finding TDC

[Wolfplace]

Why the precise accuracy of the timing mark when on the dyno we usually move the ign timing 2 degree's at a time. I have never seen anyone say that the engine had its sweet spot at 31.75 degree's sure its fine to use a piston stop to find TDC and mark the balancer but if you find the center of the TDC piston dewell within 1-2 degree's accuracy. Whats the point in the precise accuracy when after a few passes there is probably going to be 3-4 degree's in the timing chain slack. Choose your battles wisely I think the accuracy of an indexed crankshaft and degreeing the camshaft is much more important than precise external timing marks when this an abstract measurement dependent on the timing chain stretch, slack in the cam to distibutor gear, and the quality of spark control of the distributor used. If you feel the need for this accuracy you need to move to a crank trigger setup.

I guess I have a question for you,,,,,,
What is the point in being half assed about something like this when it is so simple to do it correctly?
Maybe its just me but I cannot understand someone on a performance site suggesting anything less

[kirkwoodken]

One more time: TDC is your basic reference point for cam timing and ignition, and is also important in steam and diesel engines. I find TDC on my engines with a large "T", part of which sits on the head surface, and the other which touches the throws of the crank. I do this before any assembly of rods or pistons. (Degree wheel is actually set at BDC when doing this.) When found, I scribe a small line on the flywheel even with the bottom of the block. This will be my reference for future checking of the balancer TDC mark staying in the right place, and setting the timing pointer after the engine is assembled.

Using the "T" and checking each throw after finding TDC will tell you if the throws are 90 degrees apart, assuming you have decked the block properly.

Why anyone would settle for a cam and ignition timing crap shoot is beyond me.

[user-612937456]

Why the precise accuracy of the timing mark when on the dyno we usually move the ign timing 2 degree's at a time. I have never seen anyone say that the engine had its sweet spot at 31.75 degree's sure its fine to use a piston stop to find TDC and mark the balancer but if you find the center of the TDC piston dewell within 1-2 degree's accuracy. Whats the point in the precise accuracy when after a few passes there is probably going to be 3-4 degree's in the timing chain slack. Choose your battles wisely I think the accuracy of an indexed crankshaft and degreeing the camshaft is much more important than precise external timing marks when this an abstract measurement dependent on the timing chain stretch, slack in the cam to distibutor gear, and the quality of spark control of the distributor used. If you feel the need for this accuracy you need to move to a crank trigger setup.

I guess I have a question for you,,,,,,
What is the point in being half assed about something like this when it is so simple to do it correctly?
Maybe its just me but I cannot understand someone on a performance site suggesting anything less

First some of us don't have have 20+- million in shop equipment like you at our disposal and we have learned to do the most with the least and rather efficiently too. What you people born with a silver spoon in there mouth call half assed. The less fortunate among us call it redneck ingenuity where you just call your quickway or whatever tool rep and order a new one. Where we buy your wore out equipment you are throwing away and do minor repairs and make some parts and get another 20 years out of it. In the case of the TDC stop If you have one handy there is nothing wrong with using it. I can reasonably say Most of us could rock the piston with a screw driver in the spark plug hole and determine the center of the over the top rotation and split the difference with in less than 2 degree's accuracy. For the average street engine what are the specific benefits of knowing the precise TDC you cant degree your cam with the engine already assembled and running in a car. All I here you say is "it must be done correctly". If in this persons case who doesn't know much about the internals of his engine I just made the the suggestion that the spark plug screw driver piston rock will get him PDC just to line up his pointer. He must have one hell of an engine if he finds it necessary to adjust his timing accurately to within 1 degree I feel it necessary to restate that when you tune an engine you set your base timing in the ball park. Then all you need is a reference of where you are to make incremental adjustments until you find what your combo likes. Who needs to know even cares if your final setting is 32 degree's or 31 as long as you have a reference where it runs best. I just wonder what the factory tolerance was for original timing indicator I would care to guess that tolerance was greater that 2 degree's at least for the big three even tho maybe not the Brits or Germans. Now if I am degreeing a cam or installing a crank trigger you are damn skippy I see the necessity for finding TDC accurately. But for installing a new balancer on an old engine the screwdriver test is ok and the piston stop is even better

