72 Riv cuts out over 2500 rpm

**Larry R. McGee** · 08-19-2010, 11:12 AM

Hello and thanks for the read and any suggestions. I have a 72 Stage One Riv that drives and runs fine at slower speeds (estimated 2500 to 3000 rpm's). When running along at that speed and you accelerate, the engine starts cutting out. Here is what has been done to date. Installed a replaceent 1972 LeSabre gas tank, moved the filler neck, installed new fuel sending unit (2 line/ 3/8" fuel line), new rubber connection hoses, new 3/8" fuel line, new fuel pump (Airtex #40664 for Gran Sport Stage One), new fuel filter, rebuilt carburetor. I've switched between 2 rebuilt carbs with no change. I installed a Summit camshaft. lifters and valve springs. Electrically, new points, condenser, coil (all voltages are correct to the coil), plugs and wires. And still can't get it to run smootly at higher rpm's. Any one else have this experience and what you did to correct your problem? Or, do any of 455 experts have any thoughts on what direction I should take next? Again. thanks for any and all help. Llarry McGee

**henryj11** · 08-19-2010, 03:27 PM

First t hing I would do is scrap the points ignition for at least an H>E>I> distributor.If you do, make sure the wire to the "Bat" terminal is a full battery voltage ( at least 12 volts) as some point systems use a resistor wire to the coil from the ignition switch instead of a ballast resistor. Also is it cutting out completely or just breaking up badly. Breaking up could be a coil or points dying, or bad distributor shaft bushings letting the shaft wobble causing point bounce. It would be a real pain to do, but hook up a dwell meter using real long leads so you can check the dwell from the drivers seat. If the dwell goes crazy at the mentioned RPM, that could be thwe problem. If it cuts out completely, I've seen a broken wire to the points or coil inside the insulation cause it to cut out when the vacuum advanve works. Disconnect the vacuum advance to check this out. Also make sure the alternator is putting out and you're not running out of voltage at speed. These are about the only thing you havent checked. They may sound out of left field but I've seen each of these things happen. Let us know how it works out. If I think of anything else, I'll post them. Good Luck.

**henryj11** · 08-19-2010, 03:31 PM

I forgot one of the basics that ofter gets overlooked ( almost did it myself in the earlier post) check your total timing at about 3000 rpm. Too much will cause the same thing. Maybe try hooking up the vacuum advance to a manifold vacuum source ( vacuum at an idle ) or viceversa if it's already hooked up that way. Or maybe just unhook it and try it. Let me know how it works.

**WildKitty** · 08-19-2010, 06:52 PM

Try running it with the gas cap off - doesnt sound like much, but, perhaps it's creating a air lock in the gas line

Butch

**Bob** · 08-19-2010, 09:49 PM

You may also try running a vacuum gauge to check for a pluged exhaust system, or just open up the exhaust and go for a "burn"

**flashback1962** · 08-20-2010, 10:31 AM

if all these other fixes don't solve the problem,you may be getting some vapor lock.try wrapping tin foil around your feul line where it comes over the motor.