This past weekend I was discussing bearing failure that we were experiencing in a BB MOPAR with a well known and respected racer/machinist/engine builder. This gentleman has forgotten more than most of us on this site know.
He suggested that we groove the main journals for more oil flow as he has been doing for some time. This in addition to full groove mains.
I questioned the strength of the crank. He was very convincing in his explanation. The car he is currently running is a stunning SS ride that is turning a BB mopar 8000 plus and lives.
I've been in this sport 30 years, and have never encountered anyone doing this. If anyone else had told me this, I would have called for medical help. This racers background lends total credibility to his ideas.

Anyone else doing this?? Lets hear it.

RIP

I remember seeing it in an article out of a Hot Rod or similar magazine out of the late 60's, never seen it used or referred to since then.
AL....

We have a good size scolop over the oil holes in the
crank... if thats what he is referring to

Not just a scallop. He puts his cranks in a lathe and machines a groove .050 deep and .150 wide all the way around.

RIP

I have seen that done a long time ago, back before the full groove main bearings for all Mopar motors where availble. If your expereincing oiling problems to the rods or mains with full groove main bearings now I would try and figure out what is causing the problem, not groove the crank and possibly add a weakness to a perfectly good crankshaft

That theory doesn't hold much credence as grooving the crank 360* in the middle of the journal creates an other area for weakness and potential failure,grooving the bearings gives you the same effect,the only thing either way you cut down on the total bearing surface area.With todays techonology and oils you don't see that much bearing failure.The few bearing failures we have encountered in recent years have all been attributed to some related cause.oil system malfunction,broken parts or lack of proper maintaince.If the bearing material is appropiate,parts are correct demension,oiling is supplied properly,clearences are precise and the engine is maintained,bearing life is not going to be an issue.Usually when bearing failure occurrs some thing unrealated to the bearing or crank journal will be the culprit.

I don't see what the advantage of cutting up a good crank would be, when you could get fully grooved mains that essentially do the same thing.

You'd just wind up with a ruined crank.

My thinking also.....I said the same thing @ weakening the crank. This advisor just smiled and shook his head no. Said very convincingly that the main journals were too big anyhow, and plenty strong. His crewchief was standing right there, and assured me that the motor in his SS mopar (gorgeous car, first class) had this done to its crank. His background includes MANY MANY years of comp. He has made his own blocks! in the past. I've seen his work over the years and it is simply amazing. He is very quiet, not one to push anything on anyone else. Which is why I gave any credibility to this thought. I want to keep an open mind, and not get bogged down in "conventional wisdom". Anyone here that had been a fly on the wall would have opened their mind, only because of this gentlemans background.

Our failed motor is a 543 with a 4.5 crank. Wide groove mains, Dan Olsen pan, dual pickup milodon, proper clearances. Block has had steel cross bolt caps just installed. Rotating assembly is new. Dead in 7 passes. 1,3,6,8, along with #5 main were well done. It showed clear evidence of starvation, yet had 70-75 psi until the last run. It did see 7800 on one pass, when it failed to shift.

We need to make this motor live...so I am keeping an open mind. We may try it.

RIP

I obviously don't know what killed the bottom end of your motor since I've never seen the parts, but I can tell you that you do not need to groove the crankshaft. The grooves in the main bearings are plenty. In fact, you'll find guys on here who run 800 hp motors with half-groove bearings or 3/4 grooves.

what oil filter? bypass or no?

I am in agrement with most everyone else here as well. It simply isnt necessary. Your guy may have HIS reason, just doesnt make any sense to me. Thats what the grooves in the bearings are for in the first place. There are thousands and thousands of 500+ inch mopar engines running just fine with half groove and like Andy says 3/4 groove bearings and of course full groove, both thin and wide. We used to race a Super Gas Dart, and when we had no other options ( many years ago) I'd take standard P Clevites, and drill for my own dowels due to lack of availability in -.020, and had the same problem with cranks that were -.020 on the mains. Used passenger car P bearings chamfered with no issues whatsoever. Bearing technology and availability has gotten even better, so you have something else going on.


Yours is no different. SOMETHING caused that failure, but certainly NOT the lack of a grooved crank. You need to find the problem.

Jeff is heading in a certain direction perhaps with his question as well.


Your guy has his methods, but in this case, it doesnt sound like a fix for you.

The only grooved cranks I have ever seen are on huge ship diesels from before ww2 , the kind where a guy runs around with a big Q tip and wipes oil on parts, The groove was for floating the shafts during pre oiling before start up,

we have 2 bb mopars 447 with stock crank and a 499 stroker and both turn over 8000 rpms for abour 20 sec at a time and no bearing failure with full grooved mains. although mopars do ave some the biggest mains i would not suggest grooveing crank. this is a old school trick befor we got smart and made better bearings

If there a lack of oil to the mains.. I want to know where it is going..with 75 psi ..should be plenty..

to much oil pressure is also a bad thing heats up the oil and breaks it down. but a wise guy told me 10 psi oil pressure for every 1000 rpm is all you need

That's a technique they used in the 60's. The 1965 Mustangs prepared by Shelby use to come with the grove in the crank. The crank works with that grove with no problem, but with the new bearings you don't need to grove the crank. It seems like you have oil problems. Do you have roller lifters? Do you restrict the oil to the lifters gallery? The problem might be around there.

I've watched BB Mopar engines on the dyno spin rod bearings while the oil pressure gauge reads 60+ psi. It can happen since the oil pressure comes off the back of the block and that is not necessarily the same pressure that the bearings see. It is fairly common for the passages from the main gallery down to the mains to be poorly drilled from the factory. So if you're having problems keeping the bottom end in the block that is the first thing I'd check.

The next thing I'd check is to see if you're feeding too much oil up to the top of the motor. BB Mopar engines are well known for burning up the rods that are fed by the #4 main bearing since that location also feeds oil to the top end. Most of the engines I've torn down that had a spun rod bearing had the #6 bearing out of it. I think that happens because of the oil robbed from the #4 main.

yes this is the use of the motors.
geared just about as far as i can without a $1200 slipper clutch

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both turn over 8000 rpms for abour 20 sec at a time

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wow. i'm guessing you're doing tractor pulls otherwise i would suggest changing your gear ratio.

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