Spark Plug Installation

[Stuart F.]

I probably can find this out with some research, but I'm about to do a spark plug change on my 63 L-76 (some thing that I have not had to do in over 10 years) and would like to know what the torque should be in in/lbs vs. ft/lbs. I believe my chances of applying my smaller in/lbs torque wrench to all 8 plugs is much greater than if I used my ft/lbs wrench. I have both real good tools with ratchet heads and adjustable release handles, and I plan to do the installation from under the car to increase my chances of getting the passenger side shield off easier and affording me greater use of my various sockets and extensions.

Any advice from our more experienced plug changing members will be appreciated. I expect this will be the last change for me for as long as I have had the pleasure to care for this wonderful machine.

Stu Fox

[Dan H.]

Re: Spark Plug Installation

Stu, I use 25 lb to torque my plugs, don't want to over tighten them to distort them.

[Michael W.]

Re: Spark Plug Installation

would like to know what the torque should be in in/lbs vs. ft/lbs.

The ratio is a constant of 12:1. Twelve inch pounds of tq. = one ft/lb of tq.

Plugs are torqued to between 15-22 ft/lbs depending which source is quoted so the range is 180-264 in/lbs. That's on the high end or out of scale for most 1/4" drive torque wrench

[Frank D.]

Re: Spark Plug Installation

Use an old cut off straight spark plug boot when doing the removal/installation of the plugs - makes it swift and easy and never a stripped thread or dropped and cracked plug (see picture)....then you only need a socket for a 1/2-3/4 turn or so to break loose/tighten the plug. Reduces the frustration. I always use anti-seize on the plug threads and dielectric grease in the boots so that removal the next time is easy.

You've got a few more plug changes left in you Stuart.

I've never used a torque wrench on a spark plug in 50 years and hundreds of changes on cars, boats, motorcycles, jet skis and small engines...the compression ring around the plug seals the connection and a partial 1/2-3/4 turn past snug is plenty tight if your threads are clean.

[Jim T.]

Re: Spark Plug Installation

Use an old cut off straight spark plug boot when doing the removal/installation of the plugs - makes it swift and easy and never a stripped thread or dropped and cracked plug (see picture)....then you only need a socket for a 1/2-3/4 turn or so to break loose/tighten the plug. Reduces the frustration. I always use anti-seize on the plug threads and dielectric grease in the boots so that removal the next time is easy.

You've got a few more plug changes left in you Stuart.

I've never used a torque wrench on a spark plug in 50 years and hundreds of changes on cars, boats, motorcycles, jet skis and small engines...the compression ring around the plug seals the connection and a partial 1/2-3/4 turn past snug is plenty tight if your threads are clean.

Frank with all your spark plug changing on aluminum headed engines have you tightened one too tight and had difficulty removing it later?
If you have encountered this what method did you use to preserve the threads?

[Patrick B.]

Re: Spark Plug Installation

Jim-- with aluminum heads, it is really important to use anti-seize on the threads and to thread the spark plugs in most of the way by hand before using a socket wrench. Cross threading and corrosion are far bigger problems than too much torque.

[Joe R.]

Re: Spark Plug Installation

The design of a spark plug is kinda well idiot proof as far as torque is concerned. If you notice the design of the gasket you will find it thick and rounded so that it will collapse as it is tightened (torqued). As Frank has tightened hundreds of spark plugs he has learned after contact the gasket will collapse and seal the spark plug perfectly. And yes you still have to start the spark plug in the threaded portion of the head straight so he suggested using a plug boot. Great idea Frank! I use an old vacuum hose.
Using a torque wrench under the hood of a Corvette with a 427 and AC would result in cutting a hole into the inner fender. Great idea anyway!

JR

[Frank D.]

Re: Spark Plug Installation

Basically not over-torquing and using anti-seize will prevent problems even on aluminum heads.

Aluminum is soft compared to cast iron so if you've gone overboard with tightening into the head you have to do what you have to do to get it out. Once the threads are compromised its helicoil time I'm afraid...

You want to get a nice swath of the dielectric compound in the plug boot but not on the ceramic part of the plug...
When putting the wires on you want to get a nice straight angle on the boot and give a firm push until you feel the 'snap' of proper connection.
If you don't feel that; the wire isn't on all the way.

