Any Problems With Increasing Rocker Ratio?
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Cruiser
Joined: Feb 2010
Posts: 166
Likes: 34
From: Prospect, CT
Any Problems With Increasing Rocker Ratio?
I'm considering putting Andrews 37s in my 2008 Ultra with an SE 103 kit, but the lift is pretty mild at .510. A higher ratio rocker would bring that up to .548, but also increase the lift slightly right in the middle of overlap at TDC (which concerns me). Does anyone have any experience with this type of setup, plusses or minuses?
Thanks in advance for your time.
Thanks in advance for your time.
Road Warrior
Joined: Dec 2008
Posts: 1,733
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From: Linden, NC
A little more information would be helpful. Are you using flat tops, or dome pistons to increase compression? Any head work planned?
But anyway...
IMHO, since you haven't bought the 37's yet, I'd find a cam that matches the lift you're looking for and not mess with the high ratio rockers. I believe the beehive springs on your stock heads are good for .600 lift.
Zippers Red Shift 575's, Andrews 54 or 55's, TMan TR-555's, Headquarters TC-575's just to name a few. Scott (Hillside) can give you the Woods equivalent in that range.
As for the use of high ratio rockers; well, that all depends on who you ask.
But anyway...
IMHO, since you haven't bought the 37's yet, I'd find a cam that matches the lift you're looking for and not mess with the high ratio rockers. I believe the beehive springs on your stock heads are good for .600 lift.
Zippers Red Shift 575's, Andrews 54 or 55's, TMan TR-555's, Headquarters TC-575's just to name a few. Scott (Hillside) can give you the Woods equivalent in that range.
As for the use of high ratio rockers; well, that all depends on who you ask.
Last edited by Weevil; Feb 25, 2011 at 04:44 AM.
Road Master
Joined: May 2007
Posts: 851
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From: Mitchellville, Ia.
In testing that cam at R&R Cycle, they found that the cam works better with the stock ratio exhaust rockers, the 1.72 intake rockers. They even sell a split set for doing this. Their RR525 cam is essentially the 37 with this change built in so new rockers are not needed. Great torque cam.
Road Master
Joined: May 2007
Posts: 851
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From: Mitchellville, Ia.
This is a gear drive only set, are you still interested?
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Cruiser
Joined: Feb 2010
Posts: 166
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From: Prospect, CT
Thanks for getting back to me. I think by 2008 HD had pretty much worked out the tensioner problems, so unless they're priced as a chain drive set (which I wouldn't expect you to do) probably not. But thanks for letting me know.
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Cruiser
Joined: Feb 2010
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From: Prospect, CT
Now my imagination is cranking... using a set of 1.725s on a set of R&R 525s would bring the lift to .549, almost the same lift as the SE 255, but with the duration and timing of a 37.
Here's a question - as we open up intake ports and use larger valves, we soften throttle response at low rpm, especially off idle. Does a larger lift (say, a Wood 5-6 or TW7) do the same thing?
Thanks
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Those 2 cams you mentioned are big torque builders in that are you area refering to.
Cam timing, ramp rate, lift, all contribute to that, especially if the cold cranking is set to allow the given grind produce as intended.
A Wood 555, set at 10.3-10.5, will SMACK off the bottom and keep on a truckin', with a good head.
Our Stage III for example, that carrys a 1.940" intake, rolls off @ 165 cfm @ 10" @ .650 lift, and GULPS big air coming off the seat at .100, .200, .300" lift, and contines to march from there.
A critical area in which we key on, is the all-important mid-lift area, between .200 and .400" as the valve is in that more than anywhere else, at any given time.
So bigger valves/ports, actually can/will create better/quicker cylinder fill, when correctly addressed.
Scott
Cam timing, ramp rate, lift, all contribute to that, especially if the cold cranking is set to allow the given grind produce as intended.
A Wood 555, set at 10.3-10.5, will SMACK off the bottom and keep on a truckin', with a good head.
Our Stage III for example, that carrys a 1.940" intake, rolls off @ 165 cfm @ 10" @ .650 lift, and GULPS big air coming off the seat at .100, .200, .300" lift, and contines to march from there.
A critical area in which we key on, is the all-important mid-lift area, between .200 and .400" as the valve is in that more than anywhere else, at any given time.
So bigger valves/ports, actually can/will create better/quicker cylinder fill, when correctly addressed.
Scott
