Question about torquing the heads.

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L31MaxExpress

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Yup! Maybe Chevy should have stayed with the 1/4"-20 stove bolts, with the straight blade heads....
They worked quite well except for people would over torque them. I saw a tip in the How to Hotrod your SBC book that had alot of information from Smokey Yunick in it back in the earlier 70s. They gave a part number and a tip for the Corvair load spreaders for the SBC valve covers. Wouldn't you know, low and behold I start to remove the valve covers on my 83 G20s 305 and it has those load spreaders from the factory along with a little metal tab that bolted on over them to hold the factory spark plug wire loom clips. I thought it was funny at the time that GM had added a Yunick hot rod tip to factory SBCs. I guess over time they evolved and started doing the same with the oil pan. Aftermarket companies like Champ now make the spreader rails for older 2-piece rear main blocks and Felpro makes the nice single piece oil pan gasket that works great compared to the 2 rubber ends and cork side rails that make the 4 piece garbage always leaks setup.

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0xDEADBEEF

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In theory, once it begins yielding, you don't need to turn it anymore. I think they have these weird procedures because it's easier for the machine to turn X degrees than it is to "feel" it.

I've seen some charts showing the clamping force and it rises up until it yields, then it basically stays the same for a fairly wide range, and then if you keep turning it falls. There's no significant clamping difference anywhere in that plateau, so the beginning of it is just as good as the middle or end. In theory ...
 

Schurkey

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I bought a brand new quinn torque wrench with a built in angle system
What is a "quinn" torque wrench?

Most any torque wrench needs to be cycled a couple of times before actual use. Removes excess friction from the mechanism.

I know the ultimate goal is to reach a certain stretch right?
No, the ultimate goal is to reach a certain clamp load on the parts.

TTY bolts--which these are not--have variable stretch, but consistent clamp load.

"Regular" bolts have restricted stretch, are reusable, but inconsistent clamp load. Gotta make sure all threads are in good condition, proper lube, etc.

The "compromise" between TTY and "regular" torquing is Torque-Angle. Reduces the effect of improper lube, damaged/dirty threads, etc.

The "big mistake" folks sometimes make is to lube the underside of the head bolt washer (if used) where it touches the head. (Lube the bolt-head-to-washer, but not the washer to cylinder head.) Then the washer spins on the head under torque load, reduces friction, leads to over-torquing and broken fasteners.

I found a first a while back I had not seen. I pulled the OEM 1987 TBI 305 out of the 87 G20. It had torx bit screws for valve cover bolts. It had 104K on it and by all appearences and the hardened condition of the valve cover gaskets had likely never been apart. I cannot think of another 87+ V8 I have seen with center bolt valve covers that had Torx screws holding them on.
Some of the later perimeter-bolt valve covers got inverted-Torx studs, with a kinda-self-locking nut. Nice set-up if your valve covers were thin enough (stamped steel) to work with them. The studs weren't long enough for most cast-aluminum covers.

In theory, once it begins yielding, you don't need to turn it anymore. I think they have these weird procedures because it's easier for the machine to turn X degrees than it is to "feel" it.

I've seen some charts showing the clamping force and it rises up until it yields, then it basically stays the same for a fairly wide range, and then if you keep turning it falls. There's no significant clamping difference anywhere in that plateau, so the beginning of it is just as good as the middle or end. In theory ...
Kinda depends on whether the fastener is Torque-To-Yield (TTY) or merely uses a Torque-Angle procedure on a non-TTY fastener.

TTY fasteners are one-use, disposable. Using a Torque-Angle procecure, but not a TTY bolt, may be reusable. GM is "big" on Torque-Angle head bolts that are not TTY.
 

Erik the Awful

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What is a "quinn" torque wrench?

Most any torque wrench needs to be cycled a couple of times before actual use. Removes excess friction from the mechanism.
Quinn is Harbor Freight's better brand. They're fairly nice.

Torque wrench cycling is important for cleaning off any small corrosion or hardened gunk that may have settled between uses. The best thing to do is make a fixture that you can bolt down or put in a vise. 4:10 in this video shows my fixture.

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Astro

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Guys thanks for all your posts. They were all very helpful in giving me a broad understanding of what I'm doing here. In the end, I torqued them to angle with the Quinn and everything worked out great. Truck is running well and nothing is leaking.
 
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