Fresh 383 SBC smoking, fouling plugs

[nikwho]

Hello all,
I'm stumped with my freshly built 385" SBC (3.75" X 4.040"). It is smoking, misfiring, fouling plugs and feels down on some power. It has not run properly since installed. Its an gen 1 SBC, 4 bolt main, Eagle rotating assembly. Has World Products heads, 224/224 @ 0.50", cam specs indicate 0.466" lift with factory rockers. Rockers are 1.5:1 roller rockers. Has new Quick Fuel Brawler 650 cfm carb. I live at 7,000' ASL. I re-jetted the carb from 70 (stock) to 66 primary jets and from 74 (stock) to 70 secondary jets. I also ran an Edelbrock 1406, rejetted for altitude, and it behaved the same way!

I have replaced the fuel filter. I have put an ohm meter on each plug wire, and they were all quite close, though at the moment, I cannot remember the reading. When trying to figure out my misfire, I pointed my laser thermometer at each header tube and a few were 200-300° cooler than others. So, not being 100% sure on the age of my distributor, I ordered a new Accel HEI Distributor, installed and had no effect. I pulled plugs and 5 had a good tan appearance, while the others were oily and fouled. Those were NGK UR5. I figured that I would be fine with a stock heat range plug, so I replaced all 8 plugs with NGK UR4 plugs. It ran noticeably better, and did not sound like it had a misfire at first. But, now with about 30 miles on the plugs, it has started misfiring again, and I believe it to be fouling the plugs again. It is smoking quite a bit, initially only on hard acceleration, but a bit more now, even at idle. Smells quite rich. Smoke is quite thin, so hard to call it a color. Wouldn't really call it very white or blue. Really light grey, perhaps? It looks slightly blue in color, I suppose, but not obviously blue. All four idle screws are 1 turn out. Adjusted to peak RPM, then 1/4 turn richer. Thinking intake leak, I adjusted all four idle mixture screws in and could not even get them all turned in to 1/2 turn out before the engine will die. I've played with timing, with no effect. I BELEIVE that it is sitting at about 14-16° advance at idle. No signs of water in oil, not consuming oil, that Ive noticed. I've sprayed around carb and intake with carb cleaner. No RPM change. Im running a Summit Racing branded mechanical fuel pump, and my fuel pressure regulator body cracked, so it currently does not have a regulator. The floats were set so that the fuel level is perfectly in the middle of the sight windows.

When driving, it feels loaded up, and bogs, seemingly the worst at about mid throttle, but it won't really clean up at any RPM! Seems the happiest at idle. I bought the World Products heads with a long block engine. They appeared brand new, but I didn't specifically ask. I supposed it could be a bad valve seal? I can say, that even when running at its best, it felt like it had less power than my previous 350 with run of the mill GM iron heads. I have not done a compression test, but likely will tomorrow. Obviously have not done a leak down test, either.

I'm kind of at a loss. Any thoughts? I trust the shop that did the work, though they didn't do the machine work for me. They machined the parts for a co-worker, whom I bought the engine from.

Tomorrow I intend to pull the vacuum modulator line off of the carb and plug the vacuum port, and see if it cleans up. I was thinking that a bad vacuum modulator could allow it to be sucking transmission fluid into the manifold, which could cause the smoking and explain the misfire and fouled plugs.

Thanks for any and all help! I can typically sort this sort of thing out on my own, but needing to reach out for a bit of help on this one.

Nik