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Lifter pre-load question #1467385 07/13/13 05:57 PM 07/13/13 05:57 PM
Joined: Dec 2008 Posts: 2,782 USA J JoesMopar OP master
JoesMopar OP master J Joined: Dec 2008 Posts: 2,782 USA	If I set the lifter pre-load correctly, does that automatically mean I have the correct valvetrain geometry?

Re: Lifter pre-load question [Re: JoesMopar] #1467386 07/13/13 06:06 PM 07/13/13 06:06 PM
Joined: Jan 2003 Posts: 20,826 A collage of whims topside Too Many Posts
topside Too Many Posts Joined: Jan 2003 Posts: 20,826 A collage of whims	"Geometry" relates to how the rocker contacts the valve stem throughout its arc of travel, as well as nothing hitting/binding/etc.

Re: Lifter pre-load question [Re: topside] #1467387 07/13/13 06:14 PM 07/13/13 06:14 PM
Joined: Dec 2008 Posts: 2,782 USA J JoesMopar OP master
JoesMopar OP master J Joined: Dec 2008 Posts: 2,782 USA	Isn't that done by the correct length pushrod though? If I have the pushrod length set so that it gives the correct lifter pre-load, how could the geometry not be correct?

Re: Lifter pre-load question [Re: JoesMopar] #1467388 07/13/13 06:56 PM 07/13/13 06:56 PM
Joined: Sep 2007 Posts: 14,889 up yours Supercuda About to go away
Supercuda About to go away Joined: Sep 2007 Posts: 14,889 up yours	Quote: Isn't that done by the correct length pushrod though? If I have the pushrod length set so that it gives the correct lifter pre-load, how could the geometry not be correct? Because preload isn't the determining factor in the valve train geometry. Pushrod length is, too long or too short will affect where the nose of the rocker rides on the valve stem. While it is possible to mess up the geometry with a seriously messed up valve adjustment, the correct pushrod length is one that, with proper preload (or lash as appropriate) gives the correct rocker sweep across the valve tip. They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.

Re: Lifter pre-load question [Re: JoesMopar] #1467389 07/13/13 06:57 PM 07/13/13 06:57 PM
Joined: Jan 2003 Posts: 75,062 U.S.S.A. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,062 U.S.S.A.	Quote: If I set the lifter pre-load correctly, does that automatically mean I have the correct valvetrain geometry? I'll ask the question not asked ... shaft mount rockers or stud mounted rockers ? Shaft mounted ... NO , the 2 nothing to do with each other on a shaft mounted rocker system. stud mount , yes and no ...

Re: Lifter pre-load question [Re: Supercuda] #1467390 07/13/13 06:59 PM 07/13/13 06:59 PM
Joined: Jan 2003 Posts: 75,062 U.S.S.A. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,062 U.S.S.A.	Quote: Quote: Isn't that done by the correct length pushrod though? If I have the pushrod length set so that it gives the correct lifter pre-load, how could the geometry not be correct? Because preload isn't the determining factor in the valve train geometry. Pushrod length is, too long or too short will affect where the nose of the rocker rides on the valve stem. While it is possible to mess up the geometry with a seriously messed up valve adjustment, the correct pushrod length is one that, with proper preload (or lash as appropriate) gives the correct rocker sweep across the valve tip. This is only true for stud mounted rockers

Re: Lifter pre-load question [Re: JohnRR] #1467391 07/13/13 07:16 PM 07/13/13 07:16 PM
Joined: Dec 2008 Posts: 2,782 USA J JoesMopar OP master
JoesMopar OP master J Joined: Dec 2008 Posts: 2,782 USA	shaft mounted

Re: Lifter pre-load question [Re: JoesMopar] #1467392 07/13/13 07:31 PM 07/13/13 07:31 PM
Joined: Jan 2003 Posts: 75,062 U.S.S.A. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,062 U.S.S.A.	Quote: shaft mounted Preload adjustment will not change valve to rocker tip geometry .

