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#1
06-08-2011, 10:46 PM
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Main Bearing Clearance
I was just wondering if anyone has successfully ran .004" clearance on the mains of a 455. It has 3.5" mains journals and is a full race motor. I know that this is on the large size but was curious about if it would work and how many of you all do or have run a clearance this large. Also with this clearance would you all suggest running an Mellings M54D or a Mellings M54F Oil pump? This is a bracket engine that will spin at a maximum of about 6800 RPM.
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#2
06-08-2011, 11:41 PM
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Quote:
__________________
Bill 64 GTO, tube chassis w/606" IA tall deck, PG & a pro geared Fab 9". 2750 lbs. 8.2550@164.17-1/4, 5.2901@131.97-1/8, 1.1981-60-ft. 8/10/08 
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#3
06-08-2011, 11:53 PM
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Yes I ran .004 in my 535ci with no problems. Ran a 80lb mellings pump. No problems with oil pressure. Just make sure you do ALL you can to keep your oil in your oil pan .
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#4
06-09-2011, 06:26 PM
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455 Pontiacs are fine with .002-.0025 on the rods and .003-.0035 on the mains.
So I would think .004 would be no big deal. My 455 mains were set up for .003-.0035 and has been together for 600+ runs and has had 2 sets of main bearings installed and I hand polished the rods and mains with 600 grit sandpaper both times so I bet they are at least .004. Runs great. |
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#5
06-09-2011, 08:18 PM
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I wouldn`t sweat it too much. It`s a little large but it`s a race motor. I`d at least run the Melling 10541 with those clearances.
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#6
06-09-2011, 09:57 PM
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Maybe look into getting the main bearings & main journals coated?
The coating would take up a little of that excess clearance,say .000X" and get it to like .003X" instead of .004" or so. That would also add a little more "safety margin" for the bearings/journals as well should the oils hydro-dynamic wedge get a little sketchy at some point. Just an idea... FWIW Bret P. |
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#7
06-09-2011, 10:24 PM
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I'd also use a quality synthetic, higher viscosity oil if you are down on oil pressure.
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#8
06-10-2011, 09:10 AM
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I got the block back yesterday. The actual measurements are better than I thought. A couple of the journals are 0.0035". I believe I will be alright. I will try a good synthetic oil after break in. I will start with a 10W40 and work my way up or down to get the most desirable oil pressure. What pressure do you guy recommend at idle and at WOT?
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#9
06-10-2011, 12:13 PM
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I run 3 quarts Wall Mart 20-50 mineral, 2 quarts Wall mart 10-30 synthetic and one quart Lucas.
I have 60lbs running down the track, 40-45 hot at idle. It gets down to 20-25 idling in gear on the return road. With fresh oil cold it will get to 70-75 at 2000RPMs or so. It has a lot of runs on it, it used to be 55lbs hot at idle. BTW, the Wall Mart synthetic 10-30 has the EXACT same rating as Mobil 1. Basically the same oil. You could run that with a qt of Lucas. They make Lucas for synthetic oil but it is thinner. I like that thick standard Lucas. I have never hurt a engine with it. It makes the oil a "sticky film". Its hard to get off when you tear down a engine. It might cost 1-2 horsepower but its worth it. |
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#10
06-10-2011, 05:19 PM
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I mostly just run 20w50 down here.
It gets hot as hell during summer here,the high ambient temps often causes cars to run on the "hot" side of things,and that often breaks down thinner oils pretty fast. I rarely ever run anything thinner than 10w40 in older cars here,even in the daily drivers. Straight 40w also works pretty good down here too. And I pretty much stick to using dino oils,no synthetics for me. I change my oil far too often to waste the high $$$$ stuff like that. 2¢/FWIW Bret P. |
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