R44TS @ .035 is the right plug for your heads. I changed to HEI last year on my 73 and run the same combo and it fires nice and even and smooth. 
Spark Plugs
Thread Starter
Burning Brakes
Joined: Nov 2006
Posts: 893
Likes: 7
From: Orange Park Florida
Spark Plugs
I have a '72, 350 cu vette. I have retrofitted to an HEI ignition, and, I am using stock heads. I've been using Delco R44TS plugs gapped at 50 (these are the short shank type) but they don't last. I've read somewhere that I should be using something like a Delco FR5LS or NGK BCPR5ES, which are the longer shank type, and they allow for the wider gap requirements of the HEI ignition. What plugs should I be using? Are the longer shanks going to hit the piston? I need a little insight here.
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
For performance engines a .035 gap is the best. In fact either points or electronic use the same .035. Those wide gaps were a product of ideas resulting to try and lower emissions no longer found to be necessary. The R44T or R44TS is the correct plug for tapered seat heads. A R45T could be OK also as its one step warmer. ..
Thread Starter
Burning Brakes
Joined: Nov 2006
Posts: 893
Likes: 7
From: Orange Park Florida
Thanks for the input. I've heard so many opinions on this subject I was beginning to get confused. My concern was the upgraded ignition (HEI) and what effect it would have on the original plug type. So it's R44TS set to .35 from now on.
Thanks again for the info.
Thanks again for the info.
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
I forgot to mention its also a very good ignition and fancy upgrades with there stick on decals will not give any better perfomance, all they do is just cost more for the same results.......
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Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
You might have a 'hyper coil' or an HEI that can produce 50K volts, but the plugs fire at 8-12K.
Net gain is zero.
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Tech Contributor
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
The actual discharge voltage is not set by the type of ignition system, it is set by the energy required to jump the gap in the spark plug. A typical plug with a .035" gap might take only 8-12K volts to fire depending on condition, so that's the maximum amount of energy that will be stored.
You might have a 'hyper coil' or an HEI that can produce 50K volts, but the plugs fire at 8-12K.
Net gain is zero.
You might have a 'hyper coil' or an HEI that can produce 50K volts, but the plugs fire at 8-12K.
Net gain is zero.
The usual "50kV coil" description only tells you how much voltage it takes to internally short out the coil windings. It does not give any indication of how much energy (the key ingredient) that is actually stored in the coil.
Race Director
Joined: May 2003
Posts: 10,956
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From: California
i have a 79 vett with an HEI. But I also have a a 72 jeep that had a Mallory unalight and Mallery coil , Changed it to a HEI and it starts better, runs smoother and seems to accelerate better... so.. im sold
Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
no, the mallory unalight and coil were about 4 years old, and the jeep maybe gets 5-10k miles per year, Distributor was also changed like 3 months earlier. so....this was my personal result and I would do it again in a heart beat. just starts so much better.. maybe results vary.. p:-)
