Thanks. Those are the updated rocker. That’s a bummer because it doesn’t look like they increased the nominal ratio at all.
Im glad I didn’t buy a new set to end up with the same problem of the nominal ratio being too low.
Valvetrain Geometry
- Thread starter Earlie A
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Thanks. Those are the updated rocker. That’s a bummer because it doesn’t look like they increased the nominal ratio at all.
Im glad I didn’t buy a new set to end up with the same problem of the nominal ratio being too low.
Chit. Look at a big block Chevy. LOL
Just get some Norris rockers and you'll be good to go.
Woody500
Well-Known Member
Just a quick look @their site doesn't show those or any bushed ones. Must have to dig further to find them.
Are the roller tips bushed, too?
Earlie A
Well-Known Member
https://www.prwpower.com/prw-mopar-elite-series-shaft-rocker-system-3231812/p3120
I seriously doubt the roller tip is bushed.
I seriously doubt the roller tip is bushed.
lol yeah, I’d have better luck finding a needle in a haystack than those
TT5.9mag
Two atmospheres are better than one
In the description they mention both needle roller bearings and bushings. So with a bushed fulcrum there’s only one other place a needle roller bearing could be.
Yeah but you'd have some actual good rockers. Last word was he was still making them out of his home garage.
Earlie A
Well-Known Member
I think that's just a generic description. I can't see any bearings in the roller tip.
TT5.9mag
Two atmospheres are better than one
Only one way to find out.
Bust out the grinder.
The ratio of on the old rockers might still be even less than these.
So, you think that 3 degree difference from 45 makes an appreciable difference? Comparing those 3 degrees to the 14 degree difference from 59 to 45, I can't see it. Especially if they run as well as they do with the 59 degree lifter bores. Evidently, it just doesn't matter "that much". I've sure seen that angle subtract a bit from the gross valve lift, though.
I have to look at my notes but IIRC they were 1.63-1.64 unloaded. EarlyA is doing his tests with checking springs they didn’t do much with the ratio.
I'll bet the prod angle on the LA engines is a leftover from the Poly blocks which had different valve angles & positions. Any angularity will result in a slight amount of lost lift & motion, too little to worry about.
Earlie A
Well-Known Member
How much have you seen springs change the RR? Is it mostly rocker deflection?
Earlie A
Well-Known Member
I’m not sure I understand the reference to 45 degrees. 48 degrees is perfection for the SBM lifter angle. Factory stuff was 59. That’s the comparison I see.
As far as the loss of lift - that can be recovered by designing the rocker arm properly. Move the adjuster toward the rocker shaft and the rocker ratio increases.
What the bad geometry does do is create side loading on lifters, rockers, shafts and pushrods and creates a pushrod motion that ‘see-saws’ instead of traveling back and forth in a nearly straight line. All this wasted motion creates increased friction losses, increased harmonics and other unbalance forces and makes a slightly stronger valve spring necessary. It’s just increased inefficiency.
Earlie A
Well-Known Member
Some of the losses are shown in the two drawings. 0.430” of cam lift results in 0.415” or 0.419” at the other end of the pushrod.
Yes. All rockers have some deflection which is why the actual unloaded ratio is higher than the nominal ratio. Or at least it should be.
You also have flex in the shaft and the pushrods, although if the pushrod is big enough you don’t see much loss when the system is loaded turning it over by hand.
I had some 5/16 heavy wall pushrods that came with a W2 engine I bought in 1986. I ran it like I bought it for two years and then I pulled it and went through it.
In 1991 I had it on the stand and I was using 3/8 pushrods I was just screwing around so I threw the 5/16 stuff back in and I saw the loss. And that was with about 255-260 on the seat. I forget how much it lost from unloaded to loaded but it was measurable.
Once I went to 300 on the seat I could not keep the adjusters tight. That made me chase a bunch of crap that wasn’t an issue.
I had to order some pushrods for my boss and at that time Walt Austin Racing was making pushrods. I was chatting with Walt and my junk came up and he said you can’t run that much spring load with all those funky angles on any straight 3/8 pushrod.
So he made up a set of double taper 3/8-7/16 pushrods and sent them and the issue stopped.
What was happening was the pushrods were bending and unbending so much it was like beating on the adjusters with an impact gun and it would cause them to come loose.
That drove me nuts for a while and all the whiz bang in gym shorts types said Walt was talking out of his hat and all that but they had to eat his hat when he was right.
Woody500
Well-Known Member
Any non-rotating needle bearings are bound to fail, due to back & forth motion & concentrated pressure. Rotating needles last a lot longer, like some later model rear axle bearings, which use larger 'Needles', but the same concept.
This graph and chart is interesting when thinking about the forces in play, when they occur, where they come from and how they are affected by rpm.
I wonder if the difference between the old and new design is just an increase in ratio and or something else.
Earlie A
Well-Known Member
If I remember correctly @Newbomb Turk said there was a change in the bushing. Perhaps the old style had a split bushing (two halves) where the new one is a single bushing with a groove? All of that is in a thread here somewhere.
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