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Running Issues with my 460.... keeps dying

2391 Views 7 Replies 6 Participants Last post by  kjett
Hi Gents,

I'll post up a proper log on my machine, but I need some help on the quick.

My 1975 Ranchero has had a transplanted 460 in it (probably an mid 70's lincoln motor). Whats happening is that it is dying after running around my neighborhood for roughly 20 minutes. First, I thought it was the Duraspark ignition, so I've replaced that with a 6AL box + Blaster 2 coil. This didn't remedy the situation. I also checked my timing and it's about 14° initial. I did notice it will move around a fair bit once set (every couple seconds it drops a couple of points...). Is this normal? Next, I thought maybe I was loosing fuel pressure, so I added a inline gauge and removed a filter that was mounted right before the pump. Then we figured it was running really hot and not properly circulating, so we changed the t-stat to a 180° one and checked for proper pump operation. This helped drop the underhood temps down a fair bit.

Now, when it's idling in the driveway, it's fine for 30-40 minutes, but underload, it will die after about 20 minutes of driving. I've checked the spark which is very fine, but it seems like the fuel pressure drops to 2.5 psi. After cooling off, it will jump back up to 7-8 psi and fire up. I have a feeling that this is fuel pump/carb related, but I'm not really sure. Thought about it being vapor lock, but since this is my first large V8/carb'd car I've had, I'm learning as I go.

This all started one day after driving out for a load of flooring in the city... but the day before I drove out to work, as well as to see a friend with no problems.

I know it's a novel, but I'm just trying to cover all that I did...

Thoughts? Advice? Any help is appreciated.
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I've checked this by simply removing the gas cap... but that doesn't seem to sort it out.
You said you removed the filter....was there any debris in it? Sounds like you might have pulled some debris (rust, dirt) from the tank and it might be floating around in the carb fuel bowl. Fine rust particles will run you crazy if they're in the carb. And an engine that is running lean WILL run hot.
You might check the fuel line routing, might be boiling the gas in the line.
Fuel pressure is fuel pressure. It has to be there or it won't work right. If it would run right on 2.5 psi that's what pumps would be built to run at. I'd change the pump as this is something you feel changed from one day to the next.

It would have been nice to see the inside of that fuel filter too.

Ok, back with an update...

So, anyway, after the last attempt, the carb was pooched.... so, in goes a new carb (Holley 750). Tuning wise, it's working well enough, decent enough throttle response, etc.

Anyhow, taking everyone's advise, I changed the filter setup (put it at the back, by the tank), and blew the lines out clean (100psi should do the trick). I also added a liquid filled pressure gauge to get a clearer reading.

Anyway, finally had a chance to take it out for a ride... first lap, all good, second lap, all good.... BUT i noticed that the pressure had dropped to 6.5 psi from 8-9 where it started at. So, I let it sit for about 5 minutes (chatting with neighbor....) I was about to head out .... and I noticed more heat coming from the engine bay... so I check it again.... 3 psi.

I think it's the fuel pump, or possibly the fuel lines, as they are rubber from tail to motor.... So, next step, fuel pump and fuel lines.... if that don't work... then I'm pulling and cleaning the tank/pickup... after THAT.... i'm kinda getting out of ideas...
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Ohh, get rid of those rubber lines! after a while they get soft and will sorf of suck themselves shut. Try to replace the whole line with a short piece of rubber from the tank to the new metal line then back to rubber to the regulator
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