Roger wrote:Oh dear Dave!
Duncs suggestion has merit, but if not, did you change the rings at the last build or did the same ones go back in?
If you can convince yourself its not valve related, if it was me and nothing looks amiss, another set of rings, bosh a ball hone down the bore and reassemble.
One thing though, did you get any mileage smoke free? The way it reads is that it was OK to start with.
Did you ever measure the piston to bore clearance?
yes piston to bore clearance was measured but not by me.
I can snap gauge the bores to look for inconsistency but I don't have anything big enough for a piston. well not in the correct place anyway
something is amiss
I got some mileage absolutely trouble free...
first 200-300 on the first set all ok
random spells on the second set all ok. really quite random, or smoke production was linked to certain temperature, conditions or RPM
on occasions where I ran it at speed and cut the plugs I got a good clean indicator that all was ok, nice band on the earth. plugs looked great
then later in the same journey if it idled for more than a few minutes I'd get a puff of smoke and it would start to falter
I'd get awful smoke on start up 60% of the time, but perfectly clean on others but on many occasions it just stayed
if I checked the plugs after stuck in traffic matt black
so given recent expenditure and care on the stem seals
initially only on inlets
then new on exhausts
then to totally replaced all
it must be rings/ring-cylinder wall
either overburdened with oil (dipstick depth consistent with 2 others)
snagging and sticking in the lands??
or I have knackered the bottom ring rails or expander some how
method on both occasions was the same. standard ring clamp
oiled
done up decently tight, but not stupidly tight
tap the piston down with wooden block. while holding ring installer level and in the slight chamfer at top of hole, making sure it didn't scroll out and jam the piston
I think on the first occasion I probably caused ring and stem seal issues while running in cam and then fighting to tune a set of carbs with too small idle jets (wrong combination of air flow and fuel flow promotes rich or lean somewhere up to 3000 rpm if you want it to idle), a whole complement of bore wash and oily varnish baking in
on the second the assumption was rings OK must be gasket and stem seal issue
but same issues with trying to get it to run. got decent ring seal second time possibly due to using proper break in oil. I had used standard mineral based 20w50 first time round
Compression tests indicated decent compression 185-195 across all 6 after 100+ miles
by 500 it had dropped to 165-175 on 3 cylinders with consistently worse plugs .
oil smoke less with break in oil sae30
awful once I moved on to standard 20w50.
I need to taking my time and not hurrying to do this
i'll dig out my build diary and check everything again.
one thing to note
2 different sets of E642k-20 rings side by side illustrated that checking the first set of rings the inner diameter was bigger. i.e the amount of ring material when viewed from above resulted in a narrower ring. top had dots middle had chamfer inner edge, bottom
expander was 2 rails and standard in-out zig zag with interlocking ends
I had ring seal problems with all rings after spanking it to 5k up the strip . was ok before I did that or appeared to be ok with 300 miles on it (see I was a silly boy)
second set
fatter rings i.e the hole in the middle was smaller, probably couple of thou ( but enough to be noticed by eye when one next to the other) when viewed from the top. all with dots on, middle ring has chamfer to bottom inner edge
now you would NOT pick that difference without 2 sets of rings side by side
expander was like none I'd seen before, up and down zig-zag with tangs to pick up on the rails, could have put them on wrong but to be honest that's hard to do.
both sets were unopened retail boxed sealed power rings.
either way my own clumsy analysis of the situation on each occasion is probably the biggest contributory factor.
oil smoke I expected to be blueish, fuel smoke I expected to be black coolant or brake fluid (I have no booster) I'd expect to be white
all smoke has been white and nasty, looked like dry ice, but horrible (bad-head sore throat nasty)
the original package of pistons and rings from summit had standard LA 318 rings. all fit except the oil scrapers they admitted their mistake and sent the appropriate Jeep/truck/ later/318 and V6 rings with a thinner scraper E642K-20
and you can not make that mistake the fatter oil scraper does not fit the piston at all, its way too fat.
didn't dig it out this weekend
I made brake pipes instead
dave