Not knowing that TDC is properly established with some level of accuracy is similar to "building" the engine with a screw driver, Crescent wrench and hammer

If you have redneck injunity and you are stranded in the desert I could use what I have and know and drive home where you would be walking and dieing from heat stroke and dehydration

[kirkwoodken]

Here's a quote from Gordon Jennings "Two Stroke Tuners Guide":

"Yamaha's TD-series racing engines, for example, must be timed plus or minus only
0.0012-inch of piston travel from the specified distance of TDC."

This is an example of a highly tuned race engine. With a power loss 0.0012" on either side of recommended timing, how close must TDC be determined? I'll bet it's better than 1/16" of screwdriver movement. I'm not trying to be a jerk, just showing how important knowing TRUE TDC can be. This is not some compromisable dimension. It either is or it isn't.

[RevTheory]

GVX, a piston stop is about 8 bucks, no silver spoon required. If a guy can't even take the time to find an accurate TDC, what else does he half ass?

[beaker60]

thanks everyone for all the input. gearhead mile(and i think one other member) answered my main question about me just moving my present balancer line to line up with the pointer that didnt quite reach the original tdc that was set up on engine when i bought it. the rest of the guys that chimed in and mike advised me on how to get a true TDC. i like the idea of the pointer that moves like a tire guage. could someone tell me exactly which one that pointer is. also like the idea of the one that whistles. any info on that one. thanks again to all the great members on this forum. art

Hey Art,,go online to Snap-On,or any of the other tool sites,,Whoops,,sorry,,,"Reputable tool sites",,,and put in a search for a Top Dead Center Indicater,,,it should bring up the tool I mentioned,,I'm pretty sold on the unit,,,I've used it several times when trying to find TDC on Gen1 SBC's,,although,,obviously,,working on anything new it doesn't matter,,but the shop I worked in,,we did a lot of older stuff and it came in real handy,,not having to remove anything except the Number 1 plug,,and oddly enough it really helped at lining up the markers at 9 out of 10 times,,it was accurate,,I hope this helps.

Arthur

[Wolfplace]

Why the precise accuracy of the timing mark when on the dyno we usually move the ign timing 2 degree's at a time. I have never seen anyone say that the engine had its sweet spot at 31.75 degree's sure its fine to use a piston stop to find TDC and mark the balancer but if you find the center of the TDC piston dewell within 1-2 degree's accuracy. Whats the point in the precise accuracy when after a few passes there is probably going to be 3-4 degree's in the timing chain slack. Choose your battles wisely I think the accuracy of an indexed crankshaft and degreeing the camshaft is much more important than precise external timing marks when this an abstract measurement dependent on the timing chain stretch, slack in the cam to distibutor gear, and the quality of spark control of the distributor used. If you feel the need for this accuracy you need to move to a crank trigger setup.

I guess I have a question for you,,,,,,
What is the point in being half assed about something like this when it is so simple to do it correctly?
Maybe its just me but I cannot understand someone on a performance site suggesting anything less

First some of us don't have have 20+- million in shop equipment like you at our disposal and we have learned to do the most with the least and rather efficiently too. What you people born with a silver spoon in there mouth call half assed. The less fortunate among us call it redneck ingenuity where you just call your quickway or whatever tool rep and order a new one. Where we buy your wore out equipment you are throwing away and do minor repairs and make some parts and get another 20 years out of it. In the case of the TDC stop If you have one handy there is nothing wrong with using it. I can reasonably say Most of us could rock the piston with a screw driver in the spark plug hole and determine the center of the over the top rotation and split the difference with in less than 2 degree's accuracy. For the average street engine what are the specific benefits of knowing the precise TDC you cant degree your cam with the engine already assembled and running in a car. All I here you say is "it must be done correctly". If in this persons case who doesn't know much about the internals of his engine I just made the the suggestion that the spark plug screw driver piston rock will get him PDC just to line up his pointer. He must have one hell of an engine if he finds it necessary to adjust his timing accurately to within 1 degree I feel it necessary to restate that when you tune an engine you set your base timing in the ball park. Then all you need is a reference of where you are to make incremental adjustments until you find what your combo likes. Who needs to know even cares if your final setting is 32 degree's or 31 as long as you have a reference where it runs best. I just wonder what the factory tolerance was for original timing indicator I would care to guess that tolerance was greater that 2 degree's at least for the big three even tho maybe not the Brits or Germans. Now if I am degreeing a cam or installing a crank trigger you are damn skippy I see the necessity for finding TDC accurately. But for installing a new balancer on an old engine the screwdriver test is ok and the piston stop is even better

