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Valve timing on 4.0

killer98xjsport

NAXJA Forum User
Location
Portland Oregon
I replaced my timing chain and was checking the timing after install. The maunal said the check is a rotaion of 180 degrees and count the pins between the timing marks and there should be 15 pin. This is all on a chain that the manual says should have 48 pins. My problem is that my chain has 64 pins on the old and new. I can' t get the chain to have 15 pins between the marks. Anyone else run into this?
 
Dunno about that, but the rule of thumb I use on pretty much any engine is this:

1) Line up the marks and install the chain.
2) Check mark alignment.
3) Turn the crankshaft exactly two full turns.
4) Re-check mark alignment.

If you want to worry about it; then repeat, going exactly ten full turns for Step 3. Re-check

That's how I did it before on my 4.0, and how I learned to do it 'way back when (around the time Moses was still a mess cook, I think...)

The gearing between the cam and crank is 2:1 - for every two times the crank turns, the cam goes around once. Thus, the even numbers.

If you stop after an odd number of full crankshaft turns, you'll find the timing mark on the cam gear at the top, rather than at the bottom. Use a straightedge when you check marks - you should find the cam mark, crank mark, camshaft centreline, and crankshaft centreline all on the same line if you've done everything right (whether the cam spot is at the top or the bottom.)
 
That what I was thinking but I want to make sure it right brfore putting it together and having it be off. The info I got was from Alldata and a Chilton manual and they were the same with the 15 pin check but that set up does not match my 4.0
 
killer98xjsport said:
That what I was thinking but I want to make sure it right brfore putting it together and having it be off. The info I got was from Alldata and a Chilton manual and they were the same with the 15 pin check but that set up does not match my 4.0

Yeah - that's also in the FSM, but it doesn't necessarily apply to the aftermarket parts. The critical part is that the camshaft gear have exactly twice as many teeth as the crankshaft gear - beyond that, gear pitch and actual tooth counts don't matter. It's the relative count that makes the difference.

So, the aftermarket chain is probably a finer pitch, which makes the aftermarket gear a finer pitch as well. I think I ran into the same issue (I wanted to check my work against the FSM,) so I just did it the way I mentioned and called it good.

I've put about 75K on that chain to date, so I'm sure it worked.
 
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