~Torque that Head --- Properly!~



By K. Patrick Smith

 

While looking through my FelPro torque specification book I discovered 2 standout items...

The first thing was that the 261 had a different torque pattern than the 235! I called Tom Langdon and he was also surprised. Research said that yes, this was true. It seems that the Siamese block causes different warp characteristics than the full water jacket on the 235.

If you are using a 235 (head) on a 261 use the 261 torque sequence. It’s the block that makes the difference.

The second item was that there were no specs for the GMC!

Looking through the factory manuals did show the same installation procedure for these early engines with sandwich gaskets:


Use a sealer. Copper Coat is good, as is Aviation Permatex. Silicon (RTV) is NOT.
Neither is oil, water or grease.

Guide the head down with installation studs or cut off head bolts. Failure to do this will probably cause a head gasket shift, not good on a 1/8" overbore.

Use a light oil on the threads. If the bolts go into the water jacket as on the late model Chevy 194 - 292 You should use a sealer. Aviation Permatex, or my favorite, Loctite’s Teflon thread lock and sealer. Again, NO SILICONE (RTV).

Torque down the head with at least three sequences. For example; 30 ft.lbs., then 60 ft. lbs., and finally 90 ft. lbs.

Bring the head up to operating temperature without driving it. Then shut it off.

Re-torque the head while the engine is still warm. The best way to do that is to loosen each bolt ˝ a turn. Do one bolt at a time, then bring that bolt up to the final, full torque in one smooth, even pull. That should do it, drive it and have fun. By the way while you are warming it up, if it has a new cam do not let it idle under 1500 RPM for the first hour. And make sure you have plenty of coolant, this is no time to overheat.

If you have an aluminum head, it should be allowed to return to room temperature before the re-torqueing is done.

- The Sixfiend

(Original 12 Port News Pub Date - May `94)