I have never changed spark plugs seated deeply in recessed holes. Please advise how to put new plugs in without crossing threads and should I buy a torque wrench to make sure they are not overtightened?
I have a spark plug socket taped to an extension. Installation involves simply putting the plug into the spark plug socket and gently turning until you feel the threads catch. As with all spark plug installations, the key part is to not force the plug threads to start. Let them start naturally.
We’ve had lenghty threads on this forum on the question of torque wrenches: needed or not. For many many years I never used one, but as I’ve grown older and heard more and more stories about stripped threads I’ve begun to believe in them and always use one for spark plugs. Others here feel they’re unnecessary. You can get a perfectly good beam-type torque wrench for about $25. Personally, I think it’s a wise investment.
I just use a long ratchet extension and a light touch, threading the plugs all the way snug with the same light touch. I’ve also seen people recommend a small length of appropriate diameter tubing/hose. Its weakness/flexibility won’t allow you to cross thread it.
As for the torque wrench, I use one b/c I use them for lots of things. If you’d only buy one for spark plugs it probably isn’t worth it. You can find general rules of thumb for your specific spark plug application that, e.g., would specify 1/4 past finger tight as the right torque. If I can dig up one of the links I’ve seen on this I’ll post it.
Here’s one: http://www.nology.com/torque.html
I use the same basic trick on my 98 that mountainbike uses:
I take the socket, and use duct tape to attach it to a long extension. The tape doesn’t take any torque, so all it has to do is keep the socket from coming off the extension. With a couple of inches of tape on both the socket and the extension, that isn’t very likely, as the only force really trying to remove the socket from the extension is when you pull the socket free of the plug, and that isn’t that much force - you could even grease the inside of the socket with a dielectric grease to lower the risk further. There’s plenty of room around the plug to have a decent few layers of tape on it…
And I always use a torque wrench. Harbor Freight has a pretty good deal for Pittsburgh ones right now - nice beefy 1/2" drives and a range of 20-150 ft-lbs for $9.99, I believe. I’ve got one of those, and while I’m certain it wouldn’t stand up to daily use, I’ve used it for years with no issue for heavier work and a smaller 3/8" drive that I picked up for $20 or so for lighter use, like spark plugs…
Just to be clear (I imagine this is what the others are also doing): use just the socket, the extension and your fingers to get the plug started, no wrench involved until after the plug is just about fully installed. And while I didn’t use a torque wrench with iron heads, I do with aluminum heads (like I think you have).
The best method for installing plugs is to take a length of 3/16" inside diameter, stiff wall vacuum hose and insert the end of the spark plug into the hose. The hose is then used to start the plug and this will guarantee no cross-threading, etc.
Most of the competent mechanics I know use this method and they also do not use a torque wrench. Torque specs are often a bit high (especially when it comes to aluminum heads) and working by feel is far superior to using a torque wrench.
Tapered seat plugs should just be snugged. Gasket seat plugs should be snugged and given a small bump. (1/16 of a turn, etc.)
The reason torque specs are not to be trusted is three-fold. One is the variation in specs because one plug maker may say one thing and another will state double that.
The other is that those higher end specs (such as 17 ft. lbs.) are just too high in my opinion for aluminum threads.
The third is that when you’re dealing with low torque specs a torque wrench may not be very accurate unless it’s a high dollar tool in 3/8 or 1/4 inch drive and measured in inch pounds.
I’ve got several pricy Snap-On torque wrenches and they’ve left me in a jam a few times when some threads were stripped with the wrenches actually adjusted somewhat under what was called for in the specs.
It is. I do the same for all nuts and bolts including drain plugs. I never attach a wrench until the threads are safely started. And I never use force to start them.
You may be right. It may have been the proliferation of aluminum heads that ultimately led to my torque wrench addiction. I’m unsure.
Yep, I found that method out on my old 59 Pontiac. Only way I could get one of the plugs in behind the generator, except I inserted a stiff wire in the tubing to be able to direct where the plug went.
If you get a spark plug socket, it will have a rubber insert in it to hold the plug. Then just use an extension on the socket and start it by hand. Then finish up with the ratchet. I’ve never used a torque wrench-just snug it up and a quick tug is all.
Make sure you use anti-seeze lube on the threads.
I use the rubber tubing mentioned above, but Craftsman has a spark plug starter that is pretty neat. I’m just too cheap to buy one, I’d rather get a torque wrench instead.
While it is possible to strip out the threads in aluminum heads, its not that easy. The old iron heads only had 4 or 6 threads in the spark plug hole where aluminum heads have about three times as many. The aluminum used in most engines today is a little harder than aluminum used 42 years ago. Most aluminum is the 319 alloy pioneered by the Vega. A few high performance heads use the 356 alloy. 13 to 17 ft lbs is about the right torque for most engines.
If you can get a beam type torque wrench, it will be more accurate and reliable. If you get a click type and you don’t feel the click when you think you should, stop. Sometimes these type fail where the click happens as soon as any torque is applied so you don’t feel it.
As for anti seize, it wasn’t too long ago that I would not even consider putting a plug into an aluminum head without it, but some of the new plugs out there have an anti seize plating on them. With some of these plated plugs, anti seize is optional, with some others, you cannot use anti seize at all. If you do use anti seize, use the type specifically for spark plugs in aluminum heads. Its a Zinc Oxide type. Do not use a copper anti seize or a moly based anti seize, they will gall the aluminum threads.
Have used the rubber tube method for 20 years or more. It gives a feel to the condition of the threads. If it will not thread in with the tube take it out and check!