Drilling 800 BB cases for better oiling

[Jay]

Can anyone help me out by showing/describing how to properly drill out the oil holes in the upper case half on an 800 big block to get better oiling to the crank bearings? Some guys do this when they are deleting the oil pump. I can't find anything using the search function but I know I have seen this mod on here before. Thanks for any help.

 

[Zachmandu]

You will notice an indentation in the casting where an oil hole "should" go. Upon examination, you will also notice that within this indentation is a small round depression that is not parallel to the crankshaft, but cast at an angle. This angle, roughly 45 degrees to the crankshaft centerline, roughly approximates the angle at which you need to drill the case to intercept the already drilled passage that connects to the oil pump hose leading to that side of the case. Use a drill bit the same size as the existing oil passage holes. Carefully drill out the casting, being sure to be along the crankshaft centerline so that you intercept the existing passage. Usually what happens, is that the hole ends up being drilled "shallow", and comes through the case where the bearing race rides. If this happens, carefully grind a notch connecting this hole with the existing oil passage hole. You will see that Polaris roughly did this on the MAG side oil passage/oiling hole. Be absolutely certain that oil can get around to the outside of the bearing race. Remember, the oil needs to go from the clutch side of the bearing, towards the rod side.

That's it. Nothing to it.... I just did one last night. And yes, I ended up being a bit shallow in my angle, and had to grind a notch.....

 

[Jay]

Thanks for the help, thats exactly what I wanted to know.

 

[Twostroke]

use a 1/4" bit. I just recently did mine, most stressfull hole i've ever drilled. It takes a longer then you think, you have a fair bit of material to go through. Mine came out the bottom and connected with the stock port, didn't have to grind.

 

[Ropin_tom]

any pics? just to be certain, im sure its straight forward once you pull the jugs, but a pic does wonders Thanks

 

[Jay]

There was another thread somewhere on here that goinboardin posted up some pics and gave a real good description of what he did. Maybe PM him and ask about it.

 

[Ropin_tom]

Thanks jay. Does this look like the same spot? And what did you use to cap the oil line holes.

 

[Jay]

Thats the correct spot, drill the hole as Zachmandu described. You need to split the cases first, I have never heard of anyone doing it with the crank in the cases. You can leave the small brass valve in the case half and just cap the intake.

 

[Ropin_tom]

OK. Thanks. Looks like mine have already been done must have been drilled when the big bearing kit was done. I blew air in through the oil injection line and could hear it coming up through the hole. I think I should be good to go then.

 

[Ropin_tom]

What is every one mixing for ratios? I just run castrol snowmobile oil or shell advance from crappy tire. Was just going to do the 40:1 seems to do ok on every other 2 smoker.

 

[Goinboardin]

IndyDan advised me to run 32:1 for a premix ratio. Nothing fancy for oil, I used Arctic Blue. I did just that. Bearings all look great on that crank still. I even rode it half a mile off trail with a two piece crank and it didn't lock up. And yea your case looks drilled already, that's a nice surprise! Take care of that clutch!