Cross Drilled Crank

G

Gavin

Member
I have a counterweighted B crank which has been cross drilled for pressure oiling but I want to use the standard oiling system in my A. Can anyone advise me if I need to fill the cross drilled holes and how I might do this. Cheers, Gavin.
 
No you do not needs to fill it having said that I think it may be thin (weak) when machined to A Model size
What method was used when drilled
 
Hi Gavin,
I'm going to respectfully disagree with Mike and Colin. Using a drilled crank in a splash oil system could possibly result in the following situation: If enough oil should get into the drilled passages, the centrifugal force of the spinning crankshaft could conceivably suck oil away from the main bearings and leave them oil-starved. If the crank were my own, I would carefully taper-tap the oil holes at the main bearings only, and run a very short socket head set screw into the hole with enough force so that it could not work loose (and Locktite Red?). Be careful not to force the fit, you could cause the crank to crack by doing so. You also need to use a very high quality HSS taper tap for the job, don't use a hardware store carbon tap in the manganese steel of the crank. Be sure to remove all chips from the oil passages afterward. Be careful!
 
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I'd say dont waste that crank in a plain old splash oiled " A " block. Just use an "A" crank and either save that crank for a better motor or sell it to someone who needs it, as is. To me it doesnt make sense to spend the money to plug the holes and turn it down...it just seems like a waste of money for a step backwards.IMHO. Good Luck w/ your buildup.:)
 
Chris' comment is interesting but I'm not sure it applies. When the mains are turned down to Model A size it will sever or split the hole near the end of the main journal.

I have a similar crank that's been on the shelf for over 30 years. It's probably a good candidate since it will probably need to go .040" under to clean up and probably won't be on proper centers due to previous regrinds.
 
No need to plug the holes.
Oil will slowly work its way into the drilled passageways and then stop once full, and since it is a stagnant system (no pressure coming in), that is the end of the story.

In other words, the holes will be plugged, but not by you, but stagnant oil; then oil will not enter or exit the drilled holes.
 
Speaking of crankshafts,any one have one of the counter weighted A cranks in,if so ,how is it.
I,m thinking of one for my ccpu.
Thanks Lawrie
 
Lawrie said:
Speaking of crankshafts,any one have one of the counter weighted A cranks in,if so ,how is it.
I,m thinking of one for my ccpu.
Thanks Lawrie
Click to expand...

If you mean the Burlington counterweighted crank, I've only heard good reports from those that have installed it.
I just recieved my Dan Price counterweights the other day, so I haven't had time to install them yet. I like his because they are full circle and shrunk on using heat.
 
Lawrie said:
Speaking of crankshafts,any one have one of the counter weighted A cranks in,if so ,how is it.
I,m thinking of one for my ccpu.
Thanks Lawrie
Click to expand...

I have installed at least 6 Burlingtons in the last couple of years. Every one has resulted in a very smooth running engine. Both the owners and I are very pleased with them. Those engines also all had Stipe cams, which also contribute to a smooth engine.

I do know of one guy who drilled one out and broke it, but he also broke 4 other drilled cranks, original A's and a B. They all made it about 15,000 miles before cracking at the center main. I think its the way he drives, not the cranks, but Burlington does not recommend drilling their crank.
 
Thanks to those who have offered advice. I got to this point after buying a B engine and them a few grands worth of parts only to have the block crack beyond repair when valve seat inserts were being fitted. I am using the B crank in the A block in order to use the B rods I have. I was going to have new main caps made but this proved difficult so I opted for grinding the B mains to standard A dimensions. I appreciate Rex A Lott's point of view and may one day wish I had done that!
 
I fitted a counterbalanced B crank to an A block together with conrods (bigger journals?), camshaft and flywheel and there was a noticeable improvement in performance.
I did many thousands of miles without problems and the oilways were not blanked off
 
If you don't want the cross drill holes
Sell it and buy one with no holes
You will get more money for one with holes.
In the end you will have a stronger crank and
Money in your pocket.
 
Hey Gavin,
Hmm, sounds like you have a serious decision to make, wherein lots of $ involved. Also sounds like you are using your engine for touring type work...as opposed to racing high rpm work..no?
Anyway, if low rpm use, IMO you have a nice crank to use BUT could use a less expensive (non drilled) for same engine. And, the non altered crank MAY last longer..as attested to in cases stated above. With drilled, you will always have the question...how well was that work done and how long before possibly fracturing. Who needs that on their minds with expensive A engine? Mabe make $ selling drilled, as stated.
BTW..just the other day, I was in a shop when a guy brought in an A engine with B crank, weighted/ drilled and cut for use in A engine. The machinist examined the crank drilling and shook his head, saying something about the drill path being too close (in his opinion) to the radius...for that crank to expect a long life..especially with the other equipment that was going on that block. Good luck to you which ever way you go !
 
Before you grind your crank please check measure how close the oil gallery is the bearing radius this will be your weak spot if there is not enough material
better to bore your bearing tunnels and grind the crank a minimum if you want to use the b crank
 
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