Has anyone ever look in their cylinders with a bore scope?..

TVR Beaver · Post by **TVR Beaver** » Wed Apr 30, 2014 3:27 pm

Has anyone ever look in their cylinders with a bore scope?

I’ve been complaining about oil usage since my re-build winter before last.. It’s doing about 1500 miles per ltr so is not as bad as some 5 ltrs but I’m still not keen… I had a look the other day and you can see a gloss of oil / fuel on the piston crowns and left long enough after a hot run, it runs down and pools in a small pool at the bottom of the piston dish.. all pots the same.
I also put the scope down the inlets having pulled the plenum off and the back of the valves are also oil covered….

The inlet valves have some burnt on crud visible (about 2500 miles since the re-build) but the pistons are quite clean and what’s on there does push around with the bore scope. I’m actually surprised that oil can live in there without being burnt to a crisp?

So, where is it coming from… the hone looks good and I thrashed it to bed the rings (IYKWIM), does not look glazed and why should it as I used mineral? there are some minor surface scuffs on the bore on the thrust face. The bores I know are top limit but the ring end gaps a bit big but not huge… the recirculation system put’s very little out as the plenum is quite dry so has little blow-by (you can feel it’s not blowing much from the flame trap).. the CR’s are great and all constant… the oil pressure is high so the rockers are not shot spewing oil out onto the stem oil seal.. and the seals are new… guides also were okay when the heads were re-built… and although it is a tad rich, I’m sure it’s not over-fuelling that much to wash the bores?…Plugs look fine…. Also no trace at all out of the exhaust on start-up / running or over run…so it’s a bit of a mystery…. I’d hate to look in one doing less that 1000 miles per ltr it must have loads of oil in there… !...

Anyone looked or had anything like this

Post by **katanaman** » Wed Apr 30, 2014 4:20 pm

What were your piston to bore clearances like? I did an engine a few months back (not a v8 ) that ran fine, compression was fine but it burnt oil. The end gaps were OK as well. When i striped it down I found it was the piston to bore that was out. New pistons and a hone and it's all good now. Hopefully it isn't the same as yours but you should know your clearances on such a fresh build. 1500/1lt isn't perfect but I have seen worse especially on Volkswagens who seem to think 1000/1lt is perfectly acceptable!

ChrisJC · Post by **ChrisJC** » Wed Apr 30, 2014 7:36 pm

Is it all cylinders that do this?

Chris.

TVR Beaver · Post by **TVR Beaver** » Wed Apr 30, 2014 8:42 pm

the gap was on top limit... but that said, people run a lose engine .001 thou over and they don't use oil?....
why would the gap cause it to use more?.. its the rings that stop it going north?

And yes.. all cylinders the same

SimpleSimon · Post by **SimpleSimon** » Wed Apr 30, 2014 9:32 pm

Is the hone style correct for the piston rings your using? who did it?

TVR Beaver · Post by **TVR Beaver** » Wed Apr 30, 2014 10:10 pm

SimpleSimon wrote:Is the hone style correct for the piston rings your using? who did it?

That's an interesting one? No idea?? But the pistons complete with rings came from TVR Power. And they also did the hone

But it was Dom who did the hone and it sounded like he put a right cut on (I think he stalled the machine in the first bore and had to back it off a tad. It did feal rough to me but I've since questioned it and they only use one grade of stone. Measuring the bore after the hone it measured okay. But TBH I'm not sure where they are now having worn the peaks off. That's why I'm guessing they will be top limit

Tell me more

ChrisJC · Post by **ChrisJC** » Thu May 01, 2014 8:04 pm

It could be oil from the crankcase getting in via the inlet. Have you inspected that route for excess oilyness?

Chris.

TVR Beaver · Post by **TVR Beaver** » Fri May 02, 2014 6:39 am

ChrisJC wrote:It could be oil from the crankcase getting in via the inlet. Have you inspected that route for excess oilyness?

Chris.

As I say above, the plenum is nice and not a lot coming out of the flame trap (oil / water of gas)... pipes are very good.. you can stick your finger in and its not pick much up when you pull it out

Darkspeed · Post by **Darkspeed** » Fri May 02, 2014 1:06 pm

If you have discounted everything else I would be checking the bores for ovality.

If the crankcase pressure is low, the rings are gapped right, and the stem seals are all good then that is all that is left.

Andrew

ETA

A silly thin oil could also contribute

TVR Beaver · Post by **TVR Beaver** » Fri May 02, 2014 7:13 pm

Darkspeed wrote:If you have discounted everything else I would be checking the bores for ovality.

If the crankcase pressure is low, the rings are gapped right, and the stem seals are all good then that is all that is left.

Andrew

ETA

A silly thin oil could also contribute

May be... but it was okay before the re-hone and new pistons and rings? why would a hone make it oval?... oil is 20-50...

DEVONMAN · Post by **DEVONMAN** » Sat May 03, 2014 8:36 am

Were the oil control ring gaps positioned correctly relative to the compression ring gaps

TVR Beaver · Post by **TVR Beaver** » Sat May 03, 2014 12:00 pm

DEVONMAN wrote:Were the oil control ring gaps positioned correctly relative to the compression ring gaps

??... I put them in at 1/3rd around the pistons... but who knows where they are now.. the rings rotate in use....