Thanks Bob, you're right about the end gap...manual states .008 - .014 as
ideal. Ring mfg states .025 is fine. I may have to try .040 rings and file
them down. OTOH, the rings I pulled out of the perfectly good running
engine had an end gap of .022.
Piston is within tolerance in the bore. Measured bore after hone was .031,
so not much change from prior to rebuild.
New valve seals going in this weekend and hopefully that will do the trick.
Put another 50mi on the car and smoke is getting worse if anything.
Thanks again.
Gordie
Are you certain on your ring gap numbers. As I check my shop manuals I find
numbers for the ring gap to be from .008 to .013. Your rings with a gap of
.023 are .010 too great. They will continue to use oil because they are too
loose. You should be able to drop the pan, pull the head and do the pull
the pistons with the engine still in the car. Be certain your next rings are
within specs, and it would not hurt to get cast iron rings for a quicker
seal.
You may also want to check to be certain that the piston is not too loose in
the bore. Pistons that are too loose in the bore will slap and rock,
allowing oil past the rings. It does not do the bores much good either. For
MGAs the proper clearance for a piston is, at the top of the skirt, .0035 to
.0042. More than this and you need to either re-bore or be certain you are
using the proper sized pistons.
Good luck in solving this difficulty.
Bob Shaw
On Aug 3, 2006, at 6:47 PM, Gordie's Garage wrote:
> Okay, I'll try and stir something up.
>
> Steady blue smoke, obviously oil burning.
>
> History...1622 with supposedly only @50k miles was bored to .030 upon
> disassembly, no ridge, no need to go any larger, just a hone.
> Pistons in
> good shape, gaps all looked good. Crank turned .010, new cam bearings
> with orig cam. Head was re-done with hardened seats and hot s*it
> valves, but stock valve seals. It was assembled and driven for 3k
> miles. Dry compression upper 130's all cyl, wet compression upper
> 170's, all cyl.
> Conclusion, rings never seated. Motor had to come out anyway as trans
> had a problem (turned out to be a cracked 3rd gear syncro)so re-hone
> and do it again. Discovered rings with a .030 end gap, way big. Re-
> assembled motor, all new bearings again (not cam), just because, and
> shopped rings this time and found some with only .023 end gap. All
> other gaps well within book tolerance. Oh, for the record, my machine
> shop assembled crank and pistons in the block, and I completed, the
> first rebuild. I did all of it the second.
> Well, now have @ 70 miles on second rebuild in 6 mos and steady blue
> smoke.
>
> I'm think'n valve seals. Ordered ST-2001 from rockauto.com via info
> from Barney's website and plan on installing this weekend.
>
> Any other ideas before I begin taking it apart again?
>
> Safety Fast!
>
> Gordie Bird
> '62 MGA with a sick motor
> '67 MGBGT
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