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#1 |
Registered User
Join Date: Aug 2013
Location: Poulsbo, WA
Posts: 21
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Hopefully this is an easy question for you seasoned engine builders.
I’m in the process of setting up my rocker arm geometry on a small block 350 for my 65 C10 project. I am using a stamped steel roller tip rocker from Summit (Picture) with a hyd. flat tappet lifter. AND, I am NOT using a light checking spring. (I bought the heads assembled) I am also using a Comp Cam adjustable pushrod and the Pro Tool pushrod length checker tool (Picture) to measure pushrod length. With the Pro Tool jig level/flat on the valve stem, I’m getting a pushrod length of 7.75”. BUT…when I paint the valve stem with a marker, install the rocker—with ½ turn preload—then manually turn the engine over two or three times…the roller tip wear pattern is slightly toward the back of the valve stem. Based on my research this is supposed to mean the pushrod is too short. Correct? My question is whether or not I need to factor in the compression of the lifter since there is no oil pressure? In my simple inexperienced mind, I imagine that the spring tension may be compressing the lifter enough to shift the valve stem wear pattern slightly toward the back. But with oil pressure, the rocker pivot will be slightly higher which will shift the valve stem wear pattern to the center where it should be. Am I thinking about this the right way? Or do I just need a slightly longer pushrod? Thanks for any advice! ![]() ![]() Last edited by Poulsbo; 01-31-2014 at 04:51 PM. Reason: Image didn't appear properly. |
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#2 | ||
"I ain't nobody, dork."
Join Date: Sep 2007
Location: Whidbey Island, Washington
Posts: 8,936
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Re: Rocker Arm Geometry Question
The roller tip rockers won't give you the precise measurement on the tip of the stem like a true roller rocker. The roller tip rocker doesn't have a true fulcrum on which it pivots like a true roller rocker.
The roller tip rockers aren't really all they are cracked up to be. If you insist on using them, just bolt them in with stock length push rods and adjust them as you would regular stock stamped rockers with a flat tappet cam. EZPZ. Gary
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'cuz chicks dig scars... My 1972 GMC 1500 Super Custom (Creeping Death) "long term" build thread. The Rebuild of Creeping Death after the wreck Quote:
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#3 |
Fabricate till you "puke"
Join Date: Jun 2002
Location: Ill
Posts: 9,403
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Re: Rocker Arm Geometry Question
While the roller tip rocker, wont be 'dead on" , like a full roller...it should be damn close? Every thing that you are thinking is pretty much "right on"
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69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears.... |
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#4 |
Registered User
Join Date: Aug 2013
Location: Poulsbo, WA
Posts: 21
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Thanks guys!
I think I'm going to send the roller "tip" rockers back and replace them with a set of Comp Cams full rollers. http://www.summitracing.com/parts/cc...1-16/overview/ Longhorn, I'm running a .060 block--so it's getting close to the end of its life--with a fairly mild cam. (Sealed Power 210/216 with 111 degree separation, I think. Sorry, going from memory) Heads are Dart SHP 180cc intake / 72cc combustion chamber. (I just bought them new...so I don't want to trash the valve guides in the first 200 miles. I'm also running a basic Edelbrock 600cfm carb (Item 1405) and an off the shelf Edelbrock Performer intake. With that setup, I'm looking at a static compression ratio right around 9.3:1 with a dynamic CR around 7.5:1. I'm looking for good idle, solid torque and decent top end HP. But nothing too crazy. My local guys think this combo will work...and MarvD has given me some really good advice on the heads...so I'm feeling pretty confident. But I'm getting the feeling I've just gone too cheap on the rocker arms. Agree? Last edited by Poulsbo; 01-31-2014 at 08:07 PM. Reason: icon didn't show properly. |
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#5 | |
Fabricate till you "puke"
Join Date: Jun 2002
Location: Ill
Posts: 9,403
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Re: Rocker Arm Geometry Question
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69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears.... |
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#6 |
Active Member
Join Date: Oct 2006
Location: Ohio
Posts: 1,643
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Re: Rocker Arm Geometry Question
Buy yourself a single solid lifter and use it when you check your pattern.
This eliminates the Hydro lift issue and gives a better reading.
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1968 SWB 454 + .040, 490HP x 540 FT pounds of Torque 10-1 Kb Forged pistons, recon rods w/ ARP wave loc bolts 781 heads Ported with 2.19/1.88 SSTvalves Lunati 60204 cam, Micro Trol lifters, Ported Edelbrock Performer Rpm manifold armor coated, Pertronix Triple Strike Ignition Holley 770 Street Avenger carb,Headers armor coated Built by Watson Ruppel Performance in Sarahsville Ohio. Hardshift Tranny Built Turbo 350,TSI 10" 3000 stall 12 Bolt Eaton Posi 4.10 Richmond Gears moser axles ![]() 18.5" x 31" Hoosier Pro Street Radials ![]() ET Classic 5 Wheels - polished Power Steering, Power Brakes,Disc Brakes,Tach & Gauge Dash, Tilt,Factory Air (gone) Custom Paint & Body Work Special thanks to my wife, my son and my money tree ![]() |
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#7 | |
Registered Truck Offender
Join Date: May 2008
Location: hells training ground (aka Ariz)
Posts: 3,118
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Re: Rocker Arm Geometry Question
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If you really want to be 'dead on' adjust your resulting pushrod length by 1/64" (0.015) to simulate the depth of pudhrod sunk into the hydraulics with a 1/2 turn of preload. But just keep in mind, Pushrods are available in 0.050" increments for a reasonable price (~$120) I mean Smith Bros will custom make any exact length you want,, for a price!! But unless your plaing Cmp Eliminator and spinning 12,000 rpm a $800 set of pushrods is sheer foolishness. A Stock length SBC pushrod is 7.80" If your getting 7.75" and add 0.015 for preload depth,, well.... A set of stock length pushrods is probably going to be just fine. I wouldn't sweat it too much. KUDOS to you for checking tho. You wouldn't believe how few people even give valve train geometry a second thought (and wonder why their valve guides are wearing so quickly or breaks pushrods, and springs and... )
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Still playin with trucks, even at my age! When you're dead, it's only a problem for the people around you, because you don't know you're dead. .....It's kinda the same when your STUPID. I just did my taxes and reviewed my SS statement. Thanks to the current administration it looks like I will only have to work till noon on the day of my funeral. |
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pushrod length, rocker arms, valve train |
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