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Correct Spark Plugs


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1965 Riviera--401 with a/c

The service manual calls for ac-delco 44S spark plugs. That number has been discontinued and their web site calls for 43S as the replacement. If you are using ac/delco plugs, is this the number you are using?

(granted the replacement plug would be R43S)

Frank O'Donnell

Charlottesville, VA

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I have found 44S plugs at old car swap meets and use them. With no lead in today's gas, they last a long time. You can clean and re-gap them every 10k miles. I have not looked on eBay for them but I would bet they are there.

If you have stock points ignition in your car, using a resistor plug, like the R43S, would be better than non-resistor. The 43 is a slightly cooler plug than stock (NTTAWWT).

If you have plug fouling (usually from oil, but could be from gas if your carb is out of adjustment) you can try the hotter R45S plug. You might experience "pinging" with this hot plug. If you do, swap it for the cooler plug.

Edited by Jim_Cannon (see edit history)
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  • 1 year later...

I did have sooty spark plugs using the R43Ss so I am switching over to the R45S plugs as Bernie suggested. But I have a follow up question for the group. It appears I have some oil getting into the plug holes and onto the plug tips. Should I be using the silver ring spark plug gaskets that come with the plugs in my 1965 401 engine or leaving them off?

Second question is: if I should use the silver ring gaskets, should I be turning the spark plugs a little tighter (torqueing them) more than normal to insure no oil seeps in?



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Your question is good. I just have to get the car running well enough first, so I can set the dwell and timing and do a compression test. I know the valve cover gaskets are shot, so rings and other gaskets are probably finished as well.


I wouldn't trust a compression test on these old Nailhead motors. Those tests often lie due to excessive carbon build up in the combustion chambers. You need to do a comprehensive leak down test to truly identify the health of the motor IMO.

Edited by Rob J (see edit history)
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OK Riviera People: So many tests. That's me in a few years in the doc's office. haha I agree with Rob that a leak down test is certainly a worthwhile thing to do. I would also change the oil/filter and add a quart of Marvels and drive it for at least a couple of tanks of gas before I started testing everything. Don't forget....2 cans of B-12 in each tank too. If there is a fouled plug you won't need a calculator to do the math. It's 50 years old, it's has had it's day in the sun and now....it's a better than excellent chance that it's worn out. The good news? When you go to do the turbo 400 you will be surprised how easy they are to build, parts and labor are among the most reasonable of all old car trannies and most shops won't have a problem accepting that job. A 63 with the Dynaflow.....that's another story. mitch

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I am looking at this thread and wondering when the car started running bad. It looks like you have had it for a while.

Wet oil on the tips of the plugs is not a tune up issue. I would agree that bad valve guides could be part of the problem.

A compression test is easy to do and it is not the number, but the balance you are looking for.

Do a thorough test. Write down the results. Use a screw in tester. Open the throttle plate. and test both dry and with a teaspoon of oil.

Pay particular attention to the reading compared to the oily plug cylinders.

Oil can also enter through a cracked piston. I have seen two of these.

These cars are getting close to 50 years old. That is the point where age, wear, long term storage, or a combination of all begins manifesting into expensive repairs. You see a few over 50 originals at the meets, but most over 50's are restored at least mechanically.

Post your readings. I would like to see them.


Checking the valve guides is not real hard. Just take the rocker arm shafts off and put you fingertip on the tip of the valve stem. The ones bad enough to give trouble will wiggle around pretty good.

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