Why do some 72's have a chrome distributor and coil cover? Was that only standard on the LT1 and LS5? Just curious did the standard 350 have this as an option, and what was the purpose? Thanks

 

All C1, C2 and C3 Corvettes had one type of ignition shielding or another, cars without factory radios excepted. The purpose was to reduce ignition noise though the radio.

 

Mine has the sheilds on the plug wires by the plugs. Does that mean it wouldnt have had it on the distributor? Just curious how it was decided where it went. Thanks

 

The shielding was standard. A PO removed it and didn't put it back on out of lazyness, or maybe chucked it because the surface was rusted, who knows. All my shielding was gone when I bought my vette. I'll replace it at some point and I get ignition noise in my radio.
Glenn
Edit; Here's a restored 72 LT-1. Shielding would be the same for yours.

 

The spark plug wire and distributor shielding are shown in section U69 in the AIM. That is the section for the radio option. So, I guess if you have a car with a "radio delete" order request, you would not get that radio interference shielding hardware. The other possibility is that a PO got tired of taking that stuff on and off and pitched it.

Added thought: Do you have the two upright mounting brackets (on either side of the distributor) that the chrome cover bolted to? If you do, then the hardware was origininally there but the PO dumped it sometime in the past.

 

A "regular car's" steel body shields the cars radio from interference caused by the ignition. The Corvette's fiberglass body will not prevent ignition noise from causing radio interference. To prevent radio interference, all Corvettes built with a radio, also came with some form of underhood ignition shielding.

Big Block cars only had a chromed box over the distributor, and utilized braided stainless armoured covering on each plug wire.

Small blocks cars used many more pieces of shielding, than a big block. Prior to 71, shielding on small blocks consided of a cover for the distributor, 2 verticle covers one on the left side and one on the right side set of plug wires, and 4 lower spark plug covers one each covering a pair of spark plugs. At some point, Chevrolet found that they could successfully eliminate radio interference without shielding the front 2 spark plugs, in each head. Starting in 71 (or possibly late in 1970), the front covers were dropped, and only 2 rear lower covers were used.

Over the years, the design and configuration of the shielding changed, as Chevrolet found ways to save money making the shielding. By 78, ignition shielding was nothing more than a black plastic cover with silver foil lining and a single cover on the left rear pair of spark plugs.

 

The main reason some cars have them and some don't is because the original owners usually tossed them during the first tuneup

 

Hi,
I'll just add that there was a change in the 'lower' shields in 1970. In the beginning of the year there were 4 lower shields as usual but ABOUT half way through production the 2 front shields were discontinued. This coincided to some degree with the change in the distributor cover. So you can expect to see the spark plug 'heat shields' but not the radio shields on late 70 to 72 cars.
Just a little tid-bit.
Regards,
Alan

I just realized that gbv was posting this info while I was typing...sorry.

 

I didn't know about the missing spark plug shields! That explains why I don't have them on my '72. I thought a PO lost them.

Not to wonder off topic too much but I wonder about the LT1 pictured above. Is the open air cleaner element correct? I know my L48 has a dual snorkel closed air cleaner.

 

Yes, all LT-1's had the open element air cleaners, as did the L-46 in 69-70 until a dual snorkel set up was used during the production run.

 

Once again I am amazed at all of the knowledge on this forum! You guys are the best! Thanks