Spark Plugs

[tmorefield]

I am getting ready to tackle a tune up on my 1970 Avanti and was hoping for some input on spark plug and wire choices?

Thanks for any advise,

Tony

[Gunslinger]

If you have a stock engine and stock ignition system all you need is stock spec spark plug wires and whatever brand spark plug you like as long as it's the correct application and heat range. It wouldn't hurt to have thicker plug wires with low resistance ratings, but it really doesn't matter much outside of possibly having better radio noise suppression. You can get MSD, Accel, Taylor or house brand spark plug wires. It's a '70 Corvette small block engine so finding lots of choices shouldn't be an issue.

Standard grade spark plugs like whatever came in the car originally should be fine, unless you're experiencing a problem like burning oil that fouls your plugs...then a hotter heat range plug might be called for. You don't need the expensive, exotic spark plugs as they won't help a bit and will only lighten your wallet. AC spark plugs should have been standard in a GM engine and there's nothing wrong with them. I do like the AC RapdiFire plugs. I know many swear by NGK, as some do Autolite and Champion. But, any should give you good service. Leave the exotic plugs for modern cars that call for them as standard.

I don't know if your '70 is a late RQA or early RQB, but the RQB cars should have come from the factory with transistor ignition...no points and condenser. The distributor and cap look the same, so you would have to look inside to verify if it's a points or transistor unit. A transistor ignition will also have a control box on the right front area of the engine bay.

[tmorefield]

Thank you for the information. I haven't done a tune-up on a car since the late 80's (75 Dodge Charger SE). I had ordered the AC Rapidfire plugs but was unsure of wires. I will look for a heavier shielded set. My car runs great, but I have no idea when the previous owner did plugs and wires. I was under the car last weekend changing oil and greasing the chasis and noticed several of the wires were cracked at the boots to the plugs. I figured it couldn't hurt to change things out. My car is also a stock late RQA model with points. I need to refresh myself on points; I helped a buddy years ago.

Thanks,

Tony

[Ray K.]

Thank you for the information. I haven't done a tune-up on a car since the late 80's (75 Dodge Charger SE). I had ordered the AC Rapidfire plugs but was unsure of wires. I will look for a heavier shielded set. My car runs great, but I have no idea when the previous owner did plugs and wires. I was under the car last weekend changing oil and greasing the chasis and noticed several of the wires were cracked at the boots to the plugs. I figured it couldn't hurt to change things out. My car is also a stock late RQA model with points. I need to refresh myself on points; I helped a buddy years ago.

Thanks,

Tony

[Ray K.]

Thank you for the information. I haven't done a tune-up on a car since the late 80's (75 Dodge Charger SE). I had ordered the AC Rapidfire plugs but was unsure of wires. I will look for a heavier shielded set. My car runs great, but I have no idea when the previous owner did plugs and wires. I was under the car last weekend changing oil and greasing the chasis and noticed several of the wires were cracked at the boots to the plugs. I figured it couldn't hurt to change things out. My car is also a stock late RQA model with points. I need to refresh myself on points; I helped a buddy years ago.

Thanks,

Tony

As I recall, the late GM points distrubutors had a trap-door in the side. Open the trap door and insert a 1/8-inch Allen wrench to engage the point-adjusting screw. Then hook up a dwell tachometer and, with the engine running, adjust the screw until the dwell is within spec. I don't recall the exact spec off the top of my head, but 28 to 32 degrees rings a bell. Feeler gauges cannot be used with these distributors because there is stuff in the way.

Dwell tachs are not as common as they once were. If you go to your local NAPA store, they may not know what you are talking about, but it is in their catalog and they can get it for you. JC Whitney also carries them for ~$40.

[Gunslinger]

As I recall, the late GM points distrubutors had a trap-door in the side. Open the trap door and insert a 1/8-inch Allen wrench to engage the point-adjusting screw. Then hook up a dwell tachometer and, with the engine running, adjust the screw until the dwell is within spec. I don't recall the exact spec off the top of my head, but 28 to 32 degrees rings a bell. Feeler gauges cannot be used with these distributors because there is stuff in the way.

Dwell tachs are not as common as they once were. If you go to your local NAPA store, they may not know what you are talking about, but it is in their catalog and they can get it for you. JC Whitney also carries them for ~$40.

You have it pegged exactly. The GM window distributor is the easiest distributor ever to adjust points...it amazes me why no one else copied it. Maybe it was a patent issue, who knows? If you don't have a dwell/tach, a quick and dirty way to set the points is to start the car, use the wrench to turn the points in (clockwise), and at some point the engine will cough or maybe die...back it off about a half turn and you're about right at the correct dwell setting. 28-32 degrees is correct with 30 degrees as your target. A dwell meter is still the preferred method It still takes a tach and timing light to set the timing after disconnecting and plugging the vacuum advance hose from the distributor.

I still have my Mac Tools engine analyzer from 25 years ago though I haven't had a points car in quite some time. It still has many other uses which makes me hang on to it. My Sun timing gun is over 30 years old and still does yeoman work. If you need a dwell/tach, there should be lots of automotive meters available with digital readouts that include dwell.

If you saw cracked boots on the wires, it won't be long if you don't start leaking voltage and getting misfires. In fact, you might be getting the occasional misfire now from the spark escaping and grounding out and not be noticing it.

BTW...if you can, buy a set of one piece points and condenser...much easier to install. I used to sell them where I worked years ago. I don't know if they're still marketed as I'm sure demand is low. In fact, they were made by Prestolite who made much of Studebaker's electronic and ignition stuff.

[WayneC]

Just a thought... I upgraded by installing a stock mid-70's Chevy HEI distributor and 8mm spark plug wires in my '71 Avanti years ago. It's been trouble-free.

Can't recall any issues except I had to replace a resistor wire (pink) with a normal wire, use larger wire guides, and also had to find the proper connectors to attach the 12v feed and the tach wire to the distributor.

Maybe someone else can chime in who has done an HEI swap recently.

Edited August 14, 2010 by WayneC