How far can you bore

[pittss1c]

I have seen some posts that sounded like cylinders at 65.5 weren't worth boring or indicated that it was the last bore...

I see Weisco makes pistons that go to 66.5, so what are they for then?

 

I have some jugs with damage (no sharp scrapes, but I can feel deformation) and the pistons currently say 1.50 on them...

I'd hate to have to start from scratch (since these are already ported for a 4 mil wit a long rod)

 

What is the real story on how far to bore?

[sToCk7miLL]

I have seen some posts that sounded like cylinders at 65.5 weren't worth boring or indicated that it was the last bore...

I see Weisco makes pistons that go to 66.5, so what are they for then?

 

I have some jugs with damage (no sharp scrapes, but I can feel deformation) and the pistons currently say 1.50 on them...

I'd hate to have to start from scratch (since these are already ported for a 4 mil wit a long rod)

 

What is the real story on how far to bore?

 

are they stock cylinders or do they have big bore sleevs?

 

i have a stock cylinder 7mill thats sleeved for big bores.. i got 67.25mm pistions and i could probably go to 70mm easy -73mm max.

[pittss1c]

this is the first tear down after I bought it, so I don't know 100% what I have. I expect to know everything by the time I am done though. It looks like the engine was pretty stock before he put the 4 mil in, so there is a good chance they are stock cylinders. Any guidance on how I could answer your question better would be welcome.

[Bansh-eman]

66.50 makes your bore .100 over stock. By then, the walls are so thin it is pron to failure. Most people will replace the cylinders at .080 over.

[pittss1c]

Help me understand the math first... I have 1.50 pistons (65.5mm) isn't this 1.5mm over ~=.060 of an inch (not .100)

 

Also, who then uses the other banshee pistons... 66.00,66.25,and 66.50 (or in my case with a long rod, the 66.00 pistons)?

[papa_smurf49319]

ok just outta curoisty, ive got a set of stockers that have a passion port on them, there at a fresh 40 over. Would it be more economical to sleeve them when i do reach 80 over or just replace them? I know the sleeves would have to be cleaned up for the porting and all that jazz, just wondering what most guys do. I have no idea how much sleeves cost or any of that. Not trying to thread jack either, trying to open another door for the poster.

[Bansh-eman]

Pitt: What kind of pistons are you running? If they are aftermarket i.e. Weisco, they have more numbers on them then 1.50, if your running Wiesco post the full number and it will identify the series piston and bore that your running. Each bore size being .010 is 1/4 of a MM. So a stock bore is 64mm. a psiton that is .040 over would be a 65mm bore.

 

 

Papa: The likelyhood of you still having that same setup by the time those things reach 80 over is unlikely, that is of course assuming you dont have a catastrofic failure that causes major cylindr damage making you need to bore sevral sizes at once. The cost to re sleeve and then have them ported will run you about the same amount to find a set of stockers and just have them ported. But my bt is you will go aftermarket cylinders before then.

[pittss1c]

The only markings on the top are 1.50 and an arrow.

The inside of the piston has an HR on 1 side, and the other says S1 I believe.

 

I assumed this is a hot rods piston. (should be a stroker model) that is +1.5. (I could measure the bore this weekend)

So this should be .060 over (1.5mm/25.4mm/in)=.05900551....)

There aren't tight scratches in the bore, but you can feel the deformation above the exhaust port with your finger.