#21  
Old 04-27-2019, 06:00 AM
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Cliff R Cliff R is offline
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Correct Skip.

To date I've used just about every possible rocker arm available for a Pontiac engine build. This includes Scorpion, Crane cast full rollers, Crane Gold Race full rollers, "generic" from Butler, CAT full rollers, Lunati, PRW's, Harland Sharp, Crower Enduro's, stock stamped steel....and I probably forgot at least half a dozen others this early in the morning.

A couple of times I've had to reject them as they were too short to get the pattern effectively over the center of the valves. I've also rejected a few because they were just too "bulky" and weren't going to sit under stock valve covers even with a thicker gasket under them. I've even decided to keep a few of the bulkier styles and remove a little material from them so they cleared the covers back on the pushrod end.

There just doesn't seem to be an exact "standard" in the industry when it comes to rocker arms. You've also got to figure in the fact that a rocker arm doesn't know if it's for a Pontiac, Ford, or something else. The important distance is from the center of the studs to the roller tip, but you have to factor in that the valve and rocker stud are angled toward each other. So the length of the valve plays a role here. When longer valves are used it forces the rocker arm to be positioned higher on the studs effectively making it longer and pushing the contact pattern out toward the outer portion of the valve. The manufacturers also use different diameter rollers on them, throwing another variable into the equation.

There also isn't much of a standard with everything else involved in the deal. So the best course of action is to save choosing pushrod lengths as the last step in the rebuild and to spend some time there to establish the best pattern with the combination of parts you are using.

You also have to factor in that some of the rockers currently available aren't that great for quality. They come from off-shore and as I found out with my current engine you can "grind" them up and put a lot of metal into the assembly before you discover they are self-destructing.

The best of the bunch IMHO are the Crane Gold Race, Harland Sharp, and Crower Enduro's. You woln't find me using anything else these days as we've had breaking or wearing something out issues with just about everything else.

I'd add here that there isn't anything wrong with stock stamped steel rockers if they fit the bill for what you are doing. Of course they aren't going to be the best choice for some set-ups with nearly 3/4" of lift, "battleship" valve springs and super aggressive roller cam profiles, but they do a fine job with lower lift flat camshafts and mild spring pressures........Cliff

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  #22  
Old 04-27-2019, 10:06 AM
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The Scorpions I mocked up were very bulky. I have some old Norris SS that are good quality. The Crower SS do have the biggest trunnion bearings of any . Teh HS a little more bearing slop but I have had good luck with them.

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  #23  
Old 04-27-2019, 11:51 AM
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I think the Straub video is a personal technique, that works (?), for the exact parts he's using. Those rockers and the valve angle of the BBC Brodix heads.

In the video, the imaginary line is 90° to valve stem at 1/2 lift. If the line is half lift...How far is the valve open when you add half the roller tip O.D.?

Roller rocker shapes, sizes, bearing size, roller tip size, etc.. do vary by brand.
BUT: pushrod cup, pivot point and "roller to valve stem contact" should all be the same for bolt on replacement rockers.

Longer valves does move the "narrow sweep" to the outside/exhaust side of the head and valve stem. You do not change pushrod length to move the "narrowest sweep" to the center of the valve stem. That would just make a wider sweep and not have the straightest downward push on the valve.

Changing pushrod length, from right, will change when and how far valves will open. Think that's been proved here at PY several times. Like when folks say their rocker ratio isn't what it's advertised because valve lift ends up more or less than it should be.

Don't remember for sure...But thinking it was Grumpy that said .040" from edge of narrow sweep to edge of valve was okay. (Need to do your own homework on that) When it got closer than that he added lash caps as long as the narrow sweep wasn't plum off the valve stem. Way too close to the edge, he went with the shorter ford rockers.

The OP can measure valve stem to rocker stud distance (at right angle to stem or stud) with the longer valves. Then open the valve to what stock valve stem height should have been and take another measurement. The difference will tell how far "narrow sweep" will be from the center of the valve stem.

Roller rockers are forgiving when it comes to perfect rocker geometry. Especially with aftermarket, stronger than stock, pushrods. When things are wrong, stock rockers will spit out or bend stock pushrods. BBC guys can provide lots of examples for that. Pushrod cup shape, on roller rockers, along with stronger pushrods, holds the pushrod better in the cup and helps with pushrod deflection.

