Measuring cylinder bore and piston clearance

[dmc67]

ok i rebuilt a 6bolt last summer and put it in my car, well I rolled the car and got another one to put it in but under boost it would always smoke blueish black, well I changed the turbo twice thinking that was it and wasn't so now i got the head off of it I wanna check the roundness of the cylinder wall and the piston gap, I bought a N/T motor and the pistons didn't move it in as much as they do my Turbo Motor so my question is will this gauge do the job I'm wanting to do. I dont wanna spend a tremendous amount on one b/c this will probably be the only time I use it.
http://cgi.ebay.com/2-6-BEST-BORE-G...7QQihZ014QQcategoryZ58235QQrdZ1QQcmdZViewItem

Thank you,

 

[steel_3d]

That bore gauge works pretty good. If you can find one with a dial that reads to .0001" for a decent price, you might wanna pick that up. Much easier to read off of, you don't have to guess the tenths between the marks. You'll also need a micrometer if you wanna measure piston to wall clearance (I have a set if you need it).

Blue smoke could be a head issue (valve seals), it could be high oil pressure blowing past the seals of the new turbos, and probably many other things. One thing that probably won't affect it is piston to wall clearance. The piston has no role in scraping oil, the rings do. Improperly installed rings might cause problems.

Turbo pistons rock a lot back and forth cause they need to allow for more expansion at the crown from the added heat, so don't let that fool you. If you do measure piston to wall clearance, make sure you measure the piston at the location specified by the manufacturer. Where on the skirt you measure matters because there's a lot of taper in pistons, again due to more expansion near the top.

 

[dmc67]

ok thanks a ton for that post, Are you looking to sell the micrometer? How much? I was told on another forum I could use feeler gauge to check piston to wall clearance. Also is their a way to check the rings with the pistons in the car? I replaced everything back in I had to replace the crank b/c the bearings were about gone and screwed up the crankshaft SO i replaced the rings, I didn't have the right tools so I just filed them down to the same size the old rings were, Now this kinda makes me think the rings are my problem.

Danny

Any more information would be appreciated.

 

[steel_3d]

PM-ed you about the mics.

I wouldn't rely too much on feeler gauges for this. First because every manufacturer specifies a different spot on the skirt to measure clearance, and pistons are tapered.

No there's no way to check the rings with the pistons in the block.

Did you measure your ring gaps with feeler gauges when you filed them? What were the gaps? Honestly the gap probably makes very little difference in oil burning (if the first ring doesn't get it, the second one will), and this was demonstrated in a study I don't feel like finding the link for right now.

I'd be more concerned with the rings being for the right bore size. If they're undersized they'll exert much less radial force on the cylinder wall - this is the main reason worn rings start to burn oil.

I'd also be concerned with the rings being installed upside down. Not sure if this makes a difference for all manufacturers, but I know it does for Wiseco rings since the second ring has a step in its profile to improve scraping.

The oil control rings have to be stacked correctly and butting correctly, etc.

Honestly I'd look at the other oil burning culprits first, like high oil pressure to the turbo, or bad valve stem seals.

 

[dmc67]

No I did not measure the ring gap, I bought STD size rings b/c at the time I was out of money and didn't have the money to buy the right tools to check everything out. I just dont want to have to pull the oil pan and front case again if i dont absolutely have to.