Hello!

So I bought a 4 barrel intake for my 1972 F250 with the 390. It's the cast iron s code intake from somewhere in the 60s. Stupidly heavy thing. Anyways.

I pulled off the old intake, cleaned up all the surfaces and then installed the new intake gaskets with RTV around ports for water and rtv on the cork gaskets for the bottom of the intake. I'm pretty darn sure I did it all right. I can't manage to get it to start unless it's at a fairly high RPM (above 1200rpm ish) and keep running. It will just start and run for 2 seconds and then die if I try to get it to idle. It is fairly cold here but the choke is closed and it's definitely getting gas. I just rebuilt the carburetor (it's an old ford 4160) and put on a 1" spacer to replace the heated spacer it had before with the 2 barrel.

I already flipped the distributor 180 to see what would happen before I was able to get it to run at all, and that's gotten me to where I am now. It runs like crap and if I keep advancing it, it starts shooting fireballs out of the top of the carburetor and halting while it's starting.

Is this a massive vacuum leak issue? Is it possible that I did something wrong with the intake and it's leaking from that? Or perhaps I did something wrong with the carburator when I rebuilt it. It was my first time rebuilding one. Float level looks good though and the idle needles are only out two turns. One of my friends mentioned that these engines can run with the distributor 180 out but they run like garbage? Could it be that also?

I can't get it to run for long enough without basically flooring it to get a vacuum guage on it so I really don't have a clue. I don't have a timing light either, I'm broke. Wish I did.

Thank you for any help

 

Pull #1 spark plug. Bring the #1 piston up to TDC on the compression stroke. Not exhaust stroke. Are you certain the balancer hasn't slipped, and the "0" mark is accurate for TDC? Defective balancer doesn't help matters.

With #1 piston at TDC compression, the distributor rotor should line up with the #1 plug wire distributor terminal. Or where it would be, if you didn't have to take the cap off to look. It's easy to stab a distributor off from where it's supposed to be. Now what you could do, is move the spark plug wires around clockwise or counterclockwise as required, making a new #1 terminal at whatever point the rotor is pointing. The distributor doesn't care, so long as the plugs are in correct firing order.

If everything is copacetic, plug wires in their proper order, what you can do to get ignition timing close (assuming balancer markings are accurate, see above) is set the timing pointer and mark at 10 or 12 deg. BTDC on the damper. Maybe pull the coil wire and set it close to a ground. Turn the ignition to RUN. Loosen the distributor hold down bolt and move the distributor housing slowly back and forth till the coil fires. That exact spot is where to lock it down. That should get it more than close enough to fire with timing pretty close.

 

If you’re going to tune your truck, you need to have a timing light. I’ve got an extra one the you’re welcome to have. Send me a private message with your address and I’ll mail it to you on Monday.

 

Definitely start with what Tedster9 said. If you're still having to rev it to keep running, you very well may have a vacuum leak. You're about the only person I've ever heard of using the cork gaskets. Most just lay down a bead of rtv on each china wall. They could be holding up the intake...maybe.

If you have a way to check angles, probably want to check to see if the intake mating surfaces match up to the heads mating surfaces. Not unheard of for these angles to be out of whack.

Need to find a timing light...hope you can borrow one...it's kind of important. If you absolutely can't find one, I guess you can advance it until it pings under heavy throttle and then back off until it quits. Definitely check where the pointer is with #1 cylinder at TDC, like Tedster9 said...pulley may be shot and slipped.

Edit...if resonateur is able to send a light, might want to find a way to express thanks.

 

I'm fairly certain the balancer has slipped because I can't remember being able to get it even close with a timing light the last time I borrowed one. Then again I think I was also having ignition issues at the time so I'll see if I can borrow another one or see about that extra.

I can give it a try removing the cork gaskets. The intake looks pretty settled to the naked eye. I'll see about a closer look on the morning.

I never thought of using the coil wire like that. That's a great idea! Thank you.

 

I'll guess I will have to find a way to express thanks. I had one but it was borrowed and "lost". College just started and all of my money went with it.


I sure will let you know. If I haven't figured it out Sunday I will send you my address. Thank you so much.

 

Is there any way I can rule out the carburetor as the issue? Since it does start I just want to make sure me rebuilding it didn't mess it up to cause all this.

 

It sounds like the distributor is way off to me. Did you stab it in at TDC #1? That's easiest, basically. Did the rotor line up with #1 on the cap? If not, or you believe maybe the balancer has slipped, how did you know where to install it?

Verify TDC on the balancer with a piston stop tool. TDC mark accuracy on the balancer is very important, as all ignition timing and valve timing is based on this.

 

I poked a pencil through the spark plug hole and make sure piston #1 was at tdc and then moved the dizzy accordingly and advanced it a smidge.

 

Right, I'm sure you know this, but there are two TDC events, both the compression stroke and the exhaust stroke, this is a pretty common mistake to stab the distributor out. Add a slipped balancer ring into the mix and the difuculation factor increases quite a bit. It could be a carb problem, but...

If you can get it to idle, use the vacuum gauge and rotate the distributor housing for maximum steady vacuum. At sea level this should be around 18" to 20" on a stock engine. That should be very close to correct timing till you can get a light on it.

It's a good idea to verify true TDC on any engine and bounce that off the marks on the balancer. This is important to know that it is accurate. A piston stop tool is only a few bucks. A long 18 mm bolt would work too. When you know for sure TDC indicated on the balancer really is TDC, and the distributor is dropped/stabbed correctly, engine will always start right up and timing will be fine, like nothing ever happened.

Well ... unless you leave the rotor sitting on the workbench. *cough*

 

You can make a piston stop by knocking out the insides of an old spark plug then either threading it on the inside or weld a nut to it so that a threaded stud will contact the piston.
I vote for the “slipped balancer” as the possible problem. I first encountered that 50 years ago on the 390 rebuild for my 64 XL.

 

Stop right there! I tried that for about 2 minutes, and decided it wasn't worth saving 8 bucks for a piston stop tool. That ceramic &$@t is really tough. A long 18mm bolt would work too, maybe hardware store stocks these.

 

That ceramic is pretty hard but it can be done. You may have to go to a bolt supply warehouse depending on how much the local hardware store carries.

 

So I put a rubber glove on a compression tester hose and found TDC (balancer was indeed off) and marked the balancer with a paint pen for now. I popped the wire off the coil and moved the distributor to make sure it sparked on cylinder #1. I just bumped it a little to advance it then tried to start it. The exact same thing is still happening.

It will run at 2000 rpm and then just give up living and drop down. The intake is for sure properly seated. As a last ditch effort I'll remove the cork and tighten it down again if it comes to it.

This has got to be a vacuum leak, right? I can't get the engine to run long enough for me to sprint over and spray everything with WD-40. It's either 2000rpm or not running.

The coil had minor white corrosion over it when I reinstalled it but I wiped it all off. I don't think this is a coil issue but is it a possibility that it just quits?

I do have a spacer on the carb and a few weird pipe fittings I scavanged from home Depot to adapt my original fittings to the intake. None of those look like they could leak that bad though. This sounds like there should just be a gaping hole in the engine.

 

Just a slight turn of the distributor makes big changes in the ignition timing. Maybe the width of a pencil line on the housing, might be 2°? So if a distributor is stabbed off a little bit, it will never run, or run very poorly at best. An inch or two rotation one way or another past spec is WAY off.

Finding exact TDC is an exercise in precision, a balloon will tell you if you're on the compression stroke, but how can it find exact TDC? Maybe, I guess. Never tried it. With a timing light, and known good TDC mark, can set the initial timing without it actually running, and not have to guess. Or see earlier post about using manifold vacuum to set timing with vacuum gauge.