1974 Spark Plug Wire Heatshield

[Robert S.]

1974 L48 Convertible, 4 speed. I am in process of replacing the spark plug heatshields missing when I acquired the car. I have carefully studied the AIM but am still uncertain of all of the heatshields that should be on the car.
I know the car must/should have the following:
1. Chrome cover over the distributor - orange painted supports for this as well
2. Chrome left and right side vertical plug wire covers coming down from the distributor cover
3. left and right V shields on the engine block
4. left and right chrome horizontal covers on the rear portion of the left and right exhaust manifolds. I believe these are attached by 4 small brackets and 4 wing bolts, two per side. I also believe the lower right horizontal cover attaches to the vertical plug wire cover at the lower rear corner with a chrome wing bolt. It also appears that the horizonatal left cover does not attach to the left vertical cover (ie the left side is not the same as the right side).

What I cannot determine is if there are any other missing pieces in and around the exhaust manifolds. Right now the car has nothing in the way of sheetmetal pieces attached to the exhaust manifolds. The AIM suggests there may be 4 other sheetmetal parts ( two per side) that go on the exhaust manifolds above the spark plugs that are in addition to the left and right chrome horizonal covers described above. Is that correct or should this car not have these 4 sheet metal pieces?

[John H.]

Re: 1974 Spark Plug Wire Heatshield

Robert -

Yes, you should have (4) stamped sheet metal spark plug heat shields, one for each pair of plugs; Paragon and other vendors have them.

[Paul B.]

Re: 1974 Spark Plug Wire Heatshield

...the left vertical side does indeed attach to the left rear chrome spark plug cover, however, it is with one of the same chrome wingnuts, but the top of this wingnut is very near the bottom of the left vertical piece and faces towards the firewall of the cowl. Very hard to see if you don't know it's there. Just checked my very original '74 L-48 coupe. The other four pieces are non-chrome plated and appear to maybe be a "grey phosphate" color. Also, these "inner" shields are "J" shaped and have their own bracket attached to them, which attach directly to the engine block with which I believe is a 3/8"(maybe 7/16")recessed head bolts. I believe that maybe these may be the same as what came on most Chevrolet V8 passenger cars in the '60s & '70s.

[Joe L.]

Re: 1974 Spark Plug Wire Heatshield

John and Robert-----

The spark plug heat shields are also still available from GM. They are as follows:

GM #3917664----- right rear and left front-----GM list= $13.38/each

GM #3817657----- left rear and right front------GM list= $34.63/each

By the way, the numbers above ARE the correct numbers; there is no error with respect to either of the 2nd digits----the GM #3917664 is a part originally released in late 1967 and the GM #3817657 is a part originally released in 1962.

Also, the prices are correct, too. The 3817657 does GM list for $34.63. Be thankful, the price of that one has actually COME DOWN. It was up to over $50 for awhile.

[george romano]

Re: 1974 Spark Plug Wire Heatshield

I believe the bottom of the LEFT vertical ignition shield attaches to the spark plug wire loom that is bolted to the rear of the engine block. It does, in fact, use a chrome wing bolt. This wire loom has a threaded hole to accept the wing bolt.

The RIGHT vertical does attach to the right horizontal ignition shield cover over the two rearmost spark plugs. This horizontal ignition shield has a hole in it which has a J clip behind it to accept the wing bolt.

Both are a PITA to install!
Hope this helps.

George