downsr
Well-Known Member
What is the procedure for finding tdc using piston stop. Need to make sure my balancer is correct on small block
How to find tdc
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67Dart273
Well-Known Member
Disconnect battery for safety. Insert the device in no1 making sure the piston is down. The length of the plunger is unimportant, but you want the piston to stop "down a ways." If you buy one rather than building one, make sure you get a lock nut on there to stop the stem from wobbling around
CAREFULLY wrench the engine around until the piston stops on the device. make a temp mark under TDC on your pointer tab, onto the balancer
Rotate the engine opposite direction do same thing. This will result in two temporary marks, and halfway between is TDC
If the original mark is correct, that is where it will be. This is one I built for SB Mopars in the '70s. Had it all these years
I've only seen 4 or 5 of these type here, commercially made, and in fact have one came in a Summit degree wheel kit. The plunger "wobbles" unless you screw it all the way in and tighten it down. So if you want it shorter you need to come up with a lock/ jam nut to make it rigid
CAREFULLY wrench the engine around until the piston stops on the device. make a temp mark under TDC on your pointer tab, onto the balancer
Rotate the engine opposite direction do same thing. This will result in two temporary marks, and halfway between is TDC
If the original mark is correct, that is where it will be. This is one I built for SB Mopars in the '70s. Had it all these years
I've only seen 4 or 5 of these type here, commercially made, and in fact have one came in a Summit degree wheel kit. The plunger "wobbles" unless you screw it all the way in and tighten it down. So if you want it shorter you need to come up with a lock/ jam nut to make it rigid
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67Dart273
Well-Known Member
I "learned" these when I was in the Navy at Miramar, part time job at the auto hobby shop. The "purpose" of my job was to operate the (Allen) tune up scope and assist guys with tune ups. That job turned out to be a lot more. A friend of mine came up with this, obviously LONG before the internet. Some Fords we got in obviously had either a cam timing issue or slipped balancer. It turned out to be a little of both. he came in one day and described this thing called a "piston stop" and it wasn't long before we were cutting spark plugs open and tapping the small end for a bolt. We made several while I was there
Rapid Robert
Well-Known Member
bring dampener to 15 BTDC. screw in piston stop till it contact the piston. turn crank back CCW till it stops again. you want it to stop on 15 ATDC. go back/forth 1 time to double check. if it stops on 13 then make a new white paint mark (1) degree on the side of the OE slit (I forget which side). repeat the test. You want the same degrees on each side. EDIT (1) degree is 0.0632683" or use the dampener as a ruler.
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Rapid Robert
Well-Known Member
In what way bro?
In every way known to mankind. That was the most jumbled up bunch of hooha I ever read.
Rapid Robert
Well-Known Member
I've done it before that way & it checked out fine. tell me how it would be erroneous
I didnt say it was wrong. But, it;s a pretty confusing way for someone who is not familiar with finding TDC.
Bolting a degree wheel and pointer on, screwing a piston stop into #1, turning the engine until it hits the stop, then the other direction until it hits the stop and finding the mid point on the degree wheel is so simple a chimp could do it And it works every time.
Rapid Robert
Well-Known Member
"A jumbled up bunch of hooha" and "AFU" ain't saying it is wrong? you sure coulda fooled me! yes you would need a degree wheel to degree the cam & be careful that it dont move as you are turning the crank & other caveats but just to find true TDC to confirm the dampener ain't slipped I don't see a problem with the simplicity of this & it don't see more difficult than using the wheel. I'm still trying to figure out which one of you is the one who gave me the uncalled for scathing rebuke way back for no reason when I first got on here (I gotta get my printer going). a fellow member saw it & emailed & said that you were a former naval chief or something similar & that "they are like that". I thought yeah right but I thanked him for the backup/support. Robert
Have no idea about that. That's the second time you've said that and this is the second time I have told you I have never served.
Sorry you can't take a little criticism, but that was a very confusing post. It was nothing personal.
Sorry you can't take a little criticism, but that was a very confusing post. It was nothing personal.
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harrisonm
Well-Known Member
I agree with 67Dart273. I would just add that taking out all the other spark plugs will make the engine easier to turn over.
pishta
I know I'm right....
