Crank drilling modifications for better oiling ?

[edbaus]

Guys,

I have a crank that I am looking to modify to help with oiling. This is on an 88 na race car that has lost its share of rod bearings. (not the same motor)

I am looking to understand some of the stuff I see on a crank from Lindsey that my buddy has.

It is a knife edged crank. It has perpendicular drilling on all of the rod journals, it has an extra hole added (so a total of 3 holes) in the man journal, and it has the plugs enlarged and drill and tapped.

I have heard before about perpendicular drilling the #2 and #3 journal. This one has all 4 drilled.

I have never heard about adding an extra hole to the main journals. Since the mains never have problems, I assume it is to balance out the flow between the rods and the mains now that there are extra holes in the rods?

Any insight would be appreciated.

Thanks

Ed

[962porsche]

knife edging is a wast of time and money i have done 2 of my 944 motor with the crank getting knife edged . they make no more hp or tork . the cross drilling and chamfering does help . and yes you can spin the mains too but your right it is rear . don't think that cross drilling is a cure for the spinning of the #2 rod baring . 3 weeks ago i loaned out my 944 spec car to a friend and he gave me my car back with a motor thats totaled . there is nothing that can be saved but the water pump . that motor was crossed drilled and knife edged . 9k and only 3 races on the motor . the rod went throw the block so hard it bent the balance shaft and broke the balance shaft cover in two .

[John_AZ]

Originally Posted by 962porsche

knife edging is a wast of time and money i have done 2 of my 944 motor with the crank getting knife edged . they make no more hp or tork . the cross drilling and chamfering does help . and yes you can spin the mains too but your right it is rear . don't think that cross drilling is a cure for the spinning of the #2 rod baring . 3 weeks ago i loaned out my 944 spec car to a friend and he gave me my car back with a motor thats totaled . there is nothing that can be saved but the water pump . that motor was crossed drilled and knife edged . 9k and only 3 races on the motor . the rod went throw the block so hard it bent the balance shaft and broke the balance shaft cover in two .

wow, a real shame.
John

[Porsche-O-Phile]

Knife edging isn't intended to make power, it's to reduce the rotating mass and therefore allow for faster rev-up.

[962porsche]

it give less rotating mass to keep the rev up in road racing its not a plus .you can cut the flywheel . it also remove the square edge that has to push its way throw the oil so yes on some motors it is a power adder but not the 944 motors . becouse the counter balances are only 24 mm wide on the 944 motors to say the 2.0 vw motor thats 8 mm fatter .

[Porsche-O-Phile]

I believe it also helps with reducing (but not eliminating) windage. I wouldn't call it a waste of money at all. Serious engine builders do this all the time along with lightening the flywheel, rods/pistons to the extent possible, etc. Anything you can do that will keep rotating mass weight down helps (assuming you don't sacrifice strength).

[KEV951]

porsche-o-phile +1 on windage for knife edge-ing, it really helps alot and makes a difference on high rpm motors in general in conjunction with a scraper and a windage tray. the first thing to do though is baffle the oil pan . anything you can do to keep oil at the pickup is the key and good clearances with good clean oil. I like redline 20w50 race oil or even the regular redline 20w50 . If you step into the realm of dry sump, thats another tier up for high rpm RACE motors . Everyone has their own oppinions, these are simply mine. i too have all rod/main journals cross drilled.

[edbaus]

OK,

so, has anyone ever heard of adding more holes to the main journals.

Thanks

Ed

[KEV951]

yes , my crank has both main and rod journals cross drilled

[962porsche]

yes you can cross drill mains too . my motor thats now shot it was done to that motor . any serious engine builder will tell you to do a dry sump for road racing like on 2 of my cars 962 and ITS 944 !

[edbaus]

I have a full dry sump system that came off another car, but I would rather sell it than use it.

Ed

[962porsche]

the 944 motors don't have a problem with windage . the conter weights are not that fat and the sumps are deap with a windage tray from porsche .

[KEV951]

if your racing, and turning rpms with more power, its better imho

[carlege]

Originally Posted by 962porsche

the 944 motors don't have a problem with windage . the conter weights are not that fat and the sumps are deap with a windage tray from porsche .

The only problem 944/951 have are the owners that neglect basic maintenance then sell for a project

Whether they are good racing engines or not has been determined since porsche did build the car to race and their engine isnt that far from the ones we own. Im pretty sure its a stout engine when built correctly.

To the guy who burn up his engine what oil did you have in it?

[962porsche]

why do you need to know what oil i use ???

[southwest232]

I've been considering cross-drilling and adding a remote cooler (read about that on an older post here or on Rennlist). I'm looking for a decent machine shop in the South Bay area of L.A. My motor is stripped down and I would like to have the head rebuilt, also may need some work on the cylinders.

Any recommendations?

Thanks

[carlege]

Originally Posted by 962porsche

why do you need to know what oil i use ???

oh wait i thought you spun a bearing. I now read you put the piston through the block. I guess thats just bad luck

[962porsche]

it was my friend not me ! he cased the oil pan on the ripple strips or turtle backs what ever you want to call them . cracked the oil pan lost most of the oil and then it went to a catastrophic failure . we have built 17 944 motors to date not one has spin a baring yet ! we don't use any add on oil coolers even with the 2 944's we run in the enduro series ( 6, 12 , and 24 hour races ) the oil temps and pressure are right were they should be even on the hottest days . we tend to use 10/40 oils most of the time changing the oil before every event . they are all NA cars if we run a turbo car i may think about adding an oil cooler ?

[matthewb]

For those of you claiming that the 944 counter weights are not that wide, think again. look at the weights on the 944 crank compared to the weights on this 4.6 liter crank. I would contend that knife edging on the 944 crank would be beneficial.

[KEV951]

-def need to add an oil cooler for turbo, there is simply more heat created with pressure. Also , you ultimatley should run oil weight in conjunction with bearing clearances . tighter clearance = lower weight oil . and vise versa. I know alot of guys running 15w40 instead of 20w50 on enduro motors, but again, they run slightly tighter clearances to prevent scavenging from prolonged high rpms. But start with baffling the pan IMHO for saving the bearings. if your building a street car, you dont need knife edging or add scrapers, just baffle the oil pan and keep oil where it belongs and change it more than often. using zddp helps the cam and lifters alot. and yes the counter weights are fat as hell on stock 944/951 cranks. The cheapest solution for reducing oil drag is adding a better windage tray in the oil pan.