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Theory on Timing
by
towns
on 15 Dec, 2005 21:37
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Theory; If one removes a cylinder head to rebuild it, and marks where the teeth were on the timing belt, and does not shift any teeth on the crank pulley, the cam sproket, or the injection pump pulley, and puts them back in the same position......... one would not have to re-time the engine after rebuild?
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#1
by
QuickTD
on 15 Dec, 2005 21:39
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Theory; wouldn't that be more difficult than just timing it in the normal fashion?...
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#2
by
935racer
on 15 Dec, 2005 22:28
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No it won't work, when you pull the belt off the pump gear will move unless locked in place with the pump lock pin. Also sometimes the cam moves a pinch when you pull the head off if you don't have the cam lock plate in. And last of all when you tension the belt the crank likes to move as well. So get the right tools, do it once do it right.
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#3
by
MacGyver
on 16 Dec, 2005 06:10
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This is called the 'Mark & Pray' method on the TDI Club, and yes it should work in theory. You're putting the belt back on in the same position, same teeth count, and not loosening anything where there is adjustment, right?
Well...kind of.
If you're doing the head, you're presumably replacing the belt (of course you are, cheap inscurance!!) which means it should be retimed due to manufacturing tolerances alone.
Regardless, I would do it the the normal way, thus eliminating any variables...and what makes you certain it's set perfectly now? Timing can & does move due to belts & other parts wearing & relaxing over time.
Why not start off by getting it set perfectly for your now renewed engine
*Edited due to atrocious spelling skilz :oops:
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#4
by
moosiah
on 16 Dec, 2005 10:11
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It's so easy to time these engines the right way ,,,,,,,, and the tools needed are so easy and cheap to make (at least the cam timing tools are!) why not just do it right from the get-go
then this will you
then you can avoid this :oops:
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#5
by
fspGTD
on 16 Dec, 2005 10:35
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I have done this before in a hurry and without thinking about it too much and indeed it worked, but the reason it's a good idea to try and avoid cutting corners here is that the head is sloppily positioned on the block by only the head bolts - IE: where it lands when it's tightened down can vary. There are no dowel pins making the position highly precise and repeatable. If the head were torqued down in a different position than it was before, it could change the belt lengths enough to perhaps significantly advance or retard the cam.
Another factor that likely would upset the timing in this case is any change in head gasket thickness.
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#6
by
Master ACiD
on 16 Dec, 2005 19:41
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my dad times engines the manual way. he lines up some obscure mark on the injection pump with some mark on the pump bracket and eyeballs it. he also has a crude piece of ill fitting aluminum which almost works ok for holding the cam straight. i say almost because you can still rotate the cam with his crude piece of aluminum put in place.
he actually didnt even know that you are suppose to time a pump with a dial indicator. he didnt know these tools existed! he just did it the crude way his whole life, and awalys wondered why his engines never ran good. that and he re used old heat shields.
on his rabbit truck, the timing was so basly retarded that his truck couldnt maintain 60mph in 5th gear on flat ground at sea level. his truck actually had a higher top speed in 4th than it did 5th if you can believe that.
i talked to him about buying a set of peoper tools to time the engine but his response was "blah i dont need those i been doin it my way for 25 years!"
so be being the paitent son and also kind of wanting to show him up, i personally bought him a set of diesel engine timing tools, and 4 new heat shields, we timed the engine the PROPER WAY and installed 4 new heat shields and re used his injectors, (which were rebuilt not too long ago mind you).
holy hell his truck literally doubled its acceleration. he was like "wow it accelerated like a gas engine!" which we of course know is not true but it just goes to show what a huge difference doing the job right can have. it literally transformed his truck from somthing which a bicyclist can beat to somthing that as far as normally aspirated diesels are concerned, is respectable.
please use the proper tools. there is no real way to skirt around this. its only a 1 time investment, you can re use the tools for the rest of youre life, or sell them on ebay. people will gladly buy used diesel timing tools on ebay. you cant just mark a timing mark and expect it to be right. for one thing, how do you know the pump and cam were properly timed to begin with? as they say, garbage in, garbage out! if you are doing to do something , you might as well do it right.
by the way, my dad has sence upgraded to a turbo diesel. and we times his td with those same tools i bought him. makes me feel good to know i can one up the old man atleast once in a while.
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#7
by
chrissev
on 19 Dec, 2005 08:00
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Theory; If one removes a cylinder head to rebuild it, and marks where the teeth were on the timing belt, and does not shift any teeth on the crank pulley, the cam sproket, or the injection pump pulley, and puts them back in the same position......... one would not have to re-time the engine after rebuild?
Why would you want to do this? If you have the head off, you would of course want to replace the timing belt just as a maintenance item as they are very cheap (also replace the tensioner). Then you would want to put the belt on the proper way. It's not hard to do. Once you pop off the cam pulley, you only have two things to line up, crank and injection pump. Soooo simple to do. Then you know the belt is new and the engine is timed right. I don't understand why you wouldn't want to do that, especially if you are rebuilding the cylinder head. Can you imagine how fun it would be if you put your rebuilt head on, then bent the valves because the timing was wrong?
