SBC 383 cracked rear main cap what do I do? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 08-08-2009, 09:20 PM
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SBC 383 cracked rear main cap what do I do?

Ok, guys to start thanks to all of you who have given me advise!

Took the oil pan off my (new) 383 stroker (in order to fix the dipstick tube) and in cleaning the rear main cap (where the oil pump bolts on to) I noticed a 1/2 to 1 inch piece missing on the outside of the gasket valley for the rear seal.

Can I just squirt a bunch of rtv in there and expect it to work properly? Or does the whole rear main cap need to be replaced? It is a 4 bolt main block out of a 1970 Chevelle. If I have to buy a new rear main cap where can I get one? Should I have a machine shop install it? Does all the stuff to do with my crank have to be taken apart in order to ensure it remains balanced?

I just about started crying when I saw this.

Also, I was reading another thread and I noticed that the dipstick tube slides into a sleeve type devise that actually goes into the crank case, in order to prevent the dip stick from hitting the crank and/or windage tray. Did some motors not have this feature? If I need this part where can I get and what is the name of it?





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Old 08-08-2009, 09:31 PM
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The cap will be fine, the seal is inboard of that point and it won't pose a problem. You don't even need to get specail with the sealer, it is NO PROBLEM. When you said cracked cap, I was thinking around a main bolt or the main bearing area, THAT would be a problem.

The lower dipstick guide tube came in every drivers side dipstick block, and can be made from a piece of 5/16" steel fuel line about 7" long. Buy a short piece, cut one end off and discard the nuts, leave the flared end on the other end, and drop it in from the topside before you press in the upper dipstick tube. Simple, no??
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Old 08-08-2009, 09:33 PM
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I'd put it together and hope for the best...At worst, all you'll have is an oil leak at the rear of the pan.
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Old 08-08-2009, 09:35 PM
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The small piece will not cause a problem. Just re-seal the area when you replace the gasket/pan.

The lower tube is in most early driver side dip blocks. It tends to get damaged/lost on engine disassembly. Available thru a good parts store. Pioneer products markets it as well as others.
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Old 08-08-2009, 09:40 PM
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I would not sweat that at all. I would not even do anything extra reinstalling the pan.

You can buy the tube you need from a GM parts supply like Scoggin dickey or your locale chevy dealer.....or build it yourself like mentioned.
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Old 08-08-2009, 09:54 PM
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Don't go nuts w/the RTV on the rear cap! I personally usually do not use sealant except on the end tabs- if you use RTV under (cap side) of the seal, or on the pan side of the seal, you risk it pushing the seal out of place- because the silicone sealer will act as a lubricant, not a sealer in that case.

If you have to use anything on the seal besides silicone sealer on the end tabs, I personally have used rubber weatherstrip cement on occasion.

That said, the last engine I pulled apart was a Vortec 5.7L. It used a tough, gray colored sealant/adhesive at the front and rear seal areas of the 1-piece pan gasket that was VERY durable- it was NOT "traditional" RTV/silicone sealer.

If you can get this OEM material, I'd recommend it. This stuff is tough!
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Old 08-08-2009, 09:56 PM
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I would not worry about that broken piece. Just a little extra silicone in the the area should work fine.

If you ever need to replace that main bearing cap, it would be better to find a different block, complete with the caps.

It most likely got cracked during machine work cleaning, or transporting. That area is thin, and if the block gets set down hard, or dropped it will fracture. It had to have happen prior to the crankshaft being installed.

As far as the tube? I can help.
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Old 08-08-2009, 10:16 PM
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Cobalt, the sealer you are referring to is called "The Right Stuff". Catchy name, It's awesome stuff!
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Old 08-08-2009, 10:19 PM
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Quote:
Originally Posted by ericnova72
Cobalt, the sealer you are referring to is called "The Right Stuff". Catchy name, It's awesome stuff!
Thanks, I'll keep an eye out for it next time I'm at the parts house.
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Old 08-08-2009, 10:20 PM
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Thanks guys for all your help today!

Just an FYI I am putting in a one piece blue fel pro oil pan gasket, does this matter pertaining to using rtv or not?

Also, as far as using a piece of fuel line for the dipstick guide for the dipstick tube..... does it need to be curved at all? Or is it just a straight piece?

Another FYI:

I just ordered my 700r4, once I get the motor and tranny in, I'm gonna post a video of the car! Show you guys where all your expertise is going!!!!!!!

Thanks again!
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Old 08-08-2009, 10:25 PM
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The dipstick guide is just a straight piece.
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Old 08-08-2009, 10:27 PM
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I have 1 tube left of GM part # 12346141. It has this type of properties.

It is good stuff.
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Old 08-08-2009, 10:49 PM
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On the one piece gasket install, just a dab of sealer where the T-chain and block meet, and where the rear cap and block meet. NO sealer anywhere else, it is meant to be installed dry, just like the instructions say. These are great pieces, should have been invented years ago, I know a friend that has had the same gasket on three different engines
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Old 08-09-2009, 06:51 AM
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What ERICNOVA72 said...
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Old 08-09-2009, 07:17 AM
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The one piece gasket for the SBC is one of the best things to come along. Follow the installation directions explicitly and you will have no problems. Try and improve the design by globing silicone on it will defeat the design and cause leaks.

IMHO the overuse of silicone is responsible for more leaks than it is supposed to stop. I agree with the previous comments about it actually causing the gaskets to slip away from their position.

Vince
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