This is on an 78 350, HEI. The truck starts just fine, go out to it after school, fire's right off. It idles rough and actls like it's going to stall. I know the choke is bad ( or at least pretty sure) because it doesnt do anything. It's electric choke on a holley 4 bbl.The truck puts out some black smoke whenI give it some gas, and smells terrible. Running rich? Here's what happened: Started it up, drove for about 10 minutes or so. Got to a stoplight and it stalled on me. Started back up, luckily. Drove another 2 minutes, then it stalls as im pulling into a parking lot. ( thank God, it was on Fry road for any houston/katy ppl reading) I try to start it back up, NOTHING! It cranks, but it will not fire off. We ended up just pulling it home because it would NOT start. So i went out the next morning, and it fired right off... I just put in new plugs, wires, Cap, coil, rotor, valve cover breather on pass. side, and PCV on driver's. The EGR was removed and has a block off plate by the P.O. But it still idles rough! Question: Can the idle be cause by bad timing, rich mixture, vacuum leak, and maybe a bad choke all in combination? The new carb gets here monday, and we'll set the timign then. I just want to know what else i need to check.
Yes to all...bad timing, rich mix, leak and bad choke (less likely after driving). Check firing order and wires first. Then timing. Check for vacuum leak. These are merely to rule them out. It sound to me like you've got a carb/carb mix issue. Check the butterfly before starting then as it warms up, keep watching it. The butterfly should be opening as it warms thanks to choke. If the butterfly isn't moving, choke not working properly. As I type, it sounds more like choke and the butterfly not opening when hot. A closed butterfly will definately keep it from running due to lack of air.
If it has back fired lately you may have blown a power valve. or the choke is stuck shut. On the stalling it sounds like you flooded it. I have seen HEI coils that crap out when they get hot and work when they are cold again but they usually blow the module in the process.
yes. tune the carb. it's not the HEI or the plugs' fault when they get carbon fouled. Let us know when you fixed the choke. -AND .. Don't remove it for redneck horsepower, I've picked up quite a few "ruined" carbs from that "hot rod mod"
Haha. ok. Well the firing order is good, and im confident now that the choke is not working. but anyways, i knew the carb was F'd when i got the truck, i actually just got my new one about 10 minutes ago. ( thanks UPS man) I'll use the holley for a rebuild carb in auto shop class. Could the module be like the coil you said and go out when it gets hot?
Could it? yes. Is it? 99% sure that's a no. I have had this problem before, edelbrock 750 was fine at idle but under load would dump fuel, foul plugs, when I would go to restart, nothing. Proper tune on a carb is a PITA, but well worth it.
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