Need help picking spark plugs
Thread Starter
Burning Brakes
Joined: Oct 2000
Posts: 878
Likes: 60
From: Minneapolis, MN USA
Need help picking spark plugs
Hi All,
I have a 1970 350/350 that has a modified cam (previous owner, so I'm not sure what it is) with a Edlebrock Torker intake and Holley 650cfm double pumper carb. I have not driven the car much at all over the past five years, and the last couple of times it ran like total CRAP, to the point that I couldn't even get it started last fall.
I rebuilt the carb over the winter and installed it last weekend...and it fired right up! The carb was a total mess. So, now I think I need to tune the carb...and re-time the car, etc. But I think I also should change plugs just so that I know I'm starting fresh and don't have a dumb plug or three that is giving me issues I don't know about.
This is not really a question of what brand do you prefer...but my understanding is there are different "heat" values of spark plugs. Knowing the little bit I mentioned above about my car...what sort/heat of plug would you suggest for me? If you want to give brand advice, that's fine...but I'm just trying to get the right part first.
The previous owner was racing the car...I am not...I am street driving it. Of course I want it to go fast at times...that's why I bought a Corvette, right?! But I'm not trying to get 1/4 mile times, etc.
Any advice would be greatly appreciated!
I have a 1970 350/350 that has a modified cam (previous owner, so I'm not sure what it is) with a Edlebrock Torker intake and Holley 650cfm double pumper carb. I have not driven the car much at all over the past five years, and the last couple of times it ran like total CRAP, to the point that I couldn't even get it started last fall.
I rebuilt the carb over the winter and installed it last weekend...and it fired right up! The carb was a total mess. So, now I think I need to tune the carb...and re-time the car, etc. But I think I also should change plugs just so that I know I'm starting fresh and don't have a dumb plug or three that is giving me issues I don't know about.
This is not really a question of what brand do you prefer...but my understanding is there are different "heat" values of spark plugs. Knowing the little bit I mentioned above about my car...what sort/heat of plug would you suggest for me? If you want to give brand advice, that's fine...but I'm just trying to get the right part first.
The previous owner was racing the car...I am not...I am street driving it. Of course I want it to go fast at times...that's why I bought a Corvette, right?! But I'm not trying to get 1/4 mile times, etc.
Any advice would be greatly appreciated!
Melting Slicks
Joined: May 2006
Posts: 3,438
Likes: 41
From: Raleigh NC
St. Jude Donor '13-'14
R44S was stock for your car, but they do not make this plug anymore. Unless you spend a lot of time in WOT, I think you'll find the R43S is too cool of a plug and will foul quickly. Most cruisers go with the R45S.
Melting Slicks
Joined: Oct 2001
Posts: 2,065
Likes: 1,395
From: Halifax, Nova Scotia, Canada
The 1970 350/350 originally came with 11:1 domed pistons. The R45"S" is an extended tip plug. I would have some concerns of the piston contacting the tip.
I have never used them in mine due to this concern.
I would use a R45.
I have never used them in mine due to this concern.
I would use a R45.
Melting Slicks
Joined: May 2006
Posts: 3,438
Likes: 41
From: Raleigh NC
St. Jude Donor '13-'14
I believe the "S" projection vs. a standard plug is 2.5mm, or about 3/32". You will notice no appreciable gains with the projected tip. You may foul less as the plug tip will be "washed" more with the fuel mixture, thus cleaning the tip.
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Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
The 45 heatrange is correct6
The S series are fine, wont hurt the engine....The S plug did touch the pistons on the 61`s 315, Fuel injection 283`s.....Corrected gy using 2 steel shim gasket for the 62`s and later....dropped the ratio too 11.1 from 11.25
HINT, Gap your plugs at .035 no matter what brand or number.....
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Last edited by Ironcross; Apr 18, 2015 at 02:04 PM.