Help with carb, and exhaust noise

My jeep has a chevy 327 in it. I rebuilt the carb which is a holley 4150 650 double pumper (I know! an off-road nightmare). It wouldnt stay running on its own after the rebuild, checked spark at the plugs and none to very small spark. put new wires on and same thing. Put new coil in and it will run on its own now but there is a sound coming from the passenger side exhaust. It kinda sounds like a hollow popping sound, like you unscrewed one of the plugs or something, sounds almost like a exhaust leak but isn't. Seems to not be missing though. It is slow returning to Idle rpm speed after you rev it up, and when shifting it, the rpms seem to stay up as well. The other issue im having is that my idle screws dont seem to be doing anything.. you can screw them all the way in and leave them and it makes no change in the engine.. could the carb not running on the idle circuit be causing my exhaust sound? Oh, the carb is hooked up to manifold vac.
how do I get the carb back on the right circuit? pics of what to do will be very helpful, new to working on carbs. Any Ideas?????? thx.

 

Just a guess here-A blown power valve on a Holley will cause very rich fuel mixture which will make the idle mixture screws do nothing. A rich mixture can also cause backfire & popping in the exhaust. If your carb is truly a double pumper (2 accelerator pumps & center hung floats) they are a good street carb but bad for off road use, You'd be better off with something else.

 

It has a new power valve, a 6.5. It is very rich though, thats how I discovered the screws not working, It will burn your eyes at times. It doesn't back fire, and sounds ok when you rev it up. My brother hears that hollow sound in the exhaust as well, at first I thought it might be just me. He said he wouldnl't worry about the sound but fix the carb.

 

Not sure that the sound and your carb troubles are related. Let's eliminate some variables. Is your cam stock or close to stock?

Not sure what you mean by this.

Also, do you know for certain if your idle circuit is/is not a "reverse idle" system.

 

If it's a double pumper it doesn't have a reverse idle circuit, those were used on emissions calibrated carbs.
JeepCJ-can you tell us the Holley list number of your carb (it's stamped in the front of the air horn)

 

Im not sure the exhaust and carb problems are related either. They are just the two issues im having right now. The cam is not stock, I have know idea what size it is. The motor is a 65 327, it has 69 camel hump heads I believe the last numbers were 462 on the heads. The PO used the jeep for sand drags at gravel romma. That is all I really know about the motor. The idle screws worked before I rebuilt it. The throttle shaft is worn and has some play in it. It had a bad vac leak at the carb base when I reinstalled it, which using the right gasket fixed. And this is where I am, at a loss. timing is set at 10 degrees btdc. point dwell is at 30. a/c delco r43 plugs gaped at .035, accel 8mm wires. primary jets in carb is 66, secondaries are 76. OH,, The ported and manifold vac im speaking of is the vac hook up on the carb for the vac advance.
from what I understand full vac runs off the carb base plate and draws full manifold vac. and ported vac runs off the front mettering block and pulls more vac at idle. ive read that older engines ran off full manifold and in the early 70's it switched to ported.. IDK.. The list NO. is 4777-2. under that it has 0462.

 

4777 is indeed a 650 double pumper. Should have a standard idle circuit.
It still sounds to me like a bad power valve-did you get any backfire through the carb? That'll wipe out the PV every time.
Also, make sure the little round gasket under the PV didn't slip out of place when you screwed it in.

 

Well it did pop a few times out the carb, but it wasnt very big. The rebuild kit came with two power valves for some reason, both 6.5. I will change it just to see what happens. Ok, I put in the other power valve and let it warm up, and it does the same thing. I have no affect with the idle screws, and idles rich. I did rev it up to about 2500 and held it there for a min and it sounds good and smooth, no misses or hesitation in the throttle. When I released the throttle it took it about 6,7 seconds for it to return to the idle rpm which is about 850 to 900. shut it off to let it cool and waiting to see whats next.

 

Since everything was fine (except for the vacuum leak) before you rebuilt the carb, I would tear it apart again. If you use some care the gaskets will come off fine. Take your time and be sure all the idle and off-idle circuits are clean and open.

 

thats where not knowing anything about carbs hurts me. this was my first rebuild. I dont know what the idle and off idle circuits are or what they look like. Maybe I should just save some money and buy a new carb.. After the rebuild I did take it back apart and found the wrong gasket on the primary metering block and all else looked good. If you can shine some light on the idle and off idle circuit and how to tell them apart, I will take a look for sure. Thanks

 

What are your plans for the Jeep? Honestly, that carb isn't the best choice for off roading, so if you plan to use the Jeep off-road, I'd just sell it & get something else. IMO a Holley Truck Avenger 670 would be a good choice for you.

 

yeah, my thoughts exactly.. It was set up to race. I plan on using it to run around in town and do the camping trip thing. Do some decent wheeling in it, nothing too extreme, but def some technical stuff. Ive been getting back to more of a daily driver for some time now. its pretty much ready, so I was hoping to just drive it the way it is on the street until I get it more suitable for off road. I would like some taller shock mounts, at least up front, new shocks, and make sure the clutch linkage won't bind when the frame is flexed before I venture out on the trails. back to saving money again.... It never ends.

 

I may have found the problem. I did a google search on it and read several posts, none added any further advise except one. He had all the same issues I am having all the way down to the slow return to idle speed after reving it up. He found that he had the wrong gasket between the body of the carb and the base plate. It was covering two holes that fed the idle circuit. So tomorrow or the next day I will take mine apart and see whats up. The kit I used had a couple dif carb body, base plate gaskets. I'll let you all know what I find. Thanks for all the help