How to make a piston stop [Easy Instructional] - Vintage Mustang Forums
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post #1 of 13 (permalink) Old 04-13-2019, 12:34 AM Thread Starter
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How to make a piston stop [Easy Instructional]

Hello all,

I have recently had a series of adventures in cylinder #1 but, in the process, have learned how to make a really good piston stop at home with nothing but a few hardware store parts and a 3/8" drill bit! I thought that maybe others would want to know.

For the uninitiated: a piston stop can be screwed into the spark plug hole on cylinder #1 to help you find TDC. The general procedure is that you get the engine close to TDC, then screw this thing into the spark plug hole and screw the center part in until it is close to touching the piston (or touching the piston). Then you continue rotating the motor up (by hand!!) until it contacts the stop, and make a mark on the balancer where the timing pointer is pointing. Then you turn the motor in the reverse direction until you the piston bottoms out on the stop again, and make a mark on the balancer there. The average point between the two marks you made on the balancer is your true top dead center.

Ok, so here goes - how to make a homemade piston stop! This is a handy trick to know if you find yourself in need of a piston stop but don't want to shell out $20 for a good one, or wait for shipping, or wait for the parts store to open, or whatever.

Parts List:
(1) Dorman #42002 - 18 mm spark plug non-fouler, sold at any parts store
(1) 5/16" bolt, full thread, 4" long (can be fine or coarse thread)
(1) Washer that matches the diameter of the wide end of the non-fouler
(2) 5/16" nuts, threaded to match the bolt you got
(1) piece of duct tape
(1) 3/8" drill bit + drill

Total cost: $5-8, depending on what parts you already have laying around in your shop. The non-fouler is $5.



Now, I don't know what a "spark plug non-fouler" truly is or what it's supposed to do. What I do know is that it's basically a spark plug but without the porcelain parts on either end. So it is ideal for making into a piston stop.

So here we go: the instructions!

Step 1: Drill the end of the non-fouler out with a 3/8" bit. The hole in the end is just kind of small and you want a more robust bolt sticking out of it to avoid bending it with the piston. Drilling this out takes about 2 seconds.




Step 2: Thread one of the nuts onto the bolt almost to the end, then add the washer (washer fitment flush on large end of non-fouler is shown here)



Step 3: Stick the non-fouler onto the bolt with the wide end facing the bolt head. It should slide right through but not be really loose.



Step 4: Thread the second nut onto the end of the bolt and up the threads by about 0.5-1"



Step 5: Wrap the piece of duct tape around the end of the bolt to protect the piston against marring. Make sure it is really on there, not half-assed!



And you're done! To adjust it to the correct length, I thread it into the spark plug hole, push the bolt down until it contacts the piston, then thread the nut/washer down onto the non-fouler. Then I remove it and tighten the nut on the other end to sandwich the non-fouler and bolt into place.

Works awesome, it's easy peasy, it doesn't require you to weld or tap or cut or hammer anything. So, there you go.
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post #2 of 13 (permalink) Old 04-13-2019, 02:16 AM
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Where's the part that falls into cylinder? 😆
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post #3 of 13 (permalink) Old 04-13-2019, 02:22 AM
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I'm glad I didn't have to be the first to ask that.

Cool idea, Kelly.
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post #4 of 13 (permalink) Old 04-13-2019, 07:57 AM
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Quote:
Originally Posted by Kelly_H View Post
Now, I don't know what a "spark plug non-fouler" truly is or what it's supposed to do.
The non-foulers have been around since the Model T days. If you have an engine that is burning oil and constantly fouling the plugs you install the non-foulers to get the tip of the plug out of the combustion chamber and the oil. They're cheaper than replacing piston rings.
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post #5 of 13 (permalink) Old 04-13-2019, 08:20 AM
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Quote:
Originally Posted by LeeFred View Post
Where's the part that falls into cylinder? 😆
Not pictured as it is in #1 cylinder.


Sorry, Kelly.
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post #6 of 13 (permalink) Old 04-13-2019, 11:06 AM
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Nice work,,I like the use of a non-fouler!.. can be made with a regular old spark plug of course, by taking to the porcelain with a hammer (surprisingly difficult and messy - shards.. but it will come away eventually!).. rounding the bolt tip on the grinder is a good idea a also..

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post #7 of 13 (permalink) Old 04-13-2019, 12:35 PM Thread Starter
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Yep, I thought about the spark plug to make it even cheaper, but concluded that the 5 bucks is worth the time that I would spend inevitably picking porcelain shards out of my hands

Obviously this is version 2.0... all bugs related to random pieces falling into the cylinder have been repaired
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post #8 of 13 (permalink) Old 04-13-2019, 01:45 PM
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Quote:
Originally Posted by awhtx View Post
The non-foulers have been around since the Model T days. If you have an engine that is burning oil and constantly fouling the plugs you install the non-foulers to get the tip of the plug out of the combustion chamber and the oil. They're cheaper than replacing piston rings.
My first car had one on it when I bought it, to remedy bad valve seals. I haven't seen one since 1967.

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post #9 of 13 (permalink) Old 04-15-2019, 09:05 AM
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I was wondering but afraid to ask about the foreign body in cylinder one....so now we know. Cool trick-
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post #10 of 13 (permalink) Old 04-15-2019, 12:27 PM
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I thought this was something that you put into the piston to make it stop going up and down, but I couldn't understand why you wanted to make it stop.
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post #11 of 13 (permalink) Old 04-15-2019, 01:31 PM
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I thought you were a Paleontologist!!

Nice idea!

I just happen to have a couple spark plug non foulers sitting in a bin for decades.



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post #12 of 13 (permalink) Old 04-15-2019, 02:36 PM
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Yup made mine back in 1974.

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post #13 of 13 (permalink) Old 04-15-2019, 09:58 PM
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Very cool and innovative. I almost said this in the last post and I just cant help myself this time - how on earth do you keep up with us grease monkeys without even breaking a nail My hands are trashed after a good session Even with gloves. I remain in awe...
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