Ok I'm kinda new to all this carb stuff but I just converted my tpi to carb have a 292 magnum cam from comp Vortec heads with a rpm air gap intake and a holley 750 hp my problem is its running way to rich damn exhaust pipes are getting hot enough that its burning the carpet under the passenger seat. Plugs are black as hell. I'm getting 8in of vacuum so I'm changing the pv from a #6.5 to a 4.5 but pretty sure that's not gonna solve all my issues. Just kinda looking for some advice

 

You can always adjust the Holley to squirt less gas. Holley has an amazing step-by-step on how to do this.

So your plugs are black but you are running very hot. This is probably due to your timing being very retarded. An excess of gas will actually help cool and engine but if the explosion is happening to late then the flame will travel through the exhaust and cause your situation.

Throw a timing light on and see where it is. I bet you'll find it to be very retarded.

 

I have adjusted it from 12 degrees all the way up to 20 didn't really notice a difference but I will adjust it after I put the new pv in

 

PV wont affect idle. That isn't your problem. Unhook the vacuum advance and plug it at the carb. Check your timing with the engine idle turned down as low as possible (may need a friend in the car to blip the throttle to keep it running). With that big of a cam and lower compression, you are going to need a ton of initial advance (16 to 20). Once you get that, you may need to limit your total (34 should be good for Vortec heads). Then, hook up the vacuum advance to MANIFOLD vacuum (not ported) and see what your total is at idle.

 

You also need to change the jets in your Holley, and may I ask if you changed the fuel pressure regulator to one for a carburator? Your Holley only needs 7 psi and your fuel injection had way nore than that.

 

+1 on the jet change and fuel pressure regulator.

 

Ok I will try that. And yes I have a holley regulator on it. I already have the vacuum advanced plugged off so when you say not ported what do you mean by that? Sorry I'm pretty new to this yet but I'm learning

 

Ok so your fuel pressure is correct. The next thing is to set the floats have you done that?

 

Jets wont affect idle either. You'll be chasing your tail. MOST carb problems are related to timing. Get the timing sorted out first and leave the Holley box stock for now. Read my post above and follow the suggestions. Ported vacuum is the one that doesn't see vacuum until the throttle starts to open. Manifold vacuum sees vacuum all of the time (your power brakes will be hooked to manifold vacuum too). Once you get enough ignition advance at idel, you can close up teh throttle blades to maintain a good idle speed. As it sits, idle screw is probably turned in so far just to get the engine to idle that it is uncovering the transition slot and pulling in WAY too much fuel.

 

Yea I set the floats.

 

So I got the timing set at 20 degrees and the exhaust is still getting really hot. Is there anything else that might be causing this issue?

 

I still have the stock cats on it also not sure if this will cause any issues?

 

Hot before the cats or the cats themselves?

 

what is the engine- 305? 350? stock bottom end? compression ratio?

there is no way in hell you'd ever get that car thru a smog check with the parts you've put on it - i don't know if that matters for you or not- so you might as well get rid of the cats since they are just dead weight now and do nothing but restrict airflow..

baseline everything.. Holley carbs are generally pretty close out of the box for an engine like yours, so put the carb back to factory specs- factory jets, factory power valve, factory float level, factory accelerator pump settings. set your fuel pressure regulator for 7psi with the engine idling. set the timing to 18 or so initial and hook the vacuum advance up to a port that has full manifold vacuum at idle. that is a pretty big cam and it's gonna want a lot of initial timing to compensate for the low signal to the carb at low speeds.. back the idle speed screw off as far as you can and still maintain a decent idle and adjust the mixture screws on the side of the metering block for maximum vacuum at the lowest steady idle speed you can maintain with the car in gear (if it's an auto). you might have a hell of a time getting a steady idle in gear if you've got the stock torque converter, and the car might be a slug if you've got less than about 3.73 gears.

 

The cats are getting hot so is the muffler. And its a 350 40 over bottom end is stock just had everything balanced I never changed anything on the carb besides checking the floats and adjusting the idle screws

 

If everything is getting that hot (is the CAT glowing?), I would assume there is a lot of unburnt fuel being drawn into the exhaust and combusting there. If the cat were plugged, I would think the Y-pipe would be very hot. This is my experience from working on daily driver type cars. I have never had a CAT on a performance car, but I could see a cam with lots of overlap playing havoc with the CAT.

 

I would start with what novaderrik said.
Also what torque converter do you have? Running a low stall converter will cause idle problems starting with a large rpm gap between park and drive among other things.
Also I would either remove or gut the stock cats. Running stock cats on that setup is not going to go very well. You can use aftermarket performance cats, but the engine needs to be properly tuned first.
One last thing I would do is double check your timing marks and make sure the balancer is correct with tdc.

 

I'm gonna cut the cats off. And its a 5 speed

 

What state & city are you in? Visual Inspection requires that the cat be there, even if there is no emissions test.

 

Minnesota. I'm not to worried about it

 

Timing is usually a huge cause of this. Your carb is also way big for your application unless you tailor it to suit your needs. You need to adjust the size of the power valve as well as jetting it down. 8" of vacuum is also very low you gotta look at raising your initial as well as tightening the gap in your butterfly's. I have a custom grind from comp mid 230 duration little over .480 lift and 108 LSA and I am making over 12" of vacuum with my mighty demon which is also big for my setup.