360 Main Bearing Clearance
#3208246
01/26/24 10:13 AM
01/26/24 10:13 AM
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mshred
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Doing a super budget rebuild on a late 70's 360 engine (ala no machine work, stock bottom end). Upon disassembly, I found it had .010" under bearings on the rods and mains, so I ordered some half groove bearings for .010" under for the mains and rods. I don't have access to a dial bore gauge at the moment, so I am using green plastigauge, and the main bearing clearance at the crown on every single main was just a hair under .002". I know that can be considered tight, and this is somewhat of a performance rebuild, although I don't plan to spin this past 6500rpm considering the nature of the build parts, but I am still a bit concerned
Wondering what my options are for getting more clearance, as I would truly be more comfortable with a .0025" clearance even though factory spec is between .0015-.002 if I recall, but other than crank grinding not sure anything else will get me there (I have always understood that a crank polish really doesn't gain much, and sanding bearings is considered a no no by many). Do I buy another set of bearings and hope for the best? These are Enginetech bearings and I will be running a standard volume pump with the high pressure relief spring. What would you do- slap it together? Machine work? Different bearings?
Last edited by mshred; 01/26/24 10:15 AM.
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Re: 360 Main Bearing Clearance
[Re: mshred]
#3208255
01/26/24 10:57 AM
01/26/24 10:57 AM
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Joined: Feb 2005
Posts: 20,175 PA.
pittsburghracer
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"Little"John
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Posts: 20,175
PA.
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You will never know exactly where you are until you use the proper measuring tools.
1970 Duster Edelbrock headed 408 5.984@112.52 422 Indy headed small block 5.982@112.56 mph 9.42@138.27
Livin and lovin life one day at a time
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Re: 360 Main Bearing Clearance
[Re: B1MAXX]
#3208539
01/27/24 03:52 PM
01/27/24 03:52 PM
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If the green stic ain't showing .0015 and is just a little under .002 It'll be fine.
Part of me is saying im overthinking it and I will be fine, but the other part of me is panicking a bit for my lack of self control and wanting to in tbe future at some point maybe throw a nitrous bottle or supercharger on it...
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Re: 360 Main Bearing Clearance
[Re: mshred]
#3208541
01/27/24 03:56 PM
01/27/24 03:56 PM
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Joined: Aug 2003
Posts: 43,195 Bend,OR USA
Cab_Burge
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I Win
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Bend,OR USA
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Last edited by Cab_Burge; 01/29/24 12:55 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: 360 Main Bearing Clearance
[Re: B1MAXX]
#3208742
01/28/24 01:12 PM
01/28/24 01:12 PM
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Hit them with a dry paper towel. Ill give that a try and see what I get, hopefully it gives me a .0002 lol. I looked at the specs on another stock bottom end build I did years ago, also with 360 mains, and I only had .002" clearance as well (thought it was looser) and I beat the snot out of that engine combo on the street and the track, so hopefully I will have the same luck this time around as it is going to be more of a street engine.
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Re: 360 Main Bearing Clearance
[Re: dizuster]
#3209518
01/31/24 02:07 PM
01/31/24 02:07 PM
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For what it's worth, the factory 1973 service manual calls for .0005" to .002" with a desired number of .010"
Depending on your goals I'm not sure I'd be too worried about it.
How much compression and cam is this thing getting, and with what heads/intake?
Yea, I have a 1971 service manual and a couple of engine books, so according to them I am on the looser end of the factory accepted clearance, although plastigauge obviously still has a margin of error. But im good with it now after double checking them again. Its a .030" over stock bottom end build with factory replacement pistons a mile down in the hole. Getting a street/strip flat tappet, speedmaster aluminum heads, and will have 8.5:1 compression....However, I have opened up the ring gaps as I wouldn't mind either throwing a supercharger on it or a cheater kit in the near future, and that is what I am thinking about right now even though that will be a ways off until it happens, otherwise I wouldn't have too much worry about it. As long as I let it warm up completely before I beat on it, I am hoping for it to be okay
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