So when I first got the car the kid said "The previous owner told me he swapped in a 350, but I think he was just saying that so I would buy it." So I kinda doubted to and bought it anyway, thinking its just a regular 305. Friday I picked up some AC Delco R43TS plugs to put in today. I pulled the first one and realized something wasn't right. It had an Autolite 3924 which has about twice the threads the Delco does. My Haynes manual recommends a FR3LS for aluminum heads of the same year, which cross references to match up with the autolites. I didn't think third gens came with aluminum heads? I guess the guy telling the truth and swaped in something else.

 

does it really have aluminum heads?

 

Casting number 627 on the block so its a 305. But these spark plugs still make me wonder... The heads look more like iron than aluminum and a magnet sticks to them. But if you had a plug with longer threads wouldn't it run weird?

 

Put a magnet to the head, if it sticks, it's castiron, if not, Al.

Try www.mortec.com or www.chevymania.com (probably a zillion others) for casting numbers.

 

The plug attributes:

AC R43TS:
14mm... .460" reach... 5/8" Hex... Tapered... Non-Resistor

Autolite 3924:
14mm... 3/4" reach... 5/8" Hex... Gasket... Non-Resistor

AC FR3LS:
14mm... 3/4" reach... 5/8" Hex... Gasket... Non-Resistor

Best to pull a v/c and see what you got.

 

Well they deffinatally are iron heads. I guess someone just put the wrong plugs in. Odd though because seemed to run alright.

 

What do those gaskets (on the plugs) look like?

-Steve (Black Bomber)

 

^Sorry, me... again.