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How to find TDC? found a method that might work

Posted by GSTurbo1, Jul 22, 2012

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  1. GSTurbo1

    GSTurbo1 Proven Member

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    Pickens, SC, South Carolina
    I have an aftermarket crankshaft pulley that has no marks to help me find TDC. I ended up finding this article that explains a way to find TDC. Would this work?


    You often need to look at your pulley markings when fiddling with these engines, and most of the work revolves around doing something while the piston is at Top Dead Center.

    Usually the factory stock steel pulleys are marked accurately, but they lack the finesse of a degree pulley, which allows you to see crank angles printed (or etched) right on the pulley. Unfortunately, many aftermarket degree pulleys are marked incorrectly, the TDC mark and subsequently all other degree marks are off.

    What you need to do, is find the absolute TDC of the #1 piston, and mark that on your pulley.

    The best method in my opinion is teh "dead stop" method. No special tools or gauges are needed, and the result is accurate.

    You see, one problem is that the piston stays virtually motionless while the crank turns over the TDC position. The crank keeps turning, but the piston doesn't move until the crank starts pulling it back down. This brief moment of piston wait, or "dwell", or "death", can last for several degrees of crank rotation.


    The solution is to find the middle (in crank degrees) of the piston "dead" spot. Here's how:

    You need to fabricate a simple piston travel stopper. Take an old spark plug, and knock the porceline center out. (bench vise, hammer, steel punch or something similar). Cut out the side electrode too. Then drill and tap the remaining metal part of the plug for a suitable bolt size, I use a metric M10 size.

    Now find a long bolt that you can turn in and through the plug. You will need to have maybe an inch of bolt tip exposed on the other side, and enough threaded part of the bolt visible on the bolt head side for a jam nut.

    This may take some trial and error, but next you need to "guess" how much of the bolt tip you want to protrude into the combustion chamber. Adjust the bolt accordingly, and lock it in place with the jam nut. I would also file the bolt tip round, because it will come into contact with the piston in the next step.

    Now, screw your home made dead stop "sparkplug" in, while the piston is at or near BOTTOM dead center. Nice and snug, almost as tight as a regular sparkplug.
    Now SLOWLY start turning the engine clockwise, until you feel the piston hitting your dead stop.. if the engine can turn a full turn without stopping, screw in your bolt a little deeper and lock it in place again.
    Anyway. You have now managed to make the piston come to a complete stop against the bolt coming through the spark plug. Mark this position on the pulley. One sharp, thin mark right right on the outer edge.
    Do NOT move your dead stop "spark plug" at this point.
    Slowly turn the engine over the opposite direction, until the piston again meets the dead stop bolt. Mark this position on the pulley again.

    Your True TDC is precisely half way between these two markings. Measure with a flexible tape measure along the outer lip of the pulley, or count the degree marks if you have a degree pulley to find that half way spot, and file a notch or otherwise mark your True TDC on the pulley, and rely on that in all your future adjustment procedures.
     

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    1990 Eagle Talon TSi AWD
    · 1G DSM
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  2. 3kgt2nv

    3kgt2nv Proven Member

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    you can use the trigger plate notch on the crank timing sprocket.

    or you can also stick a long screwdriver or wooden dowel in spark plug hole for cylinder 1 and turn the crank over till cams line up. when the cams are properly lined up the screwdriver/dowel will descend if you turn the crank either direction as it should be tdc. this method is for a quick check not precision timing. without the notch on the pulley i would use the crank sprocket trigger plate. line that up properly and then make a corresponding correct mark on the after market pulley
     
  3. GSTurbo1

    GSTurbo1 Proven Member

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    Where would the crank sprocket trigger plate be?
     

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    1990 Eagle Talon TSi AWD
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  4. glowryder

    glowryder Proven Member

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    Prove it.. you are lookking at the wrong thing.. you'r not doing this right. There IS a mark on the sprocket. Not the pulley...

    I dont know where you got the above but there is a decent amout of mis-information and just out write confusion in that post.

    Show some pics of this "aftermarket crank pulley"....

    You really need to learn to do things the right way or the cars always going to be half assed. Look up "dcr timing method", thats what you article is trying to expain.. poorly, .. stop trying to recreate the wheel.. its all been done before and gone over.

    Research! Or keep doing things the hard and wrong way. Your choice. Good luck..
     
  5. GSTurbo1

    GSTurbo1 Proven Member

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    Pickens, SC, South Carolina
    I have been trying to research... it does feel like i'm recreating the entire automobile. I like to do things myself and learn in the process.

    Does the car have to be at top dead center for me to do the head gasket? Or can I just mark the belt, crankshaft pulley, and cam sprockets. Then replace the head gasket, valve seals, and camshafts. Put it all back together then line all of my markings back up. Do I absolutely have to find TDC before I do everything? I'm not trying to retime it, just put it back to the same timing it is at now.
     

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    1990 Eagle Talon TSi AWD
    · 1G DSM
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  6. glowryder

    glowryder Proven Member

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    *Facepalm*
    No. if you really want to learn, go get the dam book.

    No only TDC to time, if you do the HG @ TDC , you risk messing something up.

