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MG MG Y Type - Water in the oil (cont.)

Further to my previous post on this subject, following a long layoff from Y types (due to keeping the distaff side content through decorating and gardening etc!) I have now found the source of water getting into the oil. It is from a leak between the cylinder liner and the block on No.1 cylinder. This was found by filling the waterways with soapy water with a red dye added, sealing off the water ways and pressurising via the water pump. only a very low pressure (<20 p.s.i.) was enough to show the leak (see pic). The worry is, if water is coming up, is it also going down under pressure? The possible reason is that the liner is undersize.

Advice in my previous thread suggested "Steel Seal" with good report. However, locally, opinion suggests that it may not be a long term permanent repair, with a long tour planned my confidence is low. So my bottle will go into the boot as a "get me home" measure.

So the block will have to go back to the machine shop and have new larger O/D liners fitted.

The question is in three parts.
(1) NTG sell a 1350 liner which I presume is larger O/D to account for the possibility of breaking into the waterway, before using 1350cc pistons.

Brown & Gammons sell a liner 71mm O/D.
The B&G liner bore is only 0.5mm smaller than STD (66.5mm) so I may need larger pistons than my current STD, (+0.02"?)
So, is it worth going the full hog and boring out to 1350cc ? (I already have a new set of +0.1" 69mm pistons)

(2) what is the difference (pro's - con's) of solid skirt versus split skirt pistons? the current STD pistons fitted are split skirt 4 ring, my +0.1" are 3 ring solid skirt.

(3) If I go the full hog to 1350cc what is the possible effect on the crankshaft? with the increased compression ratio approx 9.5:1 (it is already -0.06" ie max regrind about 6000 miles ago), I understand that it is vunerable between front main and No.1
the crank came out of the factory already at -0.04" according to the brass plate on the side of the block (engine no. matches the guarantee plate)I would like to keep the original block

Apologies for the Epistle and any advice would be very much appreciated.
Best Regards
Dave





D P Jones

The soild pistons should be a little lighter and because of the three rings they produce less drag.
I read that you can ditch the bottom ring on the four ringed piston to reduce the drag and I would have done so on my engine if I had read that earlier.
Willem van der Veer

Dave: I've never heard of coolant leakage from around the liners - is the affected liner/bore one that has been re-linered already? I had a cylinder relined after a circlip failed and the gudgeon pin scored the cylinder wall, but no subsequent problems occurred - you might have suffered sloppy work from the machine shop here. But it does sound like a new liner would be the best long-term solution.

As far as increasing the capacity of the engine is concerned, I think the key thing to remember is that the weak link in the power train, assuming you have a YA, is always the rear axle - specifically the half-shafts. So if you increase compression to 9.5:1 with a cubic capacity of 1350cc, with ignition/carburation upgrades to match and modern fuel, you will be looking at a power output probably 20% above the original figures. Good for those days out with a heavy load, not so good for the reliability of the drive train.... I'm sure we'll be interested to hear what you decide to do!
Tim Griggs

The half shafts are no problem Tim [see image] Snatch loading is the problem such as suddenly dropping the clutch, or cornering on two wheels. changing left for right shafts is asking for trouble, but by gentle driving they should last 100K even with an occasional caravan in tow.

My engine has been running 8.6 compression since 1960s Bryan

B Mellem

Dave,
I have had experience with exactly the same problem. My brother's race TC and them his T Tourer both had liners which went through into the water jacket and leaked into the combustion chamber. Strangely neither seemed to have any problem or leakage while running. It was time standing in the shed or on the trailer which caused a cylinder to fill with water. When this happened the engine would not turn over due to hydraulic pressure above a piston. We replaced the block on his race engine because it also developed a large (unrelated) external crack. His Y Tourer seems to have responded to use of "Bars Leaks". In fact the (very well renowned) engine machinist company suggested "Irontite" when he found that he had hit the water jacket in a fairly major way, before the symptoms occurred. I tested the block with similar technique to your photo except I used air and soap solution. I suspect from your photo that you have a much worse leak. I understand your concern. I wouldn't want to take off across a desert wondering if the "Bars Leaks" will hold.

I should say it is an unusual problem. (My brother was unlucky.) Many T Types have had a liner fitted due to a rod going through the side etc. Very few have problems unless the liner was fitted too loose or the machining was rough.

Re the pistons. XPAGs originally had solid skirt pistons. They are stronger but a bit noisier as they need a bit more clearance. Race engines MUST have solid skirt pistons.
Bob Schapel
R L Schapel

Had the liners taken out today, the problem is obvious each one was a push fit instead of an interference fit, held in by Loctite or similar. No.1 bore had penetrated the waterway and the sealant had failed. Now I need oversize liners.
D P Jones

This thread was discussed between 07/12/2014 and 30/01/2015

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