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4jb1 gear drive timing marks

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4jb1 gear drive timing marks

Postby Justsomedude » Sun Feb 25, 2018 12:23 pm

My old girls timing is off so I've bought a dial gauge and am attempting to do the 0.5mm at 11 degrees BTDC thing.

But, my harmonic balancer seems to have 6 (yes six) timing marks on it ?! Its a gear drive engine (no idea on its history) I'm fairly sure the first one is TDC, but the rest are a bit of a mystery and why there are so many. I've hunted high and low in forums and the interwebs to no avail. Anyone got any clues as to which is which ? Or perhaps another method to measure 10 or 12 degrees BTDC maybe.

timing marks.jpg
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Re: 4jb1 gear drive timing marks

Postby Justsomedude » Sun Feb 25, 2018 1:12 pm

Something else I noticed. I've got two different 'workshop manuals' for 4jb1t, one from here and the other I'm not sure. Anyways, they have directly opposite instructions on how to adjust timing :shock: It's the same image obviously, but their little table saying how to advance or retard is back to front. On mine (gear drive) moving the pump 'away' from the engine results in a bigger value on the dial gauge, so I think that means advancing? Whatever I've done so far seems to have improved it, less smoke on start up and revs more freely, in my drive anyways.

Advance-retard2.PNG

Advance-retard.PNG
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Re: 4jb1 gear drive timing marks

Postby Justsomedude » Tue Feb 27, 2018 9:14 am

Noone? Guess I'll buy a big goniometer and do it the old fashioned way.
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Re: 4jb1 gear drive timing marks

Postby geeves » Tue Feb 27, 2018 3:12 pm

I would of thought Rob could answer this. Ive never touched a gear drive engine
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Re: 4jb1 gear drive timing marks

Postby stardog » Fri Mar 02, 2018 2:02 pm

I have a rodeo 2.8td in the mu I have a spare harmonic balancer I will have to have a look how many marks are on it but im pretty sure the first mark is TDC and the second is mark is 12 degrees BTDC.
I could be wrong I cant find anything on the internet either on the marks.
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Re: 4jb1 gear drive timing marks

Postby stardog » Sat Mar 03, 2018 6:17 am

This is what I found on 1 of my manuals I have .I hope this helps you out.
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Re: 4jb1 gear drive timing marks

Postby Justsomedude » Sat Mar 03, 2018 9:31 am

Thanks Stardog :) That's the same page I've got in both my two workshop manuals I think, but their diagram only has four marks whereas mine has 6! Which is my problem. Gonimeter (big protractor) arrived yesterday so I'll have a go at measuring the angles manually this weekend and report back. Mine also advances by moving the pump 'away' from the engine, where both my manuals say it should be 'towards' /sigh. My MU isn't on the road yet so still tinkering away, lots to do yet. It's going much better since I tweeked the timing but I'd like to get it right.
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Re: 4jb1 gear drive timing marks

Postby stardog » Sun Mar 04, 2018 7:27 pm

No worries I would like to know what degrees the marks are also checked the new harmonic balancer in the box and it has six marks as well interesting.
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96 wizard 3.1 pretty stock for now but have plans intercooler bulbar winch snorkel.

Re: 4jb1 gear drive timing marks

Postby Justsomedude » Mon Mar 05, 2018 9:32 am

Ok, so I took the pulley off and centred the goniometer as best I could. Allowing for a little human error it looks like the 6 marks are as follows: (assuming mark 1 is TDC).

Mark 1: TDC
Mark 2: 5 degrees
Mark 3: 10 degrees
Mark 4: 12 degrees
Mark 5: 14 degrees
Mark 6: 16 degrees

5 degree.jpg

10 degree.jpg

16 degrees.jpg


My timing was on about 4 degrees when I got the car, maybe less, very hard to start, lots of white smoke, gutless. Pumping the prime pump until very hard was the only way to start it, excess pressure advanced the timing I think. From memory I changed it to what should be just over 12 degrees and now starts ok and very little smoke as well as pulling ok now. Will take it to a dyno guy one day.
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Re: 4jb1 gear drive timing marks

Postby Justsomedude » Mon Mar 05, 2018 9:46 am

Thought I'd add for anyone interested, this little timing kit for Bosch VE style distributor pumps worked great. Very cheap at $65 on fleabay and easy to use, I'd never used one before but wasn't hard to work out.

timing kit.jpg
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Re: 4jb1 gear drive timing marks

Postby stardog » Mon Mar 05, 2018 9:48 am

My harmonic balancer has spun so timing is way out on my engine it stars first turn of the key but is gutless at the moment.
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Vehicle: 94 mu was 3.1 turbo intercooled now 2.8td rodeo gear drive engine and intercooled and fuel delivery turned up 3" system from turbo 5 speed manual arb bullbar 13000 LB winch max winch snorkel HID headlights HID IPF spotlights blue led dash lights LOKKA front diff new bushes shocks all round 80 ch unden uhf sony xplode mp3 player back seats removed and storge system put in.
96 wizard 3.1 pretty stock for now but have plans intercooler bulbar winch snorkel.

Re: 4jb1 gear drive timing marks

Postby stardog » Mon Mar 05, 2018 9:59 am

That's a pretty good kit for $65 with the dial gauge and all of the different bits included bargain.
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Vehicle: 94 mu was 3.1 turbo intercooled now 2.8td rodeo gear drive engine and intercooled and fuel delivery turned up 3" system from turbo 5 speed manual arb bullbar 13000 LB winch max winch snorkel HID headlights HID IPF spotlights blue led dash lights LOKKA front diff new bushes shocks all round 80 ch unden uhf sony xplode mp3 player back seats removed and storge system put in.
96 wizard 3.1 pretty stock for now but have plans intercooler bulbar winch snorkel.

Re: 4jb1 gear drive timing marks

Postby stardog » Fri Apr 06, 2018 4:48 pm

I undone the crankshaft pulley on my 4jb1 today it had 5 marks not 6 closer inspection a complete different harmonic balancer the TDC mark was 1/4 of turn out compared to the new one I installed so it had spun the rubber .
I will static time it tomorrow and see if it runs any better now that I have the proper timing marks to go by.
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Location: sydney nsw australia
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Vehicle: 94 mu was 3.1 turbo intercooled now 2.8td rodeo gear drive engine and intercooled and fuel delivery turned up 3" system from turbo 5 speed manual arb bullbar 13000 LB winch max winch snorkel HID headlights HID IPF spotlights blue led dash lights LOKKA front diff new bushes shocks all round 80 ch unden uhf sony xplode mp3 player back seats removed and storge system put in.
96 wizard 3.1 pretty stock for now but have plans intercooler bulbar winch snorkel.


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