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Valvetrain deflection and geometry

Posted By: Mbrown

Valvetrain deflection and geometry - 03/17/24 02:22 AM

I am setting up the valve train on a 540 and wanted some opinions on what to do. I have always used B3 shaft relocation kits, but now I am having second thoughts. I want to make it clear that i am not bashing Mike or his products. I am just having trouble with this application.
I have measured valve lift with checking springs and the actual springs. I did all checks with 0 lash to help eliminate human error. Lobe is .465" . The rocker arms are advertised as 1.7 ratio. My springs are 255#'s on the seat and 660#'s at .770 lift.

With shaft relocation kit, lift at valve was .771 with checking spring. The lift at the valve with the real spring was .712". That is A LOT of deflection. Scrub pattern was .045-.050" wide and centered. I am not happy having that much deflection. So I decided to check without the shaft relocation kit.

Without the shaft relocation shims, the lift at the valve with checking springs was .790". The lift at the valve with the real springs is .776". The scrub pattern is huge though. .090-.100", but centered.

My question is, do I run with or without the relocation shims? I have considered machining new hold downs that would help stabilize everything when using the relocation kit. Any suggestions?
Posted By: gregsdart

Re: Valvetrain deflection and geometry - 03/17/24 10:12 AM

I am not well versed in stock type valvetrain, but my first thought was can you put a dial indicater on the shaft to see where some of the deflection is coming from? With, and without shim kit. I have often wondered if an overhead bridge of some sort might reduce shaft flex, but having switched to Jesel stuff never tried anyrhing like it .
Posted By: Harry's Taxi 2

Re: Valvetrain deflection and geometry - 03/17/24 10:49 AM

Originally Posted by Mbrown
I am setting up the valve train on a 540 and wanted some opinions on what to do. I have always used B3 shaft relocation kits, but now I am having second thoughts. I want to make it clear that i am not bashing Mike or his products. I am just having trouble with this application.
I have measured valve lift with checking springs and the actual springs. I did all checks with 0 lash to help eliminate human error. Lobe is .465" . The rocker arms are advertised as 1.7 ratio. My springs are 255#'s on the seat and 660#'s at .770 lift.

With shaft relocation kit, lift at valve was .771 with checking spring. The lift at the valve with the real spring was .712". That is A LOT of deflection. Scrub pattern was .045-.050" wide and centered. I am not happy having that much deflection. So I decided to check without the shaft relocation kit.

Without the shaft relocation shims, the lift at the valve with checking springs was .790". The lift at the valve with the real springs is .776". The scrub pattern is huge though. .090-.100", but centered.

My question is, do I run with or without the relocation shims? I have considered machining new hold downs that would help stabilize everything when using the relocation kit. Any suggestions?



I've just been through the same observation when changing to a different flat tappet cam using the B3 setup. I noticed a fair amount of fretting/walking marks on the shims so i checked side to side flex at the hold down stud and it was around .0015-.002. and this is with 150# seat pressure and .620 lift.

I switched from using the B3 kit with Hughes rockers to a T&D rocker assembly. The pattern isn't quite as centered (very close to center though) now, but is as narrow and it is much closer to full lift with flex at hold down stud gone now.

I have another engine with roller and Jesel 1.7 individual shafts and @.799 theoretical lift, it only loses about .015 to actual lift at retainer w/ 350# seat springs....scrub was minimal, but i don't recall actual width.

I think the B3 kit is a good idea, but it has spring pressure and lift limits.
Posted By: AndyF

Re: Valvetrain deflection and geometry - 03/17/24 02:50 PM

At 0.790 gross lift you should be using high quality rocker arms, especially if you're going to turn the engine past 6000 rpm. T&D is probably the best choice at that level although a switch to Jesel could also make sense if the engine is designed to make a lot of passes. I would not run anything that deflects as much as what you are measuring. That deflection will occur every rotation of the engine so those shafts will be vibrating like guitar springs at 6000 rpm.
Posted By: dvw

Re: Valvetrain deflection and geometry - 03/17/24 04:06 PM

My paired T&D 1.7 show less than .010" loss at 805lbs over the nose.
Doug
Posted By: Mbrown

Re: Valvetrain deflection and geometry - 03/17/24 06:36 PM

What's an acceptable amount of deflection? I will retest with a larger diameter pushrod when I get in the shop Monday morning. Right now without the offset shims I am at .014" deflection.
Posted By: fbs63

Re: Valvetrain deflection and geometry - 03/18/24 10:53 AM

That kind of lift and spring pressure needs individual shaft paired rockers. I cannot imagine what the rockers and shafts go through when you try to install them much less how much deflection it has running with the geometry correction hardware raised shaft position.
Posted By: B1MAXX

Re: Valvetrain deflection and geometry - 03/18/24 12:30 PM

What push rod?
Posted By: B1MAXX

Re: Valvetrain deflection and geometry - 03/18/24 12:33 PM

The only thing geometry wise that effects it will be how much adjuster you have "hanging"out.
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