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engine builders, bearing clearance?

Posted By: 68roadrunner

engine builders, bearing clearance? - 09/04/09 01:00 AM

what would be the best rod and main clearances, and do you run different weight oil with different clearances? this is a 499 stock rb block, eagle crank, eagle steel rods, milodon single line system, w/ hv oil pump. this is an all race motor, 6800 shift maybe more on 1/4 mile.thanks alot.
Posted By: Anonymous

Re: engine builders, bearing clearance? - 09/04/09 01:58 AM

minimum .001 per inch of journal diameter is generally safe. more info would be needed to make an actual recommendation though.
Posted By: 68roadrunner

Re: engine builders, bearing clearance? - 09/04/09 02:16 AM

Quote:

minimum .001 per inch of journal diameter is generally safe. more info would be needed to make an actual recommendation though.



what kind of info? 13-1 flat top around 615 gram piston, alky dominator, [Email]280@.050[/Email] 683 lift. indy -1 325cc runner. glide 1854lbs w/driver. thanks
no power adders
Posted By: Cab_Burge

Re: engine builders, bearing clearance? - 09/04/09 04:32 AM

Aluminum rods or steel? When it comes to bearing clearances your way better off having them a 1/2 thousnad to loose than 1/4 thousand to tight. Use what dram recommended Or looser BTW, I like thin oil also, 5w20 or 5w30, especially in a drag motor that never gets the oil hot
Posted By: gregsdart

Re: engine builders, bearing clearance? - 09/04/09 07:23 AM

Ran my 499 a tad loose at .0027 to .0028 on the mains, rods about .0025 to .0027 aluminum rods. 20w50 oil, safest for the power level you will be at.
Posted By: 440Jim

Re: engine builders, bearing clearance? - 09/04/09 12:14 PM

FWIW, I aim for 0.0030" on the mains (2.75" dia) and 0.0025" on the rods. Guys run them tighter and looser...
Posted By: sixpackbee

Re: engine builders, bearing clearance? - 09/04/09 12:19 PM

For your engine I would run about what the others have said, .0025-.003, with a thicker oil. Just an FYI on class engines I run about .0015 clearance with real thin oils.
Posted By: B G Racing

Re: engine builders, bearing clearance? - 09/04/09 12:23 PM

Race engines mostly like ..002+.We use .002/.0025 with multiviscosity synthetic oils and .003/.0035 with straight weight oils such as 40W,50W and 70W.
Posted By: 68roadrunner

Re: engine builders, bearing clearance? - 09/05/09 02:39 PM

if i go .003 on rods and mains both, and run a 50w or 20-50 oil this will be ok on a bracket motor? thanks guys
Posted By: 440Jim

Re: engine builders, bearing clearance? - 09/05/09 02:58 PM

Quote:

if i go .003 on rods and mains both, and run a 50w or 20-50 oil this will be ok on a bracket motor? thanks guys

That does seem like a lot for the rods. Are you running steel rods or aluminum? Are they 2.200" or 2.375" journals? It will give more oil flow to the rods for cooling.

I wouldn't run straight 50 oil on a "mild" bracket motor unless you have a good reason. 20W-50 would be fine, IMO.
Posted By: Cab_Burge

Re: engine builders, bearing clearance? - 09/05/09 03:42 PM

Quote:

if i go .003 on rods and mains both, and run a 50w or 20-50 oil this will be ok on a bracket motor? thanks guys

I run those clearances or looser with thinner oil The single wieght oil can make as much as 10 HP loss or gain depending on oil temp. differences, that is why I run 5w20 or 5w30 in my motors now. 10 HP is usually a tenth of a second defference at the track
Posted By: 68roadrunner

Re: engine builders, bearing clearance? - 09/06/09 03:04 PM

Quote:

Quote:

if i go .003 on rods and mains both, and run a 50w or 20-50 oil this will be ok on a bracket motor? thanks guys

That does seem like a lot for the rods. Are you running steel rods or aluminum? Are they 2.200" or 2.375" journals? It will give more oil flow to the rods for cooling.

I wouldn't run straight 50 oil on a "mild" bracket motor unless you have a good reason. 20W-50 would be fine, IMO.




steel eagle, 2.375 i suppose at .0025 i would be closer to the .001 per inch rule.
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