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MG MGA - Smoking Engine Solved

Hi,

Well, no wonder.

I could not figure out what my "smoking" problem was. Some may remember the thread.
Anyway, I foolishly trusted a machine shop to work on my engine without actually seeing the measurements myself.

My 40thou over pistons were fitted to cylinder bores of 3.0060 or better !!. ( specs are 2.8757 to 2.8760 for 40 thou over )
I gave these "machinists" the pistons as well. Either they over bored them or never measured them in.Needless to say they are out of business.
No wonder it smoked.

Anyway...what's to be done ??

New block...sleeve..what do you think ??



Duncan
DA MacFarlane

Duncan,
I don't know how much it costs for sleeves, but if you have a good block, and your pistons and rings are new, you might as well install sleeves, and your engine will be like new.
mike parker

Is this a 1500 or a 1600? A bore of 2.875 would be the stock bore for a 1500, so 40 over would be around 2.915. The stock bore for a 1600 is 2.968 so 40 over for it would be 3.008 or right about what you say your bore currently is. If you have a 1600, you need to check your pistons, and if you have a 1500, you could fit 40 over 1600 pistons. There are article on boring the 1500 up to 3.070. This is discussed in this thread.

http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&mode=archiveth&archiveyear=6_2003.dat&access=&subject=6&subjectar=6&source=T&thread=2003012021375415857
Jeff Schultz

Hi Duncan. That is a sad story to be sure. Cylinder sleeves are likely at least $30.00 each, plus block boring costs, and hydraulic press time. You might want to see if you can find a set of oversize pistons that would be correct for the current bore dimensions. While new pistons would also cost some coin, you would likely get a performance increase out of the deal , due to increased displacement. Hope this helps, Glenn.
Glenn

I went thru the same trouble except I got the car that way and also with a spun rod bearing. In the end since I needed new pistons was to go .060 over, I figured I could always sleeve it. You on the other hand have a problem. If you sleeve you than have to bore 40 over or buy new standard pistons,or bore 60 over and buy new pistons.If cost was a problem, going 60 over I suppose would be cheaper would not have the costs involved with buying sleeves, having them installed etc.
gary starr

Hi Duncan. Not sure if this would work or not, but years ago, I read that pistons can be chucked in a lathe, and "knurled" to increase their diameters. If you could have your pistons knurled the correct amount to be compatible with the current bores, you might get away with shelling out for only the relatively inexpensive knurling, and a new set of oversize piston rings! You might want to talk to a GOOD machinist! Just a thought. Cheers! GLenn
Glenn

Thanks everyone,

Jeff, it is a 16GA engine.

Gary ..I'm already beyond 60 thou over ( std is 2.8757 to 2.8760 )60 thou would be
2.9357 to 2.9360. And I'm at 3.0070. Hard to believe 130 thou over std.

I think that I will bite the bullet and have the block fluxed ( to make sure ), sleeved and re bored for new pistons.
I'll have to pull the engine anyway. Once it's out, I'll have it mic'd again ( just in case ). The variation ( elipse and between cylinder bores ) seems to be beyond the stated tolerances anyway.

The only other alternative is to find a standard bore in good shape and bore it out to my pistons.


Any sugesstions as to whether to go to std or oversize after sleeving ? Any particular supplier ?

Jeff - it seems that a good mechanic may be diffcault to find these days... everyone's in Ft Mc Murray :)

One person here suggested that he could do a rebuild "the right way " for $7000 !! He'd take the engine out, rebuild it and re install it !!!
I was also hoping for a free trip to Scotland.

I can get a Stage 2 for 1998 sterling in England !!

Anyway, I'll keep you posted.

Thanks,

Duncan


DA MacFarlane

I think you are looking at the specs for a 1500. According to my workshop manual, the stock bore for the 16GA is 2.968 so 40 over would be 3.008.

Jeff Schultz

I can't believe I'm reading this. I was always convinced that the smoking was due to piston blowby and crankcase pressurisation but never did I think it could have been caused by such grosse incompetence. It does however look as if you have a couple options and that you will have to work out the cheapers. I guess that you have +.040 pistons for a 1500 block in which case you could bore and sleeve the block back to this size. Secondly you could obtain a set of 1600cc +.040 pistons in which case it may be necessary to final hone the last couple of thou to suit these pistons. Whether you would need to untrasonically test the block to verify the wall thickness is in doubt but your machine shop would advise.

Now the most important thing here is to find a highly recommended machine shop and then tell them the whole sorry story. They will certainly be able to advise you of the most economical method to salvage the block but you might have to make the final decision as to whether the engine will possibly remain a 1500 or be uprated to a 1600.

I wish you well with this one as I really hate to see good people suffer in the hands sheer stupidity.
Iain MacKintosh

If you are going to resleeve the block, why not go back to standard instead of 040 over? I am guessing that the Pistons have been slapping around in this engine and may no longer be fit to reuse.
dominic clancy

That's the decision and help that the reputable machine shop will give. But remember economics in that new pistons and sleeves will be the most expensive option but hone and pistons may well be the cheapest allbeit the engine will then be over 1600cc. For a number of reasons I think that Duncan will have to decide on the final solution.
Iain MacKintosh

Duncan, sorry to here about the real cause of your problem,it sure had the rest of us guessing, and overlooking the obvious. When looking for a machine shop always get recomendations from people you trust with personal experiance on what shop to use. No competent machinest would bore a block without measuring the pistons if they are available, and then checking the fit after machining.
John H

Duncan; My 1500 has +040 1600 piston, displacment is about 1650. I would suggest you buy +040 1600 pistons. you will be money and displacment ahead. Two friends with MGB's wonder why my A climbs as well as their cars.

Glenn; Knurling raises a pattern of metal only a few thousandths of an inch which quickly wears off.
Cheers, Bill
w.g cook

He doesn't have a 1500, it is a 1600, and the bore size is about right for a 40 over 1600.
Jeff Schultz

This thread was discussed on 16/02/2006

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