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When you use a roller bearing, most of the time, the bearings float within the races allowing different portions of the bearing to absorb the load you are placing on it. If you are switching to a bushing, you are now loading one side of the bushing in the same place all the time. Aren't these going to wear on the load side since the bushing is not going to float and change the load bearing surfaces?
Good question.
In a needle bearing situation you have the “load” on only 3 to 4 of the needles that are supporting all the load. In a bushing application the load is supported by 30% of the bushing radius spreading the load out. When comparing load limits the bushing can with stand 300X the load than a needle can.
In short, the bushing is superior to a needle bearing application in spreading the load out over a larger surface area which reduces stress and pressure applied to the bushing and the trunion itself.
But, in a bearing situation, the load location is changing all the time. The same 3-4 bearings may not see the load again for several revolutions or more of the engine due to the bearing rotating. In a bushing, although the load may be spread across a larger surface, it is the same surface during every revolution of the engine.
What is the life of the bushing versus a bearing if everything else is equal?
But, in a bearing situation, the load location is changing all the time. The same 3-4 bearings may not see the load again for several revolutions or more of the engine due to the bearing rotating. In a bushing, although the load may be spread across a larger surface, it is the same surface during every revolution of the engine.
What is the life of the bushing versus a bearing if everything else is equal?
I'll answer this question this evening when I have more time to sit down and type out a response.
Before you type that out, maybe you can just answer this question. How many aftermarket bearing trunnions do you see go bad using the factory rockers? I think I have read more stories of roller lifters going bad than factory rockers with upgraded trunnions.
Not completely sure but wouldn't the same few needles be handling the load because the rocker "rocks" back and forth - rolling the needles one way and then back the same distance.
Or is something else in play that would make the whole lot migrate around the race/trunion?
Before you type that out, maybe you can just answer this question. How many aftermarket bearing trunnions do you see go bad using the factory rockers? I think I have read more stories of roller lifters going bad than factory rockers with upgraded trunnions.
I have seen aftermarket trunions fail before several times. More so the stock parts, but I have seen aftermarket kits fail as well.
As for the stock rockers, the needle bearings in a stock rocker arm do not revolve around the axle.
Originally Posted by BFASTNOTLAST
No spintron testing?
Spintron testing is extremely expensive.
Originally Posted by JaxMustang50
Not completely sure but wouldn't the same few needles be handling the load because the rocker "rocks" back and forth - rolling the needles one way and then back the same distance.
Tooley has no stock and has not had any for months. I suspect the kits are being redesigned now that a bronze bushed kit is available.
Summit has both their own brand and Comp Cams brand in stock. If I recall reading a post on here a while back, the BTR brand was reboxed Comp Cam version.
I have a set of the bushings in hand. Very nice like you would expect from Chris Straub. I have had a set of comps fail replaced them 15'000 miles ago no issues since. Going to inspect and install the bushings if it needs them
Interesting info to add to this thread, first - the stock rockers have a decent amount of taper across the tips as compared to the trunnion bore. This is due to the nature of the manufacturing process of MIM parts that are not precisely "coined" or pneumatically tapped into final shape after the powder has been cured. This explains why the set of LS7 offset intake rockers I upgraded today with this kit had .005" of taper across the tip (double what I see on others) and could be a possible root cause of the excessive intake valve guide wear consistently seen on these and the LS9. Additionally, the LS7 rockers have a trunnion bore that is .0008"-.001" tighter than any of the LS1/2 sets that I have measured and this was enough to make the trunnion barely turn in the bushing - we had to hone the bodies to proper size before being able to true and polish the tips to less than .0005" out from the bore.
Great kits, just some things to think about after having installed these kits personally...
how do these compare to the btr kit? im going to buy a a trunion kit soon.. im not very familiar with rockers
BTR utilizes a needle bearing design like the Summit, Comp and every other kit out their aside from this one and the CHE rockers.
Originally Posted by Droptopws6
Did your guy ever report back to you regarding use with 1.8 ratio rockers? Usually by the time I get home from a long work day it's too late to call.
These will work with LS7 rocker arms I have confirmed this.
Good info in Machinistone post as well for those using LS7 rockers and the bushing kits.
Originally Posted by machinistone
Interesting info to add to this thread, first - the stock rockers have a decent amount of taper across the tips as compared to the trunnion bore. This is due to the nature of the manufacturing process of MIM parts that are not precisely "coined" or pneumatically tapped into final shape after the powder has been cured. This explains why the set of LS7 offset intake rockers I upgraded today with this kit had .005" of taper across the tip (double what I see on others) and could be a possible root cause of the excessive intake valve guide wear consistently seen on these and the LS9. Additionally, the LS7 rockers have a trunnion bore that is .008" tighter than any of the LS1/2 sets that I have measured and this was enough to make the trunnion barely turn in the bushing - we had to hone the bodies to proper size before being able to true and polish the tips to less than .0005" out from the bore.
Great kits, just some things to think about after having installed these kits personally...
That is very interesting. I really appreciate you sharing that in this post so that others can learn from your experience and expertise.
I would think that the buffing and the truing of the rocker pads would help with any valve stem tip wear and rocker pad wear that could occur as well. I could also see valve stem tip wear occurring due to the taper of the rocker tips. Which is interesting that I mention that because I seem to have more customers with LS7 engines that experience valve stem tip wear with valve lift that stays in the "safe zone" of what the rocker arms pivot length can handle.
the LS7 rockers have a trunnion bore that is .008" tighter than any of the LS1/2 sets that I have measured and this was enough to make the trunnion barely turn in the bushing
So this is a guarantee we need to hone the rockers for proper trunion fit?
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