I was installing a new crank pulley (3 groove) tonigh and I couldn't get the main center bolt for the crank to tighten. It just spins loose like it's stripped. Please tell me it's not so! What is the proper length for the bolt? Would it be possible to strip the crank threads?

I noticed when I was taking off the old pulley that the bolt was not very tight. Any insights? If crank is stripped can I just rethread using a rethread kit?

Thanks!

I had this problem.

It turned out to simply be a bolt that was too short.
It was only being held on before by a couple threads. So when I put the new crank pulley on, it was a tiny bit thicker in the middle or so I assume because now I couldn't hardly get it to catch one thread.

I couldn't find a suitable replacement until I went to a place in this area called Tacoma Screw.
They have every type of screw there is imaginable.

I took them the old bolt and they told me to sink a dial calipre down the hole to get an idea of the depth I needed.
They gave me a bolt, I went home and voila`.
G2G.

I don't think its stripped, it just was too short all along. That's my wager.

i think its a 7/16-20 bolt.........use a pencil to determine the depth of the hole for the length needed.

I would go get a new 7/16 x 20 Mr Gasket or ARP crank bolt and washer , if the entire hole is not stripped. If it is, then either drill it to 1/2 20 and use a new bolt, unless you think you can install a helicoil. Do measure the entire hole depth and if possible , run a tap into and clean out.

With a thick washer, 2 1/8 inch long bolt. As Don & others suggest, clean threads with tap, 7/16-20, and use up to a 2 1/2 inch bolt. 55-60 ft/lbs.

Otherwise, its either install a Helicoil thread coil or go to 1/2-20 thread.

To provide some closure - it turned out that the bolt wasn't long enough and that threads were fine. Got a longer bolt (only could find a Grade 5 one though) and installed. Should be okay (I hope) until I get the Grade 8 replacement. Only problem now is that to get a V-belt on the groove closest to the engine block I need to remove either the crank or water pump pulley! Argh! Doesn't sound right to me - ideas?

Only problem now is that to get a V-belt on the groove closest to the engine block I need to remove either the crank or water pump pulley! Argh! Doesn't sound right to me - ideas?First belt out from engine should be alt/wp/crank belt. Shouldn't have to remove any pulleys to replace.

don't try to install your balancer with the bolt, this is a bad idea.

On your pulley problem, sounds like some mixing/matching has taken place at some time.

I keep extra pulley's laying around. And I use them to make engines run on the garage floor. It is possible to get 2 large enough pulleys on the front of an SBC that a belt won't fit onto the crank. Sounds like you need to do a search on pulleys to find which ones you need.

68z - Why is it a bad idea to use that bolt?

77wolf - But wouldn't changing the water pump pulley diameter have an effect on how fast/slow the water pump is driven?

Yes sir, it will. That's why I recommended a search, so your driving and driven pulley's have the ratio nature intended.

Doesn't mean it can't be altered, to use less power or not overspeed ancillary devices when you are building an 8k rpm engine.

The ratio is easy. Divide diameter of driving by driven pulleys, multiply by rpm of driving pulley yields rpm of driven.

A lot of times when I am re-sizing pulleys I get thinking faster than I'm pushing buttons on the calc, or maybe vice-versa:D , and always make myself stand back and look at it with some horse sense to see if I divided upside down or right side up. Maybe just me Idunno

It seems like you have a ratio close to 1. I was thinking usually GM H2O pumps run a little faster than eng RPM. I don't have one I can go look at for you or I would. Wolf don't want no stinking pulleys, 66 P/U is a mix/match, ZZ-4 is a big block water pump pulley and the 66 283 crank pulley. Sorry.

[QUOTE=scalise;792883]68z - Why is it a bad idea to use that bolt?

YOU , need that good crank bolt, perferrable ARP and the thick washer. If you cant find that, look for the Mr Gasket bolt, it will come shrink wrapped.

Sorry , I misunderstood the question. Dont use the crank bolt for balancer installation , nor the ford tool. Harbor Freight sells a nice balancer installer, just dont over tighten the adapater bolt.

i was meaning, do not draw on balancer with the balancer bolt.

[QUOTE=scalise;792883]68z - Why is it a bad idea to use that bolt?

QUOTE]

Because pulling the balancer on with the bolt puts a lot of stress on the crank threads, especially when you first start cranking, since only a few threads are engaged. A balancer installer should thread all of the way into the crank snout. The balancer is pulled on with a large nut threaded onto the installer. You can easily make your own balancer install tool. Use about a foot of GRADE 8 7/16-20 threaded rod,weld a nut on the end, get a couple of large washers with the correct diameter center hole. Use a standard chev lugnut with the flat side toward the washers to pull the balancer on.

Once the balancer is installed with the correct tool, a grade 5 bolt is more than adequate. The early Chevs (pre 68 or thereabouts) didn't even use a bolt.

On the belts - fully seat the belt in the groove of the smallest pulley, and stretch it by hand over the largest pulley.

http://img.photobucket.com/albums/v61/gort69/DSCN0213.jpg

Lots of ways to do things, ain't saying mine's right, just here it is...

I use either Cat or LE grade 8 on balancers on engines that I'll be mean to. Prefer Cat, best bolts on earth. But on a stock engine I'm not afraid to stick a good American made LE,, FC or other grade 5, there's no way the outward force of the balancer would approach the shear strength of that bolt. A stock engine can't usually make the RPM's necessary to overcome the interference fit.

The early Chevy's with no threads had a tendency to chunk balancers off at high RPM when somebody hopped them up, and then got drilled and tapped. My 66 283 case in point.

I keep an assortment of 7/16 fine bolts, and just use a long one to get the balancer on then put the standard length one in service. I torque them with a Snap 1/2" drive impact, 3/8 air hose, 150 psi air, 2 bops. Takes almost 3 minutes to install one.
The crank usually has about 1 1/2" of threads inside, and rule of thumb for fasteners is you want one diameters worth of length of threads to get bolt strength. So 7/16 * 20 you'd want about 9 threads in the crank before you have a useful fastener. I like a little more on that bolt, about 3/4 " in the threads. I don't loctite that bolt either. Antisieze. I have put loctite on the balancer to crank on my 283 and a few others.