MGB & GT Forum

I have a 3 main 18G engine out of a 64B. I pulled it a few months ago because of poor compression in 2 and 3 cylinders. 110 in 2 and 90 in 3. I don’t remember what 1 and 4 were other than they were much better than the other 2. The oil pressure was solid at about 60lbs cold and 45lbs when warm. I switched the head with a recently rebuilt one that I had used on another engine and the compression numbers did not change. There was no visible damage to any of the cylinder walls and I could not feel a ridge at the top of the cylinders. I did not do a wet test. I guess I could, the engine is still all together but I’m not sure that matters for what I’m asking.

And that is:

Can I pull all 4 of the pistons, replace the rings and rod bearings? I mean I know I CAN do it but is this something that is done to fix this type of problem?

I think that the engine has a lot of life in it based on the oil pressure and the compression in 1 and 4. I just don’t think a complete tear down and rebuild is necessary.

Am I wrong?

Based on that oil pressure, I'd say the engine is worn out and needs examination and attention. You can do the rings and rod bearings, and the bearings should help your oil pressure. I predict you will see lots of wear on the rod bearings. Give the journals some scrutiny as they may have wear and scoring too.

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Friends talking around a fire is the history of mankind.

Noble,
I think you are on the right track. Have someone (or yourself) inspect the crankshaft journals for dimensional check.
If this works out in your favor follow your plan of attack. The only thing I would add is to measure up the oil pump & hone the cylinders.

B

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Life's most persistent and urgent question is, "What are you doing for others?"

I have used this approach in the past for a budget refresh and it has always worked out well. As Bruce says, do relap the oil pump cover if it needs it. My only suggestion would be is to replace the rod bolts. Learned that the hard way.

You'll need to hone the cylinders, if you want the new rings to seat. A little harder with the crank in the way, and a dirty way to do things, but people have done it for years.

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Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com

You say you have the engine out of the car. This is the ideal time to completely disassemble it and repair it right. If you are sure the recently rebuilt head is in good condition then you can save the expense of re-doing the head. The bottom end rebuild wouldn't cost a lot more than trying to refresh it with new rings alone.

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Eric Russell ~ Mebane, NC
1961 MGA #61, 1981 Alfa Romeo GTV6, 1984 Alfa Romeo Spider, 1991 Honda ST1100

Unless machine work is needed and the cam and lifters are shot. Either way, they are what they are and should be inspected.

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Friends talking around a fire is the history of mankind.

I was thinking about this. How about flipping the block upside down and going up?

I always stuck lengths of masking tape in the sides of the main journals and taped the rods and covered the whole of everything else with towels, rags, etc. Carefully removed afterwards.
Used half STP, half oil for reassembly lube, sticky and slippery.
Used to do this type refresh every 25,000 or so with mine, always made good oil pressure and power afterward, took a weekend.
Chris...

I think more of a concern will be the post hone washing. This wants to be done thoroughly, soap & water with toilet brush, more than once that sort of thing.

Keeping the crankshaft free of this 'hone pollution' is paramount and probably not easy.

I know this was not the question, and it reads as if I am spending your time & money, but if you have the bottom end gasket set, why not just remove the front & rear end plates and take the crankshaft out. You will have the torque wrench out anyway.
Replacing the main bearing at re assembly will be a bonus. FWIW I just did exactly this 'refresh'.

B

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Life's most persistent and urgent question is, "What are you doing for others?"

Don't let anyone talk you into replacing that cam unless they can show you why. The original cam was very durable. My dad's '63 has had two engine refreshes & is still using the original cam over 200,000 miles later.

It is still gonna get in the block cavity, and then you have the dodge the main webbing as well from that angle, not to say it cannot be done with a diggleberry or expanding cheap stone hone, but not easy wya to do and control cleanliness.

I'll add this too, things needed to be measured, inspected really good like the cam and lifters, cam bearing, condition of the pistons and their ring lands etc., etc..I always tell folks, the engine tells you what it needs, not the other way around.

Mot of the time, this is either a budget deal, or experience choice, or both, just make sure you check it out all good, and not ignore the obvious, it OK to frugal, I am on my own stuff, just try to address what tells it needs addressing and don't think your eyes are precision measuring tools, because doing it twice always cost more in both monet and frustration.

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Hap Waldrop
Acme Speed Shop
864-370-3000
Website: www.acmespeedshop.com
hapwaldrop@acmespeedshop.com

I hate it when I sound like my Dad... but here's my best impression: Son, there's a right way and a bunch of wrong way's to do almost everything... but, if you have the choice, why not do it the right way?!?

This is an interesting thread.

In the old days, right Steve? my dear old Dad kept Austin & Standard on the road for years with just regular refresh as Noble is asking about.
Usually done over a time frame less than this thread has been running! I know I ws the garage urchin helping out.

I don't think Noble approach is wrong, but perhaps just different than some/most would/should do it. I have done exactly this refresh to a 3 main engine, (crankshaft out though) it runs great, spools up nicely, all the critical numbers are within range.

B

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Life's most persistent and urgent question is, "What are you doing for others?"

Don't screw around, pull the engine apart and measure and service whatever needs it.

I've replaced a single piston rehoning over a taped up crank at 3:00 AM to make a race the next day, but when your engine is out and it is a matter of a few gaskets and an hour or two to do it right.....and think, wouldn't you feel foolish if there was a thrashed chain, or tensioner or what have you that caused problems in six months that you would have spotted if only you'd spent the extra time to do it right?

The 3 main engine is a nice version and deserves a few more decades of use. My c. 1977 rebuilt 3 main B soldiers on in my 62 coupe to this day.

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Bill Spohn www.rhodo.citymax.com/carstuff.html
Current: 1958 MGA Twincam (race car (170 bhp)),1962 MGA Deluxe Coupe (98 bhp)
1957 Jamaican MGA (200 bhp)1965 1971 Jensen Interceptor (350 bhp)
2009 Pontiac Solstice GXP Coupe (375 bhp)
2007 BMW Z4M coupe (340 bhp)
Recent: 1969 MGC roadster (175 bhp),Jensen CV8 (375 bhp),
1969 Lamborghini Islero S (350 bhp), 1988 Fiero GT turbo (300 bhp)
North Vancouver BC