Thread: Crank bolt?

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Guys - I'm putting a mid-60s "Thunderbolt" 283 back together and need to press on my harmonic balancer. I bought one online that came with a bolt, but the bolt's too big for the crank.
I tried a 5/16 bolt but that was too small and the 3/8 was too big. Huh? Any ideas?

Just a thought...could it possibly be metric rather than imperial?

Unless the crankshaft has been drilled for a non-stock bolt it should be 7/16" x 20. It's a Grade 8 bolt - use Summit Racing Harmonic Balancer Bolt Kit SUM-G1677.

I was able to cut a 3/8 by 24 thread in the crank end but I'm afraid it wasn't strong enough and I'm having to re-tap to the next larger 7/16 by 20, as the factory did on later engines. I'm having trouble getting the tap started even after drilling the hole out with my 3/8ths bit. I hesitate to use anything larger, because it'd be a 7/16ths and that won't work if I want to thread a bolt in, that size. Is there a secret to getting a tap started? Crank steel is anything but mild!

You will need to use a 25/64" (I use cobalt as it will cut the best hole) drill bit to successfully tap a 7/16" x 20 hole. I know it's only a 64th of an inch larger than a 3/8" but it makes all the difference. Use a high quality bottoming tap with lots of thread cutting oil and go very slow as breaking off the tap brings a whole new set of problems.

Good Luck!
Glenn

And do not use the bolt to press the balancer on, that's not what it's there for. Get the proper tool to install your harmonic balancer, you rent them at many auto parts stores.

Thanks so much, Guys! I'll get the bit and tap lube tomorrow, Glenn, and Jimbo, I've got that tool for pressing on the balancer, having rebuilt a previous engine.
I agree... the quickest way to bugger up threads is to not use the right tools.

UPDATE: The 25/64 bit worked perfectly and a bottoming tap gave me lots of threads. My Proform H.B. Installation Tool #66515 broke while pressing on the balancer, leaving the tip inside my crank. I can't win.

Originally Posted by IowaTom

UPDATE: The 25/64 bit worked perfectly and a bottoming tap gave me lots of threads. My Proform H.B. Installation Tool #66515 broke while pressing on the balancer, leaving the tip inside my crank. I can't win.

Sorry for your continuing problems with this! Curious, did you have the the outer sleeve portion tight against the end of the crank before turning the large hollow nut that pushes the balancer into place?

Yes, everything was cinched down and the tool was in all the way.

I see there are three pipe plug holes just above the cam plug at the back of the block. They're definitely threaded and I'm assuming I need to plug those babies before adding a flywheel!

Originally Posted by IowaTom

Yes, everything was cinched down and the tool was in all the way.

I see there are three pipe plug holes just above the cam plug at the back of the block. They're definitely threaded and I'm assuming I need to plug those babies before adding a flywheel!

Yes, you do. Does that block have the provision for a road draft tube?

I don't know, Ken. What would I look for to find out? The engine came out of a Canadian made '65 Studebaker and when I got it, there wan't much left.

Originally Posted by IowaTom

I don't know, Ken. What would I look for to find out? The engine came out of a Canadian made '65 Studebaker and when I got it, there wan't much left.

Probably not being a 65, but if it does there will be a hole just to the left of the distributor hole looking from the rear. I'm not big on running a pcv system on an early block. The idiots in ca. killed a 57 Ford Custom with a 292 I had in 64 when I returned from overseas. They capped the road draft tube, plugged the breather and installed a pvc system. A month or so later the pressure in the crankcase was so great it blew the dip stick out it's tube, covered the right side of the windshield in oil, and for all practical purposes wiped out the bearings.

Unbelievable, Ken! Mine does have that hole for the draft tube and, like you, I'm in no hurry to attempt a modification - especially after hearing your story! I'm sure I can locate one that'll work. (My Rambler sports a Falcon draft tube) With Veterans Day just around the corner, thank you sincerely for your service.

Here is one for I think a decent price. https://www.ebay.com/itm/Chevy-Impal...IAAOSwW1Bdvdov

And you'll need one of these as well https://www.ebay.com/itm/Small-Block...8AAOSwsptbzhCn

These are nice as well but a bit pricey, stay away from 55-57 valve covers as they have staggered mounting holes and the only heads from that era that are wotrh anything, IMHO, are 57 Fuelie heads that are very pricey if you could find a set.
https://www.ebay.com/itm/1959-1967-C...EAAOSwWahdfEfK

Good luck and thank you