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MG MGA - They come in threes

Hi everyone,

The gremlins have been attacking my car. First I find out I have a leaky fuel pump. Replaced it. Today I was driving down the highway at about 4500 RPM and I started hear something banging around in the engine when I was heading up a hill. It would come and go and at idle I had 10 lbs of oil pressure. So I'm assuming the bearings are bad.

Is my car cursed?

Anyway, it's not smoking and was driving fine otherwise, so I guess I probably only have to rebuild the bottom part of the engine. Is this possible without pulling the whole engine? Should I have the crankshaft looked at, or would a visual inspection be fine?

This engine was rebuilt and then sat for 23 years. Could this have caused the bearings to go bad, or did I just have a Monday morning bearing?
Darian Henderson

"Should I have the crankshaft looked at" should say "Should I have the crankshaft looked at by a machinist?"

Thanks,

Darian
Darian Henderson

I've forgotten what year your car was, but it does sound like a rod bearing failure. Not uncommon on the 1500cc engine which is noted for weak oil flow to number 3. I'd recommend getting the car up on stands and dropping the oil pan and checking the rods for clearance before I went to the effort to pull the engine. There have been plenty of engines that where just new bearings were installed and they worked fine, but I'd advise pulling the engine apart and doing a full rebuild. You may be able to reuse your pistons if the cylinders aren't worn too much, but I'd get new rings. The main reason to tear it down is to make sure all crud from the bad bearing is cleaned out of the oil passages etc. to prevent further damage to the new components.
Bill Young

Correction, forgot which board I was on. The reference to the 1500 was for the later midget engine. Still it does sound like a rod bearing failure and the rest applies.
Bill Young

Darian,

Many years ago I replaced the bearings in my 1600 engine without having the crank ground. A short time later, my crank broke just ahead of the rear main. It made a horrendous clatter when I backed off on the gas, but ran well with part throttle and had good oil pressure. I recently installed a 5-main "B" engine.

Ken
k v morton

Darian,

I'll add another "home-made" rebuild story. As a poor 18 year old, I tried a partial re-build without removing the engine - bearings, rings, and ended up with a broken crankshaft as described above. Like Ken, mine made a modes rattling noise, but still drove me the remaining 30 miles home !

What a beast !

-Chuck
Chuck Mosher

I know, the truth hurts. I put in a new distributor, had the cylinder head repaired with new valve guides, etc. and put on newly rebuilt carbs and had someone tune it up only to have the engine die. Now I'm looking at an expensive rebuild if I keep the original engine. Very disappointing.

I'm seriously thinking about swapping in a completely different engine. I don't see any harm done if no cutting's involved...
Darian Henderson

Darian,

It should be less expensive to have your engine rebuilt than replaced? I assume that machining costs are similar (should be a little less over there) but you can get a short engine rebuild for well under 1000 USD. OK I know that's a lot on top of what you have already spent, but yours is an all original car with period upggrades and full history. It's a very valuable MGA.

Come on guys, who knows a good machine shop near Darian?

That way you have a "brand new" engine. If you put an MGB block in, either you pay the same for a rebuilt unit, or you take a chance on an used unit. You could then easily be in the same position again some miles down the road.

Your car has loads of history and is really worth keeping together (in this case it does mean real value too). Don't spoil the ship for a ha'peth of tar.

The diference between a used engine block and your rebuild may be a little more than half a penny but that's an old saying and if we factor in inflation...lol

Neil
Neil McGurk

I'm curious. Why would a crankshaft break just because you didn't regrind it when replacing bearings? I could understand if it was damaged from a spun bearing, but I doubt that someone would just replace a bearing on a crankshaft in that condition. I have done several in the car ring, bearing, and valve grind, rebuilds in years past. One was even a '58 Metropolitan. (My first British engine job.) My '62 MGA MK-II with a 1622 engine is one of them. The crankshaft was not worn, so all we did was polish it up and put it back in. The block was bored .020 and new bearings and pistons were installed. All of these engines had good results. Maybe if you left worn main bearings in the engine it could be a problem, but why would you not change them at the same time as the rod bearings?


