I've been doing some tuning on the Pro Systems 1200 Dom on my 572 Hemi. I have analog dual wideband gauges, one in each collector. Both read almost identically bank to bank when warmed up.

I have it close to where want it atm, with idle in the mid 15s warmed up (runs awesome/clean with low load) and at cruise in the mid to hi 14s. The engine runs beautifully, no surging at cruise, off idle tip in is great. Idle is at 1100 rpm in gear, with just a small square showing on both PRI and SEC transfer slots thanks to the locked out timing and the 112LSA.

The car has a full exhaust 3.5" into 3" after the X pipe and over the rear end. I'm running NGK BP6ES plugs - they look really good; the whole base ring of the plug has a full circle of dark brown colour. The timing is locked out at 32, the timing mark on the ground strap is pretty close to where it needs to be and the plugs are pretty close to where I want them on the street. Fuel is pump gas 98 here.

Punching the throttle puts me into the hi 10s; mid 11s after the initial pump shot wears off.

Engine made great power on the dyno with open headers/more jet/same PV so I'm a little on the leaner side of the tune now that its on the street with a full exhaust/mufflers etc.

Current tune is as follows :

Idle AB: 57
Inter air: 77
Inter fuel: 40
Main air: 37
PRI jet: 88
SEC jet: 92
PV: 5.5
PV feed/jet: 86


I'd like to dial WOT a bit better and of course I'm thinking on possibly leaning out the PCVR jets in the metering block a tad. The question is by how much and how will it affect the mains ?

I have'nt touched the Intermediate fuel jets in the metering block as the carb has responded well to the IAB/jetting changes to get me to this point.

Any thoughts as to the best way to get the WOT number into line ?

Thanx !

Good job. You have a 3 circuit street tuned that good. I'm real close with my 2 circuit, but would like to get where your at. What did ya use for IFR? Just curious

Dave the IFR is 35

Thank for posting

I'd convert it to a 2 in a second and have it cleaner n meaner yet.......They ALL respond better and are faster as long as the carbs big enuff for the application and my baby 470 BB wears a billet 1250+ and has the flattest fuel curve I've ever seen..........Smaller carb on bigger motor has a tendency to go rich because of the Hugh draw of air that the bigger motor demands.............

I would try leaning down both the primary and secondary jet size by two smaller It looks like to me that is the only part on this carb. that needs attention now
I don't like your choice on the spark plug heat range, I would try a # seven, but your using better gas than we have here in the states
I like to see between 12.0 to 13.3 at WOT here where we live(3500+ Ft elevation) on the pump gas we have in my wedge motors that make north of 650 HP

Don't forget a/f reading is not exact but a tool

My jetting on my 1250 looks nothing like yours...But mine is now a 2-circuit thanks to Thumper...Runs pretty good. A little lean at cruise with a forward facing scoop. Other than that, I like it.

92/101
71 IAB
27 HSB
#45 Squirters
PV I forget what I have in there

interesting that when the DA is below 800 I can't throw enough jet at my carb without it going into lean misfire. I considered the 4825 on my "small block" (439) fairly under carbed. Also running power valves. With 84 jets in Vegas I recorded afr on the left bank in the high 11's. At Famoso with 98 square I was at 14.6 with a DA of 800+. Sunday morning it was -800 when we set up, and around 100-200 when I made the pass which resulted in a lean misfire.

ok, thanks

I used my power valves for fishing sinkers 40 years ago and haven’t used one since

LOL ^

Cab my thought was this initially ie: pull some PRI and SEC jetting but wont that only affect the mains?

Yes AFRs are nothing but a guide - Im giving it what it likes ie in the 14s-15s at idle and cruise and still no surge and runs super clean. I could prob go a tad leaner as well but decided to leave it there for idle, transition and cruise.

PV tuning is for WOT right? My understanding was that if you have an 88 PRI jet, then the PV jets n the metering block should be in the order of around half of what your PRI jet is, in order to provide approx 25% of the extra fuel at WOT.

As mine are at 86 now, that would mean that they are way too big and allowing too much fuel at WOT which would explain the readings. That, plus the Intermediate circuit (which would still add fuel at WOT) would explain my numbers at that point in the curve ?

What do you think? Im about to grab some 6-32 and 8-2 brass blanks

Where's the misfire at rpm wise and if the problem is down low then what idle bleeds, ifr's and where are the mixture screws set at from seated if up top what hi bleeds
.............

if it were me I would adjust the PVCR down to get your wide open air fuel where you want it. If you are happy with everything else that is. When I did my 830 I was happy with the wide open AFR so I took the area of all the fuel flow orifices and wrote it down, I then took main jet and IFR out of it until I was happy with low rpm and cruise AFR, then I stuck that flow area back in via the power valve channel. I was happy with the results it was just a beat down to get there.

The header says 1250, the first line says 1200, which is it? A PS 1200 is an 1150, not a 1250.

Sorry for the typo - its a 1200

You can do it any way you like, on the PVRC go easy at first, not huge I would try .003 to .005 smaller in I.D. to start with
The primary main jets affect the light part throttle cruise AFR as well as at WOT, the secondary main jets affect WOT only, usually

Thanks Cab - Ive ordered some 6-32 screws and a tap.

Anyone else have any suggestions from experience ?

Thanks Cab - Ive ordered some 6-32 screws and a tap.

Anyone else have any suggestions / input ?