# Spark Plug for 350



## Erikh425 (Sep 24, 2013)

So I am going through the Tempest I brought home last week. I am replacing fluids, plugs and other stuff. This seems pretty basic, but I want to get it right. The plugs that are in it are Accel 576s. The shop manual calls for 44s, 45s, or 46s. I don't see any cross reference that lists the Accel 576s. I do see several others that cross reference with the 40 series but they all have thicker bases and are a bit longer from the base of the threads and do not have a tapered seat like the shop manual calls for. 

So, can someone tell me what they are using that works? I will continue searching here and the web for answers. 

Thanks in advance.


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## 704dorlemans (Oct 15, 2013)

I got plugs for my 70 lemans 4 door with a 350 off of rock auto. They matched the originals that were in the motor and installed with no problem dont remember the numbers off them but they werent too expensive might want to check their site and see if they list the numbers on the plugs


Sent from AutoGuide.com App


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## Erikh425 (Sep 24, 2013)

Thanks for the advice. I am going to see what they suggest. The more information that I find indicated that either the plugs the PO had in it were wrong, or maybe it has odd heads. Gonna have to do a little more digging, but I will start with Rock Auto.


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## 1970 Lemans (Jul 25, 2009)

I have always used (for original 350 engine) either Autolite PN 86 or AC Delco PN R46S. Both are cheap and available anywhere and seem to work just fine.


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## Rukee (Feb 8, 2007)

According to my NAPA Pro-Link site, Accel doesn't make a plug for the 350. I would use the Delco plugs. And NEVER use Champions in a GM motor.


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## Erikh425 (Sep 24, 2013)

Thanks for all of the advice. I am attaching a picture that I took of the plugs in question

The plug on the left is the plug that I removed from the engine. It is an Accel 576S It looks like it has been there for a while.

The middle plug is a Champion #18 (RV15YC4). It is the Champion equivalent to the 576S, but the length from the seat of the plug to the electrode is longer than the Accel 576S. I am not a fan of Champion plugs, but this was the only thing in stock that cross referenced to the Accel 576S.

The right plug is an Autolite 86. This is the plug that is recommended as a replacement for the plugs referenced in the shop manual, and pretty much everywhere on the internet. The problem is that this plug does not have a tapered base like what is shown in the shop manual, and it looks totally different from what was in there.

So, the car runs with the plugs that are in it (Accel 576S). Should I:

1-Just replace them with the equivalent?
2-go with the Autolite 86 seeing as it seems to be the plug that is supposed to be there?
3-Do some more research to see if there are odd heads on this engine?

I am not sure that the PO knew what he was doing, so it could be a frankenengine. There is a myriad of odd "fixes" on this thing.

Thanks again, and let me know what you think


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## Rukee (Feb 8, 2007)

What year? I looked up a `70 350 and that doesn't use a tapered plug, it uses one like you have on the right with the crush washer.


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## Erikh425 (Sep 24, 2013)

Rukee said:


> What year? I looked up a `70 350 and that doesn't use a tapered plug, it uses one like you have on the right with the crush washer.


It's a 70. I could have swore that the shop manual described it as a plug with a tapered base. I am probably wrong. I think I will go with the plug on the right with the crush washer. It makes sense that the plugs that were in it were just some plugs the PO may have already had around. 

I am sitting at my desk dreaming of 5pm, but I will check the shop manual when I get home tonight.

Thanks for the info,
Erik


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## 1970 Lemans (Jul 25, 2009)

The plug to the right is the correct plug for a stock 1970 350. 

But do check the shop manual if for no other reason than it is fun to do ... just another perk of owning an old Pontiac.


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## Erikh425 (Sep 24, 2013)

1970 Lemans said:


> The plug to the right is the correct plug for a stock 1970 350.
> 
> But do check the shop manual if for no other reason than it is fun to do ... just another perk of owning an old Pontiac.


Thanks for all of the replies. That is what I went with. I fired her up and she starts and idles much better. Then I tore out all of the seats and carpet so I could get started on that project. Watch for questions in another thread in reference to that 

Thanks again, 
Erik


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## Icefan71 (Apr 7, 2011)

Might wanna check the gap on your plugs. I bought a set that was supposed to be .035 and they were .045. I had to shorten them up a bit.


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## Erikh425 (Sep 24, 2013)

Thanks for the heads up. I checked them. They were all over the board. My 7 year old and I gapped them and changed them out. 

Erik


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