Spark plugs will not go in....

[64SF]

The casting number from the heads is 4006452. Casting list says 76-78 400/440. I did find information regarding the engine applications as 440-3. If you google it (440-3) a lot of posts regarding the big/small plug issues.

 

[coloradodave]

It appears that you have the motorhome 452 heads that use the Chevy style taper seat spark plugs with the 5/8 nut on them and not the 13/16 nut gasket style plugs.

Good call, IQ52... Your expertise is a valuable asset to this site. Thanks.

 

[Russtoy]

I had the same problem with my 440. I bought new plugs, and never paid attention to the taper. The plugs I bought were gasketed, and the heads need taper seat. It took me a while to notice the difference,( 3 min) haha I think the taper seats plugs give you a greater selection of newer technology plugs. I have e3's in it, now, I haven't done anything other then break in. I have a 440 source 512 stroker.