TBI Conversion - need timing help!

Joined
Dec 15, 2005
Messages
1,124
Location
Reno, NV
In the process of converting my early SBC 350 and I'm trying to set base timing. I'm finding conflicting information on where to set the timing...should it be set to 0 and let the ECM adjust or should it be set to 8 degrees before TDC? By the way, I have disconnected the EST wire while setting the timing so the ECM won't adjust it while I set it.

Any help is appreciated!
 

black95

 
Joined
Aug 25, 2008
Messages
2,409
Location
Colorado
I would set the base timing to match the specs for the year of truck the computer came out of. should be able to find that info in haynes or chilton manual. most likely, it is going to be 0 degrees.
 

terrx

 
 
Joined
May 9, 2004
Messages
371
Location
Santa Clara, CA
Set it the same as the initial spark advance in the bin. Should be 0 for a stock 7747 bin. What are you using?
 
Joined
Dec 15, 2005
Messages
1,124
Location
Reno, NV
Set it the same as the initial spark advance in the bin. Should be 0 for a stock 7747 bin. What are you using?
Using the 7747...so set to 0?

When I put my timing light on it, the timing mark is bouncing all over the place. I've disconnected the EST wire so the ECM shouldn't be trying to adjust, right? What am I doing wrong?
 

terrx

 
 
Joined
May 9, 2004
Messages
371
Location
Santa Clara, CA
The 4 character bin code should be on the label on the ECM, or if it's missing look for a sticker on the PROM itself (need to take inspection cover off ecm to see it). Is it stock? Has it ever been reprogrammed? You'll eventually want to know more details about it and possibly reprogram it.

Verify that the tan/black wire is disconnected at the weatherpack connector near distributor. It sounds like the ecm is still trying to control spark. You could give it throttle and watch the timing - if it advances then the ecm may still be trying to control it. If the tan/black is disconnected it should be steady.
 
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