Make a random pointer with a coat hanger under a bolt
screw stop in #1 and turn crank until it hits. Mark balancer at pointer
Turn crank backwards until it hits again. Mark again at pointer
measure distance between marks in mm's (easier than dividing fractions) and bisect it (divide by 2) make a bigger mark there...turn big mark to pointer.
now look at your stock timing tab and see if the TDC is actually on TDC, if its close, it shifted. If it is no where close, you have the wrong year damper.
you could also put damper at 10 BTDC and run the stop in, and then see if the return trip ends up on 10ATDC (you would have to adjust stop to actually be 10 BTDC before trying this)
"Got a beef? See the Chief!" They were some caustic old ****'s....
screw stop in #1 and turn crank until it hits. Mark balancer at pointer
Turn crank backwards until it hits again. Mark again at pointer
measure distance between marks in mm's (easier than dividing fractions) and bisect it (divide by 2) make a bigger mark there...turn big mark to pointer.
now look at your stock timing tab and see if the TDC is actually on TDC, if its close, it shifted. If it is no where close, you have the wrong year damper.
you could also put damper at 10 BTDC and run the stop in, and then see if the return trip ends up on 10ATDC (you would have to adjust stop to actually be 10 BTDC before trying this)
"Got a beef? See the Chief!" They were some caustic old ****'s....
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Rapid Robert
Well-Known Member
It sounded personal. Alright, My apologies brother. I thought it was a simple procedure but that could just be me. Yes you're right on the "2nd time" statement, wont happen again & it was the other guy, this guy "67dart273". I wished I woulda saved it, it was something else! & on the procedure I'm trying to remember which way (side) you remark the slit if it comes up more or less than 15 when you come back CCW to try & hit 15 ATDC.
67Dart273
Well-Known Member
No need to make this so complicated. No extra pointers, no worrying about "how far" it moves, or degree wheels. All you are needing to do is relate the original wheel mark to TDC on the original pointer if it's still there. The plunger of the stop does not need to be a specific height. All you need to do is stop the piston equi distance down in the bore, from TDC and move it far enough that the "over the top" area on the crank does not degrade accuracy. That is set by the plunger depth.
If the balancer is too dark to contrast with what you have, pencil, etc, put some masking etc tape on there
So far as pulling the plugs I never bother. I just starter / bump the engine until the mark is 'somewhere' near. If it ends up too close for the stop, just wrench it backwards 1/8--1/4 turn. You should not have to wrench the engine more than 1 turn in this whole deal.
If the balancer is too dark to contrast with what you have, pencil, etc, put some masking etc tape on there
So far as pulling the plugs I never bother. I just starter / bump the engine until the mark is 'somewhere' near. If it ends up too close for the stop, just wrench it backwards 1/8--1/4 turn. You should not have to wrench the engine more than 1 turn in this whole deal.
pishta
I know I'm right....
Early A's had a bolt on pointer that tends to disappear after the first water pump housing removal. without it or with a different year/aftermarket balancer, you got no idea where TDC is hence the temporary pointer.
Del, you are 100% correct. No degree wheel is needed at all. I merely mention it because anytime I am looking for TDC, I am also "usually" going to degree the cam.
67Dart273
Well-Known Member
That's true, as I mentioned "if it's still there." I don't remember, I THINK the 273 came out of my 67 was a bolt on deal. I'll look if I can find it
downsr
Well-Known Member
So I all I have to do is turn # 1 up on compression stroke to 10 degrees before tdc on my balancer turn in the stop till it hits the piston .Rotate the engine in opposite direction till it hits the stop. Make a mark. Then find the center between the 2 marks
downsr
Well-Known Member
Thanks for all your help I think I got it. It seems to be correct.If I line it up with 10 degrees btdc and rotate it the opposite direction it comes up to 8 degrees atdc so that is 2 degrees off so if I take half of that I should be 1 degree off .
67Dart273
Well-Known Member
Here's the caveat in this method, and I did mention this. These commercial stops WOBBLE AROUND. And if they don't use a lock nut, or if you don't screw the plunger "clear down" they will move around. I can EASILY see a 1--2 degree or more error in this wobble. This is why I insist you should "do it the other way." Set the stop and leave it be. MAKE SURE the plunger is RIGID. Make temporary marks and then measure from them to the TDC, see if they are equal. You can use dividers for this makes it very easy. If you don't have, it used to be easier for me to actually crawl underneath where I could get a "clear shot" of the marks on the wheel with a good tape or flexible scale.
Also, it does not matter whether no1 is on compression or not. All you need for this is for the mark to be "there"
Rapid Robert
Well-Known Member
I agree. with you getting 8 & 10 degrees then yes the dampener is 1 deg off (fairly common) but do confirm everything is rock solid. I've been racking my brain to figure out which side of the OE slit that (1) deg next to it is true TDC but I ain't grasping it (yet). & I will concede that if you are going further & degreeing the cam (always a good plan) then the wheel is a good plan.
so I bet..... pulling #1 plug, me putting my tongue over that hole, having the wife rotate the engine over till I scream, is just a redneck method!!?? ha ( she is supposed to stop when I scream right!! ??)
sorry for being a smart ***
an enterprising young soul could make these stops otta these old plugs, and sell them on here and help with their resto $$ ! ??? I bet
sorry for being a smart ***
an enterprising young soul could make these stops otta these old plugs, and sell them on here and help with their resto $$ ! ??? I bet
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