Hello all,
I have a 72 nova with 28 inch tires, 3.73 gears, TH350 trans, and Freakshow 3000 stall.

The engine is a freshly rebuilt 383 stroker. All machined, brand new stroker forged internals, 30 over, zero deck, 6 inch rod Skip White internals with 10cc dished pistons. AFR 64cc 195 heads, 10.5:1 compression, Performer RPM AIR GAP, dual plane, and Comp Cams XR282HR 230/226@50 110LSA CAM. Headers. Break in in has been completed. No exhaust yet. Open headers for now.

I’m using a ln AED Holley 750 HP HOHP unit. No choke. I’m using the PCV on the rear of the carb. 1/2 inch plastic spacer. Carb is brand new. 4.5 PV.


The ignition is a Progression Ignition small cap unit. Timing is 24 at idle, 36 total. 10 vacuum advance but not at idle. The distributor functions as ported. It’s electronic and controlled via blue tooth, set to idle always at 24. It’s hooked to full vacuum but uses a MAP sensor and rpm sensor. It is boost referenced.

Carb pre set. I set the primary blades 1 turn out to show a .030 of the transition slots. I opened the secondaries one turn to simplify match the primaries. Held the carb up to the light to make sure. No transitions showing in the secondaries due to being higher up in the bores. Floats set perfect. Fuel pressure at 6 psi. 4 corner Idle mixtures set to 1 turn. 900 rpm idle. 11 hg of vacuum.

It’s idling very rich. Burns my eyes bad at idle. Can barely stand next to it when idling. Blackens the plugs with soot.

it won’t idle under 900.

Some have told me to run more idle timing. Some have told me to only run the secondary idle mixture screws out a 1/2 turn and do all the tuning with the primary mixture screws only. Fronts roughly 1-1/2 with rears at only 1/2.

AED told me to shut the secondaries and only use the primaries for idle. That caused the transfer slots to be .060 exposed and I needed almost 2 turns open to idle. The front idle mixture screws did not respond and the rears were very sensitive. Didn’t work, so I returned it to my original settings mentioned at the top.

IFR are .033 and idle air bleeds are .075

Any ideas where to go from here. Sorry so long. Thank you everyone.

lastly, I do have a secondary titan1500 BRPV, for low boost application (5 psi Procharger). However I’m only working on the non boosted basics for now.

 

Check the basics, firing order and vac leaks.

 

If idle mixture screws are not responding, float level is good, and t-slot exposure is not excessive, fuel is coming in somewhere else.
My quick test is to fill the bowls to operating level. Take the carb off. Holding it level , check that there is no fuel coming out anywhere. Dont tip it too much or fuel can come out the boosters. The base plate should be dry. If not trace the wet.
Ive had power valves leaking , bad gaskets, and a common thing where aftermarket metering blocks are used that have a lower ifr location and it gets uncovered by accel port on the gasket that most gaskets have on both sides and allows fuel to get into the vac adv port.

If the power valve is leaking, fuel will be coming out of the vac. ref. port that goes to the power valve.
Or if you take the metering block off and there is fuel in the mainbody where the power valve is then it leaking. That area should be dry.

Let me know what ya find or if you have questions.

 

Firing order

Thanks Ben. Went though and checked and double checked. Plugs, wires, routing, cap, rotor distributor is all new and properly routed.

fuel system is new with A750 fuel pump and regulator. 8an lines. 6PSI. Bowls set dead on.
Not seeing vacuum leaks. Idling pig rich. Burns my eyes and sticks up everything.

 

Initially when I installed the carb set up but AED or factory settings, the secondaries where closed. The engine would not idle, so I had to crank open the primary blades. This exposed the T slot like .070 just to idle. No control of the front idle mixture screws. The rear idle mixtures were super super sensitive. I stopped trying and reverted to a popular online method. Close the primary idle to expose the primary T slot only .030. Then open the secondary blade idle to simply match the front. Checked this by holding it up to the light. Both are the same with one turn curb idle screws each. The front mixture screws are all now responding at about 1 turn.

I checked under the carb like you said and I noticed that the gasket under the 1/2 spacer is saturated with gas. What could cause that?

 

A few other things:

I checked under the carb like you said and I noticed that the gasket under the 1/2 spacer is saturated with gas. What could cause that?

Im also running open headers as of now before I get my exhaust parts. Car still a work in progress.

Lastly, my secondary power valve is a Simple Stage BRPV. This will be a low boost procharged application. 5psi. This carb’s base plate did not come with the vacuum hole under the secondary power valve. It’s blocked. Could vacuum somehow gotten to the BRPV? It’s sealed tight.

 

Even if the pv's are open, that only adds to the main metering circuit, which shouldn't be drawing fuel at idle. You could plug one or both pv openings, just to see if it changes anything. Look at the boosters while it's idling, make sure they're not dripping, or adding fuel. Do you know that the timing pointer is accurate?

 

Checked the front PV and it’s good. The secondary PV plug gasket may have been leaking. I will double check the pointer.

 

I know this is an old thread, but I wanted to update it incase anyone has the same issue. Unresolved threads annoy me.

Worked my way down to .029 IFR’s on all four corners. .070 IAB’s on all four corners. All for idle mixture screws are at exactly 7/8. Idles at the highest RPM and highest vacuum at roughly 13.5 AFR. Transition is clean at 14.

I was surprised how small the IFR’s had to be on a 383. This AED came with .035 IFR’s. When I pinned them, they were actually .036. I even confirmed the pin with my good set of reliable calipers. Even .033 and .031 were too rich. This is a 383 stroker with 10.5 compression and AFR 195 heads.