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Misfiring because of worn timing chain?


Go to solution Solved by Kai-by-Vecona,

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Posted

Sorry I don't understand why you moved the crankshaft or the camshaft.  It should have went straight on with maybe a little turning to make up for the slop in the old chain.

Posted

No... I didn't turn them. I checked the slop as discrobed and then I disassembled the timing chain. I didn't turn anything because I don't want to have any trouble installing the new one. But when I did yesterday, the only way to install the new camshaft sprocket was in opposite of the dot. Now I don't know if the dot is on the wrong position of the sproket or if theres something completey wrong.

When I turn the camshaft so the dots match like described in the manual, the rotor of my distributor point on cylinder 6. That's what makes no sense to me....

Posted

Remove the distributor. Line the marks up together and put the chain on. Then put the distributor back in. Remember it can only go in two ways........one way is 180 out of sequence and the other is correct. Hope this helps.

 

Jeff

Posted

The cam dot will always be 180 degrees off when the engine is at TDC firing #1 cyl.

Set the cam and crank gears up aligning the dots directly across from each other.

Then rotate the engine to TDC compression for #1 cylinder  (both Intake and exhaust valves closed).

Drop the distributor back in with the rotor firing #1 cylinder. Done.

 

Bob

  • Like 2
Posted

@ Jeff Yes, but when I installed it like ist was number 6 was fireing, so that's why I think the marking on the sprocket is on the opposite position

@ Dodgeb4ya  As I understand my manual, when both markings are next to each other cam, piston and distributor are in firing position. But my setup was in firing position when I disassembled it and when I installed the new one, the dot was on the opposite site so that's why I think the marking is 180° offset. I check if both valves are closed, then I set distributor on #1 if they are both open I set the distributor on #6.

 

Thanks for the help

Posted

It is highly unlikely that the sprocket is marked incorrectly. You need to put the marks together and trust that. In fact put together and don't give it another thought. If you have problems starting after this the worst it could be is the distributor could be out 180 and that is easy to fix.

 

Jeff

  • Like 1
Posted

Forget your old distributor rotor position and which cylinder was firing.... IE #1 or 6.

Assemble the chain and gears/ didtributor as if you are doing a new engine rebuild.

  • Like 1
Posted

So.... just to let you know. I checked the position of the valves and they are closed when the dot on the camshaft sprocket is on the opposit side. Seems, like the marks are wrong. Good to check twice :-)

Posted

It's been a while since I reassembled my rebuilt engine.  I did manage to get it together right.

 

But I forget what keeps the large sprocket from going onto the camshaft wrong, maybe 60 degrees off one way or the other.  Could it possibly be mounted wrong in this case? 

 

When the crankshaft rotates, are the valves opening and closing in the right phase, or are they off, one way or the other?  

Posted

The cam gear will only bolt on one way by positioning it over the three bolt holes on the cam that  line up.

Posted

So.... just to let you know. I checked the position of the valves and they are closed when the dot on the camshaft sprocket is on the opposit side. Seems, like the marks are wrong. Good to check twice :-)

So you are saying both the intake and exhaust valves are completely 100% closed with feeler guage clearance on #1 cyl.@ TDC with the cam dot180 degrees opposite  the crank gear dot?

Posted

It may be that the #1 is on tdc compresion with the cam dot opposite the crank dot,this is the case on SBC engines. As this is a common misconception. It really doesn't matter,once the engine is together you can turn it until compression comes out the #1 hole,line up the timing marks and point rotor to #1 on distributor cap. See post 79.

  • Like 1
Posted

They may be closed on 6 and 1, depending on how much overlap the cam has built into it. On the same rotaion up, compression on cyl 1 would have them both closed all the way up while on cyl 6 the exhaust valve would be closing until it reached the top and then the intake would begin to open At the very top they could look like all of them were closed.

Posted

^^^^ Thats why I mentioned checking Valves closed using a feeler guage just to be sure..

Overlap could confuse some into thinking the valve are completely closed.

A lot of talk about just setting up a couple gears and a chain :mellow: .

Posted

Yes.. crazy. I tought this is easy but it's the way it is. I turned the engine several times and had a look at the valves. By turning the engine you could see which valve is moving. They are closed when the marking is on the opposite site 0_o

And like Dodgeb4ya said, you can't bolt the sprocket in any other position because the holes are not on a symetrical triangel. Think it's like mhawkins said, that the timing chain setup is maybe for another kind of engine or something. Hope to get all the other stuff assembled this week and I let you know what happend. If I guess right the worst thing is, that I have to flip the rotor 180°.

Posted

Here's another way to tell if you have it right.   Install the gears and chain which ever way makes you happy..Then,  rotate the crankshaft clockwise and observe the valves.  The intake valve, second one back from the front, should be the next one you see moving.  It should be opening.  If not....then try again.

 

When I assembled my 218, the dots were lined up close together.  It turned over 3 times and ran great.  Good luck!

Posted

I would urge you to put the chain on with the marks together. Then turn it over by hand until you can tell #1 is on TDC. I would bet the mark on the new sprocket is where it should be. Line them up together. There is no alternative position for this arrangement and you will save yourself tearing it apart again.

 

Jeff

Posted

I did like ptwothree did with the difference that the dots line up but on opposite site like in the picture. If I would do it like Jeff told, I had to switch the distributor because both valves are open when the dots line up next to each other. We will see what happend when I start the engine :-)

New chain

Posted

That's not that I don't trust you or the manual, I just see what is. I also can't imagine, that the dot is on the wrong place, but the facts tell me something else...O_o

Posted

Oh I am certain you are convinced by what you believe you see. I have gone down paths like this before. They generally lead nowhere.

I predict you will be revisiting this shortly. As the one true fact is.....and again trust me..... it will only run one way.

 

Jeff.

Posted

All those dots do is is set the relative motion/timing between the crank and the valves. If you set it by the book with the two dots together and then rotate the crank one turn you should end up where you photo is. And it is probably easier to verify you are on the right tooth with the dots together, so why not do it like the book?

Posted (edited)

Well seeing that the gear looks like some cheap chinese cam gear with a bunch of excess cooling holes in it....maybe the 2 year old child that punched the dot possibly punched it on the back side of the gear! :D

 

 The back (wrong) side. 

Edited by Dodgeb4ya

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