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Installing Crankshaft Pulley
Posted by: Frog ()
Date: April 16, 2018 05:18AM

This might be another everbody-understands-it-but-me question:

On page 6A-52 of the 1961 shop manual, paragraph 37 describes the procedure for installing the crankshaft pulley. It says: "Draw crankshaft pulley into place on crankshaft, by turning retaining bolt until crankshaft pulley bottoms in place."

O.K. It get that; it's obvious to me.

Here's the phrase I don't get: "Back crankshaft pulley retaining bolt off one turn and torque to 40 to 50 ft. lbs."

Why back the bolt off a turn? Why not just continue tightening up to the specified torque setting?

Thank you.


Rob Lane
Clayton, in the Northeast Georgia Mountains.
1964 500 Coupe
Purchased by me in April of 1964.

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Re: Installing Crankshaft Pulley
Posted by: Murphy ()
Date: April 16, 2018 05:33AM

Engineer verbiage. You're not alone.

65 Monza Coupe
61 500 Coupe-W100181
Earliest '61?

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Re: Installing Crankshaft Pulley
Posted by: JerryM ()
Date: April 16, 2018 07:16AM

That's a common practice for electrical connections because the surface of mating parts usually have some type of plating and friction gives a false reading. So loosening then re-torqueing yields better bolt tension indication.
Maybe the designers felt the process of drawing up the pulley did something similar?

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Re: Installing Crankshaft Pulley
Posted by: cnicol ()
Date: April 16, 2018 07:51AM

If the pulley won't slip on far enough to engage the standard-length bolt, I often start the process with a little longer bolt and then switch to the standard bolt. You don't want to strip-out the crankshaft threads! DAMHIK

Craig N. Coeur d'Alene ID.
66 Black Monza 4dr, 4.2L V8 49k
61 Seamist Jade Rampside 140 PG
60 Monza coupe (sold, sniff sniff)
66 Sprint Corsa convt - First car! Re-purchased 43 years later
2+2 gnatsuM 5691

+17 Tons of parts

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Re: Installing Crankshaft Pulley
Posted by: 66vairman ()
Date: April 16, 2018 08:51AM

Jerry and Craig are both correct.

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Re: Installing Crankshaft Pulley
Posted by: oldqmguy ()
Date: April 16, 2018 10:28AM

I was told by a "real Corvair mechanic" (he worked in a Chevy dealership in Northern Indiana many years ago) that this was to prevent the Bolt from being left "over torqued!" drinking smiley

He said that most mechanics used a LOT of force getting the pulley seated. If they followed the instructions in the Manual the final torque would be correct. spinning smiley sticking its tongue out

It doesn't take much extra time and like Craig said, you really don't want to damage the Crankshaft threads!! grinning smiley

Dale cool smiley

Dale E. Smiley CPBE
Life Member The Society of Broadcast Engineers
RETIRED Broadcast Engineer
CORSA/Circle City Corvairs/Corvair Performance Group
Avon, Indiana
1967 4-Door Monza PG!

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Re: Installing Crankshaft Pulley
Posted by: Frog ()
Date: April 16, 2018 10:31AM

Thanks for the explanations.

I'm going to follow your tip, Craig, and get a longer bolt to start this process.



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Re: Installing Crankshaft Pulley
Posted by: Frog ()
Date: May 24, 2018 04:36AM

Following up on this thread:

I've been accused of "overthinking" some issues I've had regarding this and that about my car.

I bought a new harmonic balancer (on the advice of forum members) from Clark's at last month's Springfest in Helen. Also bought a longer bolt and used it to begin installing the HB. Everything's working out, or so it seems.

My question: How many repetitions of torquing up to specifications is normal?

What happens is that I torque the nut to the specification from the shop manual:40-50 lb.ft.

I've developed the habit of occasionally connecting my beam-type torque wrench to the crank nut just to check the start and rotation torque setting (counterclockwise) to make sure everything's moving smoothly inside the engine.

Last night I did that and the crank bolt turned with the torque wrench. I'm guessing that after reaching the specified torque setting that after a time the HB has "eased" its way further down and then I have to retorque until at some point the HB will seat against the shaft and stay there at the proper torque setting.

Advice, please.

Thank you.


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Re: Installing Crankshaft Pulley
Posted by: JimBrandberg ()
Date: May 24, 2018 05:37AM

I use blue Loctite to keep the 1/2" bolt from loosening when turned counter-clockwise. I've taken to turning the engine clockwise when doing a lot of things like lifter adjustment or getting back to #1 TDC.
It's scary indeed when the crankshaft threads are messed up. The stock bolt is 1 1/2". I use a 2" when installing. I've used 1 3/4 to engage some new threads when the crankshaft threads are iffy.
I need to remember to get some Grade 5 bolts next time I'm at the bolt store. The hardware store only has Grade 8. I think in a battle of threads I would prefer that the bolt would lose.
I use a block of wood to hold the crankshaft if the top cover is off, much prefered to a screwdriver wedged in the harmonic balancer slot. Is there another method I haven't thought of? Wedging something in the ring gear teeth makes me nervous, I'd hate to mess one up.

Jim Brandberg
Isanti, MN

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Re: Installing Crankshaft Pulley
Posted by: Frog ()
Date: May 25, 2018 06:24AM

Thanks for the Loctite tip. I didn't think of that--which is not unusual for my soon-to-be 75-year-old mind.


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