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Re: Roller Rockers VS Flat Tappet
[Re: Sb Valiant]
#1348361
12/09/12 02:03 PM
12/09/12 02:03 PM
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Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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As a rule of thumb.. go with roller rockers when you exceed .550 lift... I'm sure if you measure the actual ratio of the stock VS the HS rockers you will see that the stock rockers dont even have a true 1.5 ratio so IF your engine wants more lift it will be a gain... the big factor also when running roller rockers is you have a easier sweep across the valve tip which will cause wear on both the tip and the rocker using the stock stuff 
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Re: Roller Rockers VS Flat Tappet
[Re: Sb Valiant]
#1348362
12/09/12 05:21 PM
12/09/12 05:21 PM
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Joined: Oct 2007
Posts: 4,206
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,206
New York
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because they were desinged in the 1970's
Rocker arm design pretty much stalled around WW2. Everything you see today was already known but not cost-effective as a marketable product.
The relationship that determines side thrust (excess wear and lost motion) isn't only lift, it's lift as a function of the long-side rocker length. The ratio doesn't matter.
Percentages below 30% (rocker lever is 1.40", lift is .420") don't need any help, percentages above 40% (lever is 1.40", lift is .560") do. If the ratio were 200%, the rocker would point straight up and down.
This is why for most engines big block rockers need roller tips at higher lifts than small blocks.
Boffin Emeritus
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Re: Roller Rockers VS Flat Tappet
[Re: Sb Valiant]
#1348365
12/09/12 08:24 PM
12/09/12 08:24 PM
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Joined: Oct 2007
Posts: 4,206
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,206
New York
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When you say "finger type rocker" you lose your audience.
Since your rocker is about 1.515" long (according to Jesel), 60% means you have:
1. .909" lift
2. very, very bad geometry
Boffin Emeritus
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Re: Roller Rockers VS Flat Tappet
[Re: Sb Valiant]
#1348367
12/10/12 03:16 PM
12/10/12 03:16 PM
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Joined: Oct 2007
Posts: 4,206
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,206
New York
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You can call them late for dinner if you want, but there's no such thing as "flat tappet rockers".
Boffin Emeritus
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Re: Roller Rockers VS Flat Tappet
[Re: Sb Valiant]
#1348368
12/10/12 04:06 PM
12/10/12 04:06 PM
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Joined: Aug 2003
Posts: 43,127
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,127
Bend,OR USA
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Are you referring to the adjustable stock type ductile iron rocker arms as the finger type?
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Roller Rockers VS Flat Tappet
[Re: Sb Valiant]
#1348373
12/10/12 08:15 PM
12/10/12 08:15 PM
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Joined: Apr 2005
Posts: 1,505
TN
SCATPACK 1
pro stock
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pro stock
Joined: Apr 2005
Posts: 1,505
TN
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Ductile Iron Adjustable Rockers. Typically they check out around 1.40 ratio (or less in some cases) instead of 1.50. I bet you would see a noticable performance inscrease with roller rockers.
Old Geezer Racing
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Re: Roller Rockers VS Flat Tappet
[Re: SCATPACK 1]
#1348374
12/10/12 09:42 PM
12/10/12 09:42 PM
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Joined: Dec 2006
Posts: 3,395
Pa
Hot 340
master
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master
Joined: Dec 2006
Posts: 3,395
Pa
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Quote:
Ductile Iron Adjustable Rockers. Typically they check out around 1.40 ratio (or less in some cases) instead of 1.50. I bet you would see a noticable performance inscrease with roller rockers.
Are you sure about that? Those arent 273 rockers on there.. 
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Re: Roller Rockers VS Flat Tappet
[Re: Cab_Burge]
#1348376
12/10/12 11:29 PM
12/10/12 11:29 PM
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Joined: Dec 2006
Posts: 3,395
Pa
Hot 340
master
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master
Joined: Dec 2006
Posts: 3,395
Pa
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Quote:
Quote:
Quote:
Ductile Iron Adjustable Rockers. Typically they check out around 1.40 ratio (or less in some cases) instead of 1.50. I bet you would see a noticable performance inscrease with roller rockers.
Are you sure about that? Those arent 273 rockers on there..
Buy some aftermarket Ductile Iron rockers from Crane, Isky, Erson and whoever else sells them and check them at the retainers and let us know what you find I have   Why do you think RAS was so busy when they where doing business on a regular bases  Not only are the Mopar ductile iron rockers bad the Ford FE and the early Oldsmobile 303 to 394 C.I. and the early hemi where all bad 
Ill check these ones out as I get it all set up. Old bushed w2's. You might be right..
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Re: Roller Rockers VS Flat Tappet
[Re: astjp2]
#1348379
12/11/12 01:54 PM
12/11/12 01:54 PM
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Joined: Jan 2003
Posts: 9,826
las vegas
70AARcuda
master
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master
Joined: Jan 2003
Posts: 9,826
las vegas
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MP made two different w2 ductile rocker arms ...
a bushed and unbushed rocker...
sold off my unbushed rockers a couple years ago...still got a set or two of the bushed ones..
actually MP listed the unbush ones as econo and bushed one as rockers for the race w2
Tony
70 AARCuda Vitamin C
71 Dart Swinger 360 10.318 @ 128.22(10-04-14 Bakersfield)
71 Demon 360 10.666 @122.41 (01-29-17 @ Las Vegas)
71 Duster 408 (10.29 @ 127.86 3/16/19 Las Vegas)
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