1974-Spark Plug Shields

[Paul L.]

This is a bit of a non-NCRS question so if it is out-of-line please feel free to omit it.

My 1974 is NOM although it is a pretty car and runs well. The best I can trace the engine block (TZU) it is a 1978 Chevrolet pickup truck, 350cid, 165hp, and four-barrel with conventional cab. The intake manifold, exhaust manifolds, and heads are correct so something went wrong downstairs in the mists of time.

It does not have spark plug shields and I wish to order and install them. Not the entire assembly with covers but just the shields as in pic. They afix to the block with small bolts (one each) of course but given the origin of the block I wonder if the threaded holes will be there to accept the bolts. I have no idea if some or all 1970s Chevrolet engines had those holes. There is no reason to obtain the parts if I cannot bolt them on.

Can anyone advise me on this? Again, it is not NCRS but does involve the Corvette hobby. I hope you can help.

[John H.]

Re: 1974-Spark Plug Shields

They afix to the block with small bolts (one each) of course but given the origin of the block I wonder if the threaded holes will be there to accept the bolts.

Paul -

All Gen 1 Chevy small-blocks have the tapped holes for the spark plug heat shields.

[Michael W.]

Re: 1974-Spark Plug Shields

Paul -

All Gen 1 Chevy small-blocks have the tapped holes for the spark plug heat shields.

I was surprised to see that this is true- even on McKinnon blocks. How about that.

Might be wise to clean out the holes with a bottoming tap prior to fitting the bolts. They're probably crudded up if there's been no shield in place for an extended period.

[Paul L.]

Re: 1974-Spark Plug Shields

I was surprised to see that this is true- even on McKinnon blocks. How about that.

Might be wise to clean out the holes with a bottoming tap prior to fitting the bolts. They're probably crudded up if there's been no shield in place for an extended period.

What is a McKinnon block?

*Edit* - I should have known this. It is St. Catharines, Ontario. But the block should be T for Tonawanda?

[Michael W.]

Re: 1974-Spark Plug Shields

McKinnon blocks show a K as prefix, T for Tonawanda as you stated and F or V for Flint depending on vintage.

[David L.]

Re: 1974-Spark Plug Shields

Back in the 1990's when I was looking for engine parts for my 1970 Camaro SS350 long term project (Tonowanda block) I found that a lot of the 1970 Chevrolet full size passenger cars had McKinnon blocks (example of pad stamping, "K0412CMJ") with a large "M" casting inside a square on the back of the engine instead of the "GM" casting.

[Robert S.]

Re: 1974-Spark Plug Shields

These shields were missing from my 74' (original block) as well. I bought and installed them about 2 years ago. Must install from below. Three go in very quickly. The 4th is near one of the engine mounts and really tried my patience. Probably spent 3 hours getting that one bolt started and torqued. As I recall at that location the bolt also holds a clip for a spark plug wire as well as the heatshield which adds to the installation difficulty. You may want to see if you also need to order this spark plug wire clip since once you get this bolt installed you will not want to go back later and remove it to add the clip. Note also the correct bolts are about half inch long, and are 1/4-20 recess hex head with an integral star type lockwasher as I recall.

[Paul L.]

Re: 1974-Spark Plug Shields

McKinnon blocks show a K as prefix, T for Tonawanda as you stated and F or V for Flint depending on vintage.

The block is 3970010. Maybe a truck engine is OK with a TH400, might be sturdy if not peppy (which it is not).

[Paul L.]

Re: 1974-Spark Plug Shields

These shields were missing from my 74' (original block) as well. I bought and installed them about 2 years ago. Must install from below. Three go in very quickly. The 4th is near one of the engine mounts and really tried my patience. Probably spent 3 hours getting that one bolt started and torqued. As I recall at that location the bolt also holds a clip for a spark plug wire as well as the heatshield which adds to the installation difficulty. You may want to see if you also need to order this spark plug wire clip since once you get this bolt installed you will not want to go back later and remove it to add the clip. Note also the correct bolts are about half inch long, and are 1/4-20 recess hex head with an integral star type lockwasher as I recall.

Thanks Robert,

I'll look for that difficult one. Thanks for the heads-up. I believe it is the one between cylinders #1 and 3. That is where the temp sensor is and the shield is an odd shape. The spark wire clip is not important as I have other ideas for the spark plug routing (non-NCRS). If need be I will use a spacer or washers there.

Yes, the bolts are 1/4-20 x 1/2". I have now ordered (thanks John H. for re-assurance) from Paragon. My pics are their #6503k (shields) and #1850 (bolts).

I will tackle this ignition job in mid-April when I see my car again out of storage.

[Michael W.]

Re: 1974-Spark Plug Shields

Paul,

Canadian Tire has those bolts and star washers on their pick-it-yourself rack.

[Paul L.]

Re: 1974-Spark Plug Shields

Paul,

Canadian Tire has those bolts and star washers on their pick-it-yourself rack.

Mike,

I should have known. My local CTC is not good for loose fasteners, only packaged. But Home Depot is pretty good. But Paragon was only $0.75 each so what the heck.

BTW, I am hoping for April 8 to get the car out of winter idleness. Hope things in Montreal look good then as well. No driving of course at that time; still much too cold. Just fooling about in the unheated garage with all the parts that have been piling up during the winter. Nothing major really, just some tweaks. The 1974 is pretty much OK as I want it for driving.