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I , as everyone may know from previous post's, converted my 1981 3/4 ton 4x4 to 350 tbi/TH350 from carb /BO-LO setup. The motor I used was a rebuilt GMC 2500 van motor. Well I replacd all the wiring from an 87 wrangler, got it running but had bugs. I ripped the whole fuel system out and put a new tank, pump,filter in it as the old pump was losing prime and was loud..truck wouldn't start below -10 Ontario weather and rolled over like a dead duck. WELL after replacing the fuel pump etc, I tried firing it up in -29 weather and to my surprise it fired after some throttle taps while cranking. SO I checked the timing and it was 2 with tan wire unplugged. I was told I should have had it @ 4 as the 2500 350 tbi had a different cam bla bla.. The truck started with minor bugs at 4 NOW @ 6 it runs almost like new !! and doesn't do the really fast almost start while holding the starter on to get it to stay running thing. SO my question is 1. Why would it run so good @ 6 advance when stock is suppose to be 0 (which wouldn't even start when cold), and question 2 What is the timing specs of a 1988 2500 GMC work van 350 tbi. Lots of people are saying the timing chain is going and that is why I needed it so far advanced to start in cold weather.. BUT when the timing gun is on the mark, it don't bounce all over..it stays right there.. Could this motor since being rebuild have the so called bigger cam like he said and needs the advance or what.. Thanx for the ear , any help appreciated.
 

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Stock timing is zero degrees with set timing wire disconnected. Computer doesnt really "know" that timing is at 4 or 6 or what ever you set base timing to, it just gets knock signal if you advance it too far then backs off timing or turns on check engine light if knocking continuously for too long.
So if it runs decent at 6 degrees advance I would leave it.

Maybe fuel quality has something to do with being able to get away with more advance.

You can check timing chain looseness by pulling distributor cap then rotate crankshaft back & forth to see how far you can turn it till slack is taken up and rotor starts turning.

Glad to hear you got it running. :thumbup:
 
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