Old Plug removal from a 500ci in CDV
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  • 1 Post By Submariner409
500, 472, 425, 368 Discussion, Old Plug removal from a 500ci in CDV in Cadillac Engine Technical Discussion; This engine runs (been stored for some 7 years) but I need to change out the plugs or at least ...
  1. #1
    blueboy is offline Cadillac Owners Fanatic
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    Old Plug removal from a 500ci in CDV

    This engine runs (been stored for some 7 years) but I need to change out the plugs or at least clean and regap them. Looks like a bit of rust on 'em too! Shall I spray penetrating oil on them before attempting to remove? That dam passenger side rear plug is a bitch to get to....... Grrrh!

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  3. #2
    Submariner409's Avatar
    Submariner409 is offline If it won't run, install a sound system
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    Re: Old Plug removal from a 500ci in CDV

    Give each plug metal shell a decent squirt of PB Blaster and let it sit 2 hours. Now try to back out each plug 1/2 turn. Give each another shot of PB, let it sit a half hour, remove the plugs. Tedious but safe.

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    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: Old Plug removal from a 500ci in CDV

    Better safe than sorry. I think spark plugs are made cheaper all the time. I just broke one this year for the first time in my 40 years of changing plugs. Lots of rookies break the porcelain but this one broke off the entire hex and just left the threaded part stuck in the head. It was the back plug too. I am just lucky that I was removing the engine anyway. There is no way I could have fixed it in the vehicle. This just added to my rant against AC spark plugs. They were only in there 5-6 years. I guess one broken one in 40 years ain't bad but I will always spray them now if they have been in there a while.

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    blueboy is offline Cadillac Owners Fanatic
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    Re: Old Plug removal from a 500ci in CDV

    Thanks guys. I'm taking yer advice...have sprayed them and will do so again tonight and then try gentle pressure tomorrow to release them. Yes that back passenger side plug is a bugger!

  6. #5
    deVille33 is offline Cadillac Owners Connoisseur
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    Re: Old Plug removal from a 500ci in CDV

    Remember when we had point ignition systems and we had to change the components on a near annual basis, including the plugs? Most HEI systems require very little maintaining. I just started an 1979 Coupe I haven't run in 5 years. Little gas dropped into the carb reservoir and it fired and ran on it's own. With the point system I would have been messing with the components and checking gaps.

  7. #6
    Submariner409's Avatar
    Submariner409 is offline If it won't run, install a sound system
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    Re: Old Plug removal from a 500ci in CDV

    Electronic ignitions are one relatively maintenance-free development - and you can take just about any points distributor and drop in a Pertronix module and coil: BINGO ! Hot, reliable maintenance-free electronic ignition.

    Unleaded gas has significantly lengthened spark plug life, not the electronic ignition systems........ and many engines now run platinum or iridium electrode plugs - more long life stuff. All the more reason to use a tad of anti-seize on the plug threads.

    Every marine Olds 455 and GM 454 engine I build leaves here with a Pertronix-modified points distributor.
    70eldo likes this.

  8. #7
    70eldo's Avatar
    70eldo is offline Cadillac Owners Connoisseur
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    Re: Old Plug removal from a 500ci in CDV

    Do you have a partnumber or so for platinum or iridium plugs to fit a 500cid?
    I also went petronix II. I am very happy with how it runs.

    Would it be OK to use copper lube on the plugs so they come out better? Copper lube/grease withstands high temp, but I don't know if it would hold that high temp... I used it on the header bolts and that worked out just fine.

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