1966 Corvette Chassis Bolt Identification with Photos

[Christopher A.]

I decided to document the head marks on the Chassis bolts of my father's rusty 66 Big Block. For the most part, his car has never been apart-minus the front suspension that i rebuilt this past spring, but all original bolts were reused.

Production date is early June of 1966. I have made notes of head mark differences from his car to mine. My car was produced in Mid April 66.

Starting from Front to Rear

1. Lower Radiator Support- WB headmark with 3 lines
RSC Mark is on the upper radiator support bolts, but i do not have a photo currently.




2. Front Body Mount/Radiator support bolt. RBW with 3 lines



3. Front Bumper Bolts- RSC This is the same for the bolts that hold the supports in place on the frame as well.
NOTE: Bumper to front of center frame mounts are Black Phosphate with WB headmark



4. Lower Control Arm Bushing Retainer Bolts- M with 6 lines.
NOTE: My April 66 Car has TR Bolts in this location



5. Lower Control Arm Support- TR with 6 lines



6. Lower Control Arm Support- Large bolt is Black Phosphate with TR headmark, nut and lock washer.

7. Engine Mount Bolt- RSC Has pointed tip and lock nut





8. Idler arm- Black phosphate carriage style bolt for lower mount with lock nut.
Upper mount is(still need to look) with lock nut.



9. Oil Filter bolt-AP



10. Oil Pan Drain Plug-TR



11. Transmission to Bell housing-WB I am not sure if these should be black phosphate or cadmium plated.



12. Bell Housing to Block- RBW flanged head



13. Transmission Mount to frame bolt. CP with circle. Lock nut with raised dots on nut and one round hole/indent





14. Transmission mount to transmission bracket. WB 6 lines



15. Transmission Mount to transmission. M with 3 lines



16. Starter Motor to Engine Block bolt. Circle with 3 lines



17. Brake line to frame bolt. L



18. Emergency Brake Cable to frame mount. WB
NOTE: Headmark is the same for the bracket at the firewall.

19. Shifter Mount to rear of Tranmission Crossmember. Flanged head, no mark.



20. Seatbelt Cable to Frame. RSC
NOTE: On my April 66 Car, the mark is TR



21. Big Block Differential Cap Bolts. RBW with 3 marks/lines. Black Phosphate.



22. Differential Mount Bolt, Rear. M with 3 lines Passes through mount and differential from Passenger side to Drivers side.



23. Differential Bracket Mount Bolt, Front P with 3 lines, pointed tip. Uses castle nut and cotter pin. Passes from Driver's side to passenger side.



24. Differential Bracket Mount Bolt, Front. Passes from top to bottom, through the frame and cushion assembly. I believe this has a WB headmark, but i am not 100 percent sure.

25. Strut Rod Bracket to Differential. S with 6 lines
NOTE: On my April 66 Car, the headmark is WB with 6 lines



26. Rear Sway Bar to frame bolt(note shims). Flanged head with RBW



27. Sway Bar to Rear Trailing Arm. RBW



28. Half Shaft to Axle Flange. Small inner circle with 3 lines. Black Phosphate



29. Rear Differential Crossmember to Frame. Possibly WB, possibly nothing with 6 lines

30. Rear Body Mount Bolts. I find this to be very interesting. The bolt on the Driver's side is UR with 3 lines and the Bolt on the Passenger side is RSC with 3 lines. I would say that one is a replacement, but.....
NOTE: My April 66 car is the exact same.








That is all for now. I will post more when i have them. I have only posted bolts that i am 99.9999999999 percent certain are in their correct location. I did not post any of the bolts that have been replaced or that i know to be incorrect.

[Rich P.]

[Peter L.]

Re: 1966 Corvette Chassis Bolt Identification with Photos

Nice job. Thanks for sharing the photos. Pete

[Christopher A.]

Re: 1966 Corvette Chassis Bolt Identification with Photos

-Good eye, and yes, you are correct on the engine mounts and bolts. I noticed the mounts last night when i was changing out his oil pan gasket. Then i looked at my car today and noticed that the bolts and nuts are much different. I previously thought the motor had not been rebuilt in this car, but I became suspicious when i realized it had the locking style motor mounts and upgraded bolts. Once the pan was off, the marked rods and balanced holes drilled in the crank made it obvious that the motor has been rebuilt, but judging from the amount of oil on the engine, wear on the bores, etc. it was not recent.

-Concerning #2-Thanks, i have been trying to figure out that one for a while.

-#3-Rear housing??? As in the differential cover? All of the bolts i have seen for the housings are black phosphate and have the circle pattern on the head, but not the WB. I'll pull one from each car, measure them, and post again with an update this evening.

-#4-Which bolt would normally be used in the rear sway bar mount to frame location? I do not have the same ones on my 66, but i just assumed that i chose the wrong ones out of the bolt pile that came with the car.

