george.bryant Posted January 3, 2006 Share Posted January 3, 2006 How do I find TDC on my L6 on cyl #1? I'm in the process of removed the head to replace gasket, I've gottem as far as to getting manifolds off and the rocker cover. Now i need to get the cam gear off. On ZCAR.COM i asked and got the following reply for how the get the cam gear off etc, is it correct? I still dont understand all this stuff with dimples on the cam gear and such. Can someone please put it in noobie mechanic langauge? Procure the right tools for the job * Timing Chain wedge - You will need to properly address the issue of the chain before you do anything else. Unless you plan on doing the chain replacement at this time, which I don't think thats the plan, anyways ? *** Remember the wedge must fit snuggly, firmly even if you have'ta hammer it down in there, the tighter the better. * 27 mm socket, for the crankshaft dampener pulley bolt Which will allow you to manually turn over the crank, place crank @ TDC, oppose crankshaft & camshaft when you loosen the cam sprocket bolt. A necessity for the DIY Z mech. Prerequisites: * Engine / Cylinder head are bone cold ! * All eng. coolant, fuel, vacuum, electrical connections have been drained, plugged, disconnected or removed * Intake/ exhaust manifold removed , however, they can be left on but will add to the difficulty upon reassembly OK here Freakin Goes ! # Freaking one ! FIND TDC OF #1 CYL. ----- on compression stroke ------- Reference * #1 piston reaches the top of it's travel, as viewed by a dial indicator, by eye and or a mechanical device to transfer the linear motion. * Cam lobe positions away from rockers and on their heels * Crankshaft dampener pulley wheel notch alignment to the "O" indicator bolted or fixed to the front cover. ------------------------------------------------------------------------------------------------ # freaking two Visually inspect the timing chain for wear or stretch, check that the notch on the camshaft sprocket hub & ther groove on the camshaft thrust plate are in alignment. To determine if the cam timing has become retarded due to wear in the chain. The groove is above and to the left of the notch the chain has stretched and corrections can be made upon reassembly by advancing to the next higher dowel, if the cam timing can not be corrected in the #3 position the chain must be replaced as it will only continue to wear Do you know where these are? ** Take NOTE *** Of the # of the dowel pin @ the 12:00 position 1 - 2 - or - 3 Find the corresponding numbered dimple on outer circumference of the camshaft sprocket. Mark the adjacent chain link w/ paint white or yellow after thouroughly washing w/ mineral spirits or laq. thinner. ------------------------------------------------------------------------------------------------ # Freaking 3 Bust loose the 19 mm camshaft sprocket bolt, by opposing w/ 27mm socket & breaker bar on Crankshaft dampener pulley bolt. ** DO NOT REMOVE IT *** just break the torque on it. *** Realigning the timing marks on Crankshaft Dampener Pulley w/ noted crank angle indicator as before by rotating the crank slightly CW. This will or "should" theoretically set the #1 cylinder @ TDC on compression stroke. * Verify that your Crankshaft is reset @ #1 TDC & Camshaft timing is correctly marked. *Now "FIRMLY"wedge the tool in between the chain tensioner and the tension side of the chain. *Now fully remove the camshaft sprocket bolt w/ lockwasher and plain washer. ** Careful ** DO NOT DROP THESE INTO THE OPEN FRONT COVER ** * Carefully walk the sprocket off w/ chain in hand. Extract the sprocket, pile the chain carefully down inside the cavity bewteen the chain guides. *** Take special care protect the open front cover from foreign object debris *** ------------------------------------------------------------------------------------------------ # Freaking 4 * Loosen and remove the two 6 mm cylinder head bolts threading down and into the front cover. * Clean oil sludge and crud from internal wrenching bolt heads to provide adequate bearing. Slacken head bolts in reverse order of the specified tightening sequence ( * ) in half turn increments until fully loose. ( * ) Starting at extreme ends and working toward the center, alternating at each end. * Extract all 14 head bolts, 5 long and 9 short noting their positions. ------------------------------------------------------------------------------------------------ *** # Freaking 5 *** * Lift head off of engine block, making sure the heater core inlet hose has been disconnected......obviously huh? ** Remember not to set the head assy. down on the combustion surface, there are protruding valves on #2 an #3. Use wooden blocks or 2x4 pieces. from (http://www.zcar.com/forums/read.php?f=1&i=628330&t=628051) Quote Link to comment Share on other sites More sharing options...
george.bryant Posted January 3, 2006 Author Share Posted January 3, 2006 can i find TDC with a compression tester? Quote Link to comment Share on other sites More sharing options...
Guest 73Turbo240z Posted January 3, 2006 Share Posted January 3, 2006 Quote Link to comment Share on other sites More sharing options...
george.bryant Posted January 3, 2006 Author Share Posted January 3, 2006 OMG! I could of looked in my R30 FSM!! Thanks for that so much, so easy aye! I didnt understand that lining up of the bright link in the chain with that cam gear number but now i do! thankkks Quote Link to comment Share on other sites More sharing options...
