Exhaust restriction or fuel problem?

[saffron]

OK.

My 65 coupe with a stock 289 misfires and then dies at higher RPMs while driving, especially over 55. It'll start back up and maybe misfire, maybe be fine in park, but once in gear, it'll give me hell until I get home. Here is what I have and have done:

New Edelbrack 500 cfm carb
New Carter fuel pump
New fuel filter
New PCV
Re-routed fuel lines from engine to reduce heat
Replaced fuel lines from pump to carb
Tried with and without fuel pressure regulator
Pertronix Ignitor ignition
New distributor cap and rotor
Tried with and without vacuum advance

None of this has helped. It does this hot or cold, day or night, every time. So I think I have one of two problems:

1) Not enough fuel (despite the new pump)
2) Exhaust restriction (despite new exhaust)

I know you can hook up a vacuum gauge to check for an exhaust problem. What will happen to the vacuum if there is a problem? Too low? Too high? As far as the fuel pressure goes, I know too little pressure will cause the engine to run dry. All I have is a vacuum gauge/fuel pressure gauge contraption. Can I use this? Will enough volume pump through despite the tiny line needed to hook up the gauge?

I plan on checking both late this weekend beginning with the vacuum test (because it smells funny when it breaks down). Any numbers or trends to look for would be greatly appreciated. I am dying to drive this thing, but its starting to make me really mad after four weeks and about a thousand bucks into it. Thanks much for any suggestions!

 

[65up2d8]

The obvious possible culprits are fuel system, timing, ignition, and/or exhaust. First, let's rule out exhaust, which would be highly unlikely, if not almost impossible, to cause the problems you are describing.

Second, this sounds like a likely fuel system problem. Have you changed the fuel tank? I suspect that you've clogged your fuel lines and/or filter from trash in the old tank and/or old fuel, which will varnish your fuel system.

Third, its possible, although unlikely, that you could be that far off on timing, although I strongly doubt it. Get a timing light and check your timing. If you're not sure how to do so, check plenty of earlier posts under the search function dealing with this subject.

Fourth, Ignition is also a strong possibility, although my guess is fuel system problems. Update to an electronic ignition setup if you have not already done so. Use a Pertronix setup, or, even better, an MSD setup. Regardless of the problem, this is a highly recommended upgrade.

P.S. sorry, I see you have already upgraded to an electronic ignition setup, which only confirms my thought that you're looking at a fuel system problem.

 

[saffron]

Just got back from the vacuum test. It ran better this time, but it still messed up. The vacuum was at 13 in. at 85 mph and about 15 at 65 mph. The vacuum stayed pretty steady until it died, so I guess I du have a fuel problem. I'll pull the line off tonight and check. Can I blow any debris out or do I need an air tank? I don't have access to one. Thanks for any replies!

 

[saffron]

Just a post for posterity...

It turns out there was too much rubber line between the tank and the steel line. Over time it must have crimped itself, especially when at high speeds and at heavy loads. Thanks a lot, though. Now if I could just get it a little cooler. How hot is too hot on the stock gauges anyway?