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#21
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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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If you can read this, thank a teacher. If you can read this in English, thank a Veteran! https://cliffshighperformance.com/ 73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile), |
#22
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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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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
#23
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Blurrred Lines
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
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Quote:
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
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Quote:
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#26
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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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I could explain all this to the girl at the parts store, but she'd probably call the asylum. White '67 LeMans 407/TH350/Ford 3.89... RIP Red '67 LeMans. 407/TH400/Ford 3.25 |
#27
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The lifter manufacturer indicates the amount of preload.
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Will Rivera '69 Firebird 400/461, 290+ E D-Ports, HR 230/236, 4l80E, 8.5 Rear, 3.55 gears '64 LeMans 400/461, #16 Heads, HR 230/236, TKO600, 9inch Rear, 3.89 gears '69 LeMans Vert, 350, #47 heads: Non-running project |
#28
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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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I could explain all this to the girl at the parts store, but she'd probably call the asylum. White '67 LeMans 407/TH350/Ford 3.89... RIP Red '67 LeMans. 407/TH400/Ford 3.25 |
#29
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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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468/TKO600 Ford thru bolt equipped 64 Tempest Custom. Custom Nocturne Blue with black interior. |
#30
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GTOspud here ya go!
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1977 Black Trans Am 180 HP Auto, essentially base model T/A. I'm the original owner, purchased May 7, 1977. Shut it off Shut it off Buddy, I just shut your Prius down... |
#31
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Thank you, a ton of great information here!
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1967 GTO, 432 (428+.030), 4-bolt mains, factory Nodular crank, scat rods, icon dished pistons, Lunati HR 243/251@.050, .618/.622 lift, Edelbrock 72cc round port heads, 10.5:1, offy 2-4 intake, Edelbrock 650cfm carbs, Super T10 trans (2.64 first), BOP 10 bolt w/ Eaton posi and 3.36 gears |
#32
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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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. 1970 GTO Judge Tribute Pro-Tour Project 535 IA2 http://forums.maxperformanceinc.com/...d.php?t=760624 1971 Trans Am 463, 315cfm E-head Sniper XFlow EFI, TKO600 extreme, 9", GW suspension, Baer brakes, pro tour car https://forums.maxperformanceinc.com...ght=procharger Theme Song: http://www.youtube.com/watch?v=7zKAS...ature=youtu.be |
#33
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Quote:
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1967 GTO, 432 (428+.030), 4-bolt mains, factory Nodular crank, scat rods, icon dished pistons, Lunati HR 243/251@.050, .618/.622 lift, Edelbrock 72cc round port heads, 10.5:1, offy 2-4 intake, Edelbrock 650cfm carbs, Super T10 trans (2.64 first), BOP 10 bolt w/ Eaton posi and 3.36 gears |
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