Oiling issue with cross drilled crank? Old mini

Engine tech, for those engines, products, and technologies of yesteryear.

Moderator: Team

Post Reply
hydrolastic
Member
Member
Posts: 99
Joined: Sun Nov 15, 2009 2:13 pm
Location: Seattle WA USA

Oiling issue with cross drilled crank? Old mini

Post by hydrolastic »

Hello Guru's Trying to get a handle on a lower end upgrade on a 1275 vintage road race engine.
Current spec is
Longman head (big valve, ported)
Elgin cam about 304 duration
Forged pistons probably J&E
Steel main caps line bored and honed
Old crank (stock non cross drilled regular 1632 crank)
New crank cross drilled and wedged will be adding forged rods
A plus oil pump set at 70lbs adjustable relief valve
15-50 Mobil one oil. windage tray. 50 wt is for the transmission (whole other subject i really would like to avoid going into)
fully grooved 360 degree main bearings (A series)
oil cooler and accusump and external filter fram racing filter 1515 or something like that big PH8 style filter
very good light flywheel
revs to 7800 on the straight he says he is short shifting the rest of the time at just over 7000 rpm 7200. I want him to be able to rev to 8500 for more power and better use of the close ratio gears
Engine probably is making 100 Hp at the wheels based of experience with other engines with simular specs on the dyno. A bit of disclaimer and clarification Not my car I am not the driver I build the engines around the area for a couple of guys. I race in another series. This engine was built by someone else and we have slowly gotten it going faster and faster each time out. Driver is very good
Last year due to covid he ran twice. Second time out racing a main cap split. He saved the engine by shutting it off as he saw the oil pressure dropping. I have had the engine line bored and honed with all new steel main caps. I want to replace the crank and the weak stock connecting rods. I have several cranks here i can choose from. One is a wedged and cross drilled vintage crank (Photo) mains and rods. The other photo is the crank that was in the engine not cross drilled. Photo's not in order.
My question is. I want to replace the crank should i use this cross drilled crank as it is? Benefits?
Thank you. Aaron
You do not have the required permissions to view the files attached to this post.
Racecar spelled backwards is racecar!
Ks Fats
Pro
Pro
Posts: 375
Joined: Wed Feb 12, 2014 12:39 pm
Location:

Re: Oiling issue with cross drilled crank? Old mini

Post by Ks Fats »

Aaron,
I'll start with the caveat that I'm no mini expert but will start with the question: What do the bearings look like that were run with the stock crank oiling? If memory serves me correctly the system you have now is pretty much standard (accusump etc.) for racing. I usually do not use a grooved lower bearing shell on the mains, is that standard mini practice? The grind on the crankpin delivery hole in the cross drilled crank is in a direction that is unusual also. Best advice would be to continue with the existing system IF your bearings aren't indicating any problems. Past experience with inline 6 cranks indicated their longevity was lessened by cross drilling and really did not show any difference in bearing life, working with delivery hole feeds to the mains and controlling bleed-off did. Make sure your alignment and feed hole sizing is correct on the center-main also.
hydrolastic
Member
Member
Posts: 99
Joined: Sun Nov 15, 2009 2:13 pm
Location: Seattle WA USA

Re: Oiling issue with cross drilled crank? Old mini

Post by hydrolastic »

Hello Again, Ok i will look at this situation with the oil holes closer. I have the option of using a fully grooved main bearing or the later style top half grooved/bottom plain bearing i suppose with some machining to the bottom half a 3/4 groove bearing set could be made also. The photos also show a 3 hole output on the rod journal and not exactly 90 degrees to the plane of the crank shaft . The through hole in the main bearing is 90 degrees to the plane of the crank. This crank, I did the wedging on it and reduced the weight by a pound on the rod side so it will get a balance and a grind to .010 undersize bearings. I have not run a cross drilled crank in any of my own engines and the one i know of had a whipping problem that negated any other issue i could see as far as wear is concerned.
I tried to get better photos with more light and i used a drill bit to show the hole angles also the crank is missing the allen plugs and i was wondering how to install those? red locktite and possibly stake the thread at the top of the allen plug ? Aaron
You do not have the required permissions to view the files attached to this post.
Racecar spelled backwards is racecar!
hydrolastic
Member
Member
Posts: 99
Joined: Sun Nov 15, 2009 2:13 pm
Location: Seattle WA USA