    Us telling you inst you learing. I understand you want to do it on your own, thats great..but go get the book. It will tell you Tq specs, and give decent step by step.. your asking us to regurgatate whats already out there if you again .. search.. im not sure what your using for key works, but things like "timing" reveal alot.. not to mention . this has NOTHING to do with engine management, so that may be another reason your getting poor search results.

    GO BUY THE DAM BOOK
    . were not going to spoon feed you, i think we have done that quite enuff. If thesrs a step in the process you dont understand etc, then we will be alot more friendly abot helping.. you standing there and thinking about what *you* think wil work is the wrong approach... your just going to break something..

    and let us see the "aftermarket" sprocket you keep claiming you have.. im guessing they put the sprocket on backwards, which would mean the marks are hidden. Which would also mean you need to re-do it. Or option 2, you stil dont know what your looking at. You need to first understand what your looking at befor surgery....Go get the book, hell its online even somehwere...
     
  7. ramsack

    ramsack Proven Member

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    How is it accurate to find TDC to stop the piston? It's not. The exact TDC point, in mathematics, and reality, will be the point where the piston does not travel up or down. It needs to be measured with a dial.
     
  8. glowryder

    glowryder Proven Member

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    Which they call out in the book and the DCR method. This becomes more important when you deck the head, or its been decked sevral times.
     
  9. GSTurbo1

    GSTurbo1 Proven Member

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    Pickens, SC, South Carolina

    Hahahah!!!!

    Don't get your panies in a bundle... :toobad:

    1. I have the Haynes manual
    2. followed everything it has told me to do up until finding TDC, which it clearly states for me to do before removing the head.
    3. I have no marks on the pulley to help me find TDC. I'll post a picture this evening to show you what I have.

    Read :ohdamn:


    read this bicycle man
     

    535  0

    1990 Eagle Talon TSi AWD
    · 1G DSM
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  10. glowryder

    glowryder Proven Member

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    Have you removed the pully that drives your PS and alt??????????

    TDC can be found at any time using a dial. Thats what you should be using. again. DCR method.

    Theres about 4 good vids on how to time a 420a on you tube..

    I wont get my panties in a bunch if you would stop posting mis information, posting 1757659 times about the same things in wrong forums..

    "SLOWLY start turning the engine clockwise, until you feel the piston hitting your dead stop.. if the engine can turn a full turn without stopping, screw in your bolt a little deeper and lock it in place again.
    Anyway. You have now managed to make the piston come to a complete stop against the bolt coming through the spark plug. Mark this position on the pulley. One sharp, thin mark right right on the outer edge.
    Do NOT move your dead stop "spark plug" at this point.
    Slowly turn the engine over the opposite direction, until the piston again meets the dead stop bolt. Mark this position on the pulley again.

    Your True TDC is precisely half way between these two markings.
    "
    Dont do this.. *shakes head* Think about it.. what is precise about "half way between these two points".. your still guessing the halfway point!!! If your this "gehtto" about working on a car, just stop and find a new Hobby. Go buy a dial indicator if you want true TDC, OR, use your crank sprocket...that you have yet to find.

    Timing needs to be dead nuts on for an interfearance motor.

    Google: "420a crank sprocket" thats what it looks like.
     
  11. glowryder

    glowryder Proven Member

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    If your going to do a re-ring.. why not pull it and have new bearings put in..?
     
  12. GSTurbo1

    GSTurbo1 Proven Member

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    Pickens, SC, South Carolina
    I wish I could pay someone to just do the timing belt so I could watch and learn. I'm almost ready to give up, can't find any help anywhere.

    The guy who originally built the engine said that I am most likely getting blowby and low compression from head gasket. He said If I am losing coolant that fast then in must be escaping into oil vents too. Which could cause crankcase pressurization.
     

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    1990 Eagle Talon TSi AWD
    · 1G DSM
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  13. glowryder

    glowryder Proven Member

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    It not hard man, just tiedous, i know how it is doing the HG and never doing one before.

    It is hard to tell if the Low compression was caused ONLY by the HG.. thats where the gamble is, you could do the HG 100% correct, and still have low compression b.c the rings are shot.. Thats why im more pushing you to atleast pull it, and have it looked at. that way any other issues can be addressed, if they exist. It sux doing something like an HG and only fixing 1/2 the problem.. and then realizing all that work will need to be done again.

    If you want to take the risk and just change the HG, then go for it, just know its a risk.

    Here ill spoon feed.
    *assuming car is already on jack stands, alt and ps belts are off*
    1. get a jack , with a wood block , jack up the pass side of the engine, just support it as were going to remove the pass side engine mount
    2. Un bolt the Pass side engine mount
    3. Un bolt the front and back engine mounts, this will leave only the trans mount bolted, this is your piviot point
    4. drop the pass side of the engine down enuff to remove the under drive pully.
    Remove the pulley ( go get the 2 1/2 3 jaw puller form auto zone)
    5. this will expsoe your crank sprocket!!
    6. Remove all plastic timing covers
    7. turn crank till the spocket tcd arrow points at 9 oclock
    8. remove bolts holding timing Tensioner.
    9. belt should be slack now, now you can remove the belt, Water pump ( if your changing), idler, and cams (refer to cam removal process)
    Now you can remove the head. (refer to hear removal sequence)
    10 No with the head off, bam there is you HG. Clean the block surface.
    11. get your head checked out and cleaned.