The GM technique for rocker geometry has the pushrod straight in the cup, at half lift, and the same amount of tilt, in and out, from valve full open and valve closed. That stops bowing pushrods and has the rocker tip center of the valve stem with all factory original parts.

Enuff for now
Clay

  #24  
Old 04-27-2019, 12:19 PM
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Quote:
Originally Posted by chiphead View Post
When I measured for pushrod length in my motor I used the half lift method like the Straub video shows.
I used the Straub method ( center line of trunnion and roller ) also recently. I found that it is a good starting point. I adjusted from there using the witness marks on the valve top.

Using the Harland Sharp and Scorpion rockers I found that that the flex from using checking springs to actual springs to be used resulted in .025 and .020 less lift. This may affect your decision in pushrod length.

I ended up with a .040 wide mark, center of that mark is .010 off of center of the valve. Don't forget about lifter preload.

I could not use the HS rockers as the trunnion to roller distance is longer than that of the Scorpion's. The HS witness mark was too far from the center of the valve, unless I wanted a .080 wide mark and then it was still a little too far from center for me. If I had shorter valves, the HS might have worked because the distance from the stud to valve would be longer.


Last edited by tc; 04-27-2019 at 12:26 PM.
  #25  
Old 04-27-2019, 12:48 PM
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Quote:
Originally Posted by "QUICK-SILVER" View Post
The GM technique for rocker geometry has the pushrod straight in the cup, at half lift, and the same amount of tilt, in and out, from valve full open and valve closed. That stops bowing pushrods and has the rocker tip center of the valve stem with all factory original parts.
Enuff for now
Clay
This is a good reminder if two different pushrod lengths would work, to choose the length that gives better angles on the cup end of the rocker.

  #26  
Old 05-02-2019, 08:32 AM
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How much preload do you guys like on HR lifters? Specifically the H-J slow-bleed hyd rollers like Paul C likes?

With my current PR length, I'd have about .045" preload.

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  #27  
Old 05-02-2019, 11:23 AM
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The lifter manufacturer indicates the amount of preload.

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  #28  
Old 05-02-2019, 12:50 PM
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Thanks, found it in a HJ PDF:

How much preload is right? The Hydraulic lifter only needs a small amount of preload. This preload is
just to take up any lash in the system and then to remove any contact between the internal components of
the lifter and the retaining ring. We only recommend .020” to .040” of preload on any of our lifters.

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  #29  
Old 05-02-2019, 08:56 PM
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I kept my valvetrain all Lunati from the timing chain to the rockers. My machinist is measuring for pushrods because it is far beyond my capabilities. I was impressed with the appearance of quality from the voodoo roller rockers compared to some offerings I have seen for Chevrolet’s. Time will tell I guess

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  #30  
Old 01-24-2020, 12:31 AM
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GTOspud here ya go!

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  #31  
Old 01-24-2020, 01:37 PM
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Quote:
Originally Posted by 77 TRASHCAN View Post
GTOspud here ya go!
Thank you, a ton of great information here!

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  #32  
Old 01-26-2020, 01:16 PM
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Just for comparison, 400, round port E-heads, crowers, Comp 'S' HR lifters, my length came out to 8.80 using the Straub method. Pattern looks fine. (Technically, the correct length would have been 8.8125)

I switched to the Morels, due to the lifter failures previously posted here (diff thread) and ended up with 8.60 for those. (8.5925 actual)

.

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  #33  
Old 01-26-2020, 01:39 PM
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Quote:
Originally Posted by HWYSTR455 View Post
Just for comparison, 400, round port E-heads, crowers, Comp 'S' HR lifters, my length came out to 8.80 using the Straub method. Pattern looks fine. (Technically, the correct length would have been 8.8125)

I switched to the Morels, due to the lifter failures previously posted here (diff thread) and ended up with 8.60 for those. (8.5925 actual)

.
My 428 decked to .010 with felpro 1016 head gasket Edelbrock round port heads and Johnson short travel lifters came out to 9.050 pushrod length. Pattern was slightly closer to the exhaust ports but had minimal sweep of about .065-.070.

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