mikestang63
SN Certified Technician
You want the proper sized pushrod for geometry and them shim to achieve the proper preload.
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Ok I think I got it then! The .6250 Looks like it has the correct geometry so I'm going to get a set of those, 1.6 scorpion adjustable rockers, and a set of shims. Got my digital caliper in the mail yesterday and will be measuring the p2v tonight. Wont I also need to know the cam's lift to figure out how close the valve will be to the piston at full lift? How can I find that without knowing the cam specs? Maybe a dial gauge to the pushrod?
mikestang63
SN Certified Technician
Dude you are way overthinking this.
Base circle of cam, 20ft lbs and 1/2 to 3/4 turn. Use the shims to obtain the preload.
stang89bidges
Advanced Member
If your using those old rockers to do all this measuring your going to have to turn around and do it all again when you purchase the new scorpions. They might require different size pushrods than what you have found. Geometry will be different.
My advise would be get those scorpions in first. Then check geometry and P2V clearance. Everything else will just be adjustments but you need those new rockers before you know what size pushrods and shims and setting lash and etc etc etc.
My advise would be get those scorpions in first. Then check geometry and P2V clearance. Everything else will just be adjustments but you need those new rockers before you know what size pushrods and shims and setting lash and etc etc etc.
was getting ready to check p2v according to these instructions:
View: https://www.youtube.com/watch?v=Y66lvdHbm60
they say I'll need solid lifters... son of a...
View: https://www.youtube.com/watch?v=Y66lvdHbm60
they say I'll need solid lifters... son of a...
stang89bidges
Advanced Member
stang89bidges
Advanced Member
You should, but I didn't use them. I just made sure the putty was thicker than they said it needed to be. Know what I mean?
stang89bidges
Advanced Member
Ok actually check this out. With a pushrod checking tool set to 6.300 this rocker tightens to 20 ft. Lb. in 1 and 1/4 turns. This mark is nice and thin and just a hair inboard of the center of the stem:
The 6.250 that was already on the car was at 20 ft lb at around 3/4 turn and the mark was center but very wide:
I'm thinking the first length pushrod is correct but both preloads are way more than 1/2 turn preload that I was told to look for. Should I shim them or just ignore the preload and go by torque spec?
The 6.250 that was already on the car was at 20 ft lb at around 3/4 turn and the mark was center but very wide:
I'm thinking the first length pushrod is correct but both preloads are way more than 1/2 turn preload that I was told to look for. Should I shim them or just ignore the preload and go by torque spec?
stang89bidges
Advanced Member
Read this first. Engine Tech: Understanding Valvetrain Geometry and Getting It Right! - EngineLabs
You want good geometry, that roller on valve tip mark is only half the battle.
You should always follow the rocker torque specs too. Normally you want around 1/2 to 3/4 of a turn after you get zero lash set. But with pedestal mount you could be a little more of a turn.
Shims should be used to correct geometry, not how many turns on the wrench to get tight.
Geometry, geometry, geometry.
My new song I sing to my kids at night lol:
Heads connected to the.... valves and, valves connected to the.... pushrods and, pushrods connected to the.... lifters and, lifters connected to the.... camshaft.
You want good geometry, that roller on valve tip mark is only half the battle.
You should always follow the rocker torque specs too. Normally you want around 1/2 to 3/4 of a turn after you get zero lash set. But with pedestal mount you could be a little more of a turn.
Shims should be used to correct geometry, not how many turns on the wrench to get tight.
Geometry, geometry, geometry.
My new song I sing to my kids at night lol:
Heads connected to the.... valves and, valves connected to the.... pushrods and, pushrods connected to the.... lifters and, lifters connected to the.... camshaft.
stang89bidges
Advanced Member
P2V is a big deal, how is the geometry looking with the 6.250 pushrods?
I can't imagine your too far off.
How are those scorpions looking too? Pictures?
I must have done the marker test about 20 times. Other than that one time I posted above I could not discern a huge difference between the two. I think maybe the marker is drying too fast and screwing up my readings. Gonna try a dry erase next. Generally with eother size my mark is kind of wide but always in the middle. The difference is in how many turns it takes to get to 20 ft. Lb.
stang89bidges
Advanced Member
I would blame cheap rockers (or a bad batch from factory at least). Dry erase is the way to go. But bad geometry will cause that most certainly. Bad geo will cause extra stress in the valvetrain and lead to premature wear/breaks.
stang89bidges
Advanced Member
Which is why it's more important to get it right over the roller rocker position on the valves. But a true correct geo will get you damn close to centering the roller on valves.
stang89bidges
Advanced Member
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