spark plugs

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Feb 21, 2009 | 05:16 AM

eby94

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spark plugs

I am in the process of working on a 1973 440 with 400/440 motorhome heads, I am having trouble finding spark plugs for this engine. I have already tried Champion RJ12YC and Autolite AP85 with no luck. The threads are good on the heads. I have heard that these heads take different spark plugs. PLEASE HELP

Feb 21, 2009 | 06:37 PM

Commando

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From: New Jersey

What is the reach on the head for the plug, is it 3/8 or 3/4? I had Accel 437s for the stock 440 heads, but needed the 417s for the Edelbrock heads I got as they needed a longer reach.

Feb 21, 2009 | 11:04 PM

66sportfury

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autolite ap85s should be the plug.....autolites rock!

ill do some digging and see wat up. i didnt know heavy equip or industry heads were diff just knew the timing gears were.

Feb 21, 2009 | 11:08 PM

66sportfury

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but i need to know the year and make of the motor home

Feb 22, 2009 | 05:41 AM

eby94

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The casting numbers for the block show it be a 1973 440 block. The casting numbers for the heads show them to be 400/440 heads for 1973. This motor is setup for twin turbos going in a 1941 Plymouth.