I had a valley pan gasket on the rear of the motor go bad on my 78 351m, so I replaced it a few days ago, along side some aftermarket headers that I’ve had in my garage for about a month. Now the damn thing won’t start. It turns over and sounds healthy, but will not fire off. The timing could be off, considering I had to yank the distributor out to make it easier to get the intake off. I know I don’t have any crossed wires to the plugs, and I checked for fuel and spark. I have them both. Any ideas would be appreciated.

 

even if your timing is off it should do something even if it's bad. if it's not even popping and puking I'd dump a couple tablespoons of fuel in it and see if it does anything.

 

that’s just causing backfire out of the carb

 

First thing, not trying to beat up on you here - but don't roast your starter, solenoid relay, battery, etc trying to get it to fire. Starters have a duty cycle of 10 minute cooldown for 10 seconds of cranking. Something like that anyway! Nobody follows this, and that's why they are replacing starters in December.

Bring up the #1 piston to exact TDC on the compression stroke, not the exhaust stroke. Then check to see that the timing pointer is directly at the "0" TDC mark on the crank balancer. Then pull the distributor cap. The rotor should be pointing right at the #1 cap terminal location. Not #6. I would be almost sure that might be the problem.

It is also possible for an older outer crank balancer weight to slip, causing much head scratching because the timing marks are no longer aligned with the engine. This is why verifying that the #1 piston is at exact TDC on the compression stroke is important, and at the same time verifying the pointer aligns with the "0" mark on the crank balancer. Always measure, don't guess! If you drop the distributor in at this point, hold your tongue just right, and get the rotor aligned with the #1 terminal, it will start right up first time every time and run smoothly.

Even if everything is dropped in correctly, it doesn't take too much distributor housing movement to get way, way off the beam. Rotating the distributor about the width of a pencil line is equal to about 2° timing, so a 1/4" or 1/2" adjustment in the wrong direction - it either might not start (retarded too far) or (advanced too far) engine will kickback against the starter badly. Let us know what you find. Even if the engine won't start, you can use a timing light and set it correctly. The engine doesn't need to be running to set the initial timing. Or can "static time" it. Shoot for about 10 or 12 deg BTDC.

Hate to sound like a lecture, but I cringe when hearing people lean on a starter for 30 seconds at a time, it's like someone beating a puppy or something. Don't do this. We really need a Society For Prevention Of Cruelty To Old Fords.

 

If it's puking out the carb then your timing is messed
up. as tedster says you need to start from scratch and get it at least close then work from there.

 

oh I totally understand, I try not to beat on it to much considering I really want this to be a beautiful running to town rig, not just a rusty old farm truck. So, yesterday, that was the first thing I did when I tried to get it running, I pulled the distributor and moved the motor to TDC and Reinstalled the distributor. It was pointing at #1. Still nothing. I really don’t understand what the issue is here.

 

You have to be sure you're on TDC compression not exhaust. If you think you have it right move the distributor around and keep trying it. are you sure your plug wires are in the correct order and you have them set for the correct distributor rotation direction ?

Once you're convinced your timing is correct and you're sure you have enough fuel if it still won't run I'd swap the ECM assuming you have one. your symptoms are not exactly in line with a bad ECM but it's always something that's suspect.

 

If you are 200% certain you have spark, fuel and firing order is correct plus its backfiring out the carb it would seem something was overlooked during the timing setup or there is possible intermittent ignition problem. When you "moved motor to TDC" did you use the balancer marking as reference and assume correct for TDC or did you actually verify #1 piston was at top on compression stroke?
Verify integrity of wiring for the pickup coil in dist. Post a couple pics of your engine maybe someone will see something.

Was there any other work done besides what you mentioned?

 

I rotated the assembly with a wrench until I was aware that i was on the compression stroke. I actually verified the #1 was TDC by watching the valves and I used an old pushrod in the plug hole to make sure the piston was all the way up. The distributor is brand new. We’ve done a **** load to the engine. New pushrods, new gaskets on the top end, new distributor, new plug wires, new ICM, new ignition coil, new valve covers, cleaned the carb and gas lines, new fuel tank, smog delete, ETC. The reason I am where I am is because the back gasket on the valley pan under the intake blew out so I was leaking coolant. I replaced it about a week ago. It was running like a damn champ and ready to go otherwise. And the only thing I did was took the distributor and coil out, and the intake, replaced the valley pan, and reset the timing. Now the thing won’t start. Just turns over. Gas occasionally sprays out of the carb and it will occasionally backfire out of it.

I grounded a plug and I’m 100% sure it sparked. I undid my fuel line to the carb to be sure that fuel was coming out and it was spraying everywhere. The firing order has been triple checked.

 

I’ve already swapped the ICM, I did that the first time I got the truck running, a few months ago. It should be fine. I’m not sure what else it could be.

 

Another quick update, took the valve cover back off, along with the distributor cap to quadrupole check that I was at TDC. I noticed this behind the intake. There’s no smell to it. Not very viscous either. Not sure what it is, only guess is oil and coolant. So I guess the back seal is bad again on this valley pan? Not really sure.

 

You changed the valley pan/intake gasket because it was leaking coolant? Is it still leaking ? The intake manifold on a 351C/M 400 has no coolant passages. Possible bad head gasket?

 

You might check the voltage to your coil . wear spark might be the problem . an ECM can fail at any time for no reason. I'd swap the old one back just to eliminate that possibility.

Figure out for sure what the liquid is that will make it a lot easier to diagnose.

 

no it’s not the head gasket. From what I read it was the Windsor that didn’t have coolant passages and the modified did. I could be wrong on that but the head gaskets are in prime condition. I thought the valley pan and the intake gaskets are too but I assume it’s still leaking, I have more fluid buildup there. Again, no clue what it is. No smell to it, but I’m assuming it’s oil and coolant again by the look and viscosity.

 

If you decked the block and shaved the heads you may have to get your intake machined to match the new angle. normally it's not enough to prevent a seal up but since you seem to be having unusual problems maybe looking at extreme answers is in line.