Idle issue with 1000cfm 4150 carb

I have a pro systems 1000cfm 4150 carb basically is a worked holley hp style carb. The motor is a small block mopar 408 stroker, big solid roller camshaft with Indy 360-1 cnc heads and runs on pump gas. The truck doesn't want to idle on first fire up when engine cold. I have to keep it running with my foot for about the first minute of run time. Then it will idle but kinda low till it warms up then the idle rpm is about 1,100 in park. It is really fat at idle also. I don't remember what size my air bleeds are and will get that info when I get home. I do know the idle mixture screws are at 1 1/2 turns out. The cruise throttle and WOT are perfect and no issues there. I also know it ran best with a 6.5 power valve, had a 4.5 in it and it didn't like it. Rear power valve is blocked and jett spread is 84 front 94 rear. I just went through and cleaned the carb month ago before I put the motor together and have since blown out the air bleeds again to make sure they weren't plugged. I have always had this issue with this carb even with my old set-up with ported eddy heads and a .630" lift solid roller. I haven't put a wideband on it yet but I will be shortly and I also run #8 ngk race plugs as this is a nitrous motor.

what is the timing set at?

36*, also did it on old set-up at 38* I'm thinking one issue is I need to have it idle at 1,200-1,300 due to lack of low speed signal with the bigger venturi size.

i have 1 of those carbs on my 440 . Yep 2 half pumps and will normally fire up dead cold - but will have to hold idle to 900/1000 for about a minute , then will idle roughly till about 130deg eng temp .Will occasionally stall when air is cold when I have backed out of garage and then let idle .By the way mine idles around 900/950 in neutral
great carb though

Tex

Mine is JUST LIKE THIS! LOL! but I agree I dropped three tetnhs on my old set-up when I went from a 950 ultra hp to this pro systems 1000 carb doing nothing else.I do really like this carb and if i can figure out this idle issue it will be that much sweeter

Couple of things. I have one of those carbs, but its on a bigger engine, so you will have to bare with me.

Assuming you checked for vacuum leaks, and you obviously know your total timing, what is your idle timing at? Higher idle timing will drastically improve signal to the carb. I recommend 22-23° at idle if you can dial that in.

Two, #69 idle air bleeds and one turn out on the idle screws will get you more fuel. I run either #69 or #70 on all my Mopars....They like fuel at idle. Stock is #76....Too lean.

PS...That is the best performing carb I have ever had once I thru out all the jetting it came with and started over. I also went with out any power valves and square 94 jetting and got my idle better by 200rpm.....They say that means I have a vacuum leak, but I looked many times and could not find one. The car has gone 6.13 in the 1/8th geared for the 1/4 so far. I went with #28 HS bleeds from the #34's that it came with as well, but my engine is bigger...

Two people have made me multiple offers on that carb....Kinda weird cause I really don't want to sell it I picked up almost a full 1/10 in just the 60ft from a 1.40 to a 1.326 with mine.....deadly consistent.

Timing is locked out at 36*, I have checked for vacuum leaks and have none, I also have new carb gaskets and new nitrous plate and solenoids(Indutction Solutions sledgehammer plate) that were all sealed with liquid teflon sealer. I will check what my air bleeds are and let you know but I might try your suggestions after I get my wideband gauge on it.

The key thing on Holley type carbs is that the throttle blades need to be set at idle so that only a small portion of the transition slot is showing. Do not move the throttle blades once the position is correct! Changing the idle speed with the idle adjust screw is only okay for very minor adjustments.

If the engine needs more air at idle than it can get with the throttle blades in the correct location then you have to get the air from somewhere else. The newest carbs have idle air bypass the older carbs used holes drilled in the throttle blades.

The new Dominators use air bleeds in the top of the carb body that go directly to the intake manifold so you can change jet size to adjust the idle air bypass.

Never had an issue with my carb from Patrick. Had a 1050 on a 511. The idle was way better and overall performance was extremely better.
One question that I would ask is, was the carb built for you engine to start with?
Give Patrick a call his customer service is great. I would definitely buy another carb from him.

Yes ,
mine picked up over a BG825 mighty demon,20+RWHP. But street driving the 825 was nicer when cold , cleared the cold stumble off idle earlier .
I have , like you , put it down to big carb/venturi on a single plane intake . Was the same with a M1 and the current Victor .
A friends 440 with a 1050 Dom is similar . You can hear when pulling away cold there is a stumble till it gets a bit more air speed - fine when warm .
Keep with it ,Patrick said to me next carb will be a Dominator

Tex

Yes my carb was built for my old set-up then sent back to him for my new set-up and still does the same thing. Dealing with Patrick has been a pain for me as it is always"send it back to me and I will fix it" well that sucks. I will just try to fix it myself or deal with it till race season is over then i will send it in to him as I'm tired of waiting and paying shipping costs for an issue that has yet to be fixed!

