FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: Jim Comet on September 30, 2019, 10:32:16 AM
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Took the car to Rock Falls last Saturday. Really good air and my friends were running their best times of the season. I notices some smoke when I first started the car which is not normal. Made my first pass and ran a 10.77 @123.9mph 1.49 60ft. When back in the pits I checked the car over and found a bad needle and seat. I replaced that and the smoke went away. The car sounded good with no ticking so I went for another pass. The car launched and was on a PASS (1.47 60ft) when I shifted to 3rd the car stopped pulling strong so I lifted before the finish. The pass was 10.79 @115mph. I went back to the pits and checked stuff out. I did not pull the valve covers at that time because the car idled great and had very crisp throttle response. I verified float level and timing and made another pass. this time the car just didn't pull hard but ran and 11.45 @ 115mph. I checked things over again including pulling the plugs and found nothing. No ticking, no hesitation or any odd sounds. So, I tried another pass and again ran a 11.53 @115mph. At this point I didn't want to hurt anything so I loaded and went home. When I pulled the drivers side valve cover I found a broken intake rocker. It had fallen off in a spot where it didn't touch anything to make a noise. The pushrod looks straight so I think it was just a rocker failure and nothing more. 550lbs open pressure, I may need to upgrade to T&D's. Being in Minnesota, I guess I have the winter to get this thing fixed and sorted out. Jim
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Had a similar situation happen to me but the rocker on #6 let go as I was pulling up to the truck after the run. Heard a bunch of noise and shut it off immediately. Took the hood off and it looked like a hand grenade went off under the valve cover. Pulled the cover and found the same thing you did with the HS rocker. The broken rocker rolled on top of the next rocker and started to pound the valve cover. I replaced the all left side rockers with new HS rockers but left the other side alone. Pushrod was fine and other than a battered valve cover I raced that motor for years with out issue.
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Put in a Chevy LS engine...... ;)
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Were those bushed rockers just curious. 11.45 on 7 cylinders not bad thank God you didnt hurt anything. I had a rocker break on me no damage except pushrod.
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They are bushed. They are 1.85 ratio which moved the adjuster closer to the shaft. I am thinking that may have weakened the rocker also. I'll check with Blair and see which route he thinks is best. I hate to spend $2000 for new T&D's and pushrods, but I can't have these breaking on me as it sure makes a waste of the weekend. Jim
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550lbs open pressure?....That is beyond plenty :o
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Even though it is only 540int and 500exh lift it is a plenty rowdy solid roller.
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Even though it is only 540int and 500exh lift it is a plenty rowdy solid roller.
I was thinking flat tappet....
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I am glad these are bushed rockers instead of needle bearings or I would be tearing down the motor completely looking for those suckers!!
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I was wondering how they were going to manufacture the 1.85 rockers, when the 1.76 have a small-ish cross section in the pushrod area. Looks like there is almost no cross section at all with those. I know the regular bushed HS "can" handle 700+ open. I guess the only crutch is a smaller shaft and thicker body.
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I'm going to talk to Harland Sharp and T&D, see what they recommend and go from there.
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Even though it is only 540int and 500exh lift it is a plenty rowdy solid roller.
That rocker left precious little meat between the adjuster relief cut and the shaft bore. Excluding the possibility that something caused a piston to valve contact, the rocker bore looks for certain to be the failure point. I don't see any way around that when using that ratio and stock shaft set-up. I don't think I'd trust the design on the rockers with that relief cut, it's just too thin there. Since options are limited, I think I'd go T&D and not look back. Things can get bad (read: expensive) real quick when something breaks in the valvetrain.
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When you stop to think that we don't bush pistons, but just run pins against the aluminum, I've come to the conclusion that bushing rocker arms is mostly unnecessary and weakens rocker bodies so that your sort of issue comes up at least occasionally. Just a thought.
KS
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Good point. I've always wondered why they bushed rockers? Seems redundant and a source for weakness(as shown).
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My rocker set up is a mix. Unbushed Comp/Dove 1.76 on the exhaust and the bushed Harland Sharp 1.85 ratio on the intake. This was done because the Comp rockers did not give the desired intake lift with the cam Blair used. He said the T&D 1.76 rockers always check @ .525 lift but the Comp rockers only came in @.500 lift. Blair thought the motor would benefit with more than .500 intake lift so we had the Harland Sharp 1.85s made. Blair advised me to use the T&D's but due to my budget constraints thought the Comp/Sharp rockers should work and were worth a try. I will talk to Blair and go with his recommendation. Jim
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Bummer about the rocker. I wonder if the lobe beat the lifter to death?
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Bummer about the rocker. I wonder if the lobe beat the lifter to death?
Good thought, I will have to remove it and check. The odd thing about this was there was absolutely no ticking or knocking noises when running. Jim
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When you stop to think that we don't bush pistons, but just run pins against the aluminum, I've come to the conclusion that bushing rocker arms is mostly unnecessary and weakens rocker bodies so that your sort of issue comes up at least occasionally. Just a thought.
