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MGB The state of my engine -- need some opinions

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drooartz

drooartz

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Been doing some diagnostics on my MGB engine, to figure out if I'm going to do any work on it this winter. Now's the time to make a decision, as I need the car for a trip in May and given my pace of work I'd need to start soon if I have work to do.

Oil pressure: 60ish cold, 40-45 hot depending on how hard I'm pushing the car, can drop just below 40 if I'm pushing hard up a mountain road, climbs back up once the oil cools. Running 20W50

Compression (cold): 110-125-130-130
Compression (cold, wet): 120-130-140-140

Car seems to be running fine other than the (by the book) marginal oil pressure. I've no idea if the power is as it should be, as I have no experience with any other MGB. Leaks a bit more oil than it ought, but it's not the Exxon Valdez.

Thoughts?

I ask as I have no long term experience with these cars, so no frame of reference for what is "normal" running state. Performance hasn't changed in the 3 seasons I've driven the car. Generally runs better now that the dizzy and carbs have been rebuilt.
 
Not an MGB expert, but in general to me this sounds like an ordinary, mid-lifetime engine. If it were mine, I wouldn't worry about it unless it wasn't running well.
 
Drew, did you ask Hap? I am sure he'll chime in....
 
Going to call Hap this week.

Just learned that compression readings need to be corrected for altitude (I'm at 5550'). Makes sense.

So new corrected readings are:
129-146-152-152 dry
140-152-164-164 wet

Those corrected numbers are much closer to the numbers in my notes from the previous owner (taken close to sea level). I know that the difference betwen cylinders matters more than the absolute numbers, but I was thinking a bit about the drop from earlier readings in the notes. This makes more sense.
 
Worry-wart! Drive it 'til it breaks! :smirk:

Seriously, your description and those numbers make for an enviable engine condition for lots of folks. Save your money for a trick rebuild.

Mickey
 
Drew, Your engine isn't that bad. As Mickey said, Drive it! I would only be concerned if the spread between the high and low compression check progressively gets bigger in a short period of time. Nothing wrong with the oil pressure on a high time engine either. If there are no knocks, loose bearings, you can hear, drive it as you would any engine. The 1800 series engine, I guess that's what you have, is pretty much bullet proof! They'll take a tremendous beating before giving up. When they finally give up, they just slowly die. If they ever left you stranded, 99 times out of a hundred it's ignition/electrical, then fuel, in that order, not the internal workings. JMHO PJ
 
The compression numbers don't seem out of the ordinary, the oil pressure is about right for the B engine after a few years' running.

There's no crystal ball but I've only had one 1800cc MGB(GT) "grenade" itself with no outward sign of trouble. A quick count of the ones I've personally owned (or relatives owned and I was pressed to be responsible for) is seven. The number I've serviced and/or rebuilt for others while working at a shop is a LOT higher. Most of the time they will give you PLENTY of notice there's something wrong. Rods will knock perceptibly, compression will vary distinctly, tailpipe smoke, etc.

Run it 'til the time comes to swap it out for the rebuilt unit. If it helps assuage your concerns, toss an applicable amount of some 'snake-oil' in with the next oil change, the Lucas stuff comes to mind.

Do you have an oil cooler mounted in there? If not, that may give you a worthwhile "project" for now.
 
Th higher wet numbers would indicate some ring leakage, I tend to agree with the others, just a engine with a few miles on it. If you desire something better than this, maybe a good approach would be to drive on this engine, and get another engine core, and build that, as you are driving on this one.
 
Probably heresy to say it but, Lucas engine oil stabilizer makes my engine just a little happier - and the pressure just a little higher.
 
Mickey Richaud said:
Worry-wart! Drive it 'til it breaks! :smirk:
Click to expand...

It's truly not a question of worry, but one of lack of experience. I've only owned two running old cars in my life (the Tunebug and this one) so have very little frame of reference for what is normal for them. My favorite part of shop manuals: "remove part, check for wear, replace if necessary" -- not very helpful for us guys just starting out that don't know what "wear" looks like. :smile:

DrEntropy said:
Do you have an oil cooler mounted in there? If not, that may give you a worthwhile "project" for now.
Click to expand...

There is an oil cooler installed, though of unknown age.

Hap Waldrop said:
Th higher wet numbers would indicate some ring leakage, I tend to agree with the others, just a engine with a few miles on it. If you desire something better than this, maybe a good approach would be to drive on this engine, and get another engine core, and build that, as you are driving on this one.
Click to expand...

Thanks, Hap (and all) for the take on the engine condition. With my recently purchased Bugeye, the plan for this car has altered somewhat. Right now the MGB is in drive-it mode as the limited resources need to be focused on the Bugeye. If I don't have to mess with the B, I won't.

Thanks all for the advice, much appreciated.
 
JPSmit said:
Probably heresy to say it but, Lucas engine oil stabilizer makes my engine just a little happier - and the pressure just a little higher.
Click to expand...

JP, It's just the British coming out! :highly_amused: PJ
 
Just a comment about the oil cooler: most MGBs have them (from the factory) and many of the ones I see are original. Oil coolers are particularly good at trapping sludge and gunk and they're impossible to clean properly. At some point, it's a good idea to replace them (I'm in the same boat.....mine's not original but I'm not sure how old it is). Replacement coolers aren't too expensive: Moss sells them but you can also find them for good prices at discount catalogue places like Summit Racing and Jegs. You might see a slight improvement in oil pressure if the cooler is very old and partly plugged. By the way, I have similar pressure numbers in my 70,000 mile MGB (I renewed the rod bearings, rings and lifters while the engine was in the car.....but all else is original).
 
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