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For most Studes, other than possibly racing applications, I see no added benefit. I'd love it if someone would come up with reliable hydraulic lifters though. I recall there was a cam & hydraulic lifter kit available, a couple of decades ago, by Lionel Stone. But I heard there were serious problems with that kit. Would love to say good by to valve adjustments, that always seem to come about waay to soon.
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If the 1.75 in the Yella Terra info represents the rocker arm ratio, that is a decent jump from the stock 1.5:1 ratio V8 rockers. However, my guess is that quite a bit of work would be needed on both the intake and exhaust side (valve size, port configuration, intake manifold, etc) to take advantage of the increased ratio. Bottom line, I agree with Joe that these are for racing, not an almost stock street car, but I'm very interested in what Jack Vine's opinion is.
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Originally posted by JoeHall View PostFor most Studes, other than possibly racing applications, I see no added benefit. I'd love it if someone would come up with reliable hydraulic lifters though. I recall there was a cam & hydraulic lifter kit available, a couple of decades ago, by Lionel Stone. But I heard there were serious problems with that kit. Would love to say good by to valve adjustments, that always seem to come about waay to soon.
If the 1.75 in the Yella Terra info represents the rocker arm ratio, that is a decent jump from the stock 1.5:1 ratio V8 rockers. However, my guess is that quite a bit of work would be needed on both the intake and exhaust side (valve size, port configuration, intake manifold, etc) to take advantage of the increased ratio. Bottom line, I agree with Joe that these are for racing, not an almost stock street car, but I'm very interested in what Jack Vine's opinion is.
FWIW, I've run 1.6 Harlan Sharp and 1.65 Rocker Arm Specialties setup and they work well if everything else in the valve train is changed as well.
The 1.75 Yella Terra rockers would provide even greater increase the area under the valve lift curve. The downside is they also increase stress on a Studebaker weak point; valve springs. The Studebaker V8 valve spring is a 1930s technology. It's too tall and too skinny to control the valves at higher RPM/velocities. To take advantage of the increased rocker ratio, much better valve springs would be needed.
So yes, bottom line, if the intake valve is increased to 1.875", if the intake ports are professionally enlarged, if a high-rise manifold is added, if the valve springs are modern performance design, then the rockers might be worth $2000. The result would be a $7,500 Stude top end.
jack vinesPackardV8
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Harland Sharp also makes roller rocker arms for the Stude engine...for a LOT less money.
While a 1.75 rocker ratio may sound cool, it will actually TAKE horsepower to run that ratio. Crower Cams proved this years ago on a machine that they made for this type of testing in their own rocker arm work.
You will also need to grind/machine your heads for head/pushrod clearance. Making that ratio requires one of two things...either moving the entire shaft, or...it moves just the pushrod seat toward the shaft centerline. Moving the pushrod toward the shafts center, requires clearancing of the hole in the head where the pushrod comes thru the head.
"IF"...they did move the "shaft" centerline and make a slightly longer rocker arm to gain the added ratio...then, that would be a very good thing over moving just the pushrod adjuster. You will still need new pushrods.
So beside the $2000+ for the rockers themselves, add in the cost of new pushrods and the cost of the cylinder heads, pushrods clearancing.
Nuthin's good is free..!
On the other hand, they DO look like nice parts. Maybe I'll give them a call to see that their thinking was in the design...stay tuned.
Mike
On second thought, they're in Australia, maybe I won't call them..!Last edited by Mike Van Veghten; 05-29-2018, 01:15 PM.
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Originally posted by tomhoo View Post1.7's would would allow regrind valve timings that would be impossible with 1.5's.
jack vinesPackardV8
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Those look close to a Jessel system and they are good for all out full race motors. but just the rockers by themselves won't benefit much other than a lighter pocketbook. You would need much better heads and cam than what is available for a Studebaker motor to get the use of this kind of a system. There are much cheaper systems that will outrun a Studebaker head. Unless you can get flow numbers in the mid 300's and plan on mid 8000 rpm's you do not need something like this on a small block motor.
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Originally posted by PackardV8 View PostTom, maybe more explanation would clarify. When I change rocker ratio, it does not change any of the valve open/close timing. Increasing rocker ratio increases the rate of open/close and increases net lift, so greater area under the lift curve; but the timing remains fixed by the cam lobe.
jack vines
The fattest lobe (max lift and duration) on a regrind requires keeping the LSA. Changing LSA reduces the max lift/duration available on a regrind.
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Something to think (hard) about.
While a novel idea, I personally would not use 1.7 ratio rocker arms. MAYBE...on a drag race "only" engine, but in no way would I use them on the street or a road race engine.
I don't know what testing the manufacturer did, or what oil was used...but it scares me, with the oils we have to use.
Why - On THIS , this here site, people complain, whine and bitch about today's oils on a flat tappet Studebaker camshaft. While in my opinion, much of it is the "sky is falling" type a thing, BUT...on the other hand, with a 1.70 ratio rocker arm, you are putting a LOT more load on the cam-lifter interface. Thus requiring a much more substantial oil film to prevent galling or welding of said surfaces.
Add to that, a stronger valve spring will be required to control the sudden closing action that this rocker arm will provide (which in itself is a good thing !).
If this rocker arm could be designed as long as a big Chevy (or longer) rocker, things would be a little different, but it can't, not on the Stude head. Notice where the push rod cup is...right against the bearing area of the rocker. That puts a huge load on things. And sorry, without a fancy computational computer, I can't give the actual loads, but take it from a Professional Engineer (retired), I can attest to the higher loads provided by the OEM length rocker arm, vs. a 1.7 ratio rocker arm.
Interesting idea, but not for me.
Interesting note - I e-mailed the guys in Australia twice about building a 1.5, or even a 1.6 ratio rocker arm. No return e-mail either time.
Mike
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My thoughts are more along the lines of maintaining 1.5 regrind lifts but using 1.7's to move center lines.
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Yes, RR does not change valve timing when measured at .050" lobe lift. With 1.5 RR, you have .075" valve lift at .050" LL.
Using .075" valve lift as the new timing measurement, a 1.7 RR corresponds to a .044 LL which occurs sooner and later from the 0.050" LL points. This is an increase in real duration at the valve.
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Thinking about the loads between a regrind w/1.5RR and a regrind w/1.7RR that gives he same valve motion:
STATICS: Quasi-Static load would definitely be higher however those loads would be reduced due to a reduction in friction if roller rockers are used.
DYNAMICS: Inertia Loads would be lower:
- Valve, spring, and rocker travel unchanged: same Inertia
- Lifter and pushrod travel reduced: lower Inertia
Biggest concern might be Studebakers that sit for months or even years without being run. Those start ups would have higher risk of cam damage. However I've never heard of this happening from any of my car friends. I've had dual valve springs on my R2 and R3 and I've sometimes not started them for 2-5 years a couple of times - but I run 20-50 Mobile 1 which probably helps.
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