Spark Plugs
Thread Starter
5th Gear
Joined: Mar 2003
Posts: 5
Likes: 0
Spark Plugs
Hi
I have a 1970 corvette with a 350 engine. DOnt drive it nearly enough so want to go with a hotter spark plug than normal. Can seem to find out which one is best. Can anyone help with this? Suggestions?
Thanks
DOn
I have a 1970 corvette with a 350 engine. DOnt drive it nearly enough so want to go with a hotter spark plug than normal. Can seem to find out which one is best. Can anyone help with this? Suggestions?
Thanks
DOn
Safety Car
Joined: Aug 2000
Posts: 3,711
Likes: 43
From: San Antonio TX
Which of the available 350 engines do you have and is the engine stock? What issues are you experiencing with the plugs that are in the engine now?
You can find a plug on your own. All you need to do is find out what stock plug is specified for your engine and then go to the various manufacturer sites to find out how they rate their plugs. Nearly all plug manufacturers use a scale where the lower numbers are colder, higher hotter.
You'll also need to clarify what you mean by "best." Unless you have an unusual application, any of the brands will perform just fine. You don't need a rare metal plug or anything like that if that's what you mean.
You can find a plug on your own. All you need to do is find out what stock plug is specified for your engine and then go to the various manufacturer sites to find out how they rate their plugs. Nearly all plug manufacturers use a scale where the lower numbers are colder, higher hotter.
You'll also need to clarify what you mean by "best." Unless you have an unusual application, any of the brands will perform just fine. You don't need a rare metal plug or anything like that if that's what you mean.
Had a 1976 L-82, 4-sp
Joined: Mar 2011
Posts: 5,338
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From: Some days your the dog and some days your the hydrant.
Royal Canadian Navy
I've had good luck with the AC Rapidfire plugs vs the normal AC R45TS for my application before mods were done. The car actually idled about 50 rpm higher with just a change to the Rapidfire #2's.
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
+1, I agree. The important thing is to get the car fully warmed up each time you start it which means driving for a half hour or so, preferably at highway speeds. This will eliminate condensation from accumulating in the engine oil and exhaust. This will also keep your spark plugs clean assuming the engine is in good running shape.
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
Match the plug requirement to the heads! If the heads are not stock for the assumed motor, they may have a different sealing (taper seat versus gasketed), and a different threaded length. Get either one wrong, and you'll have problems worse than the wrong heat range!
As far as heat range, know your compression ratio and select accordingly.
Also beware of gimmicks such as multiple ground electrodes (who wants to impede the flame travel?). Besides, the spark will only travel to one at a time, not several.
As far as heat range, know your compression ratio and select accordingly.
Also beware of gimmicks such as multiple ground electrodes (who wants to impede the flame travel?). Besides, the spark will only travel to one at a time, not several.
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Verdad Gallardo
Team Owner
Joined: Jan 2007
Posts: 53,648
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From: Southern Cal Ca
St. Jude Donor '22
there are legitimate reasons to change heat ranges of plugs,
most just mask some problem.
generally plugs are for all around use, hiway and city speeds.
what is wrong that you want to change?
most just mask some problem.
generally plugs are for all around use, hiway and city speeds.
what is wrong that you want to change?
Drifting
Joined: May 2012
Posts: 1,353
Likes: 44
From: Calgary Alberta
I stick with the Delcos...have R43s in my 70 L46 as the optional plug listed in the owners manual, but at the next swap I'll probably put in R45s because it's just a city cruiser most of the time. No need to go outside that range I don't think, but up to you.
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
Just be careful about the letters in back of the numbers...Your 1970`should not use a tapered seat plug......the 'T' in an above quoted AC plug, {R45TS} means it is a tapered seat plug......the numbers mean the operating heat range...The 45 is a good choice for that......might as well identify the 'S too....means extended tip which could have a interference fit with the 11.25 compression ratio of the 1961 283`s......so to be safe a plain #45 or #R45 are the better choice for a 61 FI 315 engine....Oh, and the 'R means resistor........