Jump to content

Misfiring because of worn timing chain?


Go to solution Solved by Kai-by-Vecona,

Recommended Posts

Posted

Hi Tod,

 

I would really prefer doing it the easy way, but when I do it like everybody says including the book, my valves on #1 are open, so #6 is firing. In that 42 Dodge is a 1950 enginge and when I disassembled the timing chain, I found a plaque that said, there are oversized pistons in it so somebody has sometimes rebuild it. I don't know what kind of parts they used so maybe it has something to do with that and maybe it's not the original camshaft... I can only guess, fact is that the dot is on the opposit site.

Posted

Hi Dodgeb4ya,

 

that doesn't even calm me down....:-( But the dot on the opposite side is far more better as somewhere on the sprocket or two or three random dots .... :-)

Posted

Yes... and I'm very curios about the result.

 

by the way... because I was doing that... the slop with the old chain was 25-30° with the new one it's about 10-15°.

Posted

I had the engine for the blue truck rebuilt a few years back, and now we're well into the rebuild for the grey truck. My experienced Mechanic showed me early in the piece how the marks line up...

post-3915-0-24574100-1427145752_thumb.jpg

post-3915-0-25532300-1427145762_thumb.jpg

Posted

At the risk of muddying the waters even further, keep in mind that the camshaft rotates at half the RPM of the crankshaft, so you need to make TWO complete revolutions of the crank gear for one complete revolution of the cam gear.   Also, #1 spark plug wire usually plugs onto the distributor cap at around the 7 o'clock position.

Posted (edited)

So, maybe the engine will run either way?  

 

Set the timing chain one way or the other, and either No. 1 or No. 6 will be ready to fire.  Two crankshaft revolutions and the other will be ready.

 

Crank the engine until you feel the pressure on the thumb at the No. 1 spark plug hole and set the distributor accordingly, so that the rotor points to the No. 1 plug wire.

 

Probably good enough for the shade tree mechanic?     

Edited by DonaldSmith
Posted

"So, maybe the engine will run either way?" 

 

The engine can only run with the timing gears in proper alignment.   Even though the pistons don't care whether they're compressing or exhausting on the upstroke, the valves and distributor rotor need to be synchronized properly for a spark to occur at the top of the compression stroke.

Posted

I would like to draw your attention to the position of the key way in camshaft and it's relation to the mark on your sprocket (your photo)...... and now look at the same relationship in the photo sent by Desotodav. There is absolutely no question in my mind that the mark is placed correctly on your new sprocket. You need to line it up like it shows in the manual and all will be well with this aspect of things.

 

Jeff

  • Like 1
Posted

Hello Jeff,

 

that's one thing I don't understand. It's the same with the picture Don posted. If you have a look at the screws that fix the cmashaft sprocket and you turn the camshaft 180° you have the same result. That's what makes me believe the dots are correct and I'm wrong. That's why I checked again the valves and I could do what I want valves are open at #1 when the dots match. That makes me thinking, that there's something with the camshaft. Is there a possibilty that there exist camshafts which are 180° turned. I wouldn't find a reason for that but as far as I know the engine was build up to the early 70s, maybe there was a wired setup for a strange kind of use and as I told before, the engine was rebuild somehow. Who knows what kind of cam they put into that block.

On the other hand, I couldn't imagine that there are so many possibilities installing other camshafts like the regular.

 

Fact is, when the dots match, #1 valves are open and #6 is firing.

 

I just have to install the radiator to start the engine. Then we will see....

Posted

Well no real surprise there......these engines use #6 cylinder for static timing.

Trust me there is absolutely no chance the cam is 180 out. Line the marks up and all will be well.

Don't perpetuate the mystery.

 

Jeff

Posted

LINE THE DOTS UP AND PUT IT BACK TOGETHER!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! It will run this way.

  • Like 1
Posted

I think we have beat this subject half to death twice.

 

attachicon.gifmlss_mario-hammer.jpg

Well........." I'm not dead yet"  :lol: 

At some point he will come around.......not a lot of options. I for one would really like to know if the original problem was caused by excessive wear in the chain. I have a feeling it was a big contributor.

 

Jeff

Posted (edited)

I doubt the chain was the 100% cause.

Edited by Dodgeb4ya
Posted

I am in agreement with dodgeb4ya, I don't think the timing chain was at fault. I have seen these engines run with a vary worn timing chain. Sometimes folks just over analyze and I am guilty of that. 

Posted

You guys are probably correct. Certainly with points it would at leas run with a lot of slop. I am just not certain of what effect this might have on a pointless ignition system which he has indicated has been fit on his car? Let's just say I am very curious.

 

Jeff

Posted (edited)

as the engine ran before albeit with a 'misfire' there is little room here for error except for that instilled by the owner.  When you do not know what is wrong...prove what is right...suggestion....go back to square one...set the timing correctly with the timing chain...#1 TDC both valves closed..verify rotor is at #1 and you need to know if this has been changed by some PO...if you cannot verify that...orientate your oil pump to reflect proper postion with 1 at 7 o'clock position.....drop in the distributor with rotor facing proper tower and insure the cap is wired in proper firing order and proper rotation...this will remove all guess work..as you stated you have rotated the cam..and then stated rotor was at number 6 this is proper....your crank must turn 720 for one engine RPM..crank is two to one to the cam..cam is one to one for the distributor..remember this is a 4 stroke engine...

Edited by Plymouthy Adams
Posted

Hi again,

 

I also don't think it's just the chain but it was the last thing I didn't change. I also put new bushings into the distributor because there was too much play in the shaft. But I heard that the play has not very much effect using a electronic ignition but who knows. Everything else was fine. Wires, coil, rotor, cap, spark plugs everything is new and also in the right position and order :-). Last year I thought it could be something with fuel, so I installed a new pump and rebulild the carburator but this had no effect, so the chain was the only thing left... we will see.

I couldn't go on for the next week because im off for work but as soon I have some results, I let you know.

Posted

Can you post some photos of the components that make up your ignition system? After reading through all this again I am wondering if this is more than just a trigger replacing the points. If this system has a module that extends the spark .....that could be a problem. The basic Pertronix system does not....but who knows with the system you have? Just another thought......

 

Jeff

Posted

I know I'm in on this a little late. It is possible the cam & crank where not in right position when it was taken apart. I believe Kai said there were no marks on old gears. I would put it together the way it was when taken apart, then rotate til marks match & check #1 position & distributor/rotor position. If it ran when he took it apart, it should go back together same way. IMHO

  • 2 weeks later...
Posted

Hi there,

 

had some time yesterday and put everything together. I did it like janan5243 did and the engine is running. Have to tune up engine now because yesterday it was too late but the main thing is that it worked. Enclosed is a picture for Jeff showing the distributor with the electronic ignition element.

Will let you know when I did the tune up.

 

Kai

verteiler

Posted

Glad you got it running.

OK that looks similar to the trigger used in the Pertronix system. It just replaces the points and condenser. Sometimes these are combined with another ignition module in kits. MSD makes a lot of these modules and I was wondering if your system included one. Many of these modules extend the duration of the spark which works fine on modern engines but doesn't always work well on older engines.

 

Can't tell from your photos but it looks like there is no rubber grommet for the trigger wires as they pass into the distributor? If there is not you probably should look at adding one. Also I don't understand the 2 jumper wires .......don't think they are necessary but I could be wrong?

 

Jeff

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.

Terms of Use