I ordered new spark plugs for my 1933 Master from the Filling Station. They sent me six AC Delco R45 plugs that take a 13/16" socket. I pulled the plugs from my engine tonight and my car has AC C86 plugs that take a 7/8" socket to remove them. Did Chevy have different heads on the 1933 206 cu engine's? Or is the Filling Station listing the wrong plugs for my car?

Thanks,
Dennis

1934 was the first year to have the smaller 14 MM spark plugs. All1933 models had the larger 18MM thread plugs.

Thanks Gene. I guess I will call the Filling Station tomorrow and ask why they sent the smaller plugs for a 1933 car. I won't try for a refund because I actually bought the plugs almost a year ago and I'm just now getting around to installing them.

Dennis

Please check the thread size before you call. My experience is that hex size does not necessarily indicate thread size.

Rusty 37 Master....By thread size do you mean the outside circumference of the threads? I can do that with a micrometer. But I don't have any way of checking the actual threads themselves.

Dennis

Do the new plug threads fit into the holes the old ones came out of? That's what Rusty is referring to.

They may use a different size wrench but fit and work fine if the electrode end looks the same and threads in fine...

A friend of mine many years ago was once asked the question "What are the correct spark plugs for my car". His answer was: "If they will screw in they will work"!

In most cases you are right JYD but occassionally a longer plug will protrude far enough to contact the piston which is not advisable.
Tony

No need to check the thread size. If they ae 45s the thread size is too smalll for a 1933.............

A quick review of spark plug thread sizes:
1929-1932 are 18 mm
1933-1940 are 14 mm
1941-1948 are 10 mm
1949 went back to 14 mm

Yes, I am a year off. You must have an earlier head. What is the casting number?
836961 for 1933 master
836718 for 1932

I didn't get the chance to call the Filling Station today. Where would the head casting number be located? Do I need to remove the valve cover to view it? I am guessing that the suggestion that I have an earlier head would be correct. My old plugs are clearly much larger than the new ones. And I just looked at the Filling Station website and they do show the AC C87 plug for 29 to 32 chevy's. So much for my car being as original as I thought it was.

Dennis

The head casting number is underthe valve cover, drivers side.
Would also post the engine casting number on the lower right side of the block.

Thanks Gene. I'll do that as soon as I get the chance. I'll be out of town for a while.

Dennis