Crankshaft thread sizes

[dickeymoore]

I have a small block Chevy 400 and the threads on the inside of the crank where the harmonic balancer bolt screws in are stripped out what size tap can I use to rethread these threads?

 

[dickeymoore]

I have a small block Chevy 400 and the threads on the inside of the crank where the harmonic balancer bolt screws in are stripped out what size tap can I use to rethread these threads but if i screw the bolt in without the big washer it will screw in can i get a longer arp bolt if so what arp part number?

 

[lilbowtie]

https://arp-bolts.com/kits/product.php?PL=7

 

[MTP-Madmat]

I had the same thing happen to my 400. I ended up doing a heli-coil. 7/16-20 ARP # 134-2501

 

[bracketchev1221]

Either helicoil a 7/16 or drill for 1/2”.

 

[dickeymoore]

So are the ARP bolts longer than the stock bolts and will it work with a stock damper

 

[MTP-Madmat]

I believe they are the stock length and come with a new washer. And it will work with a stock damper. I would recommend a heli coil

 

[dickeymoore]

How do you do a heli coil?

 

[MTP-Madmat]

A heli coil kit comes with a drill bit and thread tap. You drill it bigger and tap it then use the tool with a bit of red loctite on the thread insert. The thread insert will be stronger than the factory cut threads

 

[dickeymoore]

Okay