Buddy bent a valve, I have questions (how to time engine)

cuban11182

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So a buddy of mine ingested some carbon, and bent a valve. He took it to a machine shop and they verified the valve, and checked out the rest of the head, and it's all good.



So with the head off, we need to time the crank, injection pump, and cam. I know with the cam, we have to have number 1 valves pointed up and lock the cam. With the injection pump, all we have to do is lock it with the tool. His flywheel has no marks on it, so I'm not sure what to do with that. I have two questions:


1. With the injection pump, as long as I lock it into the right hole as when I'm doing the timing belt, I should be good? Can the pump be 180 degrees out, or does that alignment pin link up to where it needs to be, and should be good.


2. With the crank, and not having the mark on the flywheel, can it be 180 degrees out? How do I know if I'm on the intake or exhaust stroke when the piston is up on top, or does it not matter either way since I'll be timing the cam and injection pump when number 1 is up top (regardless of whether or not it was previously intake or exhaust).


Thanks in advance.
 

eddieleephd

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The crank cannot be 180 out if the #1 cylinder is at the top. Every 180 degrees the #1 cylinder is at the top.
If the pump is pinned correct and the#1 cylinder is at the top then the head should be installed so the#1 cam lobes are up in the shape of a V then you're pretty close to TDC.
Lock the cam and the crank and put the belt on. Without the timing mark on the crank it's difficult to be precise. Kinda have to figure it out a little.
Are you sure there's no mark on the flywheel?

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cuban11182

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The crank cannot be 180 out if the #1 cylinder is at the top. Every 180 degrees the #1 cylinder is at the top.

Thanks for the reply. If the cylinder is at the top, then it could be either during the compression or the exhaust stroke. If it's on the exhaust stroke, instead of the compression stroke, it would be 180 degrees out. My thoughts are that since there is nothing that is timed on the block that it shouldn't matter (which is basically what you told me).


I'm near Fayetteville, and my buddy is in Charleston. He's saying that he can't see anything, and when I did a quick google search saw that others had stated they were unable to find their marks as well. I'm going to verify before i throw it all back together for him.


Thank you for the advice though.
 

gforce1108

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With the belt disconnected - TDC is TDC. It's only when the cam is turning that it matters. An aftermarket flywheel may not have the timing mark. You can make one when you feel its really at TDC. (may need to spit the difference on any "slop")

Ideally - you should rotate the crank 90 degrees before top dead center (CCW), install the head and then rotate 90 CW. This keeps the pistons at half height since it's hard to keep the valves closed when installing the head/cam (depending on how assembled it is). The recommendation I was given was to install the head with the cam removed.
 

cuban11182

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Ideally - you should rotate the crank 90 degrees before top dead center (CCW), install the head and then rotate 90 CW. This keeps the pistons at half height since it's hard to keep the valves closed when installing the head/cam (depending on how assembled it is). The recommendation I was given was to install the head with the cam removed.

Thank you for the information. It'll be a bit before I can help him do it, but this is what I'm going to do. Thank you again.
 

KLXD

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You say you're going to do what you quoted. I hope you're going to make a mark like gforce recommended?

To do it accurately rotate the crank CW just until the #1 piston just stops. Make a fine sharpie mark on the flywheel at the arrow. Go past TDC a bit then rotate it CCW until it stops and make another. Note that they are not in exactly the same place due to dwell.

TDC is centered between the two marks.

Repeat a few times to make sure then make a good chisel mark and fill it with paint.
 

flee

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The crank cannot be 180 out if the #1 cylinder is at the top. Every 180 degrees the #1 cylinder is at the top.
If the pump is pinned correct and the#1 cylinder is at the top then the head should be installed so the#1 cam lobes are up in the shape of a V then you're pretty close to TDC.
Lock the cam and the crank and put the belt on. Without the timing mark on the crank it's difficult to be precise. Kinda have to figure it out a little.
Are you sure there's no mark on the flywheel?
Sent from my moto g(7) power using Tapatalk
Thanks for the reply. If the cylinder is at the top, then it could be either during the compression or the exhaust stroke. If it's on the exhaust stroke, instead of the compression stroke, it would be 180 degrees out. My thoughts are that since there is nothing that is timed on the block that it shouldn't matter (which is basically what you told me).
I'm near Fayetteville, and my buddy is in Charleston. He's saying that he can't see anything, and when I did a quick google search saw that others had stated they were unable to find their marks as well. I'm going to verify before i throw it all back together for him.
Thank you for the advice though.
You guys are kind of tripping with the 180 degrees issue.
It is a 4-stroke engine. Each stroke is 180 degrees. There are four strokes = 720 degrees.
#1 piston is at the top every 360 degrees. Once at compression, once at exhaust.
If there is really no TDC mark on the flywheel, which would only happen with an
aftermarket flywheel, you need to establish TDC.
This is not difficult with the head off.
Use a dial indicator to measure TDC on #1 and mark it on the flywheel.
 

