newly rebuilt engine, trying to figure out surging issue...

scrible88

Well I just finished rebuilding my 1988 AMC 360. Rebuilt to stock other than comp 268h cam and lifter kit, full dual exhaust, edelbrock performer intake and edelbrock 750 carb with a TFI ignition setup. It runs like a charm for the most part. Amazing lopey idle at about 600rpm, 1st gear (t176 in a 1981 Jeep CJ-5 with 33's and 2.73 gears) has tons of power all the way up to 5,000rpm but I haven't taken it higher than that. 2nd gear pulls real hard too up until about 3500-4000rpm where it starts surging. It acts like it isn't getting fuel at that point, the jeep will start jumping back and forth real hard when I have my foot to the floor. The motor before the rebuild never had that problem with the same carb, intake, and exhaust. The TFI setup is new. It has a brand new stock replacement mechanical fuel pump. Fuel filter is brand new along with plugs, wires, etc. The plugs are gapped to .40 I have had some heat issues. It currently runs between 200 and 210 degrees in this oklahoma heat. It does not help that the Jeep is black. I have a 304 CJ 3 core radiator. Also I am using a 160 degree thermostat. Timing is at 12 degrees and I am running 87 octane pump gas. There is no popping or pinging or anything like that just this annoying "surging" I want to get rid of. I am currently stuck on what I should do. Could the stock mechanical pump not flow well enough for this setup? Adjusting the timing does not affect it. I thought that heat may be an issue with the high voltage coil so I relocated it to a fenderwell far away from any heat source and it didn't help. The carb shouldn't be getting too hot I have a thick nearly half inch spacer between the carb and intake made out of some kind of hard rubber that was great on the old setup and kept the carb nice and cool. This is the first time I've run the 360 in summer weather... last time the motor was in the jeep running it would be at about 180-200 degrees depending on how hard I was driving it in 50-60 degree weather. Any ideas? I am stuck for the most part. I am no master mechanic at all but I can figure most stuff out and this "surging" like it is not getting fuel constantly just boggles my mind. It is almost the same effect as when you first begin running out of gas in the tank. One more thing, it isn't vapor locking... the fuel line is well away from any heat sources. What should I try next? Help! 111!!!

dwg86

My guess would be not enough fuel. Maybe try a new mechanical pump, or a good electric pump. I use a gerotor electric pump on my jeep with a hidden toggle switch to turn it off/on. That was the only thing that kept it from getting stollen a few years ago. They couldn't get far without fuel.

1980_Cj7

Could it be an ignition problem? I would be suspicious, since that seems to be the only thing that was different from when it was last running.

AMX69PHATTY

Surging and high engine temps are both symptoms of a lean condition. May want to richen up the carb and also try a hotter 195* T-stat. A "too cold" T-stat can cause overheating as it never closes. Is it a Manual or Electric Choke Edelbrock Carb ? Electric choke models are jetted and tuned much leaner than manual choke models.

scrible88

It is an electric choke carb. Should I richen it up using the screws on the front of the carb? How should I go about doing that? It is set to factory specs Also, what is a good brand aftermarket AMC mechanical fuel pump? I don't really want to mess with an electric pump.

1980_Cj7

scrible88 wrote
It is an electric choke carb. Should I richen it up using the screws on the front of the carb? How should I go about doing that? It is set to factory specs

Also, what is a good brand aftermarket AMC mechanical fuel pump? I don't really want to mess with an electric pump.

If it's an Edelbrock Performer carb, they are set up so you can very easily change the jets, metering rods, and springs, with out even taking the carb off the engine. Just be very careful you don't drop any little parts down the carb of course. That's the way to change the fuel mixture. The screws on the front of the carb are just for the idle circuit.

You can get a kit with various size metering rods, jets, springs, squirter nozzles, etc. for the Performer from Summit for sure, and probably lots of other places too. The Performer has a great book with it on how to tune it, including charts showing what combinations to use to achieve different stages of lean or rich.

mika01

This is great info as I have the exact same problem. Only I have a 650 Edy on a 360.

scrible88

mika01 wrote
This is great info as I have the exact same problem. Only I have a 650 Edy on a 360.

Are you using the stock mechanical pump?

jeepsr4ever

Alot of times surges can be a symptom of a leak somewhere in the intake area. A vaccum line or fitting being open or a bad carb gasket.

mika01

scrible88 wrote
mika01 wrote
This is great info as I have the exact same problem. Only I have a 650 Edy on a 360.

Are you using the stock mechanical pump?

Yes the stock mechanical pump. I think my problem might be vapor lock though. Dual exhausts and even the frame rails get real hot, but engine temps stay around 180-210 range.

AMX69PHATTY

Summit or Jegs has Carter M6906 Hi-Perf AMC Fuel Pump ~$70

RobbMc sells an even better one

http://www.robbmcperformance.com/products/amc550.html

mika01

jeepsr4ever wrote
Alot of times surges can be a symptom of a leak somewhere in the intake area. A vaccum line or fitting being open or a bad carb gasket.

Kind of funny you should mention that as it's burning coolant at the moment, intake manifold leak somewhere!

scrible88

mika01 wrote
jeepsr4ever wrote
Alot of times surges can be a symptom of a leak somewhere in the intake area. A vaccum line or fitting being open or a bad carb gasket.

Kind of funny you should mention that as it's burning coolant at the moment, intake manifold leak somewhere!

well mine isn't burning any coolant, intake gasket is new, sealed up properly, nice and tight... doesn't smoke or anything...

brucel

Sometimes they suck vacuum on the underside of the intake - sounds like its time to pull it and see if it has been leaking.

tarior

What color are the tips of your plugs? I'd start with the easy stuff, and work up to pulling the intake. The 401 in my Rebel was surging while cruising, turned out to be a crack in the line going to the PCV. Check it out, my 666th post. Satan!!