    Now thats the quick and dirty, some leave the IM mnifold on, some dont.
     
    Last edited by a moderator: Jul 10, 2014
  14. jmartinez1228

    jmartinez1228 Proven Member

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    GST after reading this thread it almost seems like you are over thinking this.

    Glowrider is trying to explain that the crank pulley you are looking at is not the part that will set the timing, hence why you don't see a notch or anything it just bolts on and it doesnt matter. THe sproket that the pulley bolts into is where you should be looking at for the notch. YOu have a pulley and a sprocket. Two totally different parts. The pulley and please correct me if I'm wrong is just to turn the accessory belts (alt, power steering, etc) IF you look at the crank sproket which is attached to the motor. It looks big enough for you to put a 1/2" wrench in there to turn it. That is where you what you should be looking at.

    I could be completely wrong so correct me but I'm just going by what I read in this whole thread.
     
  15. glowryder

    glowryder Proven Member

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    ^ Your right he isnt looking at the right thing.

    2 seconds of searching:
    http://www.dsmtuners.com/forums/420a-bolt-tech/251724-420a-headgasket-change.html

    just for starters.. There are tons of posts with detailed steps..waiting to be found..

    Also , youll need a good Tq wrench that can do 8f dt LB to 180 Ft lbs (for crank pulley) and one that can do 12-9 ft LBS..

    If he built it so well, it shouldnt be having this problem.. Not sure if i would ask his advice considering..
     
  16. GSTurbo1

    GSTurbo1 Proven Member

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    Definitely looking at it wrong. Have to get the jaw tooth puller to get to the timing chain. I guess the only thing you will have to truly set up once you get the #1 piston @ top dead center is to do the crankshaft.

    Thanks for the step by step buddy
     

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    1990 Eagle Talon TSi AWD
    · 1G DSM
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  17. glowryder

    glowryder Proven Member

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    side note, did you figure out WHY you were runnign hot? Im going to bet the HG was a result of runig it hot and hard like you have been.

    Do you have an Al Rad?
     
  18. glowryder

    glowryder Proven Member

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    "I guess the only thing you will have to truly set up once you get the #1 piston @ top dead center is to do the crankshaft."

    LOL no , Im concerned that your not understanding how the motor works... Once you get to the Spcocket, the arrow will point to another Arrow on the oil pump, when these align, your at TDC.. its not hard man.. when your ready to time, simply move the spocket till the arrows match. the crank and sprocket are essintailly "one" part. Thne bring your Cams to TDC via the dowel Pin holes.. See the DCR method. works slick if you have adjustable cam gears..

    This will also be a good chance for you to verify the motor has forged internals.
     
  19. glowryder

    glowryder Proven Member

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    Just get it to the point where the head is off. then go from there once u get the head back and valve seals replaced. Then get pics up of the pistons so we can see if they need work etc.
     
  20. GSTurbo1

    GSTurbo1 Proven Member

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    Pickens, SC, South Carolina
    Looks like a stock slim radiator... whatever it might be. Probably aluminum. I'll take pics for you.

    True that... I believe it has arp head studs, forged eagle rods, and JDM piston. Or says the guy that did the build. We will soon find out.

    Do you think I should pull the engine for piston rings? Or is it semi doable with the engine still in.
     

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    1990 Eagle Talon TSi AWD
    · 1G DSM
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  21. jmartinez1228

    jmartinez1228 Proven Member

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    You actually can but I wouldnt. I would just yank the whole thing out and have it checked over.

    PS. When I say you can I mean it will be an absolute pain in the ass to do. But it is possible, I just couldnt find a good enough reason to personally. People have done it.
     
  22. GSTurbo1

    GSTurbo1 Proven Member

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    I really really really don't want to have to get that far into it, in all reality I should... I feel like i'm going to get in over my head before I even know it.

    My idea is to either get this sucker just running good enough to sell, or to truly do an overhaul.

    I mean I love the car but really want to get a 1G Talon TSI AWD that is bone stock from a neighbor. He has the tank dropped about to put a new fuel pump, I just feel like i'm going to inherit more problems though.

    I'll post pics of a step-by-step just to make sure i'm doing this right.
     

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    1990 Eagle Talon TSi AWD
    · 1G DSM
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  23. jmartinez1228

    jmartinez1228 Proven Member

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    Edit: Disregard, keep forgetting you have a 420a. Read bryanwheat's response.
     
    Last edited: Jul 23, 2012
  24. GSTurbo1

    GSTurbo1 Proven Member

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    You're the first person that has told me not to do a cometic head gasket. Why not?
     

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    1990 Eagle Talon TSi AWD
    · 1G DSM
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  25. bryanwheat

    bryanwheat DSM Wiseman

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    The car has a 420a which has a mls gasket from the factory. The oem style gasket is perfectly fine for this application.
     

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