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engine builders whats max clearence on mains #1426362 04/27/13 05:28 PM 04/27/13 05:28 PM
Joined: Jun 2005 Posts: 482 Michigan B BigFish69 OP mopar
BigFish69 OP mopar B Joined: Jun 2005 Posts: 482 Michigan	What would be max main bearing clearence on rb race motor I have .00375 to .004 on the mains to loose ? Thanks

Re: engine builders whats max clearence on mains [Re: BigFish69] #1426363 04/27/13 06:28 PM 04/27/13 06:28 PM
Joined: Jul 2008 Posts: 30,451 Florida STAYcation dOoC The village idiot's idiot
dOoC The village idiot's idiot Joined: Jul 2008 Posts: 30,451 Florida STAYcation	I wouldn't like 4 ... but maybe it would be OK using STRAIGHT-50 weight oil ..

Re: engine builders whats max clearence on mains [Re: BigFish69] #1426364 04/27/13 06:31 PM 04/27/13 06:31 PM
Joined: Jan 2003 Posts: 1,784 PA W5DART66 top fuel
W5DART66 top fuel Joined: Jan 2003 Posts: 1,784 PA	If that's with dial bore gauge and you are sure about the number run it. it will be fine.

Re: engine builders whats max clearence on mains [Re: BigFish69] #1426365 04/27/13 07:26 PM 04/27/13 07:26 PM
Joined: Jul 2010 Posts: 2,091 Delray beach, Florida P Performance Only top fuel
Performance Only top fuel P Joined: Jul 2010 Posts: 2,091 Delray beach, Florida	Quote: What would be max main bearing clearence on rb race motor I have .00375 to .004 on the mains to loose ? Thanks I'll answer the question with a question. How did you get to that clearance? Either the crank is undersize or the main housings are bigger than spec. Before i'd say run it, i'd want to know which it is and how much power is the engine going to make. If the housing bores are out of spec, fix them. that's your bearing crush. If those are okay and it's just the crank being on the small side i'd say have at it on a serious combo. machine shop owner and engine builder

Re: engine builders whats max clearence on mains [Re: Performance Only] #1426366 04/27/13 08:22 PM 04/27/13 08:22 PM
Joined: Mar 2006 Posts: 9,852 MI, usa dvw master
dvw master Joined: Mar 2006 Posts: 9,852 MI, usa	For what its worth my line hone was off so we set it at the tight end of the crank bore housing dimension. Mains ended up at .0025". I wanted more so I switched bearing manufactures(no info in front of me as I'm overseas) and got.0028"-.0029". Even though the rod journals were .001" undersize I still only had .0018" on the rods. Had BME resize the rods and ended up with .004" rod clearance. I didn't like the oil pressure so I switched the rod bearings to .001" under, rods now at .003". That really didn't do much for pressure. I ended up tightening the oil pump relief valve spring. Upped the pressure from 45 to 60 at 7000. I probably should have left the clearnce at .004". It's really about oil flow not pressure. Doug

Re: engine builders whats max clearence on mains [Re: BigFish69] #1426367 04/27/13 09:02 PM 04/27/13 09:02 PM
Joined: Sep 2004 Posts: 192 MI R RickRoss member
RickRoss member R Joined: Sep 2004 Posts: 192 MI	U need a small block

Re: engine builders whats max clearence on mains [Re: BigFish69] #1426368 04/27/13 09:45 PM 04/27/13 09:45 PM
Joined: Aug 2003 Posts: 43,228 Bend,OR USA C Cab_Burge I Win
Cab_Burge I Win C Joined: Aug 2003 Posts: 43,228 Bend,OR USA	Quote: What would be max main bearing clearence on rb race motor I have .00375 to .004 on the mains to loose ? Thanks Not in my opinion, as long as there is no other problems. I have bought used fuel crank that where not cracked and used them with those clearances on my own pump gas street motors with no real problems to speak of( 18 lbs oil pressure with hot (190+ F)5W20 Valvoline at 800 RPM idling in gear, 65 lbs at 6500 RPM with the same oil temps three minutes later Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)

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