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#1
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CP piston install question?
Ok I bought a set of CP pistons a few years ago and I知 now assembling the engine I got them for. Problem being they are L and R short skirt pistons but with double valve relief. So when I look at pistons from bottom you can see one corner is thicker than the others. I知 assuming the thicker area would be under exhaust valve or am I totally wrong?
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#2
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It is my understanding from talking to Barry Calvert (President of CP) and his brother "Snake" at the PRI shows that CP Pistons were "Non-Directional" meaning the piston does not care which set of valve reliefs you install upward.
No direction arrow on which way should face the front of the engine. But that was some years ago, just like the age of your pistons. Tom V. .
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#3
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Can you see in the picture where the one corner is thicker than the others?
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#4
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I would guess the thicker corner would be positioned to the trust side. Unless it is just because the pin is offset, could position it either way depending on the use.
Last edited by Jay S; 06-05-2021 at 01:05 AM. Reason: Add |
#5
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Non-directional means no offset like a factory piston. See post #2.
If you have a non directional piston then both sides of the piston can be the same contour/thickness and no reason to add more weight to on side of a piston to make it thicker and "stronger" on the thrust side. Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#6
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The shorter thick skirt is hard to see in the picture. Pin offset I thought I noticed was likely and optical illusion.
Main point I was trying to make was is if one side of the skirt looks like it has more support or skirt area, it was likely designed to be positioned so that the larger skirt area was to be positioned to the major thrust side of the cylinder. If the thicker looking side is thicker looking because they machined it shorter and the piston is symmetrical like Tom said, then it probably belongs on the minor thrust sided. Doesn’t sound to me like the pistons are non directional if the skirts are not identical. Fwiw Last edited by Jay S; 06-05-2021 at 01:02 PM. Reason: Ere |
#7
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The top down shot of those pistons ( if taken close to being centered) really looks to me like the pistons have valve notches for both early and late heads due to the notch off set.
You set them up on the rods for the heads you are running (since there’s no Wrist pin off set )that being 20 or 14 degree, very efficient and clever by CP!
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#8
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Quote:
Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#9
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If the OP is talking about the under side of the valve relief, then I would think the thicker area would be for the intake valve. Manufacturer leaving more material for the intake valve relief due to the valve being larger and the relief for the intake valve usually being a deeper cut in thw piston.
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#10
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Quote:
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#11
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If the Op will confirm that the valve notches are cut for both early and late valve inclination heads then whatever difference there happens to be in thickness of that corner material is a 100% moot point!
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#12
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Valve notches look to be the same both sides all are .168-.170 deep. the thick area I知 talking about is mirrored from the L to R pistons. See picture.
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#13
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The other picture was an optical illusion, No 389/421 valve reliefs on those CP pistons.
Thanks for the better pictures. Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#14
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Yup, far different then in that first photo!
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#15
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Quote:
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#16
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GLAD IT STILL APPLIES TODAY WITH THEIR STUFF.
I talked to Barry & Snake at every PRI show held in Florida back in the days when Bob, Frank, I, the Butlers, and the guy who used to make the cast iron round port manifolds worked that show every year. Promoting Pontiac HP New Parts. Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#17
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Anyone have a good guess of the cc on the pistons?? I知 thinking 16cc I never did check.
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#18
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Looks like a TRW stock replacement valve relief which would be about 6.7 cc.
__________________
1967 Firechicken, 499", Edl heads, 262/266@0.050" duration and 0.627"/0.643 lift SR cam, 3.90 gear, 28" tire, 3550#. 10.01@134.3 mph with a 1.45 60'. Still WAY under the rollbar rule. |
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