Re: Lifter pre-load question [Re: JoesMopar] #1467393 07/13/13 07:40 PM 07/13/13 07:40 PM
Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska	With the #1 cyls' cam on base circle (rotor on #1 or 12-12 dot to dot or dampener mark on TDC #1 compression). install a pair of light springs & wipe the tips of that pair of valves with dykem or a sharpie then install the rocker shaft & the pushrods for that cyl. Hand turn the crank thru 2 revolutions back to base circle. Lay a thin 6" straightedge ruler across the valve rails & touch the magic marker on the edge of the ruler to get wet ink on it then move the ruler over till it touches a pushrod & makes a small ink mark on it then unbolt the shaft or unscrew the rocker adjuster if used till the lifter cup is all the way up then slide the ruler over & make another mini mark then measure that distance between the two marks to get your preload. Take off the shaft rockers & check the wipe pattern (post a pic if you can & the amt of preload you have) live every 24 hour block of time like it's your last day on earth

Re: Lifter pre-load question [Re: RapidRobert] #1467394 07/14/13 09:18 AM 07/14/13 09:18 AM
Joined: Oct 2003 Posts: 21,345 Marysville, O-H-I-O 70Cuda383 Too Many Posts
70Cuda383 Too Many Posts Joined: Oct 2003 Posts: 21,345 Marysville, O-H-I-O	as said, the issue of geometry comes to the rocker sweeping across the valve stem, nothing to do with preload. you could have adjustable rockers, and pushrods that are too short. you can then adjust the rockers to get you the proper preload, but then your rocker arm is at an angle where it's not going to contact the outside of the valve stem. Photobucket sucks

Re: Lifter pre-load question [Re: 70Cuda383] #1467395 07/14/13 05:26 PM 07/14/13 05:26 PM
Joined: Dec 2008 Posts: 2,782 USA J JoesMopar OP master
JoesMopar OP master J Joined: Dec 2008 Posts: 2,782 USA	Ok, I'm somewhat confused here... If I have the stock shaft mounted non-adjustable rockers and I have the correct length pushrod to give me the correct pre-load, but the geometry is still off, how can I possible change the length of the pushrod to correct the geometry without affecting the pre-load? Maybe I missed something but I don't understand how the pushrod length can change without affecting the pre-load when you're making it longer or shorter to change the geometry.

Re: Lifter pre-load question [Re: JoesMopar] #1467396 07/14/13 05:58 PM 07/14/13 05:58 PM
Joined: Sep 2007 Posts: 14,889 up yours Supercuda About to go away
Supercuda About to go away Joined: Sep 2007 Posts: 14,889 up yours	Justifiable rockers is how you do that. To be honest, I would not worry about preload over proper pushrod length. Preload is, imo, turd polishing on almost all cases. If you can get everything right great, if not and preload is all that is off and you aren't running a national race program you are turd polishing worrying about it. They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.

Re: Lifter pre-load question [Re: JoesMopar] #1467397 07/14/13 06:01 PM 07/14/13 06:01 PM
Joined: Aug 2006 Posts: 162 nj N notforsale440 member
notforsale440 member N Joined: Aug 2006 Posts: 162 nj	Quote: how can I possible change the length of the pushrod to correct the geometry without affecting the pre-load? you cant......... do your rockers not reach the center of the valve stem? or do they reach too far? not reaching can be cured by shimming the shaft, but this will cause your pushrods to be too short..... if this is the case, spend a little more and do what I did I bought hughes adjustable rockers and they center perfectly...... then bought the proper length pushrods......problem solved Last edited by notforsale440; 07/14/13 06:03 PM.

