Spark plug HELP!

[9" Jimmy]

I found out the year of my motor is a '78, but are all '78 454's the same? The sparg plugs I pulled off of it don't match up to the ones I got for a '78 454 C-20. The new plugs will fit, but they're shorter and use a 5/8 socket, not the 13/16 I used for the old ones. Any ideas?

 

[dfl701]

did the new motor have headers? header spark plugs are a different length.

 

[9" Jimmy]

It has the stock manifolds. I did notice that when I unscrewed the old plugs they didn't feel like they were in all the way. I can get plugs for free so I guess I should just try the ones I have. The cap, rotor, wires and coil all fit that I got.

 

[dhcomp]

who knows if what was in there was the right plug either. What does a service manual say?

 

[9" Jimmy]

I have the manual for the truck itself, but it doesn't mention any 454's. I checked my VIN# and it came stock with a 350 4 bolt main, but the PO dropped in a '78 454, but I don't know what it came out of and if there were different 454's made that year. I looked up a C-20 and everything else fit the same, but the plugs. I'm thinking it had the wrong plugs in it. What else had a 454 other than a Sub? I'll check the plugs for a Sub and see if they match the C-20.