66 BB Spark Plug Heat Shields

[P.J. McGrath]

I recently purchased as set of reproduction spark plug heat shields for my 66 427/425. It would seem they should attach by sliding the shield into the cast depression in the head that surrounds the spark plug. My shields have an extemely loose fit in the head and will not stay in place. Should the fitment be better or is there another method used to hold the shields in place? Thanks......P.J.

[William C.]

Re: 66 BB Spark Plug Heat Shields

Real 66 (and '65) heads have a threaded boss next to the spark plug. The little tab coming out from the heat shield is bolted to the head at the boss by using a 1/4 inch thread bolt (about the same as a pan bolt) th retain the heat shield

[P.J. McGrath]

Re: 66 BB Spark Plug Heat Shields

Thanks Bill! It all clear to me now! I've got the threaded holes in the heads though I need to get the exhaust manifold gaskets out of the way. I thought the tabs were where the the plug wires clipped on but now that you pointed it out they line up perfect with the bolt holes in the head. Thanks for the help.........P.J.

[Gary Wilkerson]

Re: 66 BB Spark Plug Heat Shields

Bill and PJ,

I was wondering the same. I did'nt realize the raised boss was for the heatshield.
I have the same issue as PJ with the manifold gasket partially in the way of the mounting location.
Whats the correct way to deal with this? Did the engine originally come without a gasket?

Gary

[Dick W.]

Re: 66 BB Spark Plug Heat Shields

Originally the exhaust manifolds did not have gaskets. It was a machined surface to machined surface mating. If the manifolds are not warped there is no need for gaskets. For some reason all overhaul and valve grind gasket sets include the un-needed exhaust manifold gaskets.

[Gary Wilkerson]

Re: 66 BB Spark Plug Heat Shields

Thanks Dick. I may try my manifolds without gaskets to see how they fair. I have no leaks now with gaskets but I'm sure how true the mating surfaces are

Gary

[Dick W.]

Re: 66 BB Spark Plug Heat Shields

Old trick that I used to keep header gaskets from blowing. I would coat both mateing surfaces with Loctite or Permatex (same product, different tube) RTV Copper Coat Gasket sealant. This took my header gasket life on the 454 in my dually from about 2,500 miles to 20,000 or better. I am sure that it would seal minor imperfections on cast manifolds.

[P.J. McGrath]

Re: 66 BB Spark Plug Heat Shields

Gary -
Last night I installed my heat shields. Using a razor knife, side cutters, and needlenose pliars I was able to remove the exhaust manifold gasket material between the exhaust ports. (It doesn't look too bad, unless you look real close)This allowed me to install the shields until I get around to removing the manifolds and applying the copper gasket sealant. (It probably would have been just as easy to do it right the first time!) I also had to run a 1/4-20 tap in the threads to clean them out. I used 1/4-20 x 3/4" pan head screws but they were too long and I had to shorten them a bit. I would buy the shortest ones you can find..........P.J.

[Dick W.]

Re: 66 BB Spark Plug Heat Shields

I believe that you can find a repro bolt to attach the heat shields. Probably Central, Doc Rebuild, Old Joe Ray, Keen, etc would have them