need threads/discussion on crossdrilling cranks, knife edging cranks, engine balance
08-06-2002, 10:29 AM
#1
Drifting
Thread Starter
need threads/discussion on crossdrilling cranks, knife edging cranks, engine balance
I know this has been pounded here, but I cannot find any of the good info/discussion in the archives - like the reasoning behind drilling another hole 90 dedgrees off the existing hole in the rod journals, the effects of lightening/knife edging the crank on balance and rotation, and the proper way to lighten a flywheel...
I need this info for an engine project at work.
Anyone who has bookmarked this stuff, or is willing to reiterate, please do so.
I need this info for an engine project at work.
Anyone who has bookmarked this stuff, or is willing to reiterate, please do so.
08-06-2002, 10:38 AM
#2
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Keith -
Ok - a couple answers...
1) Crossdrilling, rifledrilling, etc the crank.
There seems to be an oiling issue with our cars at higher revs and high "G" corners, which seems to starve the #2 rod bearing of oil. Some think that it's due to the oil pickup becoming oncovered with oil, some seem to feel that the oil passage for the #2 rod bearing is in a bad place to begin with. Drilling the additional hole is one measure to attempt to fix this design issue. Many people have just insured that the oil is FULL when tracking the car, which also seems to work with most cars.
My personal opinion, there's a passage issue, than can be corrected with a well placed hole in the crank. Huntley Racing, SFR, Anderson Motors, all can help with this. I'd also update the oil pan baffle in the pan itself, and weld some additional baffleing in there to insure that it doesn't starve for oil.
2) Knife edge, balance, etc of the crank.
This procedure removes weight from the crank (while keeping it balanced). The less rotational weight the engine has to push during running the more power you can get to the rear wheels. Some feel that lightening and knife edgeing reduce the driveability of the car too on the street.
Knife edgeing also can help prevent oil foaming, which is when the ears of the crank splash the oil and mmix it with air inside the oil pan.
My personal opinion (nomex ON) is that in a street car this is unnecessary. It reduces the driveability too much for stop and go traffic.
3) Lightening a flywheel
Same idea as above for the weight issue. Less mass to turn results in more power to the wheels. To properly do it though, you need to remove material to lighten while NOT compromising strength. I'd have it done by someone who knows what they are doing, rather than attempt it myself. I do know that this will also effect driveability if it's not done right, and worse - it it's not balanced right after the fact.
Seems that you might be in the process of an engine rebuild - huh...
HTH!
Ok - a couple answers...
1) Crossdrilling, rifledrilling, etc the crank.
There seems to be an oiling issue with our cars at higher revs and high "G" corners, which seems to starve the #2 rod bearing of oil. Some think that it's due to the oil pickup becoming oncovered with oil, some seem to feel that the oil passage for the #2 rod bearing is in a bad place to begin with. Drilling the additional hole is one measure to attempt to fix this design issue. Many people have just insured that the oil is FULL when tracking the car, which also seems to work with most cars.
My personal opinion, there's a passage issue, than can be corrected with a well placed hole in the crank. Huntley Racing, SFR, Anderson Motors, all can help with this. I'd also update the oil pan baffle in the pan itself, and weld some additional baffleing in there to insure that it doesn't starve for oil.
2) Knife edge, balance, etc of the crank.
This procedure removes weight from the crank (while keeping it balanced). The less rotational weight the engine has to push during running the more power you can get to the rear wheels. Some feel that lightening and knife edgeing reduce the driveability of the car too on the street.
Knife edgeing also can help prevent oil foaming, which is when the ears of the crank splash the oil and mmix it with air inside the oil pan.
My personal opinion (nomex ON) is that in a street car this is unnecessary. It reduces the driveability too much for stop and go traffic.
3) Lightening a flywheel
Same idea as above for the weight issue. Less mass to turn results in more power to the wheels. To properly do it though, you need to remove material to lighten while NOT compromising strength. I'd have it done by someone who knows what they are doing, rather than attempt it myself. I do know that this will also effect driveability if it's not done right, and worse - it it's not balanced right after the fact.
Seems that you might be in the process of an engine rebuild - huh...
HTH!
08-06-2002, 12:35 PM
#3
Burning Brakes
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You hit it on the head with the oil frothing! I had my 87S on the dyno, we were doing a pull for laughs and grins for a top speed run. At the extreem top of the rpm band, we lost oil pressure...so we shut the car down...started it up, still no pressure...let it sit for a while to calm the oil...started it...oil pressure.
Frothing is a bad thing.
Frothing is a bad thing.
08-07-2002, 11:39 AM
#4
Drifting
Thread Starter
Thanks guys, good stuff so far, but I REALLY want to reread the heated discussions on the subject, including 90 degree angle drilling the rod journals, etc.
Does no one still have the links to those threads ???
<img src="graemlins/jumper.gif" border="0" alt="[jumper]" />
Does no one still have the links to those threads ???
<img src="graemlins/jumper.gif" border="0" alt="[jumper]" />
08-07-2002, 11:39 PM
#6
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Cross drilling the crank definately seems to be the answer to our #2 rod bearing problem. I just wish someone around here did it that I could trust. Knife edge and balance the crank, also a very good idea. I found a local shop that can probably do that, still not sure on if I would let them cross drill. Air entrainment is a big problem, knife edge, polish and windage tray helps a bunch with that. Best solution to aviod the frothing problem is a dry sump.
As for the flywheel, I wouldn't lighten it for street use. The rotational mass helps in normal driving situations. If the mass is lowered, then the clutch could be much more touchy on engagement. That mass isn't needed on a track car since once engaged, the clutch is only used to shift to a different gear, not as in a full stop at a light or an intersection.
Got a CD of pix of that 914 for Jim, will see you guys 8/8 when I pass through Charlotte.
Dave
As for the flywheel, I wouldn't lighten it for street use. The rotational mass helps in normal driving situations. If the mass is lowered, then the clutch could be much more touchy on engagement. That mass isn't needed on a track car since once engaged, the clutch is only used to shift to a different gear, not as in a full stop at a light or an intersection.
Got a CD of pix of that 914 for Jim, will see you guys 8/8 when I pass through Charlotte.
Dave
08-08-2002, 12:07 AM
#7
Three Wheelin'
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Ok. These are just the results from searching for 'perp drill' on the 944 turbo board. I think the '951 rebuild' thread is the one that you are looking for.
<a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=18&t=000669" target="_blank">951 Rebuild</a>
<a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=18&t=001384" target="_blank">Air-Oil Separator...</a>
<a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=18&t=000669" target="_blank">951 Rebuild</a>
<a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic&f=18&t=001384" target="_blank">Air-Oil Separator...</a>
