car ...'66 Barracuda Form. S
engine ... 273 commando..port/polished heads
dual H-pipe exhaust
4.10 rear - 26" tire height
edelbrock dual plane intake
holley 600 double pumper
model 4150/4160??? (no mods)
Lunati cam .515 /.525
PROBLEM - when revving the engine idling it has an initial hesitation. Even if I bring the rpms up to 2000rpms and rev it from there it still has a brief hesitation.

I've been running this setup for about 4000miles
Also new gas tank.....carb and fuel lines were airred out.

I also noticed today that the right exhaust tip is emitting warm/hot exhaust and the left side was emitting hot fumes.

Let the replies roll fellas..

273HYPO

What size jets and pump do you have in the carb?

There are so many things that this could be, you have to give us as much information as possible to get the real heavy hitters to solve your problem.

jets, power valves, squirter sizes, throttle cams, etc. Most likley one of these will jump out as a good starting point.

So lets see what you got.

It's a stock Holley 600cfm double pumper w/ a manual choke. I tried looking online to find out the jet sizes, squirters etc.. but couldn't find it. I even checked Holleys website. Any tips on how I can tell or find out?

I would suggest getting friendly with it and looking at what is exactly on your carb. Who knows what has been changed.

http://www.mopar1.us/carbs.html

Make sure that choke is all the way open. There is a good possibilty you need to simply up the jets at least 2 sizes front and rear. Try that and report back.

Look on the drivers side for numbers on the choke horn. See attached pic to get the idea.
Ron

""Okay, here are the numbers I found on the choke horn ..477B-7""

I think that your number may be 4778-7. If so than this is what I found:
4150 style, 700cfm, 69/78 jets, 6.5pv, .028 squirter.

Thanks alot!!!
May I ask where you found the info. to decode these numbers? The link I can go to for future reference?
BTW what does 6.5pv mean? 69/78 jets means the main jets up front are size 69 and the rear 78 or vice versa? I received the carb as a gift brand new and was told it was a 600cfm.

THX AGAIN, 273HYPO

I can help on the 6.5 pv. Thats the power valve. it opens when the vacuum in the engine goes below 6.5 inches of vacumm. When it opens it provides more fuel to the engine. The size is determined by your vacumm reading at idle. You divide your idle vacuum in half and that is generally the pv you should use.

when you start to move the throttle do you get an immediate stream of gas from the accel pump? & you might take out your sight plugs & check fuel level. What do your plugs look like?

700cfmDP too big for a worked 273? Just wondering.

Tom

Put bigger squirters in it, front and back. With that size carb on a 273, you might need to go up two sizes.

What do you mean by hesitation? Does the motor stall? Is this in gear from a stop? Do you mean the car stalls and then accelerates from a stop?

Is this an automatic and if so what size is the torque coverter?

Ok, I double checked my carb numbers and it is #4776-B = Holley 600cfm, mechanical secondaries & manual choke. Can someone give me the jet size, power valve, squirter and any other tech info.
I couldn't find it on Holley's website.

It is a 4 speed and the motor does not stall. When idling I'll rev the motor and does not instantaneously react to me depressing the gas pedal. It hesitates or delays for split second then revs correctly. It doesn't matter if I'm idling @ 800rpms or holding the revs @ 2500rpms and then depress the gas pedal to the floor.
When I'm driving and mashing the pedal from a cruising speed this delay/hesitation doesn't occur.
Float levels are fine...

273HYPO

""I double checked my carb numbers and it is #4776-B = Holley 600cfm""

I checked my list and it showed a 4776, then 4776-1 thru -7, but not a -B.
Maybe someone else can shed some light on this number.

Holley's website list the 4776 series as the 600cfm but only show a 4776-C & 4776-D.

Could I also have a timing issue. I had a friend adjust it about 1500miles ago. Can your timing change on its own? And what would cause it besides the timing chain snapping.

273HYPO

start with the basic stuff, check the float bowl level. adjust the idle mix screws for the highest vaccum. start at 1 1/2 turns out from bottom. see how much vaccum you can get. my quess is you will need a lower number power valve. and a little tweaking

Float levels are fine... I tried some tweaking with the pump lever spring but no difference.
I took her out for a test run and she was bogging @ WOT but if I backed off and she accelerates fine during normal acceleration. Then after 20minutes of driving she cuts out and shuts down on me. I drift off the side of the road and after a minute of scratching my head staring at the carb she restarted fine and I drove home w/o any issues. Prior to the test run I did add a octane booster that contained 'jet fuel'and she drove like an angry ape but then she began to act funny and sputter on hard acceleration. I think that was because of the oct. boost I later found out my friend got it at the dollar store...lololol

If I adjust the idle mix screws what vacuum number am I trying to achieve?

273HYPO

""If I adjust the idle mix screws what vacuum number am I trying to achieve?""

You are trying to achieve the highest vacuum reading at the N (since you have a 4 speed)rpm that you desire. If you want it to idle at 950rpms, than you adjust your mixture screws to get the highest vacuum at that rpm. As you get closer to the best vacuum number, your idle will increase, so you lower it back down and keep adjusting. Before you start the engine, count how many turns out each one of your mixture screws are set at. Then set them both to the same setting and hook up a vacuum gage so you can see it from the engine area. Then once the engine is warmed up and the choke full open, then turn one of the screws in or out (your choice) 1/4 turn and watch what the gage does. If the gage goes up then you know you are going in the right direction, if it goes down, then turn it back 1/4 turn to where you started and then go 1/4 turn the opposite direction. Once you know which direction you need to turn the screws, then wait 30 seconds or so before making another adjustment. Go to the other screw and do the same adjustment. You have to keep going back and fourth until you get the best vacuum reading and keep readjusting the idle rpms back down as needed. As you are adjusting each side, you will get to a point where you can only adjust each screw by 1/8 of a turn or so to keep the highest reading, then you may need to adjust them even less to maybe a 1/16 of a turn to get the best vacuum at your idle rpms. Don't be afraid to take your time and do this back and fourth for a while. Once you take the time to do it right, then you should have your highest reading and maybe a steady vacuum reading pending on your setup. Then you figure out what power valve to run by dividing this number in half to start with.