Can anybody tell me why my 69 has ground straps on the exhaust clamps?

 

Perhaps because a previous owner put them on?

 

They were to help prevent radio interference. The exhaust and the trim plates on the sides had ground straps added to keep them from becoming giant antenna sort of thing. Disappearing later when they added more distributor shielding
m

 

Hmmm, Thanks

dm

 

On my 1968 C3 there are exhaust straps on the exhaust clamps and they appear to have been original to the Car. Radio noise suppression was their purpose.

Our 1988 C4 has the ground straps as well, one was disconnected and that kept the antenna motor from working. I reconnected the strap and the motor raised and lowered the antenna. The C4 has ground straps in a lot more places than the C3 did in 1968.

I would recommend you repair any ground straps that are broken or disconnected, GM put them there for some reason so I try to maintain them.

 

Here is an image from the 1969 AIM showing grounds.

 

I thought the ground straps went away with the introduction of the HEI distributors because the interference was from the points.

 

I kind of think they got rid of them around when they added that RFI shielding inside the distributor (70-71???)
They were gone by 72 but I don't have a 70 or 71 AIM.
I actually added them back to mine since they came in a kit I bought at one point and you can never have too much ground on a c3)
M

 

There are several noise issues on the C3. Number one- is the body is fiberglass and doesn't shield at all.
I think GM ( especially the beancounters) decided with more and more FM radio- they could get away with less "solutions"
Now on later cars- I can see it being needed to electrically ground the O2 sensor and more sensors so more grounds.

 

On my 1968 C3 ground straps are there connecting to the exhaust at the frame crossover. On my 1988 C4 there are several ground straps even though the car came with a HEI distributor. They are there for a reason and when they fail it can have a negative effect on the car. I spend time on the C4 section and ground straps are one thing you don't remove from all I have heard and read.

The ones in the rear of my 1988 C4 connect to the exhaust on the rear left rear corner. When I looked, one was visibly broken off so I fixed it and then the radio antenna was able to start going up and down again. The biggest problem where they are used when people have an engine that is not well grounded the sensors get wacky information.

Using a Holley Stealth Sniper I do not have any issues with electrical noise even with my MSD distributor and MSD ignition system. I have rarely had any issues with any electrical noise interfering with anything, the last time was about 50 years ago with a VW.

What about the big monstrous chrome plated boxes on top of C3 engines? Does it really do anything or is it more ornamental? I am using a Factory L-88 hood and intake assembly and the chrome box just gets a bit too tight with a Holley Stealth Sniper on the engine. I used to buy the original style spark plug wires that had the sheathing built onto them. They each had a ground connection but they looked cool while they lasted.

 

A lot more computer stuff on the C4 than the poor old C3 (well, maybe the 80+ and I suspect the sensors in the exhaust might have something to do with needing the grounds again. I know they removed them by 72 and that's when they added the shielding inside the points distributor so somehow I think (maybe incorrectly) those two changes were related.
The added a bunch of the little capacitors on various switches (clock, brakes, blower motor, etc) to help keep the old radio from popping. The lack of a giant grounded metal box around the entire car caused all kinds of problems electrically

As for the distributor shielding.... if you're not running points it's not going to be doing much other than looking cool. I haven't figured out how to put mine back on since switching the HEI and haven't noticed any affect on the radio or any other electronics but I know it played hell having it off when I listened to the radio with the points distributor

M