Aussie79vette

I am in the process of rebuilding my L48 and the machine shop has come back and said both heads are cracked on 2 of the exhaust seats.
Have decided to replace them with Edlebrock E-street 5089 heads.
The Edlebrock website recommends Champion RC12YC plugs, but I have found more information about NGK-R5672A from a technical bulletin that says these are better to use.
Are the NGK better than the Champion with theses heads.

Any advice would be very much appreciated.

Jebbysan

The r5672a is correct......now pick a heat range.....
R5672A-8 is a middle of the road heat range.....7 is hotter, 9 is colder.
Excellent plugs....all I use.

Jebby

Mako72

I've never used the NGK's, so I cannot comment. However I have been using the Champions on my Edelbrock RPM head for years without any problems. Can't beat the price either.

zwede

NGK-R5672A is a non-resistor racing plug. Why would you use that on a street car?

Aussie79vette

Found the Bulletin attached below that recommended not to use the champion RC12YC plugs that are recommended on the edlebrock website ????

Below info cut and pasted from PDF at http://www.ngkplugpro.ca/en/techbull...ail.php?id=295

Topic
Recommended spark plugs for the vehicles equipped with aftermarket Edelbrock
cylinder heads.
Background
Edelbrock cylinder heads are specifically designed for high performance use and
are often interchangeable with original equipment cylinder heads. According to
the manufacturer, Champion RC12YC spark plugs can be used with their
cylinder heads on most street applications. But what happens is that when the
customers use this plug they have to advance the timing and adjust the air fuel
mixture (i.e., rich) to get proper combustion. The Champion equivalent NGK
spark plugs for these aftermarket cylinder heads are NGK FR4 or BKR5E spark
plugs.
Issue
When using the NGK FR4 or BKR5E spark plugs, because the NGK plugs have
more copper in the core of the spark plugs than the Champion spark plugs, they
pull out more heat during the start-up and can cause gas fouling issues and
intermittent misses. This problem is worse in cold weather climates. In fact, when
the cylinder head manufacturer suggests using Champion RC12YC spark plugs,
they are only specifying the basic spark plug design specifications (i.e., 14mm
threads, 5/8” or 16mm hex, and 3/4” or 19mm reach) not an actual heat range for
the plugs.
Solution
For these applications, we suggest using NGK R5672A-(X) series spark plug,
where “X” stands for the heat range for the spark plug. Depending upon the
compression ratio and horsepower of the engine, start with an“8” heat range and
move up to 9&10. There is no need to advance the timing or use a rich air fuel
mixture with these plugs and customers can simply use 94 octane fuels and
make slight adjustments for the humidity level in the environment.
Additional information
The above information only applies to specific Edelbrock cylinder heads that
recommends using the Champion RC12YC spark plugs. Please refer to the
manufacturer’s product manual for the correct spark plug specifications when
selecting the spark plugs for your aftermarket cylinder heads.

centuryoldracer

The NGK "race" plugs in my 17.2 to 1 race engine simply say B-9 es or B-8 es ect. The higher the number the colder the plug. I have seen and tried every brand on the Dyno, and for some reason the NGKs make the most horsepower. They are also easier to tune because they don't coat the metal part of the plug Black after they make them.
The way I read the plug in a aluminum head is by how many threads are discolored from heat at the end of the plug. If it has discoloration from heat 3 threads back than the mixture is about right. 2 threads it is rich, and 4 threads it is too lean. In other words the farther into the head the threads are discoloring the hotter the combustion is.
According to the EGTs 3 threads is between 1200- 1250 degrees when the exhaust leaves the port.
Making it richer (more fuel) cools combustion, less fuel (leaner) makes it hotter, but remember the saying when making power "lean is mean"

zwede

Interesting. Wondering if the lack of resistor will cause problems with my EFI... I might order a set of the NGKs out of curiosity.

Edit: A set of 8 is only $18.48 on Ebay w/ free shipping so I ordered them.

centuryoldracer

Keep us posted.

Jebbysan

Why not? Most all spark plugs wires are spiral core resistor type.....no need for resistors in plugs.
As far as the "race" part of it goes.....it is a name.
The FR4 NGK is built the EXACT same way.....which is a "street" plug.
5672 is projector tip.
5671 is clearance tip for domed pistons.

Been running them for 15 years or better in my vehicles......
I like NGK's because I grew up with them in dirt bikes.....they work and they are inexpensive.....plus I know the numbers.....

Jebby

zwede

Yeah, I've been wondering how necessary it is with resistors in the plugs with spiral core wires.

One thing I did find was that the resistors in spark plugs are all over the place, even on the same plugs (as in same part number). For instance, I measured a set of Champion RC12YC5's anywhere between 10K and 20K ohms. that's a pretty wide range!

REELAV8R

I agree. I think the NGK's are the best plugs i've run. Also always ran them in dirt bikes. Never had a failure due to an NGK.

I use the BPR5ES or 6ES for the vette.
Don't really know the difference in "race" plugs other than the presence of resistance or not.
I use the "R", resistor, for the car due to static interference in the radio, that's it.
Was always non resistor in the bikes or the "race" version of the plug and in the 8 to 10 heat range for the 2 strokes.

Had a lawn mower that was given to me last year. It didn't start and run very well with the stock plug despite it being very new from the previous owner. Got an NGK "ES" plug in the 6 heat range and cut the ground strap back. It started and ran first pull. Did the same this year after sitting for 7 months for the winter.
Plugs can make a difference.

resdoggie

I currently run the NGK FR5 in my AFR heads. No problem with them at all.

Aussie79vette

Thanks guys for all your input, I have decided to go
with the NGK-R5672A-8

zwede

I installed the NGK-R5672A plugs today. So far so good. No problems with the EFI and the radio still works. Time will tell if they stay cleaner.

zwede

Well, I'm having no luck with the R5672-8's. They are way too cold for how I use the car. I'm sure it's a great race plug, but here's what it looks like after only 20 miles of street driving. NGK to the left. To the right a AC-Delco 41-627. Put in a set of NGK FR45's. I think those will work better for me.

ddawson

Thanks for the update. Glad I didn't hit buy yet.

fishslayer143

In 45 yrs , the only brand of plug I ever saw fail early was Champion.. I won t even put one in my lawnmower... I run NGK or Autolite in all my engines ..