With my method, on my '61, I can change all 8 plugs (including R&Ring the ignition shielding) in about 25-35 minutes..
On my '63, the PS shielding is harder to remove (due to aftermarket A/C) it takes me about 45 minutes...

I use NGK-XR4 plugs in both cars.....

[Stuart F.]

Re: Spark Plug Installation

Thanks to each of you for your response and good advice. I recall that I too installed them by hand in the past using whatever tool would work the best at each location. My thought was "just this one time" I'd try to torque them and that is why I was hoping to use my in/lbs torque wrench. I have yet to find much use for it since I bought it. The other thing is that after 10 years I'm afraid I may have lost the touch. I also recall my great struggles over the past 50+ years with the one piece spark plug shield on the passenger side. It is near impossible to get out from the top.

Thanks again.

P.s. Just concluded plans to go to Carlisle with my son on Thursday the 27th and returning to Orlando on Sunday the 30th. Hope to run into some of you up there. I'll be the one sitting in the shade.

[Duke W.]

Re: Spark Plug Installation

Be very sparing in the use of anti-seize compound. I've seen cases where it looks like it was applied with a soup spoon.

Apply a narrow strip with you finger along the axis of the thread, then run the plug in and out of the thread a couple of times to spread it around evenly. (I do the same with wheel retention studs/bolts.)

20-25 lb-ft is typical for gasket seat plugs in iron heads. Taper seat plugs should be only 10-12 lb-ft in either iron or aluminum.

With gasket seat plugs you can feel the gasket compressing, and when you feel it's fully compressed, your done. I always use a torque wrench on taper seat plugs because it's easy to over-torque, which can make them difficult to remove the next time and potentially damage the head threads. especially aluminum.

Duke

[Glen S.]

Re: Spark Plug Installation

On my 63-L76, I found that pinching the passenger side one piece heat shield closed a little (narrowing the V angle) gave me slightly more clearance when removing and reinstalling it during plug changes. A little extra wiggle room is a huge improvement. Changing right side plugs is a pain!

[Stuart F.]

Re: Spark Plug Installation

Glen;

My first plug change was done down in the hobby shop at White Sands Missle Range shortly after bringing the car down there after delivery. I was used to changing plugs a lot having owned a number of SHP 283's. At the first sign of plug failure (unable to pull to redline), I would change the plugs. But, what I ran into with my 63 was more than I'd expected. As I recall, I did bend the RH shield but more like in the middle, front to back. It wasn't long after that that I started leaving it off. After all, there were not many FM stations to listen to from El Paso or Las Cruses. Long after that, when I came back to the states to stay and put the Vette back on the road, I continued to do frequent plug changes and it got old real fast. Then, I finally went to an electronic conversion ignition and did away with the points. It changed my life forever. I was then able to attack the static ignition problem with radio resistant plug wires and complete shielding so I could finally use my AM/FM radio. As I mentioned before, I have not changed plugs in over 10 years and about 12,000 miles. That period includes all the problems I went through with Ethanol laced gas with a number of plug fouling situations that would certainly kill my plugs in the old days with points. I can just go on down the road and run it up a few times until it cleared out (cleaned the plugs) and it again would make redline.

I'll look into trying your method this time if I have trouble trying to remove it from under the car.

Thanks for the tip.

Stu Fox

[Frank D.]

Re: Spark Plug Installation

Ooooo....electronic points conversion. Pure heresy to some on here and many on the Corvette Forum. Lots of blowback if you even mention it at the latter.

For the record, I have a Pertronix III billet distributor with vac advance in my 270hp dual quad '61 and Lectric Limited's Breakerless SE conversion in my '63.

[Stuart F.]

Re: Spark Plug Installation

Frank;

Those are the guys we always have to help get there rides started in the parking lots after the cruise in or car show.

Actually; To each his own. Whatever works for you and you trust and believe in. For me, I like my unscun fingers and burns, and an engine that will perform to it's best every time I put the pedal to the fiberglass. My experience spans back over 60 years and over 10 Chevy V8's I have owned.

Stu Fox