Torgue Specs.?

[wartruk44]

Can someone tell me the torque specs. for the connecting rods and the main bearings? GMC 270

[dr deuce]

Which engine:

WW2 270

or

1950's 270

I don't know if they are different, but I found out by accident that the head bolt tightening sequence is different on the WW2 270 vs the 1950's 302 engine (same design blocek and head)

[joel gopan]

The Sequence for the 270 in the early TM10 Maintenance Manual and later TM9-801 is the same and recommends 70 ft/lb. There is another sequence I use from Dec 43 and Nov 44 GM Bulletins G-82 and G-82A which are reflected in a 1950s Change to TM9-801 which increases the final Torque to 80 ft/lb. I do not have a copy of the change to pass around. The Factory service bulletin has a sequence of tightening the Head bolts to 35 ft/lb first, that "seats head gasket, and gasket to block, ironing out gasket evenly throughout." I recommend not to confuse CCKW engines with the Tightening Spec for 302 M-series as you may get into trouble as GMC had a different Sequence for that model, and threr were changes in the bolts,early bolts were tightened to 70-80 ft/lb, and the heads with later bolts were tightened to 90-100 ft/lb
If a CCKW 270 head is tightened using later spec, you may damage the block, of crack your head. Stick with the CCKW TM to be safe.
Joel

[wartruk44]

Thanks for the great info on the head bolt torque specs. but I really do need the torque foot-pounds for the connecting rods and the main bearings.

[joel gopan]

Main Bearing Bolts 70-80 ft/lb. Rod Bearing nuts, are 40-50ft/lb and are special nuts.
Dont forget to use a copper washer on the lower Timing Cover Bolts that go thru the front main bearing cap.

[wartruk44]

Thank you Mr. Gopan

[joel gopan]

You are welcome.
As for the Copper Gaskets(washers), they are important, and are hard to find loose. Dorman has assortments, but it is hard to find Dorman products the new era Parts Stores we have today. Carquest Stores up here sell Dorman, but the may not stock assortments that fit those two 5/16" bolts. The Felpro OH Gaskets sets may have fiber washers in the sets and they do not work well. My CCKW came back from Denmark in 83 with a "0" Time 270 installed, but I lived with a drip that would leave a 3" oil spot every time I shut it down for twenty years. The timing seal was changed, and I even installed a NOS Harmonic Balancer with a Redi-Sleeve kit and yet it leaked in a manner that I could not directly trace. In order to change the gasket on the timing cover, which was also suspect, it would involve removing the Oil Pan. Installing an Oil Pan on a 270 is not all that simplw, as the two Cork end Gaskets will give you fits, they keep popping out of place. Weatherstrip adhesive, or a quick setting gasket adhesive by Permatex (I have forgot the correct name, or Contact Cement will do) I finally got tired of this, and built a nearly NOS 270 starting with a crated bare block and filling it with 100% NOS parts, topping it off with a reconditioned Cylinder head. It does not leak now.

I have included this long winded reply for those of you new to 1940s technology that may encounter a similar problem with your CCKW.
Now you are all experts.
Stay tuned to ol' Joe for more good stuff.

[wartruk44]

I have the original copper washers in place they looked ok. I was wondering about bolts that are threaded into an oil chamber with nothing but a lock washer that as you know has a split in it. Good place for oil to escape, am I wrong on that? I like to use the "ULTRA" gasket maker by Permatex on the threads to eliminate any oil leaks. Is this idea a good one? Thanks Mr.Gopan

[joel gopan]

GMC has taken into consideration bolts that pass completely thru a component where there is a chance for oil to migrate to the outside. On the CCKW these places can be found wher the rocker arm Brackets attach to the Cylinder Head (you can see these threads just above the spark plugs) (not all CCKW heads were threaded completely thru) and the Lower Bolts that attatch the Transmission tohe Bell Housing. In these instances the best method of sealing is the same method used in WWII. Permatex #2 Non Hardening Gasket Sealer is applied to the bolt threads in the area where they pass thru.