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Old 08-03-2017, 08:30 PM   #7
BR3W CITY's Avatar
Join Date: Sep 2009
Location: MKE WI
Posts: 7,048
Re: Tackling a botched build, need SBC advice.

Update: Decided to not trust the timing mark at all, and pull the drivers valve cover and watch the valves. I got the valves both closed to where I could spin the pushrods easily, and checked the markings.

The balancer was no where near close, like still 40-60* off, so I'm going with the fact that the balancer either spun, or was never put in right. I put a small dayglo hash on the balancer at the 0 point with everything still lined up.

I checked the rotor, and it was correctly pointing at #1. Its hard to tell if its "perfectly" at #1, but I had placed a reference mark on the cap and the dizzy base, and the center of the rotor lines up pretty straight with those.

When I did the plug wires, I simply replaced the old wires 1 by 1, instead of starting from scratch. It seems like they PO swapped #2 and 7, but may have also started #1 on the #2 plug position? To be sure, the #1 position on a GM HEI is the FIRST pole clockwise of the wiring/module, right?

I redid the firing order the way I know18436572 (unless it changed lol), and made sure I had a solid connection on all my wires adding some dielectric for good measure.

I reset all of the relearns on the FITech, and flashed the ECM.

SO: Its now extremely hard to start, and doesn't like idling right away. I did get it started with the vac advance disconnected, and had to give it throttle to around 1500-2k as it warmed up. Allowing it to settle into idle causes it do die pretty fast, and pretty abruptly.

I was able to use my new mark on the balancer to try and set base timing, and had about 17*.

The good part, is that if I kept the idle up, the engine now rev'd way more freely, and could rev up and down (back to my hand idle speed around 1500) without misses or bogging. At that point it had sounded better than it had at any point, and wasn't shooting flames or massive gunshot backfires. It still refused to idle correctly however. I tried with the vac advance both on and off, and it prefers having it disconnected.
I bumped the commanded idle speed in FiTech up a bit (from 800 to 1000), but it still had some issues maintaining idle, almost like it was encountering resistance.

So at this point, I was able to turn up the manual idle screw on the throttle body and the truck would hold a 12-1500rpm idle. It would rev fairly freely, and still sounded the most even it had since I've seen it. It did still immediately die when I put it into gear. I tried to restart a few times, but the battery was low from all the starting for a few she's on the charger for the night.

What do ya think? It seems like straightening out the spark was crucial, but these other/new/different problems still have me a bit behind the ball.
'66 Short Step / SD Tuned / Big Cam LQ4 / Backhalfed /Built 4l80e / #REBUILDEVERYTHING

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