I have a 72 Cutlass originally with the 350 so no return fuel line. I've gotten my 455 broken in now and opened it up only to find that the engine surges above 3500RPM. Normal driving and it's fine. I hooked up a fuel pressure gauge at an idle it read 5-6psi. Even reving the motor it was still 5-6psi. So i took it for a test drive with the fuel pressure gauge hooked up and right after i floored it(from a roll) the pressure went to about 3psi. Mildly build 455 with quadrajet off an 80's truck. Stock fuel pump. Original fuel tank and lines except new rubber hoses including vent hoses. I probably need bigger rods/jets in the carb but didnt think it would cause surging.

Also i have problems filling it with gas. I can put about 15 gallons in and then I have to do it slowly for the other 5 gallons. Stopping and waiting on the fuel to go down the tube.

I pulled off the carcoal canister line that goes back to the standpipe and ran compressed air through it. I pushed gas out the filler tube. I ran compressed air down the fuel line and it shot gas back out the same end...til i opened the gas cap and depressurized it. Shouldn't the pressure vent to the charcoal canister? Is this a vent problem?

 

So I disconnected the charcoal canniser line to the tank. Didn't make a difference. Unhooked the right and left vent at the tank. Fell flat at 4 grand. Gonna disconnect the fuel line at the tank and pump and shoot compressed
air through it.

 

If it's surging under light throttle @ 3500 rpm, disconnect your vacuum advance. You may need to jet higher, and your float level may be low.

 

Light throttle its good. You don't think the fuel pressure is too low? I plan on jetting the Carb soon.

 

Fuel pressure @ 6-7 is perfect, dropping down to 3 if the bowl is filling is normal. Falling on it's face @4k could also be weak valves springs. Surging can be either fuel or excessive timing.

 

Could also be an exhaust restriction or an electrical problem, like leaky wires or a bad cap or condenser.

- Eric

 

Recommend disconnecting fuel tank and running via Wal Mart Red Can for a run to narrow down causes.

 

i have started working on my 64 dynamic 88 and am just fixing what needs to be done right now so i can drive it in and out of the garage with confidense. i have done the brakes valve covers purchased a new carb but the gas tank is full of dirt,rust and has a hole in it. i pached the hole with a screw and silicone for temp fix but need a new gas tank but can not find one yet, rock auto has supplied me with all the other parts but they do not have a gas tank and i'm looking for some one to point me in the right direction with this proplem. i am sure this will not be the last time either.
bruce-sc.

 

Bruce, I would place a parts wanted ad and start my own thread on this.

 

Oldcutlass:Valve springs have less than 1000 miles on them. Stiffer than stock springs although I dont remember the pressure. I blew out the fuel line from the tank to the pump. Also put in a bottle of octane booster with 91 octane fuel. I might try backing down the timing.

MDchanic: Exhaust is headers to 2 1/2 pipes turned down before rearend. How would I test for exhaust restriction? It's got new wires, cap, rotor on HEI and new plugs.

Koda i thought about doing that. Just thought it could be dangerous. I guess as long as everything is strapped down tight I'd be ok.

Also I pulled the secondary rods to see what they were. DP was the code and they seem to be the leanest rods available. Think it's just leaning out too much?

 

The main concern would be rodents making a nest inside a pipe.

Start 'er up, let her get warm, then have an assistant rev it up and feel the outlet of each pipe with your hand.
If one seems like it's blowing a lot less wind than the other, there's something in the way.

- Eric

 

I think it's probably time to find a chassis dyno and get it dialed in.

 

The best way to check for exhaust restrictions is with a vacuum gauge. Here is a link to a site that shows how to interpret the gauge.

http://www.secondchancegarage.com/public/186.cfm

Did you check your float level? If it is OK you can do a fuel delivery test to check out the fuel pump, tank and the line from the tank.

Disconnect the coil wire so the engine will not run.
Disconnect the fuel line at the carburetor and direct the output into a container with markings for ounces.
Crank engine until 2 ounces of gas is in the container to get full strokes of the fuel pump.
Continue cranking for 15 more strokes.
Measure the amount of gas in the container. You should have at least 8 ounces (initial 2 plus the amount from the 15 strokes.)

If you do not have enough gas, check for vacuum leaks in the input to the fuel pump, clogged lines or a weak fuel pump. If you have enough gas, check the ignition system for sufficient spark and timing.

 

I'm considering the dyno. How much money does something like that run?

I'll check the exhaust with a vacuum gauge tonight and a personal assistant.

The carb was recently rebuilt. But I could check it again.

Thanks Tomod I'll give this a try.

 

The cost varies, and they run specials for clubs and groups.

 

Does the HEI have a full 12v to it? They are notorious for dropping out between 4-4.5k without good components and especially without 12v to them.

 

HEI has 12v to it. I ran a 12v wire and pulled out the wire with the resistor or whatever it was.

I checked the exhaust with the vacuum gauge and my hand over the pipe. Exhaust is good.
I pulled the secondary rods out. They are DP 0.0686 S. I ordered CE 0.0410 M rods for it. I figured it needs rods anyway. 468, pocket ported E heads, 230@.050 cam, Headers, 9.7:1 compression. A friend of mine is convinced it's just running way too lean. We'll see.

 

So last night I stole the secondary rods and hanger out of my girlfriends 79 Trans Am. It had a one step richer hanger M and a CV 0.0527 L Rods. Test drove it and it ran about 75% better. I'm thinking with the CE rods will run better and I probably need to richen the primary side also. Hopefully I found a fix.
I also noticed the last time I filled up I was able to put 19 gal in then the last gallon was slow instead of the last 5 gallons going in slowly.

 

Just to add in to this. I removed the fuel filter in the carb...since i have an inline fuel filter also. Seems two fuel filters restricted the fuel flow too much. The richer rods make it run good up top.