[Kenth]

What pushrod length to aim for using 5.100" valves in 1971 455 H.O. heads?
Would RAIV length pushrods be fine?

[steve25]

That's answer totally hinges on if your block and or heads have been milled, what compressed thickness head gasket you are running and if the Cam you are running has a stock base circle height and how much a freshen up valve job has sunk the valves in your 455 HO heads.

Any type of roller lifter Cam will in general require a shorter then stock push rod, with stock for that motor being 9.130".

To do this right you need to get to the point of having everything ready to bolt on with the a head set up with test out springs and then get a adjustable push rod and go thru checking out what you have for geometry with the rockers you will be running.

[Cliff R]

Impossible to answer question, there are simply WAY too many variables involved with that sort of thing these days.

Those include the cam base circle, lifter plunger height/travel, valve length, decking, milling heads and type of rocker arm used.

For this reason every single engine build will require custom length pushrods determined by actually checking the geometry and establishing the narrowest possible pattern closest to being on the center of the valve tip.........Cliff

[77 TRASHCAN]

Those "checker" push rods are not all that expensive....but I'm sure being on the "other" side of the pond, doesn't help that out...

[i82much]

What sort of issues do you see when pushrods are off one size, say, .050 longer or shorter than the perfect size?

I ask because I am playing around with hydraulic roller lifter preload, but the answer may be of interest for this thread as well.

[Steve C.]

An ideal pushrod length will minimize the distance that the valve trip travels across the valve tip. Pushrods that are either too long or too short only increase this distance. A too-short pushrod positions the rocker tip too far to the intake (inboard) side of the valve tip.

https://blog.trendperform.com/how-to...%20valve%20tip.

Rockerarm Geometry and Proper Pushrod Length
Many variables directly affect determing proper pushrod length. Pushrod length is affected by all of the variables listed below.•
Block deck height
• Head deck height
• Cam base circle diameter
• Head stud boss height / rockerarm stand mounting pad
• Rockerarm design
• Lifter receiver cup height
• Valve stem height
Remember that every engine is different because the combination of these variables change from one engine to another. Take the time necessary to determine proper pushrod length with each engine you build. Do not assume that your pushrod length is the same as your friends engine.

http://mantonpushrods.com/pushrod-in...ermine-length/




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[steve25]

Whenever your off by a given amount at the valve stem, which in your case your asking about being off by .050" you need to factor that in by the rocker arm ratio you are using.

For example .050" divided by a 1.5 rocker means your only too long or too short by .033" in the needed push rod lenght.

When I am building a motor that will not need to rev at 7000 rpm for long periods of time and or run open pressure spring loads of over 380 psi I would be quite content with having my geometry within .040" of ideal.

When your checking geometry with a Cam that will run lash or preload a Hydro lifter then you need to factor that in to your needed push rod lenght.

And never forget to check thru the range of valve opening motion the rocker arm body to the side of the retainer clearance.

[i82much]

Originally Posted by steve25

Whenever your off by a given amount at the valve stem, which in your case your asking about being off by .050" you need to factor that in by the rocker arm ratio you are using.

For example .050" divided by a 1.5 rocker means your only too long or too short by .033" in the needed push rod lenght.

When I am building a motor that will not need to rev at 7000 rpm for long periods of time and or run open pressure spring loads of over 380 psi I would be quite content with having my geometry within .040" of ideal.

When your checking geometry with a Cam that will run lash or preload a Hydro lifter then you need to factor that in to your needed push rod lenght.

And never forget to check thru the range of valve opening motion the rocker arm body to the side of the retainer clearance.

So if you have perfect length pushrod with a hydraulic lifter and and the plunger centered, it seems more or less impossible to adjust the lifter to the point where you would need new pushrods as long as the plunger travel is no greater than .100, correct?

[HWYSTR455]

The 'correct' way to determine pushrod length is to ensure correct geometry:

https://www.youtube.com/watch?v=o5is9BsH5OU

No one can tell you what the 'correct' length you need without actually measuring.


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[Steve C.]

If you are concerned with the location of the roller rocker sweep path and are convinced that it should be centered, there are steps you can take to improve the situation.

https://www.hotrod.com/articles/ctrp...rain-geometry/

Pushrod Length - The Big Push
Best practices for finding proper pushrod length


http://www.sbintl.com/tech_library/a...rod_length.pdf


The internet is full of articles.


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[Cliff R]

If using hydraulic lifters don't bother trying to make one of them "solid", just check them with the oil pushed out and plungers bottomed out in the lifter bodies. You will then have to subtract the desired running room and order them shorter. I do this here and have for decades. I just get the best pattern possible closest to centered then order them .050" shorter and run with it.

I also adjust my hydraulic lifters UP from bottomed out not down from zero lash. There are just too many variety of lifters out there these days with plunger travel all over the place. Even the better USA made lifters are coming thru with varying leak down rates so I've found it's best to run them up from bottomed out vs 1/4 to 1/2 a turn down from zero lash. If you really want a quiet engine with hydraulic lifters set them with a .010" feeler gauge between the rocker arm and valve with the plungers bottomed out and the lifters on the base circle of the camshaft........Cliff

[chuckies76ta]

So when using a solid roller cam and solid lifters, do you guys take the lash out when checking for pushrod length?

Thanks

[Steve C.]