Guest 73Turbo240z Posted January 3, 2006 Share Posted January 3, 2006 Quote Link to comment Share on other sites More sharing options...
george.bryant Posted January 3, 2006 Author Share Posted January 3, 2006 ACtually my service manual doesnt cover it which sucks and it doesnt have any turbo stuff. can you scan some more pages? Quote Link to comment Share on other sites More sharing options...
george.bryant Posted January 3, 2006 Author Share Posted January 3, 2006 ok, i turned the motor over so that that the bright link in the chain was facing a one of the three dimples on the cam sprocket, It ended up matching up with #3, the cam lobes are sitting in the position as showed in the manual. Is this correct? I was going to mark the chain and gear aswell. but i was thinking that when i put the gear back on i could just match the chain upto dimple #1?? Quote Link to comment Share on other sites More sharing options...
Guest 73Turbo240z Posted January 3, 2006 Share Posted January 3, 2006 this is where i was talking about the differences in our motors coming up... either way if your whole objective is to replace the headgasket, and nothing else, then the bright links are irrelivant, you can mark a link and cog tooth with white out, and as long as you put it back, exactly on the tooth it came off, w/ out allowing the chain to slack up in the bottom end, you'll be fine. Quote Link to comment Share on other sites More sharing options...
bjhines Posted January 4, 2006 Share Posted January 4, 2006 I might add.... Do not hammer the wedge in there too hard...You will bend the chain guide rails...they are just plastic and very soft sheet metal. The tensioner spring is WEAK...but if the chain slacks off...the tensioner will pop out of its bore and hang up the entire works. The wedge needs to clamp the chain enough to prevent the lower tensioner from pulling all the slack out...getting the right angle and shape to do the job is critical or you will bend something and still have it pop out... A rough cut piece of wood will leave bits in the chain and lower front cover... Buy the correct shaped chain tension tool from MSA or where ever... It will snug the chain up securely without bending the chain guide rails. Quote Link to comment Share on other sites More sharing options...
george.bryant Posted January 4, 2006 Author Share Posted January 4, 2006 You cant buy the chain wedge in New Zealand, well not that I can find. I got a wedge of wood that worked perfect Quote Link to comment Share on other sites More sharing options...
Here comes trouble Posted January 4, 2006 Share Posted January 4, 2006 George..................I have changed some Datsun aluminum heads and my first head change was an aborted "wedge affair". As a matter of practice from then on, I remove the radiator, timing chain cover, oil pump, distributor and the front bolts on the oil pan. That way... I am certain that the dowel in the crankshaft points up indicationg TDC. The bright links are in correct position to the timing chain notches, the oil pump and distribitor shaft is properly installed and the timing chain tensioner and spring did not get loose from it's mount. I am not saying the wedge method is wrong but in a lot of hands just about everything can go wrong requiring the entire front timing chain cover to be removed anyway.I have repaired and changed a lot of heads where the timing was off a tooth with the distribitor retarded or advanced to compensate with the carb idle screw out of adjustment to mask the timing problem.. With the timing chain cover removed , you have a complete visual and can detect any mistakes in timing and proper placement of all the parts. It ain't easy and a head gasket change is quite complicated for a novice and why shops charge over$400.00 for this job. Takes me about 2 days and I would rather take a good beating than change a head gasket.The 2 members posting can get you thru it with or without the wedge.. Learn to use a wrench in one hand and a manual in the other hand without getting the pages greasey Quote Link to comment Share on other sites More sharing options...
zeiss150 Posted January 4, 2006 Share Posted January 4, 2006 What I do to find TDC of the #1 cylinder on the compression stroke is ... 1. remove the spark plug on #1 cylinder 2. put your thumb (any finger really) over the hole and keep it there 3. hand turn the crank shaft don't use the starter motor (use the 27mm socket). Also if you want to make it a little easyer to turn the crank take out all of the spark plugs. 4. as you turn the crank shaft you should feel "air pressure" on your thumb. 5. If you don't feel pressure one of two things is happening 1. you're on the exaust stroke 2. you're turning the crank way to slow to build pressure. 6. once you feel pressure on your thumb look for 0 on your timing marks 7. DONE I hope this works for you ... it always works for me Rock on Z people Quote Link to comment Share on other sites More sharing options...
