I was looking through SE catalog & I found SE Rocker Arms 1.725:1 ratio. I'm on a 103" build right now & I'm using Andrews 54H cams, according to my calculations, the cam lift would increase from .555 to .580 if I use these rockers, would I gain any power by doing that? I think I'll have to use new springs for the higher lift right?

Are there any downsides for this upgrade?

 

I believe that those non-roller units are designed to be used in applications such as yours. Gives a boost without buying another cam.
If you had a cam with more lift, then S&S roller-tipped units would be in order.
Scott

 

.555 with a 1.725:1 ratio is .589.

 

The geometry will most likely be off, roller tips would help some but the ideal geometry is the valve tip rides an equal distance before center of contact point of the roller tip before valve is open, and when fully open is the same distance from center on the other side of center line of contact point. A longer arm is going to change that geometry and put a lot of stress on the valve tip. A roller tip will help relieve that stress some, but it will still be off. One way around it is taller valves and correct springs.
I am sure the specs on the stock springs would coil bind at that lift

 

Does that then take my 37s from .510 to .544 or .541 ? Paul, please explain the math to me. I have a set of these as part of my 98" project.

 

http://bigboyzheadporting.com/tccams.htm I used this and came up with .541, I think that's a good number for me. No coil bind and no need for rollers.

 

SE catalog says stock rockers ratio is 1.65

 

be carefull changing rocker ratio`s,not only will it change valve lift,but also tdc.so valve to valve & valve to piston will be different.geomitry will also not be the same.to check for lift increase,put an indicator on the tappet itself,mulitpy the tappet lift by the rocker ratio.the only time i would increase rocker ratio is when a bigger cam isnt avaliabe,especialy on street stuff

 

Thanks Kirby, the 37's will be at .185/.157 TDC W/1.725 rockers. When the beehive springs came out they could handle more lift than the 510's that "were" par for the course. Now a Se255 or 54H are pushing .550/.555 with no problem on stock springs. While I'm still new to HD's I do feel safe at .541. And back at the me being new to the HD world, I'm always ready to be corrected. Thank You Everybody.

 

I just went by the BB site and they did say not to bet on it, the fractions and rounding things off vary, I did this on my LT-1 T/A years ago for 25HP but that was also going roller.