61" cam in an FL?

Gear Case (cams, idlers, cam cover)
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kehughes
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61" cam in an FL?

#1

Post by kehughes »

Anyone ever run an EL cam in an FL engine? The only difference between them is the cam lobe heighth(Fl lobe heighth is 1.334" and the EL is 1.328"). What effect would it have? Thanks.
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Re: 61" cam in an FL?

#2

Post by 58flh »

Running the el cam will not let the fl run to its full potential as compresion would be lowered some!--motor will run, but your betteroff with a stock fl or flh cam would be best. Helps alot when you gotta climb a steep grade & your loaded down,or riding 2-up.----richie
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Re: 61" cam in an FL?

#3

Post by RUBONE »

61 cams were used as part of the "traffic combination" on FLE engines into '56. The cam profile is very different from a regular FL cam due to the short stroke of a 61. The duration is much less. The advantage it had was very good low end, smooth operation and good acceleration in the lower gears, ideal specs for heavy traffic and inner city work. The disadvantage is that it will fall flat at higher speeds and is not a good choice for freeway riding.
So it will work just fine with limitations. It all depends on what you want to do with your bike!
Robbie
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Re: 61" cam in an FL?

#4

Post by kitabel »

as compresion would be lowered some

How does this happen?
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Re: 61" cam in an FL?

#5

Post by awander »

kitabel wrote:as compresion would be lowered some

How does this happen?
Yeah, i am wondering that as well.
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Re: 61" cam in an FL?

#6

Post by 58flh »

WELL I was thinking if the duration is significantly less & cam-lift is less isnt that filling the jugs with less ? Correct me if im not seeing something here , but the shorter stroke of the el & less inlet would give you that effect! If the el cam had more hangtime then I can see it would give ample intake(air/fuel) to have proper comp. as a fl.,Bet it would kickover nicely!---What do ya think? Also the powerband is lowered on the fl /w-el cam. smaller bore on the el as well. I think that would lower the comp. some. How bout it?
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Re: 61" cam in an FL?

#7

Post by ingram »

Any camshaft will fill the cylinders at some point. This maximum cylinder filling is peak torque. A smaller duration camshaft will have peak torque at a lower rpm than a larger duration camshaft.

The cranking pressure of the engine is determined by the mechanical (static) compression ratio and when the intake valve closes. Cranking pressure will start building after the intake valve closes. A smaller duration camshaft usually closes the intake valve sooner than the larger camshaft and will have a higher cranking pressure.

As Robbie said, the smaller camshaft (61) will give better low rpm torque.
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Re: 61" cam in an FL?

#8

Post by 58flh »

Gotcha Ingram!---makes sense at a low RPM it will work nice (light to light tourque)so to speak ,but at hier speeds she will drop off!--It will kick nice also!---as a friend has done this & it did idle good, but the E cam was outta there quick & a stock Fl was put in. It ran a hell of alot better. I was figuring the shorter stroke,lower lift & smaller-bore of the E motor as compared to the same of an fl motor--It would not fill-up the cyls. with air/fuel because of the shorter duration & other combination of said cam. Gotta love this site!--Thanks----Richie
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Re: 61" cam in an FL?

#9

Post by ingram »

58flh wrote:Gotcha Ingram!---makes sense at a low RPM it will work nice (light to light tourque)so to speak ,but at hier speeds she will drop off!--It will kick nice also!---as a friend has done this & it did idle good, but the E cam was outta there quick & a stock Fl was put in. It ran a hell of alot better. I was figuring the shorter stroke,lower lift & smaller-bore of the E motor as compared to the same of an fl motor--It would not fill-up the cyls. with air/fuel because of the shorter duration & other combination of said cam. Gotta love this site!--Thanks----Richie
The 61 camshaft just filled the cylinders at a low rpm and then it was done. The FL camshaft allowed the engine to fill the cylinders and make power at rpm's beyond where the 61 quit. Your friend obviously liked the power at the higher range.

Camshafts (among other things) will determine where an engine makes it's peak torque. That's why it's so important to pick a camshaft that works in the rpm range that you ride.

Richie...I hope this helps without making things more confusing. :)
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Re: 61" cam in an FL?

#10

Post by 58flh »

INGRAM!---I understand, very important to build where shes gonna live-(RPMs)---We constantly on our old bikes,I for 1 olny own a bike as ins. for a cage & fuel just isnt cutting it!---Most of the guys I ride with -I have built thier motors,& WE always on the freeway at 60-75 constant. I for 1 am running a flh cam that I had ground for just a tad bit of more hangtime--(yrs. ago )-& shes still in there,I run 2-up 80% of the time & have no troubles with a stock 74 .030 on the barrels thats it!-Logged alot of miles on her in the last 24yrs.!,in that time I have reb-done bottom 1-time & heads I go threu every 4-5yrs. seems to be the #--I yank em every 2, just for a looksee,& use MMO faithfully 2oz. to every 5 gallons!-olny time she dont come out is in the ice or rain--sucks gettin older! :lol: ---Richie
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Re: 61" cam in an FL?

#11

Post by Dave_R »

On my FLE (Traffic combination) motor I had this combo when I purchased the bike in 1977.

Like others said, low end torque was good, ran very smooth. But, it seemed to have its "sweet-spot" around 40MPH.

But, try to go any faster and the power just falls off big-time!

So, changed to a Sifton cam a few years later and I like it much better.

But, its all how you want to ride.

This may be unrelated, but I installed FLH pistons and then I used to "blow" head gaskets quite often when I pushed the speeds up for any length of time.

After the cam swap, it was rare to "blow" a gasket.

- Dave
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