Heat Shields 1970

[Keith W.]

Anyone know where I can obtain a schematic for heat shields? I had removed the four upper shields to access the spark plugs. While doing so I noticed there were lower heat shields as well and I am missing the front one on the drivers side. I would like to come up with an original if possible. My car is a 1970.

[Stephen B.]

Re: Heat Shields 1970

What engine?

[James G.]

Re: Heat Shields 1970

The 70 LT1 has 4 outer wire shields(chrome) and 4 inner zinc plated spark plug heat shields which are screwed to the block.
The front drivers side inner shield is difficult to see as it has an arch in the center to accommodate the tempo sending unit- that shield is the same for 69 - 73 at least.
I have circled it in RED in this photo.

drivers front plug shield.jpg

[John W.]

[Keith W.]

Re: Heat Shields 1970

F8C4002B-EC66-4EFD-92ED-E1AE4843E22C.jpg

[Terry M.]

Re: Heat Shields 1970

Keith
That illustration is of a small block engine

[Joe L.]

Re: Heat Shields 1970

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I believe I need the part that has code 3919807. This page from the 1970 assembly manual doesn’t state which engine this image is from. Maybe the SB and BB are the same for this area of the motor.

Keith------


I think that you will find that if you install the GM #3919807 spark plug heat shield then, assuming your car had the forward RF shields, it will be virtually impossible to install the left front RF shield. I believe this is why the forward RF shields were eliminated during the 1970 model year.

[Terry M.]

Re: Heat Shields 1970

Keith------


I think that you will find that if you install the GM #3919807 spark plug heat shield then, assuming your car had the forward RF shields, it will be virtually impossible to install the left front RF shield. I believe this is why the forward RF shields were eliminated during the 1970 model year.

Joe
The forward RF shields were eliminated during 1970 model year when the distributor RFI shield was introduced. I have always believed the distributor shield reduced the need for the forward shields.

[Joe L.]

Re: Heat Shields 1970

Joe
The forward RF shields were eliminated during 1970 model year when the distributor RFI shield was introduced. I have always believed the distributor shield reduced the need for the forward shields.

Terry------


Well, I suppose that's possible but it's hard for me to understand a relationship between the the distributor's internal RFI shield and the front spark plug RFI shields. It might seem a little more plausible if all the spark plug RFI shields were eliminated but elimination of just the fronts for that reason would seem very strange to me.

[Bill B.]

Re: Heat Shields 1970

I'm purely speculating here, but as a retired electrical engineer, I know that the intensity of RF radiation has a distance squared relationship from the emitter (source) to the receptor (i.e. radio). (double the distance results on 4X reduction in intensity) Because the front plugs are further away from the firewall, and that the line of sight of the front plugs/wires are interrupted (hidden) by the exhaust manifold outlet, and due to the difficulty of installing the LH front shield in place after servicing the spark plugs, perhaps the engineers re-evaluated the RF interference effects to minimize service time and effort and still maintain effective RF interference mitigation (trading the removal of the chromed front lower shields in favor of the two-piece internal distributor shielding).

I do know that every production change has a reason, and changes to a production line cost time & money to make.

I have a long list "why" questions that I would have liked to have asked Chev Eng'g back in the day ... this is just one is on that list ...

[David L.]

Re: Heat Shields 1970

Keith,
According to my notes I have 4 NOS spark plug heat shields as well as many used shields from the salvage yards. If you need one send me a PM.
Dave