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100-4 front main bearing cap issue

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WaltCasten

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Hello all,
My BN2 is being restored and I am trying to re-gasket the engine while it is out. One issue I have run into is the front main bearing cap stands proud of the front surface of the block by .010". The rear one was flush. FYI, this engine was rebuilt back in the late 1970s. Anyway, it appears the engine was leaking from this area so I would like to address this somehow.

Is it possible to loosen the front main cap bolts and tap this back flush? Even if possible is this a bad idea? Should I just silicone this area and be done with it? It seems like one would want a nice flat surface for the front mounting plate to be bolted to.

Any help is appreciated.
Thanks,
Walt
 
Yes I think as far as realigning the cap it can be done as you suggested, However, concerning the leak at this bearing I do not know how any sealant would help.-Fwiw--Keoke
 
I don't see any problem with your solution - if it works. The main bearing caps usually fit so tight that there is not much run for movement. If it doesn't get flush, you could remove it and have it milled down. Silicone is really great stuff but If it was my engine I would want a flush fit.
 
Well, loosening the nuts and tapping it back isn't an option. It appears there isn't enough clearance around the nut for the cap to move anywhere. There is a spot face where the nut bears, then a shroud of cast material around that area that wasn't machined. The apexes of the nut hit that shroud when you try to tap it back. You can move it back about .005" with the nuts loose, then as soon as you tighten them it goes right back to the .010".

I guess my only option to make it right is to either have a machine shop cut the .010" off the front or open up the spot face around the nut.
 
I guess my only option to make it right is to either have a machine shop cut the .010" off the front or open up the spot face around the nut.

Either one sounds like agood way to go .However, I like opening up the spot face the best.--Keoke
 
The machine shop also suggested just putting a ground and hardened washer under the nut. They did not have an ARP washer with that big an ID, fortunately I have a Fastenal right across the parking lot from where I work so I went that route. There was a metric size that was really close, I had to open the ID up a little. I re-assembled, torqued it to 75 ft-lbs and the cap now sits flush.

It was also suggested to chuck the nuts up in a lathe and take a little off the apexes down at the bottom as the socket can't reach down there anyway because of the cast material (shroud around the spot face).

If anyone thinks the washer is a bad idea, let me know asap as I plan on buttoning this thing up tomorrow.

Thanks for all the input!

Later,
Walt
 
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