The second article in my post #10 stated this:

" If you are using a solid lifter, set the valvetrain to zero lash. If you are running a hydraulic lifter, tighten down the rocker adjuster to your normal preload."

Nothing in other articles.

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[Schurkey]

If your rocker system is non-adjustable, pushrod length does nothing but change lifter preload--no change in rocker "sweep" over the valve tip.

If the rocker system is adjustable, pushrod length changes rocker sweep assuming the same lifter preload.

[chuckies76ta]

I just posted this in another thread. Let me know if this make any sense. Thanks

Post a pic if possible of your pattern on the valve stem.. I learned a little trick yesterday using Straub Technologies method. At 7.30 in the video he says you just established proper pushrod geometry. Once you have that, mark the top of the valve stem and move your rocker back on top of the valve stem. Hold your rocker firmly over the tip and do a side to side motion marking the tip of the valve stem with the rocker roller. You can now see exactly where your rocker roller tip is landing on the valve stem. Now all you have to do is remove a turn on the adjuster nut to move your witness mark inboard or add a turn and move your witness mark outboard. You still do all the math he tells you too in the video. The idea of his video and math is to get the rocker tip at half lift in the center of the valve tip. This is just a way to verify his work. Excellent video in my opinion. Anyone, Thoughts?

https://www.youtube.com/watch?v=o5is9BsH5OU&app=desktop

Thanks
Charles

[HWYSTR455]

Originally Posted by chuckies76ta

I just posted this in another thread. Let me know if this make any sense. Thanks

Post a pic if possible of your pattern on the valve stem.. I learned a little trick yesterday using Straub Technologies method. At 7.30 in the video he says you just established proper pushrod geometry. Once you have that, mark the top of the valve stem and move your rocker back on top of the valve stem. Hold your rocker firmly over the tip and do a side to side motion marking the tip of the valve stem with the rocker roller. You can now see exactly where your rocker roller tip is landing on the valve stem. Now all you have to do is remove a turn on the adjuster nut to move your witness mark inboard or add a turn and move your witness mark outboard. You still do all the math he tells you too in the video. The idea of his video and math is to get the rocker tip at half lift in the center of the valve tip. This is just a way to verify his work. Excellent video in my opinion. Anyone, Thoughts?

https://www.youtube.com/watch?v=o5is9BsH5OU&app=desktop

Thanks
Charles

Well, as long as you're not talking about a full turn, you might be able to use that to some degree. On a HFT lifter, there usually is an optimum adjustment 'range', example, .030-.060 preload. On a solid, it's a defined clearance.

From the Hot Rod Mag article:

"By positioning the rocker arm height in a certain way, the contact sweep path may or may not be centered on the valve stem. In a perfect world, this would be the case. But there are variations in the machining of the blocks, placement of the rocker studs, rotational length of different rocker arms, and lengths of the valves that will alter slightly the position of the rocker tip sweep path on the end of the valve stem. The critical element is not the positioning of the sweep path on the valve tip; it is the geometric angles of the rocker pivots to the valve stem."

And:

"Of course, we don't want to see the roller rocker contact point move any closer than 0.020 inch to the edge of the valve stem, as Smokey has stated, but being off-centered has little negative effect on components such as valve guides and valvetrain harmonics and no effect on performance. It is not a performance enhancement to have the sweep path centered on the valve stem, nor does it necessarily mean that we have the correct VTG if it is centered."

The visual aid attached.

Just to say it out loud, you may get a sweep path centered on a valve tip, but it doesn't mean that's correct or optimum 'geometry'.

I have heard conflicting info when people describe the desired pattern with the witness mark method, when it's stated that 'You want a narrow sweep pattern'. That may be off the center of the tip, and people may accept a wider sweep path when using this method in order to get the witness mark more centered. And THAT, would most likely NOT be achieving proper geometry.


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[NeighborsComplaint]

Originally Posted by Kenth

What pushrod length to aim for using 5.100" valves in 1971 455 H.O. heads?
Would RAIV length pushrods be fine?

Simple answer yes, it is the same setup as a RAIV. Assumes heads and block have been surfaced only for squareness and gasket retention, no excessive milling for higher compression. The pushrods are 7.16" so you may need to clearance the guide plates. I tapped the plain shank of a 7/16" bolt between the lips of the guide plates to clearance them, no grinding needed.

[Tim Corcoran]

If you don't want to buy an adjustable pushrod you can make one pretty easy. Take a pushrod and cut off ( a hack saw won't work you will need a cut off wheel) near the end so you can adjust it while installed. you will need to shorten it a bit then drill and tap it and put in a piece of threaded rod to match the threads in the pushrod halves and install a nut on the rod so you can lock it in place. You don't wan to guess on pushrod length you need to set it up as stated above.

[NeighborsComplaint]

Originally Posted by NeighborsComplaint

Simple answer yes, it is the same setup as a RAIV. Assumes heads and block have been surfaced only for squareness and gasket retention, no excessive milling for higher compression. The pushrods are 7.16" so you may need to clearance the guide plates. I tapped the plain shank of a 7/16" bolt between the lips of the guide plates to clearance them, no grinding needed.

That's what I run in mine with 6X heads, 5.095" length valves, 1.70" Installed height springs and 1.52:1 roller tip rockers. Roller rockers run dead center on the valves and no rocker to retainer interference as with a shorter pushrod. Yours would be no different.