Not knowing that TDC is properly established with some level of accuracy is similar to "building" the engine with a screw driver, Crescent wrench and hammer

If you have redneck injunity and you are stranded in the desert I could use what I have and know and drive home where you would be walking and dieing from heat stroke and dehydration

Really,,,, What are you,, 10?
Silver spoon,,, 20+ million in equipment
WTF are you babbling about & what does anyones equipment have to do with anything here?
We are talking about a friggin tool that cost maybe $10, free if you have all that common sense you talk about & this is the best you can do???

Well I guess all I can say is what I stated above

I have a question for you,,,,,,
What is the point in being half assed about something like this when it is so simple to do it correctly?

I am done now this is just getting stupid & it is obvious all you want to do is argue an indefensible position

[user-612937456]

Here's a quote from Gordon Jennings "Two Stroke Tuners Guide":

"Yamaha's TD-series racing engines, for example, must be timed plus or minus only
0.0012-inch of piston travel from the specified distance of TDC."

This is an example of a highly tuned race engine. With a power loss 0.0012" on either side of recommended timing, how close must TDC be determined? I'll bet it's better than 1/16" of screwdriver movement. I'm not trying to be a jerk, just showing how important knowing TRUE TDC can be. This is not some compromisable dimension. It either is or it isn't.

But does Yamaha use a sloppy timing chain driving a 24" metal shaft which drives a 9 tooth distributor gear driving a spark distribution device which at a minimum differentiates 2-3 degree's when it is all brand new before any stretch and break in wear occurs. Also What is the dwell time in degree's inc the .0012 before and after TDC for instance with a 5.700 con rod with a 3.50 stroke crankshaft at .001 before and after TDC dwell is approaching 5 degree's that's 2 1/2 degree's before and after true TDC so shorter stroke with a shorter con rod has an even greater TDC dwell time so this means you will exhibit minimal or no power loss if you have the Yamaha timed in a 5 degree window? so how important is it to know your TDC on your average 4-500 HP street rod is precisely less than 1 degree off if your timing mark is 3 degree's off you will more than likely be within the Yamaha specification.

what you guys don't realize is I am a general mechanic I see from 3-to 20 different cars daily and it is common place for me to need to find TDC several times a week and there are many different applications that there just arnt a $8.00 piston stop available on the tool truck , the local Napa, or sears. I bet you cant buy a piston stop tool for a Hemi for $8.00. So how do you find TDC on a 5.4 ford or a toyota 5SFE it a late 2.3 Mazda MX3 there are other tools for these applications but you have to use the screwdriver method to get you close and I usually find that I am dead on or nearly at the correct crank angle when I install the crank stop or alignment pin.

I'll bet it's better than 1/16" of screwdriver movement

If I couldn't differentiate anything less than 1/16 of an inch I think it would be time to hang my monkey wrench up and retire. A sensitive hand can feel as little as .001-.002 of movement. Can you touch your wrist and feel your heart beat? Can you lay a .001 feeler guage on a flat table and feel the difference in the smoothness of the table with your finger tips? So yes If I had someone rocking the crankshaft and I notated about 6 degree's of crank movement between the drop off's feel. I could set the crank in the middle of the 6 degree window and be sure I was within 1 1/2 degree before or after true TDC (totaling 3 degree's tolerance)

There are times when it is appropriate to use the proper tools to find TDC precisely but don't trash talk someone for half assing cause they don't do it the way you do.

