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Comp Roller Lifters Problem |
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SKeown 
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Joined: Jul/30/2009 Location: Texas Status: Offline Points: 3085 |
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 Posted: Jun/30/2010 at 12:19pm |
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You need a larger base circle for flat tapits, otherwise the lifter's edge will scrub. The larger diameter the roller wheel is, the further the lifter body is raised. It's all about properly balancing everything. Notice how the roller cam doesen't have an oil groove on the front journal, it relys on grooved bearings only.
SKeown
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Red Devil
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Joined: Jul/10/2007 Location: Canada Status: Offline Points: 1743 |
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Posted: Jun/30/2010 at 12:45pm |
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Does a 0.390" flat tappet have a taller nose than the 0.390" roller? IIRC, the nose on the roller wasn't much lower than the rear cam journal ... but didn't measure it, so not sure? For shrouding, guess it depends on wheel diameter, wheel width and how they can machine it? Be interesting to see the results and also the oil band design.
Thanks, RD.
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Hornet_X
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Joined: Jul/30/2007 Location: none ya Status: Offline Points: 306 |
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Posted: Jun/30/2010 at 1:29pm |
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I think RD is on to what i was trying to say.
put a old crane and Comp next to each other. other then were the oil bands were different, the Comp lifter had a bigger (read beefier) wheel, wich handle spring pressure better then the smaller Crane wheel did. And the bigger wheel mean that the lifter lives longer before needed Maintance Swap out. Skoewn, i run .750 lift, not .750 diam. Wheel, unless that is the diam of the old Comp wheel. Dont have one close by at the moment to measure the size of the wheel, but could if needed. I have a spare set at the house. Mike |
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SKeown
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Posted: Jun/30/2010 at 1:43pm |
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I just measured a Crane roller, it's exactly .750, measure a Comp if you get a chance. I cain't deny the old Comp's looked better than Crane, unfortunately they presented problems with big lifts. I haven't held their new version.
SKeown
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Red Devil
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Posted: Jun/30/2010 at 1:56pm |
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IIRC, a Comp is 0.820" ... but they list a few different diameters.
Based on 73XBGT's base circle of 1.168", assuming #4 cam journal is the limit for the nose (nom. 2.030" dia. ??), could go to max 0.431" lobe lift vs. his 0.385", so + 0.046" before needing to reduce base circle ... but likely needs a bit less lobe lift with that base circle just for some installation clearance. So a bigger wheel, axle and bearings, pressurized axle oiling and maybe 0.020" - 0.040" more shrouding than a Crane would likely work for most.
Thanks, RD.
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SKeown
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Posted: Jun/30/2010 at 2:17pm |
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It's all about meeting you're particular needs, some have the cam bore enlarged for larger cam journals along with bushed lifter bores. Those like you & me, we don't need any of that. You're cam can be safely run with the new Comp lifters.
Unless a persons heads flow better than 99% of the those being used at the big lifts, there's not much to be gained by getting into all the clearance issues. The cam's timing events and lift rate plays much more roll than lift after a practical amount. Yes, we like to brag about big lift cams though.
SKeown Edited by SKeown - Jun/30/2010 at 2:26pm |
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Hornet_X
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Posted: Jul/01/2010 at 9:44pm |
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.798-.799 with my dial caliper.
Very nice size wheel, and all the would have had to do was move the oil band for that lifter to work in a iron block.
(old comp amc part number i am refuring to)
Mike
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SKeown
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Posted: Jul/01/2010 at 9:53pm |
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The oil band isn't the problem, it's the cutout for the wheel that exposes the oil galley.
SKeown
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amx39068
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Joined: Feb/21/2008 Location: Arizona Status: Offline Points: 11576 |
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Posted: Jul/01/2010 at 10:17pm |
I agree. When I pulled my comp lifter equipped engine back apart and watched the fountain of oil coming out from around the lifters, it was clear the cutout was the culprit. Edited by amx39068 - Jul/01/2010 at 10:18pm |
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Dan Curtis-Owner and CEO AZ AMC Restorations; Facebook: https://www.facebook.com/amcmusclecars/ & Curtis Real Estate Development
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forest
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Posted: Jul/01/2010 at 10:20pm |
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got a new lifter here today, will go to .418 lobe lift with a base circle of 1.168... with a .811 dia roller wheel... working on an even bigger shroud next week..
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setting guys out by car lengths....
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SKeown wrote: