Running extremely lean!

[brothers69c-10]

It's been a while since I've been on here, but I'm back with more questions. Some of you may remember my old 78 K10 that i had a 427td in. Well i finally got tired of trying to get it right and found a good deal on a 454 with high miles on it. Never heard it run, but the price was right. I put it in 3 weeks ago and got the truck running and driving. The motor ran better then i actually expected it too. This last weekend after i put some miles around town on it, I took it on its first trip over 15 miles in 3 years. Truck ran great, drove great. Half way to my destination it started running rough, like it was struggling. It acted like it was overheating/vapor locking, or even a possible vacuum leak. It never died and it idled fine. Now this happened when i was doing about 55mph down the highway at about 2000rpm's.

So i checked the obvious, made sure no vacuum lines came off or cracked and they were all fine. Next step was change spark plugs. The plugs that were in it when i bought supposively only had about 2000 miles on them so i reused, but they were black as coal when i put them back in. When i pulled them out after it started acting up they were all white like a brand new one. I put new ones in anyway and that had no effect. The fact that they were white and the engine was running very lean really surprised me since i have a 780cfm holley on 2oo and some horsepower motor.

Tonight I changed the carberator out with an old quadra jet and that really didn;t have any effect. I don't know if the quadrajet is any good or not, but since there was really no change in how it ran, I'm guessing its not the carberator.

Anybody have any ideas? Its really hard to hear any vacuum leaks thanks to the crappy headers I have on it and all the exhaust leaks. I'm going to get a can of brake cleaner and spray around while its running to see if i can find a vacuum leak or not.

Also forgot to mention that at idle in park the motor runs just like it did, firing on all 8 cylinders. Once in drive it starts surging a little. Then when trying to take off or diving down the road it spits and sputters and every now and then it will kick in for about a second and run normal.

I think this truck is just cursed, but any and all help/advice is appreciated.

[frog210]

Fuel pump?
any filters?
Maybe a fuel line got kinked or is being squeezed?

[brothers69c-10]

Guess i should have mentioned that i checked the fuel filter and its fine. Seems be getting enough fuel outof the pump and its brand new. I will have to check fuel lines collapsing but there is less than a foot of rubber hose in the whole system. Also runs the same with or without air filter.
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[KQQL IT]

Distributor move and go retarded?
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[INSIDIOUS '86]

Check that the intake bolts are tight and that the Holley didnt have a bolt come loose on one side check that your brake diaphragm holds vacuum and the check valve works. Also it's possible that the intake gasket got sucked in underneath in the cam valley

Also since your engine is high mileage check and make sure your cam didn't go flat
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[brothers69c-10]

I checked the distributor and it didn't move.

I wondered about the intake gaskets going bad, thats why i'm going to test with brake cleaner tonight. There isn't any vacuum noise coming from the brake booster and i disconnected it last night and plugged the vacuum port to test that. I don't think the cam went flat because it was an instantaneous change that occurred and there is no top end noise at all.

[INSIDIOUS '86]

A flat cam won't make any noise. Your vac advance and mechanicle advance still in working order?
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['82 steppin]

Run the engine and spray WD-40 or Carb cleaner on the intake manifold where it sits on the head if it run stranger then the intake is leaking
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[1LowToy]

check the fuel lines at the tank/under cab. Sounds like your (engine) sucking air. Those headers may be a problem being so close to the fuel line.