MGB: Sealing rear crank cap - and other issues

Hello,

I'm currently in the process of doing my first engine rebuild ever. It's my 1969 MGB which I have owned for about 4 years. There are several issues I'm wondering about.

I've been consulting the Haynes manual and it says to put some kind of sealer or some such on the rear main crankshaft capl. I presume they mean between the sides of the cap where it makes contact with the engine block.

I have two questionsconcerning that: 1) Is this really necessary? On my engine, that baby is tight. It's all I can do to soft hammer it back in. Is there really a danger oil would penetrate?

2) If it should be sealed, what do I use?



A few other small issues maybe someone with experience can advise me on:

Is it important to get new washers for the nuts that hold the crank journal caps on? If I get new ones, is there any special kind I should buy?

It appears my machine shop installed my pistons on to the connecting rods backwards. In other words, where "FRONT" is engraved on top of the piston actually faces the back. My engine has angled rods so they will only go in one way and allow the crank to turn. So I have to put the piston in with the "FRONT" engraving facing the back of the engine. Does this matter? It looks to me like the piston is symmetric with respect to turning it front or back.

I also wondered a little bit about crank endplay. I couldn't seem to get the crank to move back and forth at all. Yet it turns freely. I think there is some space between the thrust washers and the crank blades.

Thanks for any help.

As important as getting your seal on right is the surface on the crank it will run on. http://www.rlhudson.com/Shaft%20Seal%20Book/design-shaft.html if not finished correctly, you will not get the best service life and sealing out of it. Something not always considered in this project. If you find your surface is questionable, you can correct it by using a Speedi-Sleeve, available from Moss and other suppliers.

BTW, If want to know more about seals and how they work and how to install them, take a look around the rest of this site.

The rear main is "sealed" with a rubber oil seal. No "sealant" compound should be used on such.

IIRC early engines used a different type of thing, using part of the oil pan as a rear main seal (?)....and the manuals far too often do not properly differentiate between an 18G engine and a GF. Also look to see if there is an Aa section (an update to the A section on engines)

David,

First off as been already mentioned here, you had a rear seal with a MGB, so addtional sealent of any kind is needed, make sure you seal retianer than bolt on the rear engine palte is in good shape, if not get a new one. I get all my rear main MGB seal for Gordon at the B hive, he as a improved rear seal (it's black, rather than orange) and has a little tighter fit, I also has started in most cases using the Speedi sleeves on the seal are at the rear of the crank, Moss has a reat price on these, much less than my local bearing/seal suppliers, they are easy enonugh to install (just follow the instructions) and thats about the best prep you can do for a rear of a MGB as for prepoping the rear seal to ward off leaks.

The piston orientation, I I think you need to need to fix that, MGB pistons are offset. Now this is something you can do yourself, since you have the ealrier floating rods. Notice that your piston pins are secured with c-clamps, so all you need is a set of c-clamp plier to remove the c clamp and and rearrange the pistons in the correct orientation, the pisn will simply slid out, they are not press in, just use a little motor oil to lube the pin upon reassembly.

Hope this helps.

I read the same. I think the terminology in your post is throwing off the answers. The service manual recommends a sealer on the rear main cap to block vertical surfaces. Maybe that will clear up the question.

I used the Permatex stuff in a little white bottle with a brush inside. It's thin, brown, and real sticky.

Hylomar is another good sealer.

You're right. It is in fact the rear main cap I was referring to. Thanks for making that clearer.

Thanks for setting me straight on that. Unfortunately I had already installed three of the pistons. But I pulled them back out this afternoon. (Fortunately I had not torqued the bolts all the way to spec yet.) Have also already removed a couple of the pistons from their rods and refit them in their correct orientation with respect to the rod. (That part is easy enough.) I'm not crazy about having to re-install the pistons into the engine block again, but I guess a little trouble now is better than a lot of trouble after the engine is in the car.

One minor related question: one of the snap-rings flew off under tension from the pliers when I removed it. Can I replace it with a generic snap-ring? Or is their some kind of special snap-ring for pistons needed to withstand the heat generated when the car is running?

Actually it was the rear main cap I was referring to. I called the it "crank journal" and confused people. I edited my original post now to reflect that.

Do you have a used one from your old pistons? I'd go that route if it is the same type.

No, unfortunately the machine shop took the liberty of disposing of my old pistons.

I have bought a couple generic snap-rings in auto parts store and hardware store. They will work, but although the diameter is correct, they appear to be just slightly narrow smaller in the shank. Maybe it won't be a problem, but I'd just feel better with the original snap-ring. I havem't researched it thoroughly, but a quick look at some MG parts suppliers has not revealed that they have those available for sale.