bearing clearance for std. oil pump with some rpm?
January 17 2012 at 11:02 PM
(Login mach72) Member from IP address 67.217.158.103
I am building a 408c stroker for a street car that will only occasionaly see the 1/4 mile strip. I will try to keep max rpm around 6200, but no more than 6500. I am going to use a std oil pump instead of a hi-volume. How tight can I run bearing clearances using a thinner oil like 10w-30?
clevochild (Login clevochild) Member 60.230.159.55
bearings
January 17 2012, 11:11 PM
Mate, with those revs I'd be OK with 2 1/4...2 1/2. Wouldnt bother with a full groove main.
Depending which stroker kit you have you should come in at this range out of the box. Last eagle one I did (old stock eagle) came in very close to 2 1/2 with clevite bearings.
I like to hit around .0025" for my street stuff...
January 18 2012, 6:59 AM
...on 2.100" rod journals and 2.750" main journals. I like to see a little more main clearance on my larger journal engines (385 series, Windsors, etc).
I usually use .025" clearance on rods/mains, but I also use a hi-volume pump. This time I am going to use a std. volume pump, and I wondered if I should tighten up the clearances some.
Street motor dimesions that have been used for 40 years
Main clearances = 0.0020" - 0.0025"
Rod clearances = 0.0025" - 0.0030"
The conservative dimension for the mains helps keep the oil pressure up and encourages oil to flow to the rods. The rod clearance is in line with Clevite's recommendation for a performance motor having 2.31" journal diameter.
By the way ... Grinding a high nodularity iron crankshaft "opens" the graphite nodules located at the surface of the journals leaving microscopic ragged edges which will damage bearings. The crankshaft journals should be polished in the direction of crankshaft rotation to a finish of 10 micro inches Ra. In order for polishing to be most effective it is also essential that the crankshaft is ground in the opposite direction of rotation and/or polishing.
I've always used .0025~.003 on mains, close to .0025 on rods. Bearings always looked good on teardown. Just make sure when you put them in that the saddles, caps, and bearing backs are clean enough to lick. If you lick 'em, blow them off with air again after.
