1964 GMC Typhoon What are the correct spark plugs for engin

  • 1964 GMC TYPHOON

Engine Performance problem
1964 GMC Typhoon 6 cyl Two Wheel Drive Manual 79000 miles

I was going to do a tune up and replace the spark plugs. When the plug in the engine was removed and compared to the new plug from the auto parts store there was a big difference. The plug that was removed is an Autolite 24. The new plug is a Champion 3405. The old plug requires a 5/8 inch socket the new plug requires 13/16 inch socket. The new plug is longer then the old plug by 1/2 inch. Will the new plug hit the cylinder head? How can I tighten the new plug if the socket does not fit in hole in the head for the spark plug? Do I have the correct plugs for my engine? The VIN on the vehicle is I1002WF2457A. I think the engine is a straight 6 cylinder 230 cid. The numbers on the engine block are 88403466.


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Saturday, July 18th, 2009 AT 11:00 AM

2 Replies


The 3405 is too long of reach the piston will touch it-Try and have the partsman cross reference it with a different type of tapered plug the same diameter and reach w/ the 5/8 head.

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Saturday, July 18th, 2009 AT 8:24 PM
  • 2,322 POSTS

See if you can find the casting number on the head, but it might be under the valve cover.

A few things to do.
Look where the spark plugs go,
use a screw driver and clean the bottom of the hole as best you can.
Is it flat, and would accept the sealing washer that's on the top plug,
does it have a tapered edge of the threaded hole, and would use a plug like on the bottom.

Can you see how deep the threaded hole is on the head?

And finally, as a last resort.
Get some silly putty, plumbers putty, or play dough.
Rotate the engine over so that #1 is at TDC,
put a blob of the putty on the end of the long sprark plug and screw it in to the hole by hand, as deep as it will go.

Then pull it back out. Is the putty smashed from hitting the top of the piston?

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Saturday, July 18th, 2009 AT 8:28 PM

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