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MG MGB Technical - Rebuilt engine smoking

72 gt engine pulled and renewed main / big end bearings new oilpump new rings ,head skimmed new exhaust valves new timing chain and tensioner new gaskets .
No I did not hone the bores !
But now smoking
Do I drain 20/50 oil and put in a running in oil.
Or bite the bullet and pull engine again and hone bores or WHY?
bxnsphjii

Hiya

New rings and not honing is a waste of time unfortunately.
You really need to take it to bits, hone it, and, if the wear ridges come out with honing, re-ring.

Peter
Peter Burgess Tuning

Hi BX
One of my friends had the same problem on his MGC
Rather than take the engine apart he used some kind of abrasive running in oil that wore the rings into the bore
D DODDS

An old trick for bedding in rings was to squirt telcom (baby) powder into the intake of the running engine. First though I would be inclined to run the car well loaded for a few weeks, as I have seen engines come good and bed the rings over time. don't rush in.
Denis
Denis4

My friends Dad used scouring cream in the bores of tractors with arrested running in problems....make or break.

I suppose, as I earn my living from heads and engines, I would always recommend strip and hone. I think the rings will have to work very hard bedding in to an already polished surface, let alone the risk to the top ring if there is a wear ridge at the top of the bore, the top ring, especially under load might well try and ride over the ridge and snap in the process. That is why I said hone (get rid of the ridge) not glaze bust.

Peter
Peter Burgess Tuning

I am with Peter but, with the proviso that it is also essential to remove the crud from the grooves in the pistons - particularly the scraper grove.
Roger W

I had a simlar problem a couple of years ago after a rebuild of the engine that included a rebore. It smoked on heavy acceleration and used more oil than before the rebore. Ihad used semi synthetic oil and I believe it had not been honed after the rebore. I drained and changed to a straight 20/50 and the good news is that after about 2000 miles the smoking has gone and the oil consumption is no longer a problem. So I would advise to change the oil to a non synthetic and be patient.
Trevor Harvey

That's why it's often advised to use straight 30 for 'running-in'. When these engines were built they were put on a travelling conveyor, with an oil supply and something to spin the crank. I can't remember how long they spent doing this, but I wouldn't be surprised if that used a bedding-in oil as well.

Modern engines have similar problems as they have to use modern synthetics, it was said that you had to give the K-series engines a good thrashing before oil consumption reduced.
Paul Hunt

"you had to give the K-series engines a good thrashing before oil consumption reduced"
Not my experience either of the K's we bought new, (the F had only 11 miles on the clock when we bought it) - never used a drop of oil.
But yes, I would certainly use mineral oil in a new engine.
Paul Walbran

Honing is the way to go - recommend having it done with a Sunnen vertical hone or equivalent - then fit Total Seal file-to-fit rings - then run in using a lot of engine speed variation up to 4000 rpm - stick to heavy city traffic not open roads for first 500 miles - a little oil consumption is fine.
That said back in the 60s in the Bathurst 500 the works Ford Falcon GTs put a few spoonfuls of Ajax powder cleaner down the plug holes to deglaze the bores during the great race - but their engines only had to do 500 miles.
Mike
Mike Ellsmore

Mike, You sure they weren't putting Bon-Ami down the plug holes instead of Ajax? It's far more civilized!

Charley
C R Huff

I was there at Bathurst that day as a spectator - I always thought that it went into the carburettor!

David
David Overington

Charley and David - you are most probably both correct - it was the sixties so if I remembered it correctly I wasn't there! On reflection it would have definitely been down the carburettor - not sure whether it was Bon Ami or Ajax, both have the ingredients to rough up the bore.
http://www.bonami.com/index.php/products/powder_cleanser/
http://en.wikipedia.org/wiki/Ajax_(cleaning_product)
Mike
Mike Ellsmore

This thread was discussed between 30/04/2014 and 10/05/2014

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