Re: Oiling issue with cross drilled crank? Old mini

Post by hydrolastic »

Hello again, I also just read this (about english stuff) so it could be useful i think i may be plugging the outer holes. Thanks modok !
Re: Cross drilled billet crank
Report Quote Like
Post by modok » Fri Jan 29, 2016 8:26 pm

The drillings can be in a X pattern, or a T, or a T at both ends........which is like a sideways H? or diagonal and across.........any way you can imagine, has been done.
General rule.....just keep the oil holes on the sides. Oil the NON loaded areas. The only really wrong way to do it is come straight out the rod journal, which they did do on some English stuff, and it was "fixed" by plugging it and drilling across.
Racecar spelled backwards is racecar!
User avatar
Sir Yun
Expert
Expert
Posts: 571
Joined: Fri Feb 17, 2006 7:16 am
Location: No longer near ze germans (Boston MA)
Contact:

Re: Oiling issue with cross drilled crank? Old mini

Post by Sir Yun »

@hydrolastic It's an old thread but still there's good information to be found here.

http://russellengineering.com.au/projec ... gine-pt-1/
“There is no authority who decides what is a good idea.”
― Richard Feynman

Expert ? Me ? ...whhhhaaahahhaahahaha
pamotorman
Guru
Guru
Posts: 2802
Joined: Thu Mar 06, 2014 11:55 pm
Location:

Re: Oiling issue with cross drilled crank? Old mini

Post by pamotorman »

cross drilled mains should not be used with full grooved main bearing inserts as it causes turbulence in the oil flow.
Circlotron
Guru
Guru
Posts: 1141
Joined: Tue Feb 05, 2013 6:56 am
Location: Melbourne, Australia

Re: Oiling issue with cross drilled crank? Old mini

Post by Circlotron »

Whenever I hear of grooved lower half bearings it always makes me think of the difference in behavior between a grooved and a bald tyre on a wet road. There may be some degree of correlation.
User avatar
Sir Yun
Expert
Expert
Posts: 571
Joined: Fri Feb 17, 2006 7:16 am
Location: No longer near ze germans (Boston MA)
Contact:

Re: Oiling issue with cross drilled crank? Old mini

Post by Sir Yun »

https://asmedigitalcollection.asme.org/ ... m=fulltext

in the end of the paper they have some minor references that by using only one oil port the laminar flow was greatly extended and a reference to a very old german paper about half grooved bearings I can't access
“There is no authority who decides what is a good idea.”
― Richard Feynman

Expert ? Me ? ...whhhhaaahahhaahahaha
Kevin Johnson
HotPass
HotPass
Posts: 9365
Joined: Tue Nov 22, 2005 5:41 am
Location:

Re: Oiling issue with cross drilled crank? Old mini

Post by Kevin Johnson »

Sir Yun wrote: Fri May 12, 2023 12:55 pm https://asmedigitalcollection.asme.org/ ... m=fulltext

in the end of the paper they have some minor references that by using only one oil port the laminar flow was greatly extended and a reference to a very old german paper about half grooved bearings I can't access
If you use his paper title and name as search parameters in Google Scholar, many other references come up including ones without paywalls.

https://scholar.google.com/scholar?q=re ... s_sdt=0,10

Good paper:
https://www.sae.org/publications/technical-papers/content/860229/1986-02-01 wrote: Lubricant Flow to Connecting-Rod Bearings Through a Rotating Crankshaft 860229
The flow of oil into a rotating crankshaft has been investigated. Analysis of the physics of the problem together with dimensional analysis indicates, for a given journal geometry, that a relationship exists between Reynolds number, non-dimensionalized pressure drop, and oil flow. Data obtained from an oil flow test rig are used to determine explicit correlations for two oil feed configurations; one journal with and one journal without a lead-in groove.
Driving Force Online: BREAKING NEWS—Ohio Governor Signs SEMA-Supported Vehicle Freedom Bill Into Law!
Post Reply