Ed Bell

Fix your own engine. It is EASY. If there ever was an engine to learn on this is it.
The only machine work is to the block, crank and rods. Check the bores. Hone if possible bore only if you must. Have the cam bearings replaced. Check the crank, polish if possible turn under sized only if needed. Check/recondition rods. Check cam and lifters, replace if questionable.
Parts list: rod, main and thrust bearings. Lifters, cam and bearings. Pistons (if oversize needed) rings. Timing chain set. Gaskets. Oil pump as needed.
From your description the crank and rods probably need the work.
Go for it. This way you learn and save money. Remember the only stupid question is the one you fail to ask.
Before assembly CLEAN everything. TWICE.
That 1622 engine is very valuable. That value is even greater if it is in the original car. Save the engine ID plate. Some "Hot Tank" cleaning methods destroy aluminum.
R J Brown

Something similar (broken crankshaft) happened after one of my dad's early attempts at a rebuild shortly after he got the car in the mid 60's. After he bought a reground crank, and had the block align honed, the basic engine was good for 20+ years excluding a later head swap due to valve recession. Since your engine was rebuilt and then not used, without any operating history you can't assume that the job was done right. Even if it was your dad who did the work.
Del Rawlins

If the machine shop that turns the crank does not radius the inside corners it can form a stress point where the crank can fracture. A crank that breaks shortly after an over haul is usually a mistake of the crank grinder.
R J Brown

Ed,

I'm not saying you will get a broken crank if you don't grind it when you replace the bearings, I'm just saying that I did. I don't even know for sure that it was related, but I suspect so. This was in 1970, and some of the details are a little fuzzy in my mind now. I would just encourage Darian not to skimp, but to do a thorough job while he has the engine out and opened up.

Ken
k v morton

Thanks for the support everyone. Right now I feel like taking this block out and shooting it. My wife doesn't care about cars at all and even she is a little saddened by the latest news. Oh well, at least it happened at the end of the trip and my son and I had a good day in it first.

There are good machine shops here. I suspect that the mechanic who worked on the engine back in the early 80's just replaced the bearings without paying attention to the clearances, though I'll never know for sure of course. I noticed that Moss and VB don't even sell bearings for .060 overbore pistons, so I'd have to find someone who's creative.

But at the risk of offending the purists, I'm thinking about a different engine altogether. My only condition would be that it would have to be something totally reversible with absolutely no cutting involved. I know this is heresy, but my idea is that I would keep the original parts in case I ever decided to sell the car (very unlikely.)

Darian
Darian Henderson

Darian

You may not need new pistons. 060 are available, so don't give up on the engine just on that basis.

A recon B engine should be a blast with your other period acessories, so I wouldn't dicount that out of hand. Bit you will need an early B pne to make it an easy job.
dominic clancy

I have always believed that with old English sports cars you should have a spare engine.
For a small outlay you can spend your time driving you car while you rebuild another engine in slow time.
This gets totally rid of that depressing feeling you have when major problems occur.
It makes all the difference to your enthusiasm if you can drive your sports car and work on an engine at the same time.
There are many engines for sale e.g. item 200200796317 on http://www.ebay.com

Mick
Mick Anderson

Darian,

No need to worry about the bore diameter, any qualified machine shop can sleeve the block.

Neil
Neil McGurk

Darian you mention bearings for an .060" oversize bore. Do you mean .060 undersize crankshaft journals?

Mick
Mick Anderson

I'm actually not sure, Mick, I just know the pistons are .060" overbore.

Thanks everyone.

Darian
Darian Henderson

Hi Darian,
since your post I have had a puncture in my 'A', the garage mechanism has broken and a large piece of metal has fallen on my boot(trunk)lid, and now requires painting, and my daily car has electrical problems. So thanks!!
Nigel Munford

This thread was discussed between 19/02/2008 and 24/02/2008

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