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Clearance between rocker arm and pushrod cup #952947 03/18/11 01:18 AM 03/18/11 01:18 AM
Joined: Oct 2003 Posts: 3,698 NE Oklahoma V Von OP master
Von OP master V Joined: Oct 2003 Posts: 3,698 NE Oklahoma	What is the minimum safe clearance between the pushrod cup and rocker arm? Thanks 72 RR, Pump gas 440, 452s, 3800 lbs, Corked, ET Radials,. 11.33@117.72. Same car, bone stock 346s, 9.5 comp, baby solid. 12.24@110.

Re: Clearance between rocker arm and pushrod cup [Re: Von] #952948 03/18/11 02:10 AM 03/18/11 02:10 AM
Joined: Oct 2010 Posts: 606 Montana Y Yancy Derringer mopar
Yancy Derringer mopar Y Joined: Oct 2010 Posts: 606 Montana	?????????????You are going to have to....explain.......?????????????? VALVE LASH or VALVE CLEARANCE is measured between the top of the valve stem and rocker, not the push rod. If you run hydraulic lifters, they are always under "some" preload If you run mechanical lifters, the "push rod" clearance is never actually measured. It would be somewhere in the vicinity of the valve clearance multiplied by the rocker ratio, I guess In other words if the valve clearance is .025 (say) and you have 1.5 rocker ratio, the (in theory) clearance at the pushrod would be .025 / 1.5 or about .016

Re: Clearance between rocker arm and pushrod cup [Re: Yancy Derringer] #952949 03/18/11 02:22 AM 03/18/11 02:22 AM
Joined: Jan 2004 Posts: 27,347 Today? Who Knows? 1_WILD_RT Management Trainee
1_WILD_RT Management Trainee Joined: Jan 2004 Posts: 27,347 Today? Who Knows?	Quote: ?????????????You are going to have to....explain.......?????????????? VALVE LASH or VALVE CLEARANCE is measured between the top of the valve stem and rocker, not the push rod. If you run hydraulic lifters, they are always under "some" preload If you run mechanical lifters, the "push rod" clearance is never actually measured. It would be somewhere in the vicinity of the valve clearance multiplied by the rocker ratio, I guess In other words if the valve clearance is .025 (say) and you have 1.5 rocker ratio, the (in theory) clearance at the pushrod would be .025 / 1.5 or about .016 I think what he's asking about is clearance between the pushrod cup & the rocker when the valve is fully opened if the pushrod is to long & the ball adjuster is backed out to set valve clearance the pushrod cup can rub the rocker arm as things change due to thermal expansion & as an effect of high RPM valve train oscillation/flexing/what ever you want to call it... I think a minimum of .060 would be safe & .100 is likely better... Typically the rule of thumb when measuring for pushrods is three threads showing on the adjuster screw then set your adjustable mock-up pushrod to length with valve clearance built in & use that measurement to order your pushrods... "The Armies of our ancestors were lucky, in that they were not trailed by a second army of pencil pushers."

Re: Clearance between rocker arm and pushrod cup [Re: 1_WILD_RT] #952950 03/18/11 10:14 AM 03/18/11 10:14 AM
Joined: Oct 2003 Posts: 3,698 NE Oklahoma V Von OP master
Von OP master V Joined: Oct 2003 Posts: 3,698 NE Oklahoma	quote Typically the rule of thumb when measuring for pushrods is three threads showing on the adjuster screw then set your adjustable mock-up pushrod to length with valve clearance built in & use that measurement to order your pushrods... Actually the # of threads showing is more or less minor....The number of threads isnt what is important, getting a straight shot of oil from the feed hole to the cup is IMO what is VERY important...In other words get the pushrod length correct to get a straight shot of oil to the cup and the # of threads falls as it may. The comment was told to me by a very respected builder on this site and he is dead nuts on...After fighting cup burning issues for a year and after mocking another motor, I see exactly why I was burning cups going with the 3 of threads showing rule of thumb. Yes, I was asking about the clearance from cup to rocker body! Thanx for the measurements, Im about .025 too long on my pushrod. 72 RR, Pump gas 440, 452s, 3800 lbs, Corked, ET Radials,. 11.33@117.72. Same car, bone stock 346s, 9.5 comp, baby solid. 12.24@110.

Re: Clearance between rocker arm and pushrod cup [Re: Von] #952951 03/18/11 07:44 PM 03/18/11 07:44 PM
Joined: Feb 2005 Posts: 4,313 Prospect, PA BSB67 master
BSB67 master Joined: Feb 2005 Posts: 4,313 Prospect, PA	I've run as little as .020" with no problem. That clearance will not change much. I've also chamfered or rolled the outer edge of the cup for a little clearance. Some claim that there could be an oiling issue if the cup is up too close to the rocker body. That would be a function of the oiling design on the particular rocker body. That would be worth checking.

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