Oil Control
10-11-2008, 10:14 PM
#1
Oil Control Here is the situation: Engine A has problems with spinning rod bearings. More of an inheritent defect of the entire family of engine, rather than being limited to this specific one. Instead of using a conventional Callies rod using a SBC bearing, a special rod is used which was spec'd by another party. It is designed for a bearing which is about .026" thinner and the rod itself is about .008" thinner, leaving more rod side-side clearance and more room between bearings and crank pin radii.
I am aware that this area has some effect on oil control around the rods, but to what extent is this change significant?
I am aware that this area has some effect on oil control around the rods, but to what extent is this change significant?
10-18-2008, 09:15 AM
#3
Really? I thought I had read somewhere that it had an effect on how well the oil could evacuate from around the bearing. As far as I could tell, there wasn't really any other significant differences other than a 2.2542" housing bore, compared to 2.2247".
Kent
10-18-2008, 09:51 AM
#4
FormerVendor
Unless the collective side clearance curtain area is less than the bearing clearance it can't really limit the oil flow out of the bearing. So if you did have like .0025 bearing clearance you'd need essentially .010 side clearance or more and you usually already have double that. Some NASCAR stuff has over .100 side clearance and they definitely don't want lots of oil flying around!
10-18-2008, 10:04 AM
#5
Unless the collective side clearance curtain area is less than the bearing clearance it can't really limit the oil flow out of the bearing. So if you did have like .0025 bearing clearance you'd need essentially .010 side clearance or more and you usually already have double that. Some NASCAR stuff has over .100 side clearance and they definitely don't want lots of oil flying around!
God I am gonna feel stupid if this was just a "Mopar" thing.
10-18-2008, 12:21 PM
#6
FormerVendor
The area the oil escapes from is between the edge of the rod bearings and the crank which is your oil clearance there. Then depending on the construction of the crank it also has to exit out of the side clearance between the rods and on the sides of the rods. Whichever is smaller in area is what limits the oil flow out of the bearings.
If you have .0005 bearing clearace it doesn't matter how much you open up side clearance since no more oil will flow. Also if you have .004 rod oil clearance but only .008 rod side clearance you effectively are running the same as if you had .002 oil clearance since each rod now has only that much area on the sides now.
You have the 4 sides of the 2 rods where oil comes out and only .008 total side clearace so it's basically .008/4 or the same as .002 to each rod's side which is way tighter than the .004 actual oil clearance you had so now you ARE limited by side clearance.
If you have .0005 bearing clearace it doesn't matter how much you open up side clearance since no more oil will flow. Also if you have .004 rod oil clearance but only .008 rod side clearance you effectively are running the same as if you had .002 oil clearance since each rod now has only that much area on the sides now.
You have the 4 sides of the 2 rods where oil comes out and only .008 total side clearace so it's basically .008/4 or the same as .002 to each rod's side which is way tighter than the .004 actual oil clearance you had so now you ARE limited by side clearance.
10-18-2008, 02:49 PM
#7
The area the oil escapes from is between the edge of the rod bearings and the crank which is your oil clearance there. Then depending on the construction of the crank it also has to exit out of the side clearance between the rods and on the sides of the rods. Whichever is smaller in area is what limits the oil flow out of the bearings.
If you have .0005 bearing clearace it doesn't matter how much you open up side clearance since no more oil will flow. Also if you have .004 rod oil clearance but only .008 rod side clearance you effectively are running the same as if you had .002 oil clearance since each rod now has only that much area on the sides now.
You have the 4 sides of the 2 rods where oil comes out and only .008 total side clearace so it's basically .008/4 or the same as .002 to each rod's side which is way tighter than the .004 actual oil clearance you had so now you ARE limited by side clearance.
If you have .0005 bearing clearace it doesn't matter how much you open up side clearance since no more oil will flow. Also if you have .004 rod oil clearance but only .008 rod side clearance you effectively are running the same as if you had .002 oil clearance since each rod now has only that much area on the sides now.
You have the 4 sides of the 2 rods where oil comes out and only .008 total side clearace so it's basically .008/4 or the same as .002 to each rod's side which is way tighter than the .004 actual oil clearance you had so now you ARE limited by side clearance.
Thanks Erik.