Correction, I went with #27HS bleeds.......and 94 jets in all four corners. Mine also has the 50cc accel pumps on it instead of 30cc pumps...That is why the 60ft improved.

Mine also has dual 50cc pumps on it, I'm really thinking about going no power valve in front and square 94 jets on mine aswell.

thats what I would do, and check the transition slots like mentioned above

what should they be at? .040" exposed?

Doesn't say much for the company you got it from, if it was supposed to have been tuned for your car when you got it.

I start with about .020 .030 or square and go from there. If that has the 5 e holes with one plugged it's already jacked there plus the 45 squirters and on and on. Good carbs with the wrong peeps tunin em.

I agree, i also open the rear blades a little if I need more.

That can work but can also make idle and cruise rich.

I'm watching this thread, because I have the same thing going on with mine. I don't mess with it much but at some point I would like it to idle clean when good and warm

I've been reading this since I'm also running a P-S 1000HP on my 414 that was originally on my 517B. Mine isa 3 circuit primary plate and the small block needed just a slight amount of tuning to idle. It's a "typical cold natured Chrysler Product" as one of my old mentors used to always say, once it warms up it seems fine. I think I'm at 88/6.5 and 94/plugged F/R, I've wondered would there be any major benefit to plugging the primary and square jetting (since I'm Foot-braking at 3000 off the 2-step so I'm really just launching off the Back shooters anyway). I'm thinking since the PV is vacuum/load sensitive just square jetting it might be more consistent and may actually make a little more torque. Thoughts?

BTW... I have nothing but High praise for Patrick, I gave him my BB 517 to SB 414 parameter changes and he told me where to jet.

IMO, you can't have clean hot and cold idle without a choke. Cold engines like to be rich (choke on) until they warm up (choke off). I have the hot idle on my 950HP nice and clean and just deal with it being cantankerous when cold.

Idle gets better when warmed up but it is still too rich at idle when warmed up. Shoot I gotta go look at the air bleeds, be right back.

My jets are 84 front and 92 rear with #76 idle air bleeds and Hi speeds are #32

Here's how mine idles, bout as good as it gets for what it is, I reckon

https://www.youtube.com/watch?v=Fnv3UJB6xxk

Have you checked the throttle blade yet to see how much transfer slot is showing? You may be able to lean it out with IAB and mixture screws. If not you'll need to change the IFR's which will also change the cruise afrs.

The money I spent on my LM2 was well worth it.

I haven't yet, I will check it either tonight or saturday as I'm still finishing up on the interior right now and want to get it done before saturday afternoon.

I'm looking at the MTX wideband set-up

I have not had good luck dealing with him. Both of my carbs were way off, and I found him tough to deal with. This is why I decided to try a G3 Holly on my latest purchase. I will be getting that on the dyno soon, and I will take my SV1 with me, but it will be the G3 that wins I will bet....




Scrap the #76 idle bleeds and switch to #70's.......That is for chevy calibrations as they idle a lot leaner. Mopars need fuel at idle.

Me, I would remove the power valve and square it right up with 92's or 93's and then work the HS bleeds down a little towards #28's and see. Maybe go a #31 or #30 to start with after you have made a couple of runs squaring it up. Mine was much more responsive that way.

The 76 idle bleed is cos of a rich mixture and a 32 hi bleed is too big.

Got a suggestion where to start with the air bleeds?

Idle is too rich now, but I like the block off power valve in the front and run 94 square idea.

What size ifrs and how much t slot showin

Can somebody respond to my question of the benefits of square jetting/blocking the PV in terms of throttle response/consistency for a 3000 rpm/stutter 2-step launch on a 5000 stall converter. Am I likely to see any real difference (60' et improvement) since I'm essentially shooting off the rear pump shot anyway? I mean it seems logical to me (take the potential PV "flutter" out of the equation and truly equalize the A/F ratio from F/R) but want to get my head around the real reasoning or something I'm not considering. I know it's easy enough to try but before I do I want to hear other opinions....thanks!

The 1000HP 4150 carb was originally on a 508" street driven Big block where the PV was beneficial for cruising.

As I stated, I got a stronger signal and instantly better idle and throttle response, almost like it had a small vacuum leak, but I never found one and yet I checked many times. I do not trust the PV delivers fuel evenly with a nasty cam. With a street car, its probably a lot better, but when you have real duration and a real lack of vacuum signal I think its best to get rid of it. I have the best idle on this thing and yet my duration at 50 is over 300......