cuban11182

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You guys are kind of tripping with the 180 degrees issue.
It is a 4-stroke engine. Each stroke is 180 degrees. There are four strokes = 720 degrees.
#1 piston is at the top every 360 degrees. Once at compression, once at exhaust.
If there is really no TDC mark on the flywheel, which would only happen with an
aftermarket flywheel, you need to establish TDC.
This is not difficult with the head off.
Use a dial indicator to measure TDC on #1 and mark it on the flywheel.

Not tripping, but wanting to make sure that I don't destroy my buddies car.


The reason I came here was to verify that there was nothing that I was missing in my thought process as to something else that was unknown to me that was driven off the stroke of the engine.



I've been a diesel mechanic for the Coast Guard for almost 20 years now (retiring in August) so I'm well aware of the Otto cycle, lol. I'm just verifying with those that are more knowledgeable than me on this engine.



I have a Mitutoyo magnetic base dial caliper for my micro-lathe, so I'll take that and mark TDC.



Thank you for your advice.
 

steve6

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On the crank pulley there is a dot.. the dot can be used as a reference(youll have to look up details). the flywheel probably has the mark, its very hard to see sometimes and goes by the hole very quickly.
 

KLXD

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But an Otto cycle is a gas engine. :D At least they used to be. They're getting fancier nowadays with valve timing.

Diesel engines are Diesel cycle.

Doesn't matter as far as finding TDC is concerned though.
 

Vince Waldon

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I have a Mitutoyo magnetic base dial caliper for my micro-lathe, so I'll take that and mark TDC.
That will be perfect.

One hint that may help: since there's some rotational dwell right around TDC the really accurate way to find it is to:

- approach it from one direction (say, CW) to within a set amount of piston deflection
- scribe a temporary mark
- approach it the opposite way to the same set amount of piston deflection
- scribe another temporary mark.

TDC is now exactly between the two temporary marks.
 

wonneber

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I have a Mitutoyo magnetic base dial caliper for my micro-lathe, so I'll take that and mark TDC.
I used a magnetic base dial caliper to verify the TDC on my old 1.5 / 1.6 engines when I had the cranks cut.

If the machinist did not have the crank indexed correctly it could have thrown the TDC off a bit.

Never had the issue but I still checked all 4.
 

cuban11182

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But an Otto cycle is a gas engine. Diesel engines are Diesel cycle.

You're right but they work on the same concept (4 stroke per cycle). The only difference is how they supply heat to work the ignition. Otto heat occurs at constant volume vs diesel where it occurs at a constant pressure.


One of the new cycles is the atkinson cycle which is used in Toyota.


On a side note, I see you like CJs. Here's mine. I just installed a Sniper EFI on it.


But yes, for the purpose of discussion of TDC, neither of the cycles matter (and I was wrong calling a diesel an otto).
 
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KLXD

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Don't forget the 2 stroke Diesels. :p

That CJ looks a lot better than mine.

We're about to retire the '02 Jetta. I don't think I can get much for it since the body's pretty banged up and I wouldn't feel right selling an auto with 180k on it even though it still works fine so guess where the motor's going.
 
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cuban11182

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1984 CJ w/ ALH GTD1756, 260 injectors, and Tekmektronics tune
Don't forget the 2 stroke Diesels. :p

That CJ looks a lot better than mine.

We're about to retire the '02 Jetta. I don't think I can get much for it since the body's pretty banged up and I wouldn't feel right selling an auto with 180k on it even though it still works fine so guess where the motor's going.

Those were the first that I worked on when I joined, the fairbanks morse opposed pistons in an ice breaker.


Mine is a Texas Jeep. It spent all it's life towed behind a driveable RV, staying in Texas. Original everything (including vacuum operated solenoid bank). It now has a Newcomer Racing 4.7 stroker in it.



I want to do the same thing, but already have a sweet engine in my CJ. I might just pull the motor and rebuild it getting it ready for a swap. Mine has 172K and was an auto that I converted to a manual. Best of luck in your swap.
 
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