Which spark plugs to use?
04-08-2007, 01:58 AM
#1
Le Mans Master
Thread Starter
Which spark plugs to use?
Picked up the subject from a thread a couple of months ago. I'm trying to find the correct plug to use on my 327. I do have the TRW pop up pistons and I'm running 64cc Edelbrock Performer RPM heads. I also have Hooker side mount headers so I need a plug that is as short as possible. I'm not a big fan of Accel and I read in the quotes below about the NGK's. My only question is are the NGK's correct for my application (Summit says I need an "S" heat range plug) and are they shorter than stock?
Thanks in advance.
Scott
Sorry - I meant to add I'm running a stock HEI distributor.
Thanks in advance.
Scott
Sorry - I meant to add I'm running a stock HEI distributor.
The original plug for Corvette 327s through '68 was the AC 44. In 1969, it was the R44. The 44 series is not available anymore, but no matter as it was really a bit too cold for normal driving. The 45 series is better.
There is no real performance difference in the 45 or R45. The R is for resistor plugs which help reduce ignition noise in radios. The R45S has an extended tip which helps keep it cleaner from fouling and so it runs a bit better. However, if you have high domed pistons or the heads have been shaved, you could hit. You need to install the plugs, turn the engine over, and then check the plugs if you have any performance work done on the engine.
If you are running the R43S, you'd better be doing hot laps most of the day, because it is far too cold for the street.
There is no real performance difference in the 45 or R45. The R is for resistor plugs which help reduce ignition noise in radios. The R45S has an extended tip which helps keep it cleaner from fouling and so it runs a bit better. However, if you have high domed pistons or the heads have been shaved, you could hit. You need to install the plugs, turn the engine over, and then check the plugs if you have any performance work done on the engine.
If you are running the R43S, you'd better be doing hot laps most of the day, because it is far too cold for the street.
Last edited by sperkins; 04-09-2007 at 12:28 AM.
04-08-2007, 09:00 AM
#2
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The plug laying on the box looks like a standard length tip. The PICUTURE of the plug on the box looks like an extended tip. Look at the difference in how far the white ceramic sticks out of the plug shell. If you're talking about overall length for header clearance, I can't help you. I also have no knowledge whether your engine can use the extended tip plugs as I've never owned a set of those heads.
On a AC plug R45S for example:
R= resistor
4= I don't remember
5= heat range=
S= extended tip (no S= standard length tip) The S has nothing to do with heat range but it's supposed to run cleaner.
On a AC plug R45S for example:
R= resistor
4= I don't remember
5= heat range=
S= extended tip (no S= standard length tip) The S has nothing to do with heat range but it's supposed to run cleaner.
04-08-2007, 09:32 AM
#3
I can tell you from using these same heads on my 327 with the pop ups that you can't use the extended tip plug. It will hit the piston. First of all, you have to use a 3/4" reach, 5/8" hex, gasket seat plug. Edelbrock recommends one but it is an extended tip plug. I used a regular tip NGK R5671A-8 and they worked fine. But, they are a standard length plug and may hit your headers. I don't know what the equivilent is in a shorty plug, sorry. These heads work really good, but I had too many problems trying to get them to seal with the factory aluminum intake. I ended up putting my original 461's back on my motor.
04-08-2007, 11:37 AM
#4
Le Mans Master
Thread Starter
I can tell you from using these same heads on my 327 with the pop ups that you can't use the extended tip plug. It will hit the piston. First of all, you have to use a 3/4" reach, 5/8" hex, gasket seat plug. Edelbrock recommends one but it is an extended tip plug. I used a regular tip NGK R5671A-8 and they worked fine. But, they are a standard length plug and may hit your headers. I don't know what the equivilent is in a shorty plug, sorry. These heads work really good, but I had too many problems trying to get them to seal with the factory aluminum intake. I ended up putting my original 461's back on my motor.
The picture on the web page is not the actual plug. Mine is pictured below. (Sorry for the fuzzy shot)
http://store.summitracing.com/partde...0&autoview=sku
04-08-2007, 11:53 AM
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04-08-2007, 12:03 PM
#6
Le Mans Master
Thread Starter
04-08-2007, 06:00 PM
#7
Check out the instructions you got from Edelbrock and their recommended plug. It is an RC-12YC. But that plug is an extended tip. It will hit the piston. I know. I did a lot of measuring before I installed the heads on my motor. These Edelbrock heads do NOT take the same type of plug that a stock Chevy 461 type head takes. Edelbrock tells you that these heads can be used with any factory type piston. But the way the chamber is designed, the plug extends pretty far into the chamber and you have to be careful if you are not using flat top pistons. The NGK 5671 is not an extended tip and will work fine. But, it might be too long for your headers. It is a standard length plug and your plug pictured appears to be shorter. Hope this helps you.
04-10-2007, 12:37 PM
#8
Le Mans Master
Thread Starter
Check out the instructions you got from Edelbrock and their recommended plug. It is an RC-12YC. But that plug is an extended tip. It will hit the piston. I know. I did a lot of measuring before I installed the heads on my motor. These Edelbrock heads do NOT take the same type of plug that a stock Chevy 461 type head takes. Edelbrock tells you that these heads can be used with any factory type piston. But the way the chamber is designed, the plug extends pretty far into the chamber and you have to be careful if you are not using flat top pistons. The NGK 5671 is not an extended tip and will work fine. But, it might be too long for your headers. It is a standard length plug and your plug pictured appears to be shorter. Hope this helps you.
Scott
