Problem with ACL race rod bearings?
06-27-2010, 11:02 AM
#1
8 Second Club
Thread Starter
iTrader: (39)
Join Date: Aug 2008
Posts: 90
Likes: 0
Received 0 Likes
on
0 Posts
Problem with ACL race rod bearings? I am seeing about .002" out-of-round with these ACL race bearings. I have brand new CompStar rods, which measured 2.2501 on the bore gage with less than .0001" out-of-round. On the rod centerline I measured about .0031" clearance. When I rotated the bore gage around to the bearing split line, the clearance grows to about .005". All 8 bearings measured very similar within a couple of tenths...
Sounds normal after responses from engine builders.
Thanks guys.
Sounds normal after responses from engine builders.
Thanks guys.
Last edited by TransAm-Z; 06-28-2010 at 08:17 PM.
06-27-2010, 11:17 AM
#2
FormerVendor
iTrader: (3)
Join Date: Jun 2007
Location: Virginia Beach,Virginia
Posts: 2,991
Likes: 0
Received 2 Likes
on
2 Posts
I am seeing about .002" out-of-round with these ACL race bearings. I have brand new CompStar rods, which measured 2.2501 on the bore gage with less than .0001" out-of-round. On the rod centerline I measured about .0031" clearance. When I rotated the bore gage around to the bearing split line, the clearance grows to about .005". All 8 bearings measured very similar within a couple of tenths...
Is this normal for these bearings or are these ACL bearings junk? Any suggestions?
Thanks
Is this normal for these bearings or are these ACL bearings junk? Any suggestions?
Thanks
06-27-2010, 06:16 PM
#4
Eccentricity The out of round spec. of .002" is average for most race style bearings. Not enough eccentricity and the bearing will pinch the crank at high revs due to distortion of the con rod big end.
I don't know what you are building there but three thou is a bit much for vertical clearance regardless.
I don't know what you are building there but three thou is a bit much for vertical clearance regardless.
__________________
Steve Demirjian
Race Engine Development
Oceanside, Ca.
760-630-0450
web: www.raceenginedevelopment.com/
e-mail: race-engine-development@***.net
Steve Demirjian
Race Engine Development
Oceanside, Ca.
760-630-0450
web: www.raceenginedevelopment.com/
e-mail: race-engine-development@***.net
06-27-2010, 07:40 PM
#5
8 Second Club
Thread Starter
iTrader: (39)
Join Date: Aug 2008
Posts: 90
Likes: 0
Received 0 Likes
on
0 Posts
The out of round spec. of .002" is average for most race style bearings. Not enough eccentricity and the bearing will pinch the crank at high revs due to distortion of the con rod big end.
I don't know what you are building there but three thou is a bit much for vertical clearance regardless.
I don't know what you are building there but three thou is a bit much for vertical clearance regardless.
My build is a Turbo 408 est 1000FWHP. Not sure if I can really hit that number, but it should be close. I was going to shoot for .0025-.0030 for all rods and mains. I am about a tenth bigger than I was expecting, but I'm not sure if I should buy another set of bearings.
06-28-2010, 08:22 PM
#7
8 Second Club
Thread Starter
iTrader: (39)
Join Date: Aug 2008
Posts: 90
Likes: 0
Received 0 Likes
on
0 Posts
Am I correct to assume that the main bearings will not have this eccentricity built into the bearing (or not as much) since the cap and block are so stout and should not see much close in?
BTW I got my Trick Flow heads in today you sent and they look nice! Thanks for all of your work switching the AFR for these. I will definitely be buying more from you in the future.
Trending Topics
06-29-2010, 12:48 PM
#9
Like Shawn said, you need the out-of-round area to build a hydrodynamic wedge of oil between the journal and bearing. It's the same reason the thrust bearing suface has those little troughs on them. Clevite has a nice bit of info on this in their catalog, which you can even find online.
