questions about timing chain. -

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post #1 of 3 Old 09-13-2013, 08:46 PM Thread Starter
mustanggarage's Avatar
1990 YJ Wrangler 
Join Date: Nov 2011
Location: atlantic
Posts: 267
questions about timing chain.

Hello. I am posting this thread here and in the YJ section because I really need some help as soon as possible.

I am in the process of doing a head swap 4.0 onto a 4.2 and doing the MPFI conversion at the same time.

I set the engine at TDC and took the distributor cap off confirming that the rotor was pointed at number 1.

so I pulled the head. then I checked the timing chain and found it had a bit too much slack so I pulled the harmonic balancer and the timing cover.

when I pulled the timing cover I found the crank sprocket positioned with the dot toward the cam sprocket. the cam sprocket dot however was 180 out. I rotated it around so the two dots are aligned. here is the pic.

however the rotor looks like this.

now keep in mind this engine was running just fine when I took it apart. but this as far as I know looks like the distributor is in 180 out of time. I called Hesco and asked them about it and they said to just re install everything like I took it out.

so I swapped the timing chain. it looks like this now.

the distributor looks like this.

before reinstalling the head I rotated the engine so the cam sprocket was at 1:00 and the crank sprocket was at 3:00 and counted pins. 15 count just like it should be. reinstalled the head, torqued it properly.

now I need to pull the distributor. the new distributor has a pin in it to keep it from rotating. My concern is that this looks like it is 180 out to me. should I reinstall it like it was? I know it is not that big of a deal to pull the distributor and swap it 180 but I wanted to get some more opinions before I pulled the distributor.

so anyone out there have any opinions?

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post #2 of 3 Old 09-17-2013, 01:49 PM
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1989 YJ Wrangler 
Join Date: Nov 2010
Location: Sin City
Posts: 2,881
4 stroke engine. every 180 degrees it comes to that position so i would imagine one or the other is off. Check again to make sure keep things marked or take pictures.

89YJ 2.5L TBI, AX-5, NP231 SYE, Ford 8.8, Yukon Grizzly, Tom Woods Shaft, 33" BFG T/As, 4" lift, Warn VR10000s.

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post #3 of 3 Old 09-17-2013, 03:58 PM Thread Starter
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1990 YJ Wrangler 
Join Date: Nov 2011
Location: atlantic
Posts: 267
actually I have been working on this for a while since I posted this question. this is the one reply I got that actually seemed to fit my problem. it was from Leee from hesco.

"The timing dots when aligned has the engine at TDC firing #6, also at this time the #1 valves should be a "SPLIT OVERLAP" (that means the exhaust is almost closed and the intake is starting to open). Most engine builders use this to rough degree a cam in."

prior to receiving that answer I had confirmed by placing my finger over the spark plug hole that I am indeed on the compression stroke of number one cylinder.

apparently for some unknown reason that is the way it is supposed to be.

anyway I think I have it figured out now.

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