Cruez Posted January 4, 2006 Share Posted January 4, 2006 That will get you close... there is going to be some "dwell time" where its not moving for a few degrees. You can't always go by what the marks on from that degree plate, although it should be close. One way I found to get true TDC is to weld a rod on the end of a spark plug, put it in the cylinder. Do this on the compression stroke.... Turn the crank by hand clockwise until it just touches the end of the rod. Mark that position. Turn the crack again (by hand) in a clockwise direction until it stops again. Mark that position and divide the difference by 1/2. That would be true TDC. Quote Link to comment Share on other sites More sharing options...
zcarnut Posted January 4, 2006 Share Posted January 4, 2006 ...One way I found to get true TDC is to weld a rod on the end of a spark plug' date=' put it in the cylinder. Do this on the compression stroke.... Turn the crank by hand clockwise until it just touches the end of the rod. Mark that position. Turn the crack again (by hand) in a clockwise direction until it stops again. Mark that position and divide the difference by 1/2. That would be true TDC.[/quote'] This “tried and true†method only works for pistons that do not have an offset piston pin. Nissan uses a 1mm offset to reduce piston slap noise on its stock pistons. Hence, this method will introduce a slight error when attempting to correlate mechanical TDC with the crankshaft pointer. I do not know why none of the “How To†manuals fail to mention this! Quote Link to comment Share on other sites More sharing options...
Cruez Posted January 4, 2006 Share Posted January 4, 2006 This “tried and true†method only works for pistons that do not have an offset piston pin. Nissan uses a 1mm offset to reduce piston slap noise on its stock pistons. Hence' date=' this method will introduce a slight error when attempting to correlate mechanical TDC with the crankshaft pointer. I do not know why none of the “How To†manuals fail to mention this![/quote'] If this is true, that 1mm offset would incurr how many crankshaft degrees? and is that going to be fore or aft the "found" TDC ? Quote Link to comment Share on other sites More sharing options...
zcarnut Posted January 4, 2006 Share Posted January 4, 2006 If this is true, that 1mm offset would incurr how many crankshaft degrees? and is that going to be fore or aft the "found" TDC ? If this is true? You seem to be doubting basic mechanics! As my Statics and Dynamics instructor always told the class, “to begin the solution, draw the free body diagramâ€. A sketch of the crankshaft throw, the connecting rod and the piston will illustrate the problem. Kidding aside, the error is a function of “where†(relative to the crankshaft angle) the “stops†are. Because of this I created a spreadsheet program where you input the “stop†locations from the degree wheel and the program determined the location on the degree wheel where the mechanical TDC location is. The error is also a function of the rod length and the stroke of the particular Nissan engine. I’ll see if I can remember where I put the program (that was a few computers ago). Quote Link to comment Share on other sites More sharing options...
Cruez Posted January 4, 2006 Share Posted January 4, 2006 No, not doubting... actually I don't know why I worded it that way If you can dig it out that would be great... I'm not sure that it makes that big of a difference, but the Haltech setup states to find TDC before allowing the computer to take over the ignition timing. Quote Link to comment Share on other sites More sharing options...
george.bryant Posted January 5, 2006 Author Share Posted January 5, 2006 i got head off easy. wedge worked a treat and it seems secure. head is in the shop getting surfaced. Quote Link to comment Share on other sites More sharing options...
dapiper Posted January 6, 2006 Share Posted January 6, 2006 Positive stop must be right length (long) and very strong steel to avoid bending and/or breaking. Do not put too much force on crank; remove plugs and rotate slowly. Mechanical advantage is high and angle is shallow enough to cause pos stop to bend, fatigue and break. Bummer if it breaks off inside your cyl. Quote Link to comment Share on other sites More sharing options...
bjhines Posted January 6, 2006 Share Posted January 6, 2006 ok.... For all the NON-engineers.... I can't even get auto-cad to payoff in time spent for productive results. there is always some adjustment built into any system... I tend to find what the limits of adjustment are and shoot for initial settings that give me "room to play". I used the old paperclip in the spark plug hole... I was able to see it move up and down around the TDC point... It didn't take very much effort to find a DAMN NEAR PERFECT TDC.... then I just went to a club dyno day event and spent 75$ making 5 or 6 runs to get everything dialed in. I tend to plan my car projects around our club dyno days... Cheap runs... and you can space them out over an entire day to allow major changes in between.... It only takes an hour or so to change dowel positions on the cam sprocket although I have never gained anything by advancing or retarding from initial assembly... you can change ignition timing with the engine running.... Don't get all hung up on accuracy... just make sure you have room to adjust... Cam and ignition timing are pretty easy... there are not very many settings that will work properly at all... you can bet that once you find the right setting it will be right under all driving conditions..... Tuning a set of Triple Weber DCOEs is an entirely different kind of tuning... there is NO SCIENCE to tell you the perfect settings are for your car... There is so much variability in that kind of system that it is only possible to tune them on an open road or race track... even then.. what works at one venue does not work well at another.... even a dyno is worthless when it comes to fine tuning Webers. Quote Link to comment Share on other sites More sharing options...
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