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MF engine. Finding crank top dead center TDC WITHOUT timing belt or flywheel
by
Scrambles118
on 31 Aug, 2017 08:19
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Like the title says
Yes I have a bently and it doesn't show a method for finding TDC without a timing belt previously installed
Yes I did a search and couldn't find the perfect answer, the sticky on how to time is pretty useful but also doesn't say how to find TDC on the crank without a flywheel when no timing belt is installed
So the story so far...
Bought a caddy, in the process of going from NA to turbo
I removed the timing belt without setting TDC when installing a new head gasket, turns out that was a mistake.
Injection pump is set and sprocket locked
Cam lobes for #1 are up per Bently
But as the engine sets on an engine stand I can't find TDC on the crank
Thought about throwing on the trans and flywheel and hanging it from the gantry crane to set the timing but I would have to tear it all apart to set it on the stand again. Looking like my best option so far though. But I've seen quite a few threads where people need TDC without a belt or flywheel and there really was no accurate answer. The crank gear is keywayed and has an alignment mark for the pulley, is there a way to set it off of that? Or leaving the belt off until after engine install and time then? What other options are there for engine stand crank TDC? Setting it with the head off would have been smart also lol.
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#1
by
ORCoaster
on 31 Aug, 2017 08:33
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Search this site for inserting a wire or a probe into the injector hole and turn the engine by hand until the wire comes to the end of the upward travel.
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#2
by
Scrambles118
on 31 Aug, 2017 11:48
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The wire method is helpful but not accurate enough when it comes to the timing belt
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#3
by
RabbitJockey
on 31 Aug, 2017 12:45
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the only way to do it would be the head off and with a feeler gauge, mark tdc on the flywheel when you find it spinning clock wise, then mark tdc when you find it spinning ccw, then mark in between and that is the true tdc mark.
why do you need to time it on the stand? just wait until the engine is in the car or on the ground with the transmission bolted on before u install it in the car. whats the purpose of installing it on the stand? you can't start it
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#4
by
RustyCaddy
on 31 Aug, 2017 12:49
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ORCoasters an RabbitJockey's suggestion is the best idea. It should be accurate enough; many of us have done so without issue. The bolt pattern at the gear end of the crank shaft is eccentric; i believe that when the "out-of-line" bolt is straight down relative to the block the crank shaft is at TDC (there is a reference mark IIRC); or may be it is straight up, something like that.
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#5
by
libbydiesel
on 31 Aug, 2017 14:22
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A couple times I have found TDC VERY accurately using the following method. Remove the #1 injector or glow plug. Get a piece of clear flexible hose that fits tightly into the opening. You need an airtight seal but you can add grease around the tube if necessary. Run the other end of that tube into a jar of water. Crank the engine slowly. If water gets sucked UP the tube, then rotate the opposite direction. The exact moment when air stops being pushed out of the tube and instead water starts being pulled in is TDC. I have found that method to be extremely accurate, even more accurate than a dial indicator reading on the piston crown.
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#6
by
ORCoaster
on 31 Aug, 2017 20:45
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Simply Brilliant Libby, and cheap too
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#7
by
fatmobile
on 01 Sep, 2017 12:53
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I pull the #1 injector and use clear tube to do the same thing.
With colored water,.. I use yellow food coloring because all the other colors get used to color/paint snow in the winter.
I don't use food coloring for yellow snow, ha.
Easier to get to the #1 injector than the #1 glowplug,.. I suppose you could use #4, that glowplug is easier to get to.
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#8
by
libbydiesel
on 01 Sep, 2017 14:12
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Indeed, #4 will work the same and is easier for either glow plug (or injector if the aneroid is in the way of the socket).
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#9
by
air-cooled or diesel
on 01 Sep, 2017 15:20
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note: theres a certain amount of dwell where the piston is at "TDC" you will then need the flywheel timing mark. its best to clean it, i use a qtip- spray brakecleen on it, clean flywheel mark, use whiteout, after it drys you can also use a marker if you want.
ive found another way to find TDC, 1 of course is standard and is somewhat cumbersome, remove camshaft (use shop manual, and do correctly). another-2, with a good eye looking for flywheel mark easily rotate crank, if you now touch a valve, easily that is, rotate crank a little back, go up top, now rotate cam 1 cylinder forward, now go back to crank, again easily rotate forward, do this till your helper sees TDC flywheel mark, again clean, mark TDC notch on flywheel. i now mark pulley side of crank (a simple whiteout mark will do) you can now tell by rotating crank back 1/2 a piston stroke where crank is, so now all pistons are (aprox) even, and at a 1/2 stroke, you can now turn cam back to its TDC and lock it out. continue timing procedure.
like i said turn crank easily so when you bump a valve and back crank off you wont have problems.
^have helper use a shop light.
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#10
by
libbydiesel
on 01 Sep, 2017 17:53
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The liquid method I mentioned will pinpoint TDC more accurately than the stock TDC mark due to the amount of slop in the stock crank to flywheel/pressure plate holes.