cylinder bore

[fts1966]

what is the factory bore, our car has 3.945 i'm wanting to get started on the rebuild and machining

[nick c]

3.875"

[fts1966]

so I have the original pistons then, can i go up in rings and keep my pistons?

[nick c]

Did you measure the bore with an inside mice? did you measure the outside of piston just below the bottom ring?
If the bore is 3.945" and the piston is stock 3.875" then the clearance is .070"
On a new rebuilt engine the clearance between the piston and cylinder is .0035" to .005"

[v8fordman]

Short answer...No. I'm assuming you are saying the pistons are standard and you want to know if you can put oversized rings on them and things will be ok. No. Your numbers indicate you have .070 wear in the cylinder. Have it re-bored to .080, buy pistons and rings to fit the new bore...finish the rebuild and have a great time with a fresh engine.

[Kurt in NJ]

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I have seen .040taper, still standard at bottom --original pistons with expanders, you need to measure at the bottom too
If you don't have the measuring tools measure the end gap of a piston ring, move it to bottom ,measure gap, 1/3 of the difference will be close to the taper

[updraught]

Originally Posted by fts1966

so I have the original pistons then, can i go up in rings and keep my pistons?

Not sure how I know but you will have about 50psi and some blow by and some oil burning. A few links from Google.
https://www.hotrodders.com/forum/ove...glepost11.html
https://forums.aaca.org/topic/324870...omment-1863525
https://www.youtube.com/watch?v=Wadmzv1Vs0Q

Those NZ'ers know a thing or two.
https://www.youtube.com/watch?v=hXc3iXGucFs