Jeep 4.2 timing

[daily_destroyer]

Hey everyone,
I have a 258 or 4.2l in a 85 cj7 I have gotten rid of the carter crap and threw in an motorcraft 2150
I have also upgraded to an hei dist
Any idea as to what the timing should be I have tried the vacuum method and have tried to adjust by timing light but unsure where it should sit the book says alot of different btdc times. My main issue is I live at 9100 ft and work at 5200 ft, also the book has sometimes 4 or more advance for high alt.
All on the same motor I have disconnected the ecu it runs ok but great any ideas I think I am at 6 btdc at the moment
Thanks
DD

 

[superj]

8 is what everyone says usually is the best point

 

[daily_destroyer]

Interesting cause I am still getting engine ping and some poor exceleration

 

[daily_destroyer]

I'll work with it some more thanks superj

 

[superj]

i set mine at 10 but get i get light pinging on hot says climbing the on ramps.

did you change to the old school distributor or are you still running the electronic one, like i am? i know that is my trouble but i had to do some adjusting and testing to find the right spot and that is where mine landed. once i get an old school distributor, pre 81, i will be fine because the curve is set up for a non electronic carb

 

[Jester32]

Best thing is see what your advance is. As you rev it up it will automatically advance. If you can you may be able to change the springs so you can run more initial advance with less mechanical eliminating ping. And helping with drivability.

 

[Jester32]

Have your timing light on it and rev it up to about 3000-3500. Shouldn't be much more than 30-34 degress if it is you need heavier springs if not. Vice versa. You want a fair amount of initial advance. Say 12-15 degress. Will help driveability ten fold. So adjust springs based on that. But every engine is different. So it may like 8. Or it may like 18.

 

[daily_destroyer]

Yea I am set at 10 right now was a little better at 8 so I will try 6, and I went HEI distributer I figured it would be better than the old one. I also went new I did not want to have to rebuild anything really and going with another distributor from an older jeep I would have done a rebuild right off. So I will play some more and let you know the out come. But at least I now have a ballpark range the book was saying 16 btdc
Thanks everyone

 

[daily_destroyer]

Ok guys 8 it is now I just have to try to done time the carb (oh boy!!!)

 

[elevatorman]

i just recently changed out my timing chain etc and retimed mine.Was a pain at first as my harmonic balancer had slipped so my mark was off.
I used a dial indicator to find actual TDC and then remarked it.
I have since changed that.
Although my 87 is pure stock (thank to Calif regs) I am running at 10.
I live at 1450 elevation and visit the Eastern Sierra's constantly at elevations from 5000 to 10,000 ft.
I have no performance issues but I do get slight pinging on hot days with the air on.
My friends 90 same equipment and mileage on motor wont run past 7 degrees.
I will be changing out his timing chain as well cuz the plastic gears were completly gone on mine at 100,000 miles

 

[superj]

we have plastic timing gears? oh shizznit!!

 

[elevatorman]

well mine were plastic coated and the coating was GONE and laying in the oil pan

 

[Syko]

Mine did the same thing. I heard some rattling when I was working on it, pulled the cover off and it was missing a few teeth.. Thankfully its not an interference motor.. I changed mine at 199,000 miles..... Doubt it had ever been done before.

Justin

 

[Don Stephens]

Full steel timing gears are available if you look. They are a bit noisier though. I bought mine years ago. When you are adjusting the timing, and the mark on the balancer seems to bounce around, then its time for replacement. A timing chain will stretch out in around 50k or so. I'm not sure about the hei units, but the stock jeep motorcraft has an adjustable vacumn advance by inserting an 1/8 allen wrench in the advance unit where the hose goes over. It has only a limited adjustment but can stop pinging issues. Combined with a big cap conversion, the motorcraft is just as good as an hei, providing it is adjusted correctly.

 

[elevatorman]

Plastic coated gears are utilized for sound deadening purposes only.Think of a racing engine under tremendous stresses. Plastic will not last!
Torque that motor hard lose the plastic ,jump a few teeth and bend valves ,breaking pistons and losing a whole motor gets real expensive.
I will deal with the noise.

 

[superj]

all hte bad damage only happens on interference engines though. i know because bmw engines are interference, i found out the hard way on the wife's 325is. i was told out jeep engines are not interference so if your change jumps all you get is bad running and maybe no running.

 

[Gronk]

make sure your distributor advance is connected directly to ported vacuum. Set your timing at 650rpm and at 9000' your timing should be 18deg, at 5000 your timing should be at 14deg. Cap the vac source when setting.