mknight318 Posted April 9, 2011 Share Posted April 9, 2011 I have a 1997 SE 4x4 3.3, I just swapped the engine from a 99 to it using most of the parts from the 97 attached to it. How do you find TDC if the distributor was never installed on it and do not want to pull the valve covers to look at the valves? I used the service manual to change the timing and everything seemed to work out as detailed but now I have had a thought about something. Would the mark on the crank pulley for TDC always indicate TDC or are there several revolutions of this mark to get to actual TDC? Link to comment Share on other sites More sharing options...
sewebster Posted April 9, 2011 Share Posted April 9, 2011 Crank pulley rotates twice for every complete 4-stroke cycle, so that isn't quite enough. Link to comment Share on other sites More sharing options...
mknight318 Posted April 9, 2011 Author Share Posted April 9, 2011 Crank pulley rotates twice for every complete 4-stroke cycle, so that isn't quite enough. So TDC + 2 rotations = TDC? Link to comment Share on other sites More sharing options...
sewebster Posted April 10, 2011 Share Posted April 10, 2011 So TDC + 2 rotations = TDC? Umm, yeah. You are really looking for #1 TDC, the number one cylinder at top dead center, on the compression stroke. If you rotate the crank one rotation from there the number one cylinder will still be at the top, but this time on the exhaust stroke. I don't have an R50, so I don't want to give specific advice really, but if it was me on my wd21 I'd probably pull a rocker cover or the upper timing cover. I guess you could also just wing it, because if you put the distributor in wrong then you won't be able to start the truck. But this will send unburnt fuel down your tailpipe. I exploded my muffler once by doing this. Link to comment Share on other sites More sharing options...
mknight318 Posted April 10, 2011 Author Share Posted April 10, 2011 Umm, yeah. You are really looking for #1 TDC, the number one cylinder at top dead center, on the compression stroke. If you rotate the crank one rotation from there the number one cylinder will still be at the top, but this time on the exhaust stroke. I don't have an R50, so I don't want to give specific advice really, but if it was me on my wd21 I'd probably pull a rocker cover or the upper timing cover. I guess you could also just wing it, because if you put the distributor in wrong then you won't be able to start the truck. But this will send unburnt fuel down your tailpipe. I exploded my muffler once by doing this. That would be bad. I guess I need to pull a rocker cover and luckily the easiest one to do is the one with the No. 1. Might as well get it correct. Thanks a lot! Link to comment Share on other sites More sharing options...
BowTied Posted April 10, 2011 Share Posted April 10, 2011 pull plug #1 and put your thumb over the plug hole. As your buddy rotates the engine by hand the compression should want to blow your thumb off the head. Then you know you are on the compression stroke and the piston is approaching TDC. If you suspect the mark on the damper is not accurate, purchase a piston stop (a hollow brass tube with spark plug threads and wrench flats). Thread it into the #1 plug hole all the way (not stupid tight). Rotate the engine by hand till the piston hits the stop, gently. Mark the damer with a temporary mark at the timing tab. Do this again but rotate the engine the other way. TDC will be half way between your temporary marks. Link to comment Share on other sites More sharing options...
aranay Posted April 10, 2011 Share Posted April 10, 2011 If you suspect the mark on the damper is not accurate, purchase a piston stop (a hollow brass tube with spark plug threads and wrench flats). Thread it into the #1 plug hole all the way (not stupid tight). Rotate the engine by hand till the piston hits the stop, gently. Mark the damer with a temporary mark at the timing tab. Do this again but rotate the engine the other way. TDC will be half way between your temporary marks. ahhhh that's a fantastic idea! never heard of such an animal and I had wondered about how a guy would correctly time an engine if he got it partially put back together and had no way of trusting the timing that was done by the previous guy. sometimes perfect TDC is very hard to find without being able to go by timing marks with the head on. These things sold at auto parts stores or usually just off snap-on or mac trucks? Link to comment Share on other sites More sharing options...
mknight318 Posted April 10, 2011 Author Share Posted April 10, 2011 Wow you guys are great! Those are really good ideas as well. I might acyually get this thing running today and have my first Pathy experience. Link to comment Share on other sites More sharing options...
BowTied Posted April 10, 2011 Share Posted April 10, 2011 I bought mine at a discount store in Canada called princess auto a few years ago, but I would hope you could get it at any good auto parts store. If you find these stores do not have it, almost certainly a performance shop that serves muscle cars and tuner cars should have this. 99% of the time the factory TDC mark should be spot on as in general things are keyed to the crankshaft. I don't know nissan engines very well to be honest. In a chevy engine the damper is constructed of two steel rings with a rubber material between. With age of the ruber the outer ring (with the mark) can slip and then you'd use the above to verify the mark (and then know you should replace the damper). If you find your TDC mark is off, double check with a nissan engine knowledgeable person to be certain what I wrote applies, though it should apply to any piston engine of any make. I should also add to disconnect the battery if using a piston stop.... Link to comment Share on other sites More sharing options...
sewebster Posted April 10, 2011 Share Posted April 10, 2011 Why do we regard this as so critical anyway? You just need to make sure your timing belt is on right (count teeth between sprocket marks, since sprockets are keyed) and then get the ignition timing close, so you can fine tune it with a timing light. Right? Link to comment Share on other sites More sharing options...
BowTied Posted April 11, 2011 Share Posted April 11, 2011 ^ because he had the distributor out of the engine. Link to comment Share on other sites More sharing options...
sewebster Posted April 11, 2011 Share Posted April 11, 2011 ^ because he had the distributor out of the engine. Right. In his particular case though, he only needs to figure out which crankshaft rotation is the compression stroke. Once he knows that, he just lines up the crank pulley mark and puts the distributor in. In general, for installing the distributor, you are just trying to get it on the right tooth of the cam gear. Even if you get it wrong by a tooth, it's not big deal as you'll just find that you can't adjust the timing properly (with a light) and you need to bump it over a tooth. Not that there aren't some good reasons for properly finding TDC in an engine, it's just that I don't think people usually end up in those situations during even fairly significant maintenance? Link to comment Share on other sites More sharing options...
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