Fixture & Methods for measuring pushrod for offset rockers. Exc

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Justa1time
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Fixture & Methods for measuring pushrod for offset rockers. Exc

Post by Justa1time »

Good Afternoon,

I have been thinking for a while now about how to accurately measure how "straight" a pushrod is in relation to its two mechanical connection points - the lifter pushrod pocket centerline and rocker arm pushrod pocket centerline. Does the pushrod stay on the same plane throughout the valve opening and closing cycle with all loads considered in the perspective of standing on the side of the engine staring at the engine valley? I realize the cam lobe drives the opening ramps motion side of the valvetrain and the spring drives the closing ramps motion of the valvetrain... a 180° swap of foreclosure! How does one measure to ensure the pushrod stays on the same plane both resting and under opposing loads?

I have tried line of sight method and I am not satisfied with that. None of the surrounding areas are even remotely straight on the casting except other push rods which are in fact potentially not sharing the same plane as their moving counterparts either!

Has anyone made a fixture that pilots off the cam or crank journals and extends up 90° to the top of the engine as a point of reference to then measure from that point to each lifter bore centerline. Then to measure to each rocker stud to determine offsets needed for the pushrod to start at and remain on the same plane as its mechanical counterparts throughout the valvetrain motion?

Do you guys calculate what the lift should be at the tip of the pushrod and measure the lift at that point and if the numbers don't match up you determine the pushrod is "Crooked" and lift is compromised? I could only see this working with a solid lifter that would accurately transfer the lift of the lobe through the other parts to be measured at the rocker tip (pushrod pocket side, not multiplied by ratio yet)?

I really am lost on what the best point of reference is here to measure off of. Cam centerline in relation to lifter bore centerline at 90°, crank centerline to lifter bore centerline at 90°. Triangulated crank centerline to both heads rocker stud centerline at 90°. How do you engine block blueprinters do this? Am I looking at this all wrong?

I appreciate everyone's time,

Bryan from Oregon
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Re: Fixture & Methods for measuring pushrod for offset rockers. Exc

Post by ProPower engines »

Do you have a set of adjustable push rods for checking length??
depending on what your working on will dictate what push rods to use if you have guide plates to locate push rods or if you are using a shaft rocker setup.
the reason I mention it is some push rods use a nut that interferes with the push rod going through the guide plates or if they are tight to the pinch portion of the head the type that uses a small nut to lock the length is a PITA to use.
the push rods with internal thread without the lock nuts are the same OD the length or the push rod making their use much more user friendly.

More context as to what engine and heads and rocker system your using will help to figure a solution :D
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Re: Fixture & Methods for measuring pushrod for offset rockers. Exc

Post by Dragsinger »

A note of consideration. In ref to the nuts and locknuts interfering with the guide plate, but the pushrod in with the nuts at the lifter. {of course, intake must be removed}
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Re: Fixture & Methods for measuring pushrod for offset rockers. Exc

Post by Justa1time »

Good evening,

1st engine is a 400sbc sportsman block. Brownfield 215cc heads that are stamped AFR (having a lot of trouble finding information on these). The engine currently has a roller rocker combination on it consisting of studs and rockers of 1.5 ratio along with non adjustable guideplates. The pushrod is close to the casting already. I posted about this engine and it's anomalies a few times on here in the past and a few folks suggested T&D and Jessel shaft rocker set up $1600ish. I have looked at AFR 6103-8 adjustable guideplates and for the price point they may be worth trying but I can't get a confirmation on if they will work or not. I have posted two photographs of the rockers roller in relation to the valve stem. With no pressure applied from the cam lobes the rocker is right where it should be. As lift is introduced the pushrod gets "crooked" and the issue compounds at max lift- the roller shifts far to one side of the valve stem as see in my other photograph. One member on here said I am loosing valve lift and he is absolutely correct.

2nd engine 1pc rear main seal 350 with vortec 906 casting heads. Stock self aligning 1.5 ratio rocker arms and a cam that will have .340 lobe lift. I am trying to have foresight into this engine as I will be addressing the pushrod angle on this engine very soon (as soon as the cam shows up there are core availability issues.

I ordered an Alex Parts adjustable pushrod with the nuts to mock everything up to get the sweep and length dialed in. Smith Brothers is in my back yard so I will have them make the end result push rods. Is there a different pushrod I should be using for my mock up? I am not too concerned about the sweep motion as I have a good understanding of this (I think). It's more the issue of the pushrod not sharing the same centerline of the pushrod lifter provision in the lifter and the pushrod provision located on the rocker arm. As lift is introduced the pushrod seems to become "crooked". Almost like I have a 5' broom handle I am trying to push in a straight line on the floor. The thing isn't staying straight and I have nothing around it to measure off of to try and correct the problem.

How do you guys measure to make sure your pushrod stays straight (sharing the same centerline of the lifter bore and pushrod provision in the rocker) in the engine valley through the lift and closing cycle of its movement?


Thanks for your time,

Bryan
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Re: Fixture & Methods for measuring pushrod for offset rockers. Exc

Post by dannobee »

Are you sure that the trunnions in the rockers aren't cracked? How about the trunnion bearings?
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Re: Fixture & Methods for measuring pushrod for offset rockers. Exc

Post by cjperformance »

Justa1time wrote: Sat Jul 10, 2021 6:17 pm Good Afternoon,

I have been thinking for a while now about how to accurately measure how "straight" a pushrod is in relation to its two mechanical connection points - the lifter pushrod pocket centerline and rocker arm pushrod pocket centerline. Does the pushrod stay on the same plane throughout the valve opening and closing cycle with all loads considered in the perspective of standing on the side of the engine staring at the engine valley? I realize the cam lobe drives the opening ramps motion side of the valvetrain and the spring drives the closing ramps motion of the valvetrain... a 180° swap of foreclosure! How does one measure to ensure the pushrod stays on the same plane both resting and under opposing loads?

I have tried line of sight method and I am not satisfied with that. None of the surrounding areas are even remotely straight on the casting except other push rods which are in fact potentially not sharing the same plane as their moving counterparts either!

Has anyone made a fixture that pilots off the cam or crank journals and extends up 90° to the top of the engine as a point of reference to then measure from that point to each lifter bore centerline. Then to measure to each rocker stud to determine offsets needed for the pushrod to start at and remain on the same plane as its mechanical counterparts throughout the valvetrain motion?

Do you guys calculate what the lift should be at the tip of the pushrod and measure the lift at that point and if the numbers don't match up you determine the pushrod is "Crooked" and lift is compromised? I could only see this working with a solid lifter that would accurately transfer the lift of the lobe through the other parts to be measured at the rocker tip (pushrod pocket side, not multiplied by ratio yet)?

I really am lost on what the best point of reference is here to measure off of. Cam centerline in relation to lifter bore centerline at 90°, crank centerline to lifter bore centerline at 90°. Triangulated crank centerline to both heads rocker stud centerline at 90°. How do you engine block blueprinters do this? Am I looking at this all wrong?

I appreciate everyone's time,

Bryan from Oregon
When working on canted valve stuff you get this all the time if lifter pushrod cup height changes.
Really the rocker pivot c/l 'should' be at 90 to the pushrod centerline and the pushrod c/l 'should' be inline with the lifter c/l.
Take any canted valve pushrod engine and change designed pushrod cup height and you start to get side movement of the pushrod centerline thru the lift cycle. With a pushrod guided stud mount rocker you then see this at the rocker tip/valve tip interface. Having a canted valve engine where the lifter centerline is NOT on the pushrod centerline you are always getting a slight variance in pushrod c/l thru the lift cycle , then change cup height and increase the range of lift and things get worse!
In your case you have layed the pushrod over away from lifter c/l and your rocker pivot c/l is not on the pushrod c/l , so you're in trouble!
You need to use offset pushrod cup lifters (if running roller lifters), relieve the pushrod holes in the heads, use adjustable or cut/weld guide plates and align rocker tips.
OR , use offset pushrod cup shaft rockers, OR use offset cup shaft rockers and offset lifter cups so that the pushrod is on center with everything.
Anytime the pushrod is not on center to rocker pivot and lifter you will lose lift and the shorter the pushrod the more lift you lose.

With an assembled inline valve head you can check pushrod front to rear 'tilt' using a small machinists square and go off of the valve cover rail (its square enough for this purpose), the pushrod should be at 90 to the rail in the front to rear plane of tilt.(to address the problem of side movement at the valve tip). Checking off of the rail its easy to make reference marks on the rail of where the pushrod is straight, fit a rocker with the valve tip centered then check how much the pushrod has moved over. If the pushrod has moved over say .150" then you need a .150" offset lifter cup OR shaft rocker.
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Re: Fixture & Methods for measuring pushrod for offset rockers. Exc

Post by Ken_Parkman »

There is a big geometry problem here somewhere.

The rockers are not parallel, and in a normal wedge world they should be. Looking at it the rocker pivot direction is not in the same plane as the valve movement, why the variation through the lift curve. This is big time wrong unfortunately.

I'm not a chevy guy, but would guess there is a mismatch in valvetrain components and heads. The heads may have valve centerlines moved apart to install larger valves? If so with a conventional rocker something else should also be offset to try to keep the pushrod loadpath as straight as possible. If the stud mount is offset to match the moved valve centerline you should have a rocker with an offset pushrod cup to bring the pushrods back in line and minimize the side loading on the guide plate. If the stud mounts are stock location you should have rockers with the tip roller offset the other way, again to keep the pushrod loadpath as straight as possible.

With conventional rockers offsets are bad. No matter what there will be a side load somewhere that it really is not intended. With offsets a shaft rocker setup is better as those can much better deal with offsets. But clearly lots of offset "conventional" rockers have been used successfully but you do have to pay attention to the details.

I've also seen heads where the guy designing it did not have the engineering skills to do the job, and geometry was really messed.
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Re: Fixture & Methods for measuring pushrod for offset rockers. Exc

Post by Ken_Parkman »

A little further investigating:

Comp 4009 stud girdle is for a conventional sbc, so logically has stock stud spacing. Comp lists 4011 for Brownfield heads so logically the studs are moved away from stock location to somewhere else. There is probably some offset rocker arrangement somewhere to suit the Brownfield heads which logically should take a standard guide plate to keep the pushrod loadpath straight. This is of course assuming there is correctly designed aftermarket hardware out there, which you cannot always assume.

But the picture showing a conventional spacing stud girdle on a Brownfield head with rockers at an angle is showing a pretty bad mismatch of parts. There has to be all kinds of bending and weird loads happening. The loss of lift is the least of your problems.
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Re: Fixture & Methods for measuring pushrod for offset rockers. Exc

Post by NewbVetteGuy »

These Brownfield heads are "AFR before they were called AFR" AFAIK.

If anyone else on here contradicts what I say, then listen to the other guy as I have VERY little experience, but I had this same issue on my pre-assembled SBC heads also with non-adjustable guideplates. I was able to make the horizontal alignment MUCH better by loosening up the rocker studs and moving the guideplates side to side until I got each rocker as horizontally straight as I could over the valve and then locking down the rocker studs / guideplates in the now "as close to center as I can get them" location. (Whoever assembled my heads didn't really seem to care where the guideplates were when they got tightened down.)

-They're pretty good now, but I'm sure the adjustable guide plates would be best... I'm still on the fence on whether to buy adjustable guide plates and redo it before I fire the thing up or not.

(If you have the wrong stud girdle for the heads, though...)


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Re: Fixture & Methods for measuring pushrod for offset rockers. Exc

Post by cjperformance »

NewbVetteGuy wrote: Mon Jul 12, 2021 8:28 pm These Brownfield heads are "AFR before they were called AFR" AFAIK.

If anyone else on here contradicts what I say, then listen to the other guy as I have VERY little experience, but I had this same issue on my pre-assembled SBC heads also with non-adjustable guideplates. I was able to make the horizontal alignment MUCH better by loosening up the rocker studs and moving the guideplates side to side until I got each rocker as horizontally straight as I could over the valve and then locking down the rocker studs / guideplates in the now "as close to center as I can get them" location. (Whoever assembled my heads didn't really seem to care where the guideplates were when they got tightened down.)

-They're pretty good now, but I'm sure the adjustable guide plates would be best... I'm still on the fence on whether to buy adjustable guide plates and redo it before I fire the thing up or not.

(If you have the wrong stud girdle for the heads, though...)


Adam
Guide plate positioning is something that needs to be done on the specific engine. There are too many variables to 'pre position' a guide plate when using a host of aftermarket parts. This is why even 'non adjustable' guide plates have some movement in the stud holes. Beyond what this movement allows its cut/weld or adjustable guide plates. What the OP is facing is another issue.
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Re: Fixture & Methods for measuring pushrod for offset rockers. Exc

Post by Justa1time »

Good Evening,

Propower: How do you choose to measure the pushrod for offset rockers or to make sure the pushrods are going straight up and down during the lift cycle from the point of view we speak of? Do you also base your measurment from the valve cover gasket mating surface of the head?
Danobee: I am not sure about cracking. These have sure been side loaded though. I will look into it.

Craig: Thank you for taking the time to articulate the situation and also for giving a solution on how to measure the pushrod angle in the way I am looking for. I had not even thought of using the valve cover gasket mating surface area of the heads and a square to form a 90° line to measure off of and I really appreciate that. I have also never considered a higher lifter height for a roller lifter casting the distance to be shorter and therefore the pushrod angle front to back being even more awkward. The situation I am experiencing is challenging to describe and you absolutely nailed it.

Ken: Thank you for pointing out the Stud girdle part number situation. I had not even thought about working the equation in this manner! Ken, how do you choose to measure your pushrod angles in relation to the lifter bore pushrod provision and the rocker arm pushrod provision centerline throughout the lift cycle in the front to back engine perspective?

If anyone else has a method of measuring for offset rockers or front to back of engine pushrod angles please chime in. This topic does not have much avaliable that I could find and I cannot be the only person trying to learn about this.

Thank you guys. This is why I enjoy this forum. I am constantly learning something.

Bryan from Oregon
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Re: Fixture & Methods for measuring pushrod for offset rockers. Exc

Post by Ken_Parkman »

What is important is the direction of motion. The rocker has a sweep motion and that is dictated by the pivot direction, and this creates a plane. The valve stem movement should be parallel to this sweep plane to prevent sideways scrubbing or an uneven tip contact angle. Similarly the pushrod movement should be parallel to this pivot direction to prevent sideways scrubbing and loads on the guide plates, and back and forth movement of the roller tip.

With a wedge valve engine this means these planes need to be parallel in a side to side direction. With the rockers angled you are not. The pushrod should not have a front to back angle at all between the lifter and the guide plate. I do not agree with an angled pushrod relative to the pivot (note properly designed canted valves also have a canted pivot), but some manufactures do this to clear larger ports. It is not the correct design methodology as you are imparting an intentional sideways load on a rubbing surface that is not the correct design. It's a matter of degree, and the more angle the more screwed up. A little bit would probably work. If you need an angled pushrod front to rear you should be using shaft rockers which are much more appropriate.

If the stud girdle really is the wrong one with the wrong stud spacing (this needs to be measured) you are bending the studs and really messing with the above planes into something totally unknown. But with how far off the tip is through the travel something is really wrong.

If you need an offset front to back between the lifter and the valve stem that can be achieved with an offset (not angled) rocker. the pivot should be parallel side to side, and the offsets should correspond to the lifter plane and the valve stem plane - whatever it takes to achieve.
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Re: Fixture & Methods for measuring pushrod for offset rockers. Exc

Post by amcenthusiast »

The slight variation of pushrod angularity while they function to operate the rocker arm is beneficial to draw in lubrication/cooling oil.

Otherwise, with no angularity or movement on either pushrod cup, no fresh oil is introduced to the working interface and this would produce what is called 'galling'.

Same goes for the rocker arm tip on the valve stem: the constant rubbing action allows introduction of fresh oil into the loaded area.
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Re: Fixture & Methods for measuring pushrod for offset rockers. Exc

Post by Justa1time »

Good evening,

NewbVetteGuy: I forgot to thank you for your reply in my last post. I appreciate your input and I am going to nail down an adjustable guideplate solution and weigh this against the shaft mount rocker combination.

Ken Parkman: I appreciate your detailed posts in response to my questions. I agree with your reasoning of the stud girdle. I would like to do a shadt rocker combination on these heads and they are certainly in good shape to justify the upgrade. Measuring for the appropriate dimensions for the shaft mount rocker set up is my next quest. The points to measure off of are indeed in question but as Cj mentioned using a square off the cylinder head mating surface area to the valve cover @90° may get me close enough. Is this how you measure for said distance as well?

Amcenthusiast: Thank you for reaching out about the oiling viewpoint. I had never thought about this. How much of a pushrod front to back of engine angle is desired in your experience on pushrod to lifter and pushrod to rocker arm provision? I guess I always thought the hole in the pushrod needed to be centered in their corresponding pockets- especially the lifter for the oil to travel up the pushrod to the valvetrain components. So the roller tip of the rocker should travel to one side slightly but NOT off the valve stem in its sweeping motion? Would this sweeping motion promote the valve to spin slightly?

If anyone else has input on the way to measure this or theorie on said situation please respond to the thread.

Thank!

Bryan from Oregon
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