billrob71

Know this is a long shot, looking for 1 standard bore 455 HC piston with V notch part number 398666.


I have a broken one

billrob71

1970supremevert

I have one for you

1970supremevert

I have 7

1970supremevert

Pm sent

billrob71

Pm back

ROCKETMAN269V

You may want to check the deck of your engine block adjacent to the cylinder that the broken piston came out of. If you'll notice in post #4 above, the piston has a "B" stamped in it at about the 4 0'clock position. This was done on Olds engines to denote the "relative size" of the piston. Pistons were made in A, B, C and D to accommodate minor differences in the machining of the blocks. It's a good idea to match the letter on the piston to the one on the block.

billrob71

Only stamp I found on it was a F

MI68442W30

the stamp is visible in your second picture C

billrob71

I’ll half to clean the top to make sure but I sure don’t see a C on my piston
can see a B on the other picture

rocketscientis

Toronado being the flagship got the best of the best A bores containing A pistons....
W -30 & associated oai cars for racing lived a rougher life at higher temps & extra clearance of a size smaller piston than bore designation was SOP.

I would be shocked if I did not have piston you reqire in Lansing Michigan



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billrob71

Ok I’ve cleaned the tops of 3 pistons and there is no stamp on the top the only stamp I have is the F for the front , part number and the GM date code

second pic is a different piston

billrob71

So which pistons were larger to smaller ?

MI68442W30

the C is clearly visible at the bottom of the picture 45 degrees from the notch on the outside of the piston not in the dished area and I can still see it faintly after being cleaned ,it is still there

ROCKETMAN269V

If the tops of all of your pistons look like the ones that you have posted I would seriously consider a replacement set. They appear to have suffered from detonation. Can you post a pic of the broken area on the first piston? If it came out of the engine with pieces missing between the ring lands, then you definitely have a problem. Factory high compression pistons weren't made to run with today's low octane gasoline and have a tendency to self destruct.

billrob71

there was a detonation problem

im putting this motor back together so I can drive my car
I’m building a 462 forge piston roller motor but want to drive the car in the mean time

the ring land was cracked and I dropped the piston and broke the side out

ROCKETMAN269V

The good thing is with replacement (read thicker) head gaskets, your compression ratio will drop to a more tolerable level. Good Luck with your project.

billrob71

Got a piston coming thank you

My question I’m staring at this piston I can not see a C on this piston , I’ve zoomed in on the picture

I can not see It

68HurstOlds2

Hey all,
Wanted to jump in here as I am looking for the same piston but when I tore down the engine I had 1 that was an aftermarket.
My number 3 piston clearly shows a C, but this is for the #5 cylinder.

Any help would be greatly appreciated.

ROCKETMAN269V

The letter designation, from the factory, is stamped in the deck surface of the block adjacent to each cylinder.

68HurstOlds2

I found a CC between 1&3 a CC between 3&5 and a B between 5&7.
how do I interpret that?

Thanks

v8al

See this thread: Stamp on the block deck

68HurstOlds2

I found the one for #1 with you help. My block is still stamped CC not just a single C.

Added pic. So I would need a C piston then.

68HurstOlds2

Learn something new everyday. #5 is the aftermarket piston, I will try and pull the part number from it and measure the cylinders.

Thanks for the help