Carter carb tuning help

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scottymizt

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Hey guys i looked around and i need help. I am a fuel injection guy and this whole V8,4BBL carb thing is driving me nuts!!!!! I rebuilt the stock carter carb for my cuda and when i brought her home it ran great. Now it runs like crap basically seems much slower and i can feel it trying to pull harder under acceleration. To me it is a fuel issue, like not getting enough. I have checked the float levels and cleaned the carb again and i am having a heck of a time getting it pull like it use to. Anyone got ay ideas?
 
A couple of quick things that come to mind....is the choke coming off completely? You will see there is a secondary lockout tang in play when the choke is on,even a little bit. This will lockout the secondaries,so the carb will on be on 2 barrels ,even at full throttle. Check your accel.pump...make sure you are getting a full,steady shot out of the squirters. Its not carb,but,check your vacuum advance to make sure you're getting it all.

Just my thoughts...Hope it helps...
 
Thanks val i'll check the vac advance i know the 4bbls are working i seel the choke opening when just reving up. It is getting a steady stream of fuel out of the squirters. Is there any way to richen up the fuel mixture?
 
You can richen these carbs up by changing the rods that go into the jets.

I would want to check the mechcanical advance on the dist with a timing light -- need a total advance of aprox 32 degrees or so (excluding vacuum advance). At WOT, vacuum is close to zero and thus no vacuum advance on hard acell.

Most likely not an issue, but keep engine breathing in mind. Unrestrictive intake and exhaust are needed for good power. The problem started after the carb overhaul, so unless something has changed in the intake or exhaust, these are most likey fine -- but they are part of the picture.

Fuel pressure and volume are another thing to put on your check list.

Are you running points type ignition? They may have worn closed a little.

Is the carb the only thing that has changed?

Good luck.

Brian
 
I'm running the electronic conversion on the dist, the car ran great after the rebuild of the carb a while ago but now it runs crappy. Also i know this sounds bad but i don't know my exact timing. The timing mark is gone and i dont know how to remark it, the balancer was so rusty i lost the factory mark. I will check fuel pressure tonight and let you know what i find, I really appreciate the help guys. Like i said fuel injection i can figure out no prob but carbs are a little weird for me right now, but i will learn them...........oh yes i will learn them :evil2:
 
That is had more pull, would spin the tires in first just by stepping on the gas, would spin the tires alot more going into second. Wouldn't hesitate when i floor it in any gear.
 
Another quick thought....could the timing chain have skipped a tooth? If its old ,it's probably sloppy and the retarded cam timing will cause very slugish running.
 
Just checkin to see if it sat over a few moth period. Sometimes guys write what you have after it sits over the winter. Long wiat between runs is probably bad gas.
I'll assume yours has good gas.
Check for debrise in the carb/filter.
I like an o2 sensor to help tune.
Carbs fall in and out of tune easy because theres no self adjusting feature like FI has. Whats a good set up (Needle and rod combo) one day is garbage a month later. The extra or lack of heat and hunidity in the day throws it all off.
 
ok it did sit but i ran it as much as i could and it's a fresh rebuild so not much old on the engine, or anything that hasn't been gone trough. Gas is fresh i have been driving it as much as i can to get some miles on the engine.
 
Since you have no timing mark, I'd ajust the timing by the power tune or detonation method.

Warm the car up.
Be sure distributor is loose, but not so loose to move when the engine fires.
Hook up a diagnostic tachometer.
Rev the car to @ 2500 RPM.
Advance the timing until the engine JUST starts to run rough, then retard it back until it smooths out.
Let off the RPMS.
Tighten the distrubutor and drive it to see if there is any difference.

This is only something Ive done to eliminate detonation as a posibility for a car running crappy, but generally this is a good way to baseline the timing to what the fuel will handle, so that you can try other things.

Keep in mind that the fuels we run in everyday use are blended for the temperatures and weather anticipated. We are about to switch over to "winter blend" fuels, which will again affect tune.

Mark.
 
Thanks alot mark, that made a HUGE difference. I run 93 octane in the cuda and another thing i was wondering is if the hipo 273's use a different head gasket that the 2bbl 273? My compression is a bit low from what i gather. i am getting a consistant 135lbs on each cyl and the engine was just rebuilt so i know things are good. This is one of the best forums for info i have found and i really appreciate all the help guys.
scotty
 
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