360 Main Bearing Clearance

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?

You will never know exactly where you are until you use the proper measuring tools.

I dont have the tools, and have to use plastigauge like many do, to check.

So bearing that in mind (no pun intended ahaha) what would you do?

If the green stic ain't showing .0015 and is just a little under .002 It'll be fine.

So my options seem to be limited after doing some digging. Clevite is the only manufacturer I can find who makes a .009 undersize set of main and rod bearings (yet to check the rods) but they arent available anywhere until April.

I did all my measurements in a pretty cold environment when I did check the other day. Ive got the fireplace on in the garage right now to get the garage and the parts all warm before checking again.

Is it possible to turn a crank .001"? Or does it have to be a larger amount like .010"?

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...

I have sent cranks back to have them made another .0010 smaller, lots of general, not race machine shops, automotive machine shops like tighter bearing and piston to wall clearances
More oil flow means more bearing cooling to me
I've never spun any automotive engine bearings from being too loose (Correction, sorry), I have seen spun cam bearings as well as rod and mains spin from bearing to crankshaft contact from being to tight whiney:

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.

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?

.010 is for endplay. But this correct buy the book. You won't know the exact clearance, but the plastiguage puts it in the .0005-to-.0025 range for sure.

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

It calls for .010 end play on the crankshaft, not .010 main bearing clearances

may have been a fat fingered .001 ?