobe is designed the same. "Asymmetrical" would mean that the opening and closing side of one lobe is different. I will stop now before I make things worse. :)

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Re: Cam Spec. Questions

#9

Post by Hauula Pan »

Ingram, Thanks I do understand what you are saying. The specs. I have for the stock FL cam has duration and timing listed for each of the 4 lobes. The after market grinds just give lift & duration as single numbers because most are the same on all lobes & they just don't list the timing. I'm sure if someone wanted more exact info. on a specific cam's profile the manufacturer would supply it, its just easier to list the basic info. in the catalogs. I was curious because I had such detailed specs. for the stock FL cam & couldn't find the same for the FLH & after market Andrews #1.

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Re: Cam Spec. Questions

#10

Post by Cotten »

Ingram!

I shall avoid using 'assymetrical' in that context in the future, thanks.

Now for the obvious question:
If the MOCO found reason to vary the two intakes,
why do aftermarket designers ignore it?

....Cotten

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Re: Cam Spec. Questions

#11

Post by ingram »

Cotten wrote:Ingram!

Now for the obvious question:
If the MOCO found reason to vary the two intakes,
why do aftermarket designers ignore it?

....Cotten
That's a good question.

The Shovelhead was to be an improvement over what came before. The different intake profiles was a way to help even-out the fuel distribution and the power between the front and rear cylinders. This is still done today on performance racing engines. That was "hi-tech" for Harley to do that.

It costs more to make a camshaft with multiple cam profiles. The "real world" results from doing this for a street application probably does not justify it. I think it's a good approach, but I would not pay more to get this type of camshaft made. It's also a small market for the camshaft manufacturers.

The EVO engine had a much improved head design over the Shovel, so it wasn't necessary to use this type of camshaft. On modern EFI engines the fuel distribution between the cylinders is controlled by the computer.

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Re: Cam Spec. Questions

#12

Post by Cotten »

Ingram!

Pans and shovels used the same Victory cam through '69.
The parts catalog suggests the standard FL cam was also available for shovels.

My Knuck cams are quite worn, but the intakes appear the same.

FLH, FL, and 61" Pan cams all show obvious different intake profiles, so the varied intakes are a Pan-era innovation.

....Cotten

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Re: Cam Spec. Questions

#13

Post by ingram »

Cotten wrote:Ingram!

FLH, FL, and 61" Pan cams all show obvious different intake profiles, so the varied intakes are a Pan-era innovation.

....Cotten
Thanks for the research. That is news to me. I actually thought it started with the alternator Shovel in 1970. The "H" camshaft.

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Re: Cam Spec. Questions

#14

Post by Hauula Pan »

My main reason for asking about the differing specs. was mostly out of concern for proper timing. For example, even though the FL & FLH cams have entirely different lift, duration and timing profiles the manual shows that initial static timing is set the same. I would have thought that with the valves opening and closing at different degrees that would change the entire timing profile and possibly require a change to the initial static timing setup. And even though the manual shows the initial timing to be the same for the FL & FLH cams I'm wondering if this is true for other after market cams too? And especially how this might effect starting. Since I will soon be replacing my cam, (not happy with the combination of low compression pistons & Andrews #1) (going back to stock compression pistons) I'm looking for something close to the stock FL cam but can't find anything in the after market with that profile or an FLH profile either. I'm currently considering an Andrews A or J cam unless someone knows of something closer to the FL or FLH that's available in the after market. And I wanted know if changing to one of these after market grinds would require me to change my initial timing set up or not. As well as how it might effect starting.

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Re: Cam Spec. Questions

#15

Post by RUBONE »

I feel like you are way over-thinking this. Keep in mind that many tens of thousands of engines have aftermarket cams in them. The manufacturers of said cams as well as H-D know where the valve opening and closing are optimized. The ignition timing is a function more of quality of fuel and compression ratio than it is of cam timing, and is not affected by different profiles to any extent. V-Twins (in fact most 4 stroke engines) are timed very similarly, usually at about 35 to 38 degrees before top center at full advance. That is regardless of displacement, cam timing, carburetor used, etc. Old high octane fuel and high compression ratios could sometimes support a more advanced timing, most modern fuels are happy at stock or even slightly retarded. But we are talking one or two degrees here, not a major change. A few thousandths off on point setting or rubbing block wear change it that much or more.
Starting is a totally different issue. Cams with extreme overlap tend to be much harder starting mostly due to lack of cranking compression.
A J grind is closest to stock specs for a hydraulic lifter engine. It is similar to an FLH which is a much better cam than an FL for general performance. What makes you feel you need an FL type cam? Do you prefer to ride at slow speeds in traffic? Because that is where it works best.
Robbie

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