MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Engine over bored

Hi all,
Removed a few more bolts from the project and found my next challenge. The cylinders on my 1622 have been bored out to accept MGB 1800 standard sized pistons. The cylinder walls look to be in good shape and should be good to go with a honing and new rings. The engine was running before I took it apart. My question is does anyone know if this engine will be reliable bored out about .155 over standard? Any thoughts appreciated.
John Cline

Hi John. From your wording, it sounds like the engine has previously run for some time in it's overbored state.
Apparently cylinder wall thicknesses could apparently varyconsiderably in B series engines, and overboring sometimes caused problems where cylinder walls became very thin, and perilously close to the coolant water jackets. If your engine was overbored, and had run for some time in this condition, then it is probably fairly safe to assume that it would continue to do so. Actually, overboring of B series engines is quite common, and many people have excellent results, reliability and performance after doing so. If the engine is assembled carefully, and to factory specs, and broken in properly, the engine should end up being as reliable as any B series engine. B series engines are actually quite reliable and can be made more so, if Lucas ignition components such as points and condensor are replaced with better quality parts. You might want to check your carbs, and make sure that MGB needles are fitted. The extra displacement your engine has will likely increase it's demand for fuel. Hope this helps, GLenn
Glenn

Glen,
Thanks, that all makes sense. The car was running with a Weber and included a set of B carbs with it. The interesting part was it was running with a 1500 head. Once I find a suitable head I'm hoping to see some more power when it's all back together. The car was interesting to rebuild. It seems like there was some decent work done to it followed up pieced together stuff like fiberglass rockers, lots of filler and an MGB rear axle. So I'll be back at it hopefully finishing up the car in the next year or so.
John
John Cline

You could also take it to a engine shop who has what I believe is called a sonic tester. They can put it in each cylinder and measure wall thickness.They use it to measure core shift when building high performance engines to see if they can in fact overbore with out creating thin spots.
gary starr

John

You want an earl B head (2H-1326: casting needs no eyebrows in the block for an A engine - I run one on my 1622 engine)

see here

http://www.flowspeed.com/cylinder-ident.htm
dominic clancy

Hi Dominic,
Great site on the head. Once I get things going with the engine that's my next step. I've looked around some and found that an original 1622 head is a rare thing indeed so it's time to focus on finding a good early B head. There is a 1622 head on E-bay with a couple of cracks but everything I've read cracks can be difficult if not impossible to fix. I've seen the eyebrows mentioned other places also. Is this something a machine shop would cut in?
John Cline

Hi John. When you are re doing your cylinder head, you might want to think aobut doing some modifications. bronze valve guides, hardened valve seat inserts, (especially exhaust seats), and stellite exhaust valves will give you a head that runs perfectly well on lead free gasoline. For a bit more performance, a little light porting and polishing is good. Be sure to replace all the old tired valve springs! You might want to replace the silly stock o-ring valve seals with honest to goodness proper "on the guide" seals. If you use bronze valve guides they will require an extra 2 or 3 thou clearance, and will need to be reamed that much larger. Hope this helps, Glenn
Glenn

John,

Once apon a time I spoke to Dave at ATP who mentioned that back in the day, people would punch out the 1622 block to 1800 frequently. I'm sure that there may be some cases of casting shift that would potentially cause problems but I'm sure this is rare.

Regarding eyebrows, it depends on your block deck height and head thickness. Barney has a link on his site showing how to DIY or a machine shop can do it for you for very little additional money if already working on the block. My last block needed eyebrows due to block height flush w/ tdc (11.5:1 compression).

You might also want the stiffer valve springs if your going to spin it hard.
JohnB

Thanks all for the information and advise. I dropped the block off at the machine shop today. The guy said crank looks fine and showed me where the engine has been resleaved on the number 2 cylinder. Have pistons/rings on the way, and it's time to order cam bearings etc.. The swap meet in Wheaton Il. is coming up in Feb. I'll probabaly start the search for a head to restore there.
John Cline

This thread was discussed between 23/01/2007 and 27/01/2007

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.