Torque on Balancer Bolt (?)

[Stuart F.]

Was just getting set to adjust my valves and was testing various methods to bar the engine over in the process. I placed a 5/8" deep well socket and half inch flex drive on my balancer bolt to see if I could turn the engine over this way (strong enough). Much to my surprise, I found the bolt loose! I've checked my service manual and it doesn't show a torque value, or even state that it should be torqued! What gives?

There seems to be a thick shoulder under the bolt head, but I can't see into the end of the balancer area.

Before I put my torque wrench on that bolt, I need to determine if it is to be torqued and to what value. Thought I'd throw this out there to see if someone knows about this, and I will keep checking my books in the mean time.

Stu Fox

[Stuart F.]

Re: Torque on Balancer Bolt (?)

Suppose I should mention that I have the 63 340 hp L-76 engine.

Thanks.

Stu Fox

[Jack H.]

Re: Torque on Balancer Bolt (?)

Interesting, the Corvette Shop Manual doesn't list a torque spec for the harmonic balancer! But, when I check specs in my '71 Chevy Chassis Service Manual, they group the flywheel with the damper listing the same 60 ft-lb specs for all SB's...

[Chuck S.]

Re: Torque on Balancer Bolt (?)

Suppose I should mention that I have the 63 340 hp L-76 engine.

Thanks.

Stu Fox

My 66 Chassis Overhaul Manual shows 60 ft-lb for small blocks (7/16-20) and 85 ft-lb for big blocks (1/2-20).

[Domenic T.]

Re: Torque on Balancer Bolt (?)

Stu,
My guess is that for the length and hardness of the bolt & crank that about 50lbs should be safe as it is a safety bolt for a press fit balancer.

I would turn the engine over a different way to be safe if the plugs are in.

DOM

[Timothy B.]

Re: Torque on Balancer Bolt (?)

Stu,

1967 GM service manual calls it out at 60ft lbs.

This bolt should be grade eight and I believe there is supposed to be a external tooth star washer under the head, from memory it's 2 1/4" long.

[Stuart F.]

Re: Torque on Balancer Bolt (?)

Thanks fellows. I'll put my torque wrench on it and run it up to 50 ft lbs to start with, then 60 if it feels right. I was just so surprised to find it loose, and no value given in the service manual.

Stu Fox

[John H.]

Re: Torque on Balancer Bolt (?)

Thanks fellows. I'll put my torque wrench on it and run it up to 50 ft lbs to start with, then 60 if it feels right. I was just so surprised to find it loose, and no value given in the service manual.

Stu Fox

Stu -

The torque is shown in the Assembly Manual. If you'll look in the L-75/L-76 section, sheet 2.00, under "Miscellaneous", it shows that the crank pulley, bolt, lock washer, and washer are installed the same as with RPO L-84. Section L-84, sheet 2.00 shows that installation, and the bolt torque is shown as 60-90 ft-lbs (item #15, torque symbol 3).

[Duke W.]

Re: Torque on Balancer Bolt (?)

I've always used 80 lb-ft.

Are you ever going to just try bumping the car in top gear with the brake off? It's the easiest way IMO.

If you insist on using a breaker bar on the balancer bolt, removing the plugs makes it easier to turn the engine, but it's not necessary. You just have to turn it slow to give the compression time to bleed down.

Duke

[Stuart F.]

Re: Torque on Balancer Bolt (?)

As a follow up; I was able to adjust the valves w/o any problems. I used my large torque wrench to bar the engine over. I hadn't intended it that way, but wanted to put some torque on the bolt first. Starting at 40 ft lbs, and the engine rotated. So, I just kept going until I was finished with the adjustment. The car was on ramps as I first applied the timing tape from below (that went well also). The torque wrench has a ratchet head so that worked out better than a flex head, what with the limited throw space around the fan and belts.

Now then, I'd like to still put some torque on that bolt. My plan is to incorporate a reverse of the "bump" method (so to speak) to lock the engine from rotating, i.e. put it in gear, then block the wheels. Does this sound practical or is there another (better) way. I don't have a helper, and I can't access the flywheel to engage the ring gear with a screwdriver like we used to do back in the 50's (no bottom pan on bell housing).

Any suggestions?

Stu Fox

[Richard M.]

Re: Torque on Balancer Bolt (?)

Stu, That's a good idea IMO....just PLEASE make sure you disconnect the battery first.

So this came up on the 427 I'm working on right now after being rebuilt. I got it in last Friday, and have been test fitting things before it goes back in the car. Yesterday I wanted to install the fuel pump, so I put a 1/2" bar on the 3/4" crank bolt. All plugs were out. The bolt turned some. I was wrenching clockwise. This is a fresh rebuild so it's tight inside.

I could just go out and start my '59 and see which way the engine turns, but I'm lazy. What is the SB & BB rotation direction, looking from the front.... CW or CCW?

If it's CW(which I recall it is), the crank bolt will have a tendency to loosen due to opposing inertia. Maybe some threadlocker on the bolt is in order? Also, I know my C6 requires a new crank bolt whenever the damper is removed as it's a stretch bolt.

Should a new bolt be used on our old ones if it's suspect? I seem to recall reading that somewhere.

Rich

[Stuart F.]

Re: Torque on Balancer Bolt (?)

Rich;

Your asssumption is correct on the rotation. I learned in my high school auto mechanics class that you always are to refer to anything position wise on or of the engine as from the driver's seat. Therefore, it is a CCW rotating engine, but from the front, of course, it is barred over in a CW direction. Ironically, the timing tape I put on is marked a little strange which caused me some concern. In order to read the indicators and numbers right side up as you view the timing tab (indicator), I had to put it on so it reads; TDC, 270, BDC, 90. When following the Williams/Hinkley valve setting guide, which reads; TDC, 90, 180, 270., I had to do some mental conversions and found myself at the wrong valve a few times. I also had a bit of a set back when I'd done a few intakes and then noticed I had a .006" gauge stuck to my .008" for a total of .014"!!! (don't laugh).

Thanks for the battery reminder. I have a ground interrupt knife switch.

Stu Fox

[Duke W.]

Re: Torque on Balancer Bolt (?)

Put the tranmission in fourth, apply the parking brake firmly, and torque the bolt to 80 lb-ft.

The engine rotates CW viewed from the front, so turning the engine in the normal direction won't loosen the balancer bolt, but it should not take 80 lb-ft to turn, so turning it CCW should not loosen the bolt, and the bolt can be reused as long as the threads aren't damaged or it hasn't been significantly overtorqued.

It's not a "stretch bolt" that are common on modern cars. Stretch bolts can usually be reused. For example, the head bolts on my Mercedes can be reused as long as they don't exceed a specified length. My understanding from others is they can be used about three times before they exceed the specified length.

Duke

[Stuart F.]

Re: Torque on Balancer Bolt (?)

Thanks Duke. That's how I will do it. Imagine my surprise when the engine turned at 40 ft lbs. (w/plugs in)! This is a new wrench and they tell you to work up from lower torques to ensure the wrench release mechanism is working properly, so I'll probably go 40, 60 then 80 ft lbs., even though it's only one bolt.

Your method worked fine on the valves. I didn't, however, find more than .002" difference from my old setting - and those were mostly the exhaust valves.

Thanks again;

Stu Fox