My intent was to hopefully help others that have found themselves in the same dilemma that i found myself in with my 66 BB that came in boxes. I certainly do not want to give bad or incorrect information about the bolts and I appreciate you correcting me on the engine mount to frame bolts and others that are potentially wrong.
I'll do my best to research the other bolts mentioned and post updates with new pictures and corrections soon.

Thanks!!!!

[Rich P.]

Re: 1966 Corvette Chassis Bolt Identification with Photos

Don't think your giving bad info and I want to thank you again for taking the time to show the hardware. It is great refrence for those who see them. And the motor mounts and bolts are correct for late 69-up so all this is usefull and helpfull.

Definitly looking forward to more pictures!!! Thanks, Rich

[Christopher A.]

Re: 1966 Corvette Chassis Bolt Identification with Photos

Has anybody else observed the two different head markings, UR and RSC for the rear body mount bolts??? Like i mentioned in the initial post, i thought that this was a mistake on my car or that a bolt had been changed, but my father's 66 has the same thing.

[Rich P.]

Re: 1966 Corvette Chassis Bolt Identification with Photos

UR is correct. RSC is most common but UR was widely used. Check the mount at the firewall and see if they are UR or RSC.

Rich

[John H.]

Re: 1966 Corvette Chassis Bolt Identification with Photos

Has anybody else observed the two different head markings, UR and RSC for the rear body mount bolts??? Like i mentioned in the initial post, i thought that this was a mistake on my car or that a bolt had been changed, but my father's 66 has the same thing.

Christopher -

Remember that fastener bins on each side of the line were replenished only by PART NUMBER, with each fastener generally sourced to three different suppliers, each with their own headmark. Nobody in the plant paid any attention whatsoever to headmarks - only to part numbers. It's also very common to find different headmarks on the right and left side for the same part number fastener for the same right/left applications.

Repairmen at the end of each group also tended to use either the correct fastener or one that was "close" if they didn't have the "correct" one handy on their bench.

[Ronald L.]

Re: 1966 Corvette Chassis Bolt Identification with Photos

Chris I have an April 66 that's pretty much the same as yours. One comment was the bumper bolt RSC - that one is zinc, the darkness you see is due to most of the zinc being gone. I'll have to get out & check the body mounts that have never been touched to see if they are as you have observed.

Another thing I noted was the seat belt anchor, I'll check those too, but I doubt a grade 3 bolt was used there.

Last and very important - that shifter mount - bingo!

Those bolts when introduced did not have head marks!

[Jim D.]

Re: 1966 Corvette Chassis Bolt Identification with Photos

Remember that fastener bins on each side of the line were replenished only by PART NUMBER, with each fastener generally sourced to three different suppliers, each with their own headmark. Nobody in the plant paid any attention whatsoever to headmarks - only to part numbers. It's also very common to find different headmarks on the right and left side for the same part number fastener for the same right/left applications.

Repairmen at the end of each group also tended to use either the correct fastener or one that was "close" if they didn't have the "correct" one handy on their bench.

All the bumper bolts on my 65 are "M" on one side and "TR" on the other. Every bolt on my car is original but I never saw the value of posting them since they varied from car to car. The documentation of a single car proves nothing.

[Timothy B.]

Re: 1966 Corvette Chassis Bolt Identification with Photos

Christopher,

Great pictures, thanks for posting the information.

I wanted to comment on Rich's #3 response to be clear. The WB grade 1 1/8" bolts would go to the rear crossmember to frame like you pic shows and also the rear crossmember to rear cover (four bolts w/flat washers) where you can't see without taking the crossmember down. It's possible these transmission bolts shown in your picture belong there and grade five bolts with the large washers go at the transmission location.

Also, I question the grade five spindle bolts as my experence with these bolts is grade eight with the french locks. It's a easy change but the grade eight bolts are very important at these locations for obvious reasons.

[Ronald L.]

Re: 1966 Corvette Chassis Bolt Identification with Photos

Regarding a previous comment - data is built one car at a time - makes this pretty valuable given it survived 45 years. To the contrary.

[Joe R.]

Re: 1966 Corvette Chassis Bolt Identification with Photos

Christopher -

Remember that fastener bins on each side of the line were replenished only by PART NUMBER, with each fastener generally sourced to three different suppliers, each with their own headmark. Nobody in the plant paid any attention whatsoever to headmarks - only to part numbers. It's also very common to find different headmarks on the right and left side for the same part number fastener for the same right/left applications.

Repairmen at the end of each group also tended to use either the correct fastener or one that was "close" if they didn't have the "correct" one handy on their bench.

John,

That's the best explanation I've seen of the variation of the bolts. Thanks for posting!

Joe