RFI Shielding

[Tom R.]

What years was the RFI shielding used ? It covers the the points inside the distributor. Can't find a part # in the G M catalog ?

[Dick W.]

Re: RFI Shielding

1970 1/2 to 1972 I am sure. May have been used until the end of 1974. The usage began when GM went from the "box" type ignition shielding to the shield that basically just covered the upper area of the distributor cap.

[Jack H.]

Add on...

Reading the service bulletin provided to cover '70 Corvette (delayed to production with '69 model year cars extended through 12/31/70) which was left out of the 1970 Chevy Chassis Service Manual's coverage gives insight on the distributor internal RF shields...

Their purpose is defined in that bulletin: to support the 'new fangled' option of having the radio antenna embedded in the windshield glass vs. by way of discrete antenna masts as in past years. This required an engine compartment 'hush up' improvement with respect to RFI and the hemisphere of shielding inside the distributor was found to be adequate in passenger car applications vs. Corvette's FULL spark RF shielding system (pass cars had metal body providing significant 'natural' shielding).

It appears that the shields could have been left out of Corvette distributors, but designers found they could simplify and cost reduce the existing Corvette RF system with the shielded distributor now being used on passenger cars. Hence, the 2-piece 'big box' surrounding the distrubutor was reduced to a single L-shaped shield and the front bank spark plug shields on Corvette were deleted about the same time as the new, internally shielded, distributor came on stream.

My parts books call the distributor internal shields as being applicable to late '70-74 distributors. Plus, the same system was used on other GM cars beyond Chevrolet (e.g. Oldsmobile). But, try to find a set of shields today! They were quickly discarded by prior owners and 'Bubba' mechanics as being superflowous components!

[Dennis D.]

Re: Add on...

I have an NOS in the box one of these somewhere. Picked it up for my 70 L-46, but I believe the discussion here, way back when, led me to believe my car didn't use it.

[Chas Henderson #28127]

There in the Chicago Corvette catalog *NM*

[Jim T.]

Re: Add on...

Dennis my original owner 70 350/300 has the two piece shielding from the factory. I believe there is a sticker on the inside of one of the pieces. I never let anyone tune up my 70 is why I still have it. I am pretty sure the reason mine is not installed is because when I began using the uniset Delco points it would not fit back on. I removed it at least 20-25 years ago. I do still have it.