Hopefully someone can help me,

I have a 1977 Ford Bronco with a 1969 351 Windsor Engine (Block and Heads). The engine is pretty fresh only been running it for 2 years. Heads were just done last year....New valves, bronze guides, seats, studs....etc. I have a 600 cfm Holley Carb w/ vacume secondaries w/ 65 Jets (Just rebuilt last week), a Holley Street Dominator Intake Manifold, Edelbrock Performer Cam (Stock Replacement) w/Roller Timing Set and Flat Tappet Hydraulic Lifters, Crank, Rods, Pistons (Flat top w/valve releif), Oil Pump, Oil Pan, Heads, valvetrain are all stock. L&L Long Tube Headers w/3" collector w/ 2 409 Stainless Flowmaster Mufflers w/3" Tailpipes out infront of rear wheels, C4 Trans (Stock) w/B&M Aluminum Pan, Accel Dual Point Distributor w/mechanical advance, Stock 302 Radiator w/internal trans cooler (RE-CORED), new water pump, All new hoses and fuel lines, Mechanical Fuel Pump, 4.10 Rear End w/traction loc (Stock). I think that is all.

I am having a lean condition on all 8 cylinders. When I pull the plugs they are white on the side electrode but around the outer edge of the spark plug it is sooty or rich looking. I have a point gap of .017 and a dwell of 31 degrees. Plug gap is set at .034. My timing is set at 6 degrees BTDC. I have 15 inches of vacume at idle. I have exactly 150 PSI of compression on all 8 cylinders. I am runnnig regular fuel now but have run premium in the past. I have enough fuel pressure to fill the bowls and keep them there. It doesn't hesitate or bog. It runs absolutely ok except for the lean. The truck ran fine for 2 years before all of this. It started 2 weeks ago when I was going down the freeway at 4500 rpm and the engine hickuped and blew some smoke out the back but continued to run absolutely fine. I decided once I got home I should check it out. Found nothing external....no fluids...dry as a bone. Engine runs at 210F. A little warm for my tastes. I am stumped. ANY HELP WOULD BE APPRECIATED! Thank you.

Sam

 

Hmm, I would think a blown power valve from the hickup you describe, but that would cause a rich condition rather than lean, and you say you've rebuilt the carb since then...and if it's a new enough Holley, they have power valve protection built in to them now. Do you have another carb you can try on it, just for the heck of it?

Yes, 210º seems a little warm but with 4.10s cruising at 4500 I would expect it to be a bit warm.

Let's see if we can get some other suggestions here...

 

Yeah I stuck a 750 DP on it and it did the same thing. Thanks for your input. Hope someone else can shed some light on my troubles.

 

In that case I'd start looking for a small vacuum leak. There are several ways to do this, like using an unlit propane torch and directing it at different places where a leak might occur while listening for any change in idle RPM, or doing the same with carb cleaner.

 

Yeah, already tried that unfortunately....around the entire intake, and carb base. Even checked all my vacume fittings and lines. I think I may have burnt valves from overheated fuel. I had a see-through fuel filter and the screen is encased in a plastic framework and the fuel deformed the plastic.

 

I have some pics of the heads, fuel filter, carb, plugs, and the way my fuel line is routed from my mechanical fuel pump to my carb but don't know how to post on here. You can check them out here: 8 pics in all....

http://pg.photos.yahoo.com/ph/eclips...m?.dir=f18are2

If this is not ok moderators please let me know. Thanks.

 

Linking to them like that is perfectly acceptable. You can also start a gallery here as long as it's Ford truck and related content.

Those are definitely some white plugs. I hope you're not seeing any little grey speckles on them...!

But before this all happened you had checked them and had a nice tan color?

 

Yes, I had checked them all and had a nice tan - brown color....was running soooo good. Then I went on a little road trip and it is running lean. No grey speckles!

 

Has it always run at 210? That's high for an EB on the highway even at 4500 rpm. It's pretty common off-road without much airflow. I'd check your fuel flow coming out of the pump. They are known to go bad and supply enough fuel to run it at idle but not enough to drive it.