yellow rose
Overnight Sensation
True. IIRC, to get a roller that has the radius of the pad on a 273 rocker the roller would have to be like 3 inches in diameter. That's IIRC. You know that's a crap shoot.
Cam Install Question
- Thread starter midnight340
- Start date
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True. IIRC, to get a roller that has the radius of the pad on a 273 rocker the roller would have to be like 3 inches in diameter. That's IIRC. You know that's a crap shoot.
midnight340
Well-Known Member
Not checker springs, I used my old 95# seat springs (but not the new double 115# springs.)
And I’ll take a closer look at the intake to piston radius. Should be OK as they are the old TRW forged stock style and valves are 2.02. They should be cut for 2.02s I’d think.
Rather than pulling the inner of the new set, I’ve considered using the old springs for cam break in.
And I’ll take a closer look at the intake to piston radius. Should be OK as they are the old TRW forged stock style and valves are 2.02. They should be cut for 2.02s I’d think.
Rather than pulling the inner of the new set, I’ve considered using the old springs for cam break in.
yellow rose
Overnight Sensation
Thats ok, even with those springs, you've got plenty. You did degree the cam didn't you? It makes a difference and I don't want to reread the thread. If so, you've got plenty of room.
midnight340
Well-Known Member
As I picture the ratio thing it seems roller arms would in effect get incrementally shorter past 90 degrees relative to the valve tip, whereas the contact point on the pad moves further from the fulcrum increasing the ratio as th valve nears full open.
Is this what you are saying?
Is this what you are saying?
midnight340
Well-Known Member
Yes, degreed so all numbers good. (Info on this earlier in the thread.)
nm9stheham
Well-Known Member
Yes. IMHO, the engineering and thought that went in to the stock design had a lot going for it that most folks don't see or give credit for. They had been playing with this stuff for decades!
Edit to add: BTW, I have only checked the stock stamped and 273 rockers' behavior up to around .500" lift. If you are going for .600" lift, I don't know what happens at the peak of lift.
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Wyrmrider
Well-Known Member
midnight
NM has the short answer given:
roller tip You want the center of the shaft to the center roller perpendicular at half valve lift
iron rocker you want the line to be the center of the shaft to the pad face/ valve tip perpendicular to the valve stem at half lift
you will have to adjust your shafts (B3) on roller tip and maybe on iron rockers to get there especially if you insist on the witness stripe to be centered on the valve tip
given that shaft is in the correct place the ratio increases till you get to half lift and decrease from half lift to fully open- simple geometry
you want the same angle up with valve closed as angle down at full lift
anything else has tradeoffs- some major - and most likely your camgrinder has engineered the cam for this scenario (recent cams without old theories)
on iron rockers this minimizes side thrust
now watch your pushrods at the same time
NM has the short answer given:
roller tip You want the center of the shaft to the center roller perpendicular at half valve lift
iron rocker you want the line to be the center of the shaft to the pad face/ valve tip perpendicular to the valve stem at half lift
you will have to adjust your shafts (B3) on roller tip and maybe on iron rockers to get there especially if you insist on the witness stripe to be centered on the valve tip
given that shaft is in the correct place the ratio increases till you get to half lift and decrease from half lift to fully open- simple geometry
you want the same angle up with valve closed as angle down at full lift
anything else has tradeoffs- some major - and most likely your camgrinder has engineered the cam for this scenario (recent cams without old theories)
on iron rockers this minimizes side thrust
now watch your pushrods at the same time
midnight340
Well-Known Member
*Edited* (see photo in next post)
Here is a photo of the rebuilt 273 rockers (using my existing Erson chro-mo pushrods) at exactly 50% lift and with lash set at .014”
Here is a photo of the rebuilt 273 rockers (using my existing Erson chro-mo pushrods) at exactly 50% lift and with lash set at .014”
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yellow rose
Overnight Sensation
midnight340
Well-Known Member
OOPS!!! YellowRose, it’s good you asked!!! I screwed up, must be Friday night! So half of exhaust lift of .546” is shown below and it looks better to me. .273”.
Am I on the right track looking for a 90* angle between “center of shaft to valve contact point” and the stem?
That looks like a “by the book" example of a properly set up Mopar rocker assembly, I would have zero worries running that providing they are centered side to side as well.
midnight340
Well-Known Member
Thanks!! I have extra shims if needed, I’ll make sure they are centered over the valve stems.
nm9stheham
Well-Known Member
FWIW..... Perfect side-to-side centering has little to do with anything here; the forces don't change in any significant way if it is off a bit. Centering across the tip (in the direction of sliding motion) is only important to keep the pad off of the inboard and outboard edges of the valve tip. The 'pependicular to the valve stem axis at mid-lift' is the most important factor, as it keeps the side forces on the stem minimized. The pad surface being parallel to the bore of the lifter is important too, but is not something we can fix in assembly.
IMHO, I'd be curious to put some marking dye on the tips and see where this slides on a few valve tips and pads. The lift is a lot higher than the original intended design so it may get 'close to the edge'. And if the pads were re-machined on the rebuild process, that needs to be done right.
IMHO, I'd be curious to put some marking dye on the tips and see where this slides on a few valve tips and pads. The lift is a lot higher than the original intended design so it may get 'close to the edge'. And if the pads were re-machined on the rebuild process, that needs to be done right.
midnight340
Well-Known Member
midnight340
Well-Known Member
Good, because with the first build I did not have them centered too well. (Hadn’t learned much about this stuff.) Part of the fun is getting things better the next time around.
I’ll put some dye on the tips and check them later today.
I’ll put some dye on the tips and check them later today.
midnight340
Well-Known Member
midnight340
Well-Known Member
Wyrmrider
Well-Known Member
nice work
well you certainly do not want to add any shims do you
if you think the open is too near the edge you could try a lash cap and post the results of your sweep test
but just putting a piece of paper across the top of the retainer (on the computer screen) and then raising it up to the valve tip shows you are close to the center of the shaft
you can do it with a machinist rule and get closer
you guys with roller rockers give it a try through the center of the roller and the shaft at half lift and see where you are...
well you certainly do not want to add any shims do you
if you think the open is too near the edge you could try a lash cap and post the results of your sweep test
but just putting a piece of paper across the top of the retainer (on the computer screen) and then raising it up to the valve tip shows you are close to the center of the shaft
you can do it with a machinist rule and get closer
you guys with roller rockers give it a try through the center of the roller and the shaft at half lift and see where you are...
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