Cams
Road Master
Joined: May 2010
Posts: 1,005
Likes: 4
From: Alabama
Its true stock heads don't flow better above .500 lift.
The benefit of a .500+ lift cam on a stock head is that the valve will stay at .500+ lift for a longer period, increasing flow and performance.
The flow on my race car heads peak at .600 lift. The custom camshaft designer spec'd a .690 lift cam to keep the valve in peak flow for a longer period for better performance. Pretty much standard practice in performance engines to open valves past cylinder head peak flow rates.
Higher lifts above .500 will increase performance on a stock HD heads.
Road Warrior
Joined: Jun 2012
Posts: 1,672
Likes: 17
From: Orange, VA,
Its true stock heads don't flow better above .500 lift.
The benefit of a .500+ lift cam on a stock head is that the valve will stay at .500+ lift for a longer period, increasing flow and performance.
The flow on my race car heads peak at .600 lift. The custom camshaft designer spec'd a .690 lift cam to keep the valve in peak flow for a longer period for better performance. Pretty much standard practice in performance engines to open valves past cylinder head peak flow rates.
Higher lifts above .500 will increase performance on a stock HD heads.
The benefit of a .500+ lift cam on a stock head is that the valve will stay at .500+ lift for a longer period, increasing flow and performance.
The flow on my race car heads peak at .600 lift. The custom camshaft designer spec'd a .690 lift cam to keep the valve in peak flow for a longer period for better performance. Pretty much standard practice in performance engines to open valves past cylinder head peak flow rates.
Higher lifts above .500 will increase performance on a stock HD heads.
Road Warrior
Joined: Apr 2010
Posts: 1,648
Likes: 37
From: Monroe, Louisiana
I agree on the OEM cams not being as good as the aftermarket. The only cam in the drop in that Harley makes that doesn't fit the restrictions/design boundaries is the SE204 and 211. I know of a 14 SGS with SE204 and Power duals dynoed at 96hp and 114 torque. I know that is exceptionally high numbers. It does compare to the Andrews 48, Feuling 543, Andrews 57, TW 222/555, on a stock head compression engine. The 211 is also good but has a little too much duration to suit me, unless in real light bike with stock heads.
Road Master
Joined: May 2010
Posts: 1,005
Likes: 4
From: Alabama
Increasing the duration will net the same results without increasing lift, increasing lift gives the cam a steeper ramp increasing valvetrain stress, in racing engines they do this because your not building a 100k mile engine, my race engine gets rebuilt after 10 races, the valvetrain takes the most beating so it all gets replaced.
More lift Does Not require more compression to compensate and will increase torque at given duration because the duration can stay the same with more cylinder filling from the increased lift.
As far as valvatrain durability, the agressiveness of the ramps is up to the cam designer. The total lift number really doesn't tell the agressiveness of the ramp. You have to look at the duration @ .200, .300, .400 .500 lift to see how agressive the ramps are. The ramps can be somewhat mild to very agrressive.
I was discussing lift and duration numbers with a cam designer several years ago and he had a very good analogy. He said the path from the base circle of the cam to the nose of the cam was like a roadmap. Same starting point, same destination, but several different routes to get there.
Obviously the more agressive ramps will make more power at the cost of longetivity. There are always trade-offs in getting more performance. If someone wants a 100,000 mile Harley they better leave it stock. LOL.
Please don't think I'm being argumentative, just a friendly discussion.
Cruiser
Joined: Sep 2007
Posts: 190
Likes: 3
From:
If you just like to cruise around and like low end torque go for it. It will pull harder on the low end and properly tuned it will run well. Most people hate them but I suspect they haven't ridden a bagger with 255s in it tuned properly.
Remember you don't ride the dyno sheet, other cams will make more power but do you typically shift at higher rpms?
Remember you don't ride the dyno sheet, other cams will make more power but do you typically shift at higher rpms?
Road Captain
Joined: Jul 2012
Posts: 633
Likes: 4
From: missouri
I'll answer the question asked 
I have ran several 255's in 103's. What you can expect is more low end grunt. It helps a bagger thats loaded down get going. If you ride 2-up your bike will feel more responsive. You can roll on the throttle and not have to down shift. It will fall flat on the top end but the truth is most touring people aren't running up on the top end. You will be able to use 6th gear more often.
I have ran several 255's in 103's. What you can expect is more low end grunt. It helps a bagger thats loaded down get going. If you ride 2-up your bike will feel more responsive. You can roll on the throttle and not have to down shift. It will fall flat on the top end but the truth is most touring people aren't running up on the top end. You will be able to use 6th gear more often.
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Road Warrior
Joined: Apr 2010
Posts: 1,648
Likes: 37
From: Monroe, Louisiana
Increasing the duration will net the same results without increasing lift, increasing lift gives the cam a steeper ramp increasing valvetrain stress, in racing engines they do this because your not building a 100k mile engine, my race engine gets rebuilt after 10 races, the valvetrain takes the most beating so it all gets replaced.
If running an engine with less than .600 lift and set up right with the right springs and good valves, floating rollers in the lifters, and roller rockers, and keep it cool and maintained and it will last. Will it outlast a stock engine, who knows. I will say I would have lot more fun than I would with a stock engine. If you want to run it completely stock just go right ahead and enjoy doing it. If you want to run performance get the right combination and have fun. If it breaks fix it and don't break it again. I like the sound of a performance engine and knowing the power is there if I want it. Just my contribution to the conversation.
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