Guys,

I seem to remember reading a little something about it being a good idea to cross-drill L6 cranks when you start asking them for big revs/power.

Obviously I'm not looking to do this myself, but just to clarify, is this where you drill a secondary hole through the main/rod journal on the crank to make a X and give the oil two paths to the bearing?

Dave

_________________
USA Daily: 2014 Nissan GT-R, very minor modifications for the track
USA Project: 1978 280Z, minor suspension upgrades, VK56DE conversion in progress. SOLD
AUS Race Car: 1973 240Z, L28ET, Autronic, GT35R. SOLD
AUS Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild. SOLD

would'nt it loose some "structial integrity"?

Yes it will. Its a matter of weighing up the option of not enough oil supply and roasting a bearing, snapping a rod and pushing it out the block; or lowering the torque limit of the crank a few Nm.

Dave

_________________
USA Daily: 2014 Nissan GT-R, very minor modifications for the track
USA Project: 1978 280Z, minor suspension upgrades, VK56DE conversion in progress. SOLD
AUS Race Car: 1973 240Z, L28ET, Autronic, GT35R. SOLD
AUS Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild. SOLD

To quote the book "How to modify Datsun 510 610 240Z Engines and Chassis"
The L16 race crank rod journals have the usual hole (that the stock crank has) plus a cross-drilled passage, making a total of three holes in each rod journal. This seems to work fine up to about 7500rpm or so. About then the oil pressure shown on the guage drops off 20 psi or so.

What he guage doesn't tell you is that the rod and main bearings are starving for oil, even though there may be 50 psi or so in the mani oil gallery - and showing on the guage.

The crank acts like a centrifugal puomp at high RPM. Centrigigul forces try to sling all available oil out of the passage to the journal, which tends to starve the main bearings. When the mains starve, there's no longer enough oil for the rod journals. Blah blah bad stuff'll happen. The stock crank is bad enough with its single hole pointing from the main out thru the rod journal.

Dolf van Kesteren plugs the hole at 90 degrees to the cross-drilled hole. Some further advantage may be gained by plugging the x-drilled passage on the trailing side of the journal (side opposite to the direction of rotation). You may want to remachine the stock crank to make all rod journal oil holes lead the crank rotation as shown in the accompanying diagram.

Machine aluminium plugs and fit them into one or two of the holes in each rod journal with 2 - 3 thousands of an inch interference fit and Loctite.

Polish the hole as far in as you can reach with various tools. Drive the plugs into the centre holes forst. Make the plugs long enough so they protrude slightly into the cross-passage. You can reach through the cross-passage with a punch to bend or peen the plug end to ensure it will stay in place. The surface of the plug should be 1/16 to 3/16 below the journal surface. All oil holes must be carefully polished and radiused."

Phew, fingers worn down to the frst knuckle

I drew a nice picture using MS Paint to show the diagrams, but got this message when I tried to attach it (its only 16k)

Sorry, but the maximum filesize for all Attachments is reached. Please contact the Board Administrator if you have questions.

Huh

_________________
1970 ex Group A Rally P510
1971 P510
1972 180B SSS
1965 SP310 Fairlady
1966 SP311 Fairlady

Dave,

Thanks for that. I'm looking at that attachment error atm. Keen to see the pic.


Dave

_________________
USA Daily: 2014 Nissan GT-R, very minor modifications for the track
USA Project: 1978 280Z, minor suspension upgrades, VK56DE conversion in progress. SOLD
AUS Race Car: 1973 240Z, L28ET, Autronic, GT35R. SOLD
AUS Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild. SOLD

Fixed.

Dave

_________________
USA Daily: 2014 Nissan GT-R, very minor modifications for the track
USA Project: 1978 280Z, minor suspension upgrades, VK56DE conversion in progress. SOLD
AUS Race Car: 1973 240Z, L28ET, Autronic, GT35R. SOLD
AUS Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild. SOLD

Ok, now for my beautiful effort with good ol' Microsoft Paint..

the caption is

"Drill new hole at C to lead crank rotation if one is not already there. Hole C must clearly intersect with oil passage OP.

New oil passage MP can be cross-drilled as shown to ensure adequate oil to conrod bearings"

_________________
1970 ex Group A Rally P510
1971 P510
1972 180B SSS
1965 SP310 Fairlady
1966 SP311 Fairlady

OK, you're probably not that interested in the brand new Honda crank for a monkey bike that I was selling on eBay

Try THIS file called crank1.jpg instead of crank.jpg

_________________
1970 ex Group A Rally P510
1971 P510
1972 180B SSS
1965 SP310 Fairlady
1966 SP311 Fairlady

I was wondering about that actually..

so what you are doing is stopping the centrifugal forces of the crank sucking more oil from the crank gallery than the pump can supply?

Dave

_________________
USA Daily: 2014 Nissan GT-R, very minor modifications for the track
USA Project: 1978 280Z, minor suspension upgrades, VK56DE conversion in progress. SOLD
AUS Race Car: 1973 240Z, L28ET, Autronic, GT35R. SOLD
AUS Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild. SOLD