What if Columbus had taken the popular view that the only way to sail around the would was to sail in 4 straight lines and 4 precise 90 degree right hand turns at the end of each line?

Where would NASCAR be if Columbus had listened to the Europeans?

Be careful not to box yourself into what some consider be narrow minded view. Look at it like this there is more than 2 ways to kill a bird with 2 stones

Really,,,, What are you,, 10?
Silver spoon,,, 20+ million in equipment
WTF are you babbling about & what does anyones equipment have to do with anything here?

The point is you are privileged with every too you could every need and this could focus your view and narrow the options of how you approach a job or solve different problems
Sure you are through with this you are the one who started this robust discussion by trash talking me saying I half assed everything I do and had no place here because I have an alternative view of how to approach a problem that differs from yours. So piss off and let me have the last word if your EGO will truly let you be done with this

[kirkwoodken]

This discussion is sitting on TDC!!!!

[CNC BLOCKS]

i have a motor i bought in my car and would like to verify the trueness of my tdc mark on balancer(ATI) and the timing tab mounted on engine. is there any accurate way to check this now with engine in car.

If you read the original post - the question is the accuracy of the pointer on the balancer. He is attempting to get the pointer as
close as possible to TDC. Thus, the easiest, yet most accurate method - is the best answer. The slack in the timing change will
allow movement of the crank without movement of the cam and therefore can give timing readings (which is what the original
issue was!) that can be off as previously stated........ Sorry if this confuses you. The original post references possible inaccuracy
of the pointer to TDC. Not the same as DEGREEING the cam, the interest would appear to be verification of the ignition timing as
that is the only true purpose for the pointer......

I ain't confused, been doing this stuff for almost 60 years & have a reasonable grasp on it,,,,,, apparently reading comprehension is not your strong point

Again,,,,
what does the timing chain have to do with finding TDC?
Last time I checked the piston was not attached to the cam or driven by the chain

And again why do it half assed when it is so simple to do it correctly?

Mike sounds like your dealing with is a real KNOW-ALL-IJEST here. Is this guy for real?????????????

I thought Butch was bad but this guy has him covered by far!!!!

[user-612937456]

This discussion is sitting on TDC!!!!

WHAT HE SAID ^^^^ lol

[motorvation2go]

Experienced guys [just] kick their tires for pressure checks don't they?
A little bit of 'funnin's' ok me thinks.

[beaker60]

thanks everyone for all the input. gearhead mile(and i think one other member) answered my main question about me just moving my present balancer line to line up with the pointer that didnt quite reach the original tdc that was set up on engine when i bought it. the rest of the guys that chimed in and mike advised me on how to get a true TDC. i like the idea of the pointer that moves like a tire guage. could someone tell me exactly which one that pointer is. also like the idea of the one that whistles. any info on that one. thanks again to all the great members on this forum. art

Hey Art,,go online to Snap-On,or any of the other tool sites,,Whoops,,sorry,,,"Reputable tool sites",,,and put in a search for a Top Dead Center Indicater,,,it should bring up the tool I mentioned,,I'm pretty sold on the unit,,,I've used it several times when trying to find TDC on Gen1 SBC's,,although,,obviously,,working on anything new it doesn't matter,,but the shop I worked in,,we did a lot of older stuff and it came in real handy,,not having to remove anything except the Number 1 plug,,and oddly enough it really helped at lining up the markers at 9 out of 10 times,,it was accurate,,I hope this helps.

Arthur

Hey Art,,,Art here again,,give me a couple of days and I will get a part number and a price on that TDC indicater from Snap-On,,I will PM you with the info,,,sorry your post turned ugly,,actually,,I got real confused with all of the posts,,BUT,,that's not hard to do for me,,with as many scripts that I take,,my brain stays kinda fuzzy,,Talk to ya soon,,,,,,Arthur

[CNC BLOCKS]

Be careful as some TDC stops will not with Vortec type heads.

[MrBo]

You have a degreed ATI balancer?
Use compressed air (about 100psi) to find BDC. Do it from both directions if you wish and find the middle. You will have to loosen your valves.
Knowing where BDC is at works if you think a bit about it.