[Formulabruce]

This is a STOCK Bore 400, with its Born with pistons. It is the earlier style of
Piston WITHOUT the top tapered edge you see on say a '76 400 that looks similar. So, What is the original CC of this Piston. ( we are NOT discussing its location at TDC) . Thanks for your exact info, or educated guesses.

[b-man]

6.7ccs.

[Formulabruce]

Originally Posted by b-man

6.7ccs.

Thanks! The recessed button had me thinking it could be more, but now I know, !

[Pontiac Derek]

If that is a stock engine it’s never been machined can you measure how far down the piston is in the bore at top dead Center? I’d like to know

[25stevem]

Dereck, 389 and 400s should be .023” according to a factory chart and a 455 is said to be .013.
With factory machining tolerances on rod center to center, piston compression height , crankshaft stroke and deck height I would say that these factors could make for the .023” and .013” numbers being ,010” larger or even smaller.

For example factory tolerance on the connecting rod center to center is said to be on there blue print 6.623” to 6.627.

I don’t know what the tolerance would be for 421s and a 428.

[Formulabruce]

Originally Posted by Pontiac Derek

If that is a stock engine it’s never been machined can you measure how far down the piston is in the bore at top dead Center? I’d like to know

I have to borrow a "bridge" from a buddy. I will let you know. Its all stock 1970 400.
Caliper says its less than .023, so I will verify.

[Pontiac Derek]

Originally Posted by Formulabruce

I have to borrow a "bridge" from a buddy. I will let you know. Its all stock 1970 400.
Caliper says its less than .023, so I will verify.

Thank you I appreciate that

[steve25]

If the OP really wants to get focused more on what the CCs are then calculate what the volume of the big factory taper is on the top of the Bore to guide the rings in.

It looks to me like it's atleast.130" tall.

The first part of the displacement formula would then be 4.125" x4.255" by my guess.

[Formulabruce]

Originally Posted by steve25

If the OP really wants to get focused more on what the CCs are then calculate what the volume of the big factory taper is on the top of the Bore to guide the rings in.

It looks to me like it's atleast.130" tall.

The first part of the displacement formula would then be 4.125" x4.255" by my guess.

The OP is trying to determine if the original advertised CR is the actual CR on a original, not worn, engine. There is only .001 taper in 3 inches.

[mgarblik]

Originally Posted by steve25

If the OP really wants to get focused more on what the CCs are then calculate what the volume of the big factory taper is on the top of the Bore to guide the rings in.

It looks to me like it's atleast.130" tall.

The first part of the displacement formula would then be 4.125" x4.255" by my guess.

I think what looks like a very large taper/chamfer at the top of the bore is an optical illusion. Only Chrysler blocks I have worked with have a chamfer approaching 1/8". Seems like most Chevy and Pontiac blocks, they break the edge and maybe chamfer .030".

[steve25]

Opp's Sorry, that's where the ring travel stops.

[Formulabruce]

Originally Posted by Pontiac Derek

Thank you I appreciate that

Here is the evidence. Block and piston clean. Block has some dark between the broach marks, but its flat and level.

[Pontiac Derek]

Perfect, thank you!!!

[steve25]

Close enough to dead on factory spec ( .023" ) for me!

In fact if you had not yet tapped the Bearing clearance out of it very well may be 100% dead on!