Machined hole in top of piston. Why???

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duster360

duster360

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Took this picture from another thread. Why do some factory big block pistons have this hole in the top?

A6314EB7-05CC-4E3A-8C88-EDE0EEA74DC2.png
 
I believe that is a center drill hole to machine the pistons between centers. BTW, some SB pistons are done the same way. 65'
 
Don’t all TRW pistons have that hole?!?!
:rofl:
 
pistons are not cut on a lathe, are they? I thought they were slightly oval for expansion? Or maybe cam cut so the center wobbles to keep the piston oval shape.
 
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That is for a live center on a lathe. Piston skirts are ground not turned, oblong.
Piston was probably rough turned to size first before grinding. Also as mentioned, ring land area would be done on a lathe.
 
For whoever gave me the red X, go run the numbers, L2350 is the old TRW slugs. I have a set in my 67 383
 
You guys got it all wrong, that hole is a starter hole for pre-ignition. I would put some 2-part epoxy in there to prevent that hole from exploding thru the bottom,cuz then you have to take everything apart to properly weld it it all up.
If yur not willing to do that then make sure the compression ratio is down below 8/1 and put the 2bbl back on.And stuff a big cam in there with a very-late closing intake.
Pre-ignition is usually immediately followed by detonation; and once it starts, it sets off a chain reaction, often ending in divorce and homelessness. Pretty soon you will be contemplating death because you hate chitting on the street and eating out of dumpsters.Not to mention your azz is on fire cuz you haven't had a bath in six months.
I'm telling ya, that hole is gonna be the death of ya.
For definitions and detailed explanations ; refer to page 101; where it clearly says ; lol.
 
AJ/FormS said:
You guys got it all wrong, that hole is a starter hole for pre-ignition. I would put some 2-part epoxy in there to prevent that hole from exploding thru the bottom,cuz then you have to take everything apart to properly weld it it all up.
If yur not willing to do that then make sure the compression ratio is down below 8/1 and put the 2bbl back on.And stuff a big cam in there with a very-late closing intake.
Pre-ignition is usually immediately followed by detonation; and once it starts, it sets off a chain reaction, often ending in divorce and homelessness. Pretty soon you will be contemplating death because you hate chitting on the street and eating out of dumpsters.Not to mention your azz is on fire cuz you haven't had a bath in six months.
I'm telling ya, that hole is gonna be the death of ya.
For definitions and detailed explanations ; refer to page 101; where it clearly says ; lol.
Click to expand...

No worries. If you run those pistons, you are almost guaranteed 8-8.5 to 1 comp.
 
It's a Karman vortex ebb! That will promote vortices and distortion to the incoming air charge.
 
Are you guys saying if I drill a small hole in each piston I'll gain horsepower?..
 
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