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Discussion Starter #1
I have a 65 with a 289 but when I bought it, the owner told me it had a different cam. I'm pretty sure it was running on the 15426378. It ran pretty well for months then all of a sudden started running rough. The timing chain was a little loose so it was changed but now I can only get it to run on the 13726548 after trying with the old firing order but I can tell its not right. My question is if the timing is set correctly and I switch the wires to the other firing order, shouldn't the car keep that timing but just change the firing order?
 

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- The cam determines the firing order.

- You must connect the spark plugs to match the cam's firing order.

- Changing the timing chain will not change the firing order.

- If the new timing chain was not installed correctly, the valve timing will not be correct

- If the engine was running well with 15426378 firing order, it would not run at all if you connected the plug wires for a 13726548 firing order.

- At this point, the cam's firing order and the timing chain installation are both suspect. To proceed, you must resolve both potential anomalies.

- I'm not sure how best to resolve said potential anomalies. If, for example, you installed the timing chain with the gears about 12 degrees off, it won't be obvious. And pulling the timing cover on a small block Ford is non-trivial.

- I'm hoping some other people have some suggestions which does not involve pulling the timing cover. I suppose you could compare the position of the number piston at TDC to the position of the number one cylinder rockers arms, but I don't know how to measure subtle differences there.
 

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Discussion Starter #4
The original sprockets on the timing chain were not lined up correctly, and were installed correctly with the new chain. Would this have an change in it not running now?
 

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Then maybe it already has a newer cam with revised firing order?

Makes no sense why it would have run fine before.... probably impossible that you could do both by just changing timing sprocket and firing order....

I can’t see that being possible.



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Discussion Starter #6
With the 15426378 firing order I got backfire out of the carb. It seemed that I would have the #1 at TDC and the distributor correct but when I would try to put the timing light on startup it would be off. Not sure how that's possible.
 

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A foolproof easy way to find top dead center #1 compression stroke is to remove the left valve cover and watch the #6 cylinder (assuming standard 289 firing order) valve action as you rotate the engine. As the exhaust valve is closing and the intake starts to open there is a point when they are exactly level with each other (easily eyeballed) and at that precise point #1 will be at tdc compression stroke. It is a great way to set as it works on any engine as long as you know the firing order, you always check on the cylinder that is opposite of number one in the firing order so in this case the firing order is one542, six378 if that makes sense.
Use this method and you can verify your cam timing without pulling the timing cover as your tdc mark on the damper will be on the mark when the valves are at the even stage. You can rotate the engine back and forth a hair when you get close and get the passing exact. Try it, it works flawlessly!
 

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The original sprockets on the timing chain were not lined up correctly, and were installed correctly with the new chain. Would this have an change in it not running now?
Yes, if the marks weren't aligned on the old set and you had to turn the crank or cam to get them lined up then that would affect timing.
 
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