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#8
by
towns
on 19 Dec, 2005 09:34
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Thanks everyone, im just trying to get some feedback, as i have never timed a diesel before and am a little aprehensive because of the drawbacks of incorrect timing. Also, the last time i had the timing belt replaced, my mechanic charged me about $400... and i'm hoping if i can do it myself i can save some $. I will be replacing the belt, and scrapping my 'timing theory' following with the famous quote "Do it once, do it right" or something like that. THanks again everyone
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#9
by
Northern RD
on 19 Dec, 2005 09:35
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Theory; If one removes a cylinder head to rebuild it, and marks where the teeth were on the timing belt, and does not shift any teeth on the crank pulley, the cam sproket, or the injection pump pulley, and puts them back in the same position......... one would not have to re-time the engine after rebuild?
A bud tried what you`ve outlined here and wound up with an $800 bill when 2 pistons collided with valves. Needless to say he times his `92 with a dialo gauge now,.... :? :? :?
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#10
by
BlackTieTD
on 19 Dec, 2005 09:59
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just make sure to turn the crank pulley over by hand a few revolutions to ensure that pistons and valves won't meet.
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#11
by
Northern RD
on 19 Dec, 2005 11:13
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Theory; If one removes a cylinder head to rebuild it, and marks where the teeth were on the timing belt, and does not shift any teeth on the crank pulley, the cam sproket, or the injection pump pulley, and puts them back in the same position......... one would not have to re-time the engine after rebuild?
A bud tried what you`ve outlined here and wound up with an $800 bill when 2 pistons collided with valves. Needless to say he times his `92 with a dialo gauge now,.... :? :? :?
Timing the injection pump with a dial indicator has absolutely nothing to do with pistons meeting valves. The injection pump can be completely out of time and no interference will happen. It won't run, but it won't hurt anything (other than wasting fuel).
The cam to crank timing would be the culprit if there was an interference and that is timed with the bar it the slot of the cam. Very good idea to doublecheck the cam timing.
If I had just changed the belt 10,000 miles ago or less and no oil or diesel had gotten on it then I would probably put it back on. Then again belts are cheap. Regardless, even if the belt is swapped to a new one, I would bet $10 that if the teeth of the three sprockets are aligned relative to one another in the same way as before the swap, then the injection pump (if it hasn't been messed with) will be within .01mm. Probably exactly the same. Still good to check.
Uh, nowhere above in my quote does it make mention of eyeballing in an IP: whatb I was clearly referring to was taking short-cuts like the mooted above.
Too much Christams Eggnog maybe?? :wink: :wink: :wink:
Andrew
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#12
by
Northern RD
on 19 Dec, 2005 12:19
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What was the comment about using the "dialo gauge from now on" referring to? Actually, what is a dialo gauge? I assumed that it was a slang term for a dial indicator. Again, a "dialo gauge" (if it is a dial indicator) will be useless to prevent piston to valve contact.
Is the eggnog comment a confession that you have overimbibed and are not thinking straight? :wink: :wink: :wink:
For that matter I never mentioned eyeballing in an injection pump, either. Regardless, the comments I made after the first two paragraphs were referring to comments that others made in previous posts not yours. Cheers.
Andrew
Sloppy short-cuts of that sort generally tend to be more trouble than they`re worth as they seem to fail with depressing regularity: you then have to go back and do it again, an exercise in futility that could have easily been avoided if you`d taken the trouble to do the job right the first time,....
Also I`m curious: if yor rerk refers to others, then why quote me and send the remark my way?? avery roundabout way of making a point,..
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#13
by
zyewdall
on 19 Dec, 2005 14:13
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Sloppy short-cuts of that sort generally tend to be more trouble than they`re worth as they seem to fail with depressing regularity: you then have to go back and do it again, an exercise in futility that could have easily been avoided if you`d taken the trouble to do the job right the first time,....
.
Exactly what I've learned. Plus, you should see everything as an opportunity to buy more tools. Sure, you could probably manage it without the dial indicator if you were clever enough. But wouldn't it be neat to own one?
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#14
by
Northern RD
on 19 Dec, 2005 15:56
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Sloppy short-cuts of that sort generally tend to be more trouble than they`re worth as they seem to fail with depressing regularity: you then have to go back and do it again, an exercise in futility that could have easily been avoided if you`d taken the trouble to do the job right the first time,....
.
Exactly what I've learned. Plus, you should see everything as an opportunity to buy more tools. Sure, you could probably manage it without the dial indicator if you were clever enough. But wouldn't it be neat to own one?
Hah! I tried the" you can never have enough tools" line on the wife once and woke up a little while later with a mild concussion,... :lol: :lol: :lol: