Ok guys i just picked up a 78 F250 4X4 with a 400, i have run into an issue with timing. I replaced wires, plugs (.042 gap), and rebuilt and put on a holley 600cfm carb, also put a new edelbrock 14" air filter on it, it came with an edelbrock intake manifold on it. So now that the small details of the truck are covered the problem. I have been having an issue with timing and keep fouling plugs. I hooked up a timing gun and the timing is off by alot, i have the mark at 10 degrees btdc like manufacture recemends but its firing at like 30 atdc and plugs are going out, mostly the #4 cyl. I tried advancing the distributor but the vaccume hose that is attached is hitting the ac compressor mount so i cant turn it anymore. Any ideas, could it be the carb, do i need a new ignition module, new distributor assembly, all the above? Any help will do!!!

 

Maybe the timing chain jumped a tooth?

 

I will have to check that out could be it, do you know if when your masing with the idle/air mix screw on the carb will you notice the charge in how the truck uns right away? It seems like when i adjust them there isnt a change so maybe those are plugged up

 

Not sure if it's your problem, but to get more adjustment room take the cap off the distributor and make a mark on the lower plastic part of the cap where the rotor is pointing. Then undo the distributor raise it up and move it a tooth or two on the cam then line the distributor back up to the rotor with the mark you made and you'll have more room for adjustment rotating the distributor so it won't hit the compressor.

Another thing to mention is are you sure your balancer is ok? The outer ring hasn't slipped any because of the rubber squishing out? To verify make sure the engine is at number 1 TDC and look at the balancer to make sure it corresponds.

 

Do you have the vacuum line off the dizzy and plugged when you checked the timing ? If it's plugged in it will read wrong.

 

Nice thats what i was wondering if there was a way to pull out the distributor without messing up the timing!!! I will do that tonight i hope it will help some

 

Yeah i plugged the vac line when i checked the timing and its good when i do that and when i put the line back on and it again its way off

 

You need to be sure you have that vac line going to a "ported" vac source at the carb. No vacuum at idle.

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Manifold vacuum is a no-no.

 

I just had the same problems with my 351m. After tearing everything apart the problem ended up being a badley reman'ed 600cfm Holley. Couldn't get it in time. Running like junk & fowling plugs. Put a brand new carb on it and it purrs like a kitten. That was just my experience but it sounds similar to your situation.

 

Did you look into sending it back to holly and having them fix the carb?

 

It was a 3rd party carb company that rebuilt it and sold it to an overstock buyer who sells them on eBay. Moral of the story is you get what you pay for. While I purchased it cheap it cost me about $600 more in the long run.

 

So i think i may have foundthe prob! In the secondary bowl there is a plate that goes between the main body gasket andthe secondary fuel plate body gasket that was missing! I am not sure if that would cause the truck to run like crap but i do t want ro put ot back on until i get some insight

 

I would think that if anything is missing it would cause problems. From what I know the metering block gaskets are ported differently for different carbs and cause different flow. Sounds completely possible that the missing plate could be causing the carb to dump fuel. Which plate is it?

 

It is the the that goes in between the metering body and the main body, just a thin peice of metal that is in between the two seals.