Fender and body bolt question

[OrrieG]

I am getting close to doing final fit assembly before painting.

Are the fender and body bolts (radiator shroud, etc.) with flat area under the bolt head designed as an interference fit? They are assembled without lock washers so I assume they are to combat loosening from vibration.

I need to start buying the new bolts for final assembly and need to justify the expense of the "correct" fasteners vs. ones I can get locally. Thanks Patrick

[Fred T]

None of the fasteners on these trucks are an interference fit, which puts your bolt and hole tolerances in the thousandths. Most of the holes are considered a class 3 fit, which is roughly a .250 diameter bolt in a .281 diameter hole.

I consider the fastener kits a good investment. I bought a Totally Stainless kit for my 69, everything was labeled for where they went. They were the correct length and diameter, and far cheaper than buying the bolts from a hardware store. You also get the correct lockwashers.

I bought one kit that was from a foreign maker, but will not repeat that mistake. I had problems and showed the results to a metallurgist at work. We determined that the bolts had not been heat treated.

If you go with a stainless bolt kit, all of the bolts need to have either a thread-locking compound or anti-seize compound to prevent thread galling, which is where the metal of the bolt and nut threads become one, making it impossible to remove the bolt. I also will not put a stainless bolt together with a stainless nut, which will gall even with a compound.

My experience comes from engineering at Boeing, where I did a lot of work on B-52 structure repair, fastener design and corrosion control.

[OrrieG]

Fred - I guess I used the wrong term, but you answered the question. I assume on the fender type bolts then that the fender metal itself and the capture nuts act as a lock washer? Good tip on the anti-seize compound, thanks. Who did you get the kit from that you liked?

[Fred T]

Originally Posted by OrrieG

Fred - I assume on the fender type bolts then that the fender metal itself and the capture nuts act as a lock washer? Good tip on the anti-seize compound, thanks. Who did you get the kit from that you liked?

Most of the sheet metal bolts have either a serrated flange or a lockwasher permanently attached bust below the bolt head. This is the locking device. GM didn't use a locking type nutplate much on these trucks. They cost more and took more time to install.

I am a big believer in blue loctite whenever possible. It seals the threads from corrosion.

The bolt kit for my 69 came from www.gmcpauls.com. His on-line catalog doesn't list for the AD truck, but that doesn't mean he doesn't carry them. These kits are from www.totallystainless.com, who now sell direct. www.americanclassic.com shows kits that look identical to the totally stainless packaging. I would think they would tell you if you called.

[britnjc]

who sells a stainless bolt kit for ad trucks?

[robin58]

Originally Posted by britnjc

who sells a stainless bolt kit for ad trucks?

Brother's lists various stainless bolt kits for AD trucks.

[mylow53]

i've heard of guys buying bulk stainless steel at a swap meet like pomona. it would be a bunch cheeper than the hardware store. i've spent near 300 on bolts over the last year and i still need more!
GT

[BIG CHEVY 3600]

Amen on the blue loctite.
The best bolt kit seems to come from Totally Stainless.
http://www.totallystainless.com/totally.html

Fred, you say you never use a stainless nut with a stainless bolt because of the galling of the threads; do you use an anti-seize material when the nut is not stainless?

[Fred T]

Originally Posted by BIG CHEVY 3600

Fred, you say you never use a stainless nut with a stainless bolt because of the galling of the threads; do you use an anti-seize material when the nut is not stainless?

I use blue loctite most of the time. Otherwise grab the anti-seize. There are two issues. Galling can occur between stainless and alloy steel, but galvanic corrosion is a bigger issue. That's where dis-similar metal form an electric field and corrosion sets in. The result is usually cracks forming in the threads.

[renegade6]

Does anyone make a good standard (not stainless) kit?

[BIG CHEVY 3600]

Most vendors carry them.