KS
Couple thoughts on that; a piston pin has two surface areas to rotate in, the piston pin bore and the rod pin bore. If each is working properly, that cuts the rotation sweep down by half (half being in the piston, half being in the rod). A piston pin is also loaded in one direction, then unloaded and loaded in the other direction, so the pin is only seeing a full load on half of its surface about 1/4 of each revolution, as opposed to a rocker which is fully loaded on one surface the entire time, and at great pressure.
Not saying unbushed aluminum rockers don't work. Guys ran unbushed Dove rockers for many years with success, but every used one I saw had fairly significant gouging in the bore. Although back then, they were about the only option.
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Ask T&D if they'll still make their rocker in steel, they'd made their aluminum rocker out of steel before for durability.
Here's the link to the set I saw made out of steel... https://www.youtube.com/watch?v=5EmYsEBuWzw&t=442s
Discussion about the rockers starts about 7 min's in.
I'm going to talk to Harland Sharp and T&D, see what they recommend and go from there.
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Timely subject as I broke a Dove HD Rocker this past weekend. Engine went bad top end of 4th gear and it sounded like a piston with a hole in it. Clicked the thing off and got towed back to my pit. Turned out to be the #1 Exh. and luckily I had a spare. I didn't find any other damage and also didn't have time to run the thing before 1st round. Car went 10.04 on the breakage run and 9.96 after so I guess things are okay, Tach recall said 7700 RPM and I still have plenty of confidence in these old used and abused Dove rockers.
As for Aluminum vs Steel.. Each has their advantages but my opinion is design has more to do with longevity than material. My friends SBF has a Cam with a rather large amount of lift and springs to match and never has rocker problems.
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Timely subject as I broke a Dove HD Rocker this past weekend. Engine went bad top end of 4th gear and it sounded like a piston with a hole in it. Clicked the thing off and got towed back to my pit. Turned out to be the #1 Exh. and luckily I had a spare. I didn't find any other damage and also didn't have time to run the thing before 1st round. Car went 10.04 on the breakage run and 9.96 after so I guess things are okay, Tach recall said 7700 RPM and I still have plenty of confidence in these old used and abused Dove rockers.
As for Aluminum vs Steel.. Each has their advantages but my opinion is design has more to do with longevity than material. My friends SBF has a Cam with a rather large amount of lift and springs to match and never has rocker problems.
Where did the rocker break? Which cam, and what spring pressures? I have several rollers, a couple a bit under .700, and a .725, and have been told that the Doves are pretty safe up to around .700, then get "iffy"
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Where did the rocker break? Which cam, and what spring pressures? I have several rollers, a couple a bit under .700, and a .725, and have been told that the Doves are pretty safe up to around .700, then get "iffy"
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Guess I'm in the "iffy" territory. Cam is a custom Comp of just over .700 and the Springs are probably in the 700# open range. Never checked the springs nor know the part number so that's just a guess. More Comp parts though. Rocker broke on the underside a ways below the adjuster. They are non bushed and at least this one showed no signs of galling. I'll try post a picture later.
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I've broke quite a few of those dove rockers too. I'm switching to t&d for next year
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Yep, I have a .760 and a .785 that I wouldn't even consider used the Doves on- just have this 454 that's a center oiler that hasn't had the lifter galleries drilled so it could use T&Ds
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Timely subject as I broke a Dove HD Rocker this past weekend. Engine went bad top end of 4th gear and it sounded like a piston with a hole in it. Clicked the thing off and got towed back to my pit. Turned out to be the #1 Exh. and luckily I had a spare. I didn't find any other damage and also didn't have time to run the thing before 1st round. Car went 10.04 on the breakage run and 9.96 after so I guess things are okay, Tach recall said 7700 RPM and I still have plenty of confidence in these old used and abused Dove rockers.
If it didn't bend the intake pushrod, you got lucky. I snapped an exhaust rocker on my old engine and it definitely bent the intake. Pushrod was fine on the exhaust that broke. Air and fuel goes in, goes bang, exhaust doesn't open, then something has to give with all the pressure in the cyl., pushrod usually.
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If it didn't bend the intake pushrod, you got lucky. I snapped an exhaust rocker on my old engine and it definitely bent the intake. Pushrod was fine on the exhaust that broke. Air and fuel goes in, goes bang, exhaust doesn't open, then something has to give with all the pressure in the cyl., pushrod usually.
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Valid point and not something I had considered. I did however use the intake rocker lash as a reference and suppose I should recheck them all on that side of the engine since the shaft was off. I do have spare pushrods. I'm hoping for 1 more race weekend before seasons end but the weather may decide that for me.
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I kinda think that there may have been too much pressure on the bushing. If it is overstressed, it could contribute. I imagine some HS rockers run and run while some might fail. I don't usually see that happen, but valvetrain pieces can fail for no apparent or visible reason.
T&D does not offer a steel option for the single shaft sets, and I really think the aluminum is fine for the application. We use the steel T&D on the paired shafts in some circumstances. I think we should replace just that one rocker. It may run for years with no issue. If it breaks another in short order, the T&D would be the way to go, but I'd give it a chance if it was mine.