nate99

I did a bit of searching, and could not find definitively what the sequence needs to be for torquing four bolt main bearing caps.

I know that, in general, you need to go inside out, but does anyone have a link to a diagram or something?

I have a 290 HP GMPP engine that will be going in my '81 shortly, and I have read about several people having bad experiences with the mains not being properly torqued down from the factory.

Many thanks...

TimAT

Inner bolts first in steps and then outer. Make 100% sure the cap is seated in the register BEFORE you start tightening anything.

nate99

Thanks. I am presuming that everything should be seated properly from assembly at the factory, but the issue seems to have been too little torque applied.

Jughead

When I did my BB, I think it was in 3 steps, 60lb, 85lb and then 110ftlb if that helps

TimAT

Be sure you check the torque specs. I think the inner (long) bolts get more than the outer (short) bolts.

kevinator80

I am afraid you came to the wrong place for anything definitive.

All we have around here are opinions.

fauxrs2

yeah better go buy a book ar head to your nearest bookstore with a pen and paper...big block specs are different than small block.. 75# inner 65# outer on a small block IIRC - but again get some reference material...

As far as pattern goes... #3 (center main first) #2 - #4 - #1 - rear main last is the pattern I use.

nate99

I have a haynes manual that I need to look through, but I'm not sure that it would have four bolt main specific recommendation since (to my knowledge) C3's did not come from the factory with anything but 2 bolt mains.

I need to get a better book anyway, maybe the "how to rebuild the small block chevy" will have it...

Barry's70LT1

Hi,
Here is the page from "How to Hotrod Small Block Chevys". It gives most of the torque specs you should need. I verified the torque specs for the mains with a Chevrolet service manual, which states the same.

Also, just to clarify, there were several C3 small blocks that came with 4 bolt mains.
All the L46 and LT-1, I'm not sure about the later L82s.

Regards, Barry

PeteZO6

Various C3s came with 350 4 bolt blocks. My late '69 with the base motor has them. Not sure of all the years, but they did appear over the years.

Here's the straight scoop from the 1969 Chassis Overhaul Manual (Official GM book), Engine Torque Chart - page Specifications 11:
7/16-14 Main Bearing Cap - 75 ft. lb. with a note, Outer bolts on engines with 4 bolt caps 65 ft. lb. There is no chart giving the order.

No guesses, that's the official word.

Cheers,
Pete

nate99

Many thanks...

I will use those specs and just basically work from the inside out on the inner bolts, then do the same on the outers.

I did not realize that there were ever any 4 bolt main SBC cars from the factory, but I suppose that I should have known better, thanks for the info...

topless 77

i am glad you started this thread because i will need this info soon also. but i thought all c-3 vette engines were 4 bolt. Does anyone know anybody who had a 2 bolt factory? I have never heard of any.

nate99

I could be completely up a tree, I just assumed (obviously incorrectly) 2-bolt mains all around...

jackson

With rare exception, all L48 & L81 are 2 bolt.
Similarly, most LT1, most L46, most L82 are 4 bolt.

FB007

Pattern? What pattern? Inside/outside. Any order is fine.

fauxrs2

The order I gave is the Order I use...not in any way official

stingr69

75# on the longer ones 65# on the shorter ones for 4 bolt mains. It does not need to be in a pattern. You might want to sneak up on the final torque reading by going around in several steps like 35#-55#-Final# but honestly that is probably overboard.

Get Vizard's book - It's the Bible.

-Mark.