Re: Lifter pre-load question [Re: Supercuda] #1467398 07/14/13 06:02 PM 07/14/13 06:02 PM
Joined: Dec 2008 Posts: 2,782 USA J JoesMopar OP master
JoesMopar OP master J Joined: Dec 2008 Posts: 2,782 USA	Gotcha, that's pretty much the answer I needed. Thanks

Re: Lifter pre-load question [Re: notforsale440] #1467399 07/14/13 06:06 PM 07/14/13 06:06 PM
Joined: Dec 2008 Posts: 2,782 USA J JoesMopar OP master
JoesMopar OP master J Joined: Dec 2008 Posts: 2,782 USA	Quote: Quote: how can I possible change the length of the pushrod to correct the geometry without affecting the pre-load? you cant......... do your rockers not reach the center of the valve stem? or do they reach too far? not reaching can be cured by shimming the shaft, but this will cause your pushrods to be too short..... if this is the case, spend a little more and do what I did I bought hughes adjustable rockers and they center perfectly...... then bought the proper length pushrods......problem solved I'm still putting the engine together but was looking at this kit: https://board.moparts.org/ubbthreads/show...e=2#Post7774480 They come with pushrods, but if they aren't the correct length, I didn't want to spend the money and have to buy another set. I just couldn't wrap my head around how exactly this works.

Re: Lifter pre-load question [Re: JoesMopar] #1467400 07/14/13 06:12 PM 07/14/13 06:12 PM
Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,041 Lincoln Nebraska	Quote: If I have the stock shaft mounted non-adjustable rockers and I have the correct length pushrod to give me the correct pre-load, but the geometry is still off, how can I possible change the length of the pushrod to correct the geometry without affecting the pre-load? Maybe I missed something but I don't understand how the pushrod length can change without affecting the pre-load when you're making it longer or shorter to change the geometry. (1) correct you cannot. You change the geometry of the wipe pattern of the rocker/valve contact area by adding shims inbetween the 5 pedestal half moon depressions & the shaft to raise the shaft (easy) or mill off the 5 OE cast in pedestals & add new bolt on units that are shorter to lower the shaft (hard/$$$). (2) you get the pushrod length correct to get the preload correct & that's strickly a vertical measurement relationship difference (.020" longer pushrod = .020" more preload).Not sure if a longer pushrod will affect the wipe pattern but I believe someone said that it will not but I am not sure & also Hughes engines has a flier where they want a right angle where the pushrod meets the rocker arm at a certain percentage of lift looking at it from the side view. & that percentage is different between small blocks and big blocks. It should be on their site & is worth reading. live every 24 hour block of time like it's your last day on earth

Re: Lifter pre-load question [Re: JoesMopar] #1467401 07/14/13 06:17 PM 07/14/13 06:17 PM
Joined: Aug 2006 Posts: 162 nj N notforsale440 member
notforsale440 member N Joined: Aug 2006 Posts: 162 nj	Quote: Quote: Quote: how can I possible change the length of the pushrod to correct the geometry without affecting the pre-load? you cant......... do your rockers not reach the center of the valve stem? or do they reach too far? not reaching can be cured by shimming the shaft, but this will cause your pushrods to be too short..... if this is the case, spend a little more and do what I did I bought hughes adjustable rockers and they center perfectly...... then bought the proper length pushrods......problem solved I'm still putting the engine together but was looking at this kit: https://board.moparts.org/ubbthreads/show...e=2#Post7774480 They come with pushrods, but if they aren't the correct length, I didn't want to spend the money and have to buy another set. I just couldn't wrap my head around how exactly this works. im just wrapping up my build..... hughes was very helpful I bought the 1.6:1 roller rocker set with shafts; as I said,they center over my valve stems perfectly they will loan you a solid adjustable lifter and an adjustable pushrod with detailed instructions.... then you mail them back and they will make the pushrods mic your hydraulic lifter and set the adjustable solid lifter about .050 shorter to simulate the preload

Re: Lifter pre-load question [Re: notforsale440] #1467402 07/14/13 10:35 PM 07/14/13 10:35 PM
Joined: Dec 2008 Posts: 2,782 USA J JoesMopar OP master
JoesMopar OP master J Joined: Dec 2008 Posts: 2,782 USA	Thanks guys. So when I bolt the shafts down, if the rocker centers over the valve stem, I should be ok....but still need to double check with the method Robert suggested.

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