I run this carb on my 512 and the jetting and air bleeds posted above flat out works. I trap 110-111mph in the 1/8th with this thing. The way he sent it did not. And it took a while to sort it out, but its about as good as I think it will get and I want to focus on the SV1 a little.

i had the same problem with my engine when it was cold, it took a few minutes of foot assisted idle to keep it running til it was able to run by itself. one day i used a higher grade fuel. instantly it ran like a regular streeter. no foot assisted idle, could select a gear without it stalling, the engine ran real nice even in our winter, (no snow). my suggestion, use a better grade fuel.

Put #70's in for the idle air bleeds....start at 1 turn out on the idle screws.

I finally had a chance tonight after working on everyone elses car to mess with my R/T. I pulled off the carb and not touching anything from where I have had it. the transition slots have .020"-.030" showing on the primary and secondary throttle plates.

What is the IFRS?

It does this on my shell V-power 93 or VP 110 race gas, so it isn't a fuel issue.

Since I also do street driving would blocking the front PV be a bad idea for me?

Removing the pv on a street driver will cause over fuelling at lower rpm and cruise rpm . Some like to set dyno af ratio then fit pv and jet down some . I have thought to change air bleeds but never got there - slackarsed i guess . I am happy to accept a larger cam ,big carb and single plane will often lead to a rough low idle when dead cold .

Tex

I can live with a rough idle when cold, but too rich at idle when warm is an issue I would like to correct. Cruise and WOT on this carbv is awesome though.

Well I put the carb back on and decided I will double check my idle mixture screws. They were at 2 1/4 turn out, so yeah just cause you are sure doesn't mean you are... you know what I mean. So I have them at 1 1/2 turns out and will double check warm idle tomorrow, after some burnouts

don't worry about it, tuned right it's not an issue. ran plenty of non PV carbs on the street. as long as it's not fouling plugs you are good imo.

The idle mixture screws carry out farther in the rpms than most may think and with lowered ifrs they become even more sensative.

I'm 99% certain that if a Pro-Systems carb (with F and R idle screws as I presume most are) is correctly sized and calibrated for a motor combo, you shouldn't need anywhere near 2 1/2 turns out on the Idle screw. Check with PAtrick because mine only needs maybe 3/4-7/8 of a turn from bottomed out. He said if it cranks with 1 full turn its In the right range and turn them In until you get a stumble. They are much more sensitive than an oem calibrated Holley.

Cold start (or Especially if it hasn't been cranked in a while) I'll sometimes fatten it up a 1/8 turn and turn the idle screw a full turn for a few minutes, then I back it back down to normal and I'm good for the rest of the day, as said its a price unwilling to pay for a non choke racey motor combo. Once it's warm its 110%

So we went to opening day at Empire today....Ran my Engine builders 69 Barracuda with the 477 Hemi pump gas street motor. It has a .540 solid lifter cam and a RBRE single plane intake. Your basic 10:1 street hemi with a 4.15 stroke.

We put my 1000cfm 4150 on it and it fired right up....All with the settings above:

94 jets square, no power valves, 45 squirters front and rear, 50cc accel pumps front and rear, #70 air bleeds for idle, #27 hs bleeds....

Only made two passes...

Off the trailer she went 10.57 at 127.3mph....

Next pass 10.52 at 127.8mph with #28 hs bleeds was the only change. All that with a slower 1.48 60ft over the first pass. Track was off a little and we are not sure where to run the tire pressure yet.

Fires up the minute you touch the button, no input from your gas pedal needed, and runs just as awesome as it did on my 512...

Time between trails was really long, plus a swap meet so I only made two passes....And nothing broke.

I have a Prosystems 950 4150 that I bought from John at Induction Solutions, he used to work at Prosystems so he set it up for my 500" low deck street combo. It runs awesome, fires right up in any temperature and drives around town perfectly, I can stab the throttle at any speed or RPM and it's perfect.
With that said, I don't think there's any high performance carbureted combos that will fire up dead cold and idle perfectly, without a choke. I don't have a problem with taking a minute to feather the throttle a little til it's warmed up. If I'm really worried about it I just give the idle screw a half turn clockwise so it idles higher, after a minute or so I turn it back down and go cruisin. On my 69 Dart I rigged up a rod that ran from the idle screw to a knob on my dash, I could adjust the idle while sitting in the car.

I'd have to check my build sheet for the bleed sizes but my jets are 76 front with 6.5 power valve and 86 rear with no power valve.
Back when I raced I ran my carb square jetted with no power valves, always seemed to work a hair better on the track with a slightly better 60 foot.
On the street it was fine but was pretty choppy slowly pulling away from a stop. Sometimes if I was planning alot of weekend cruising I'd throw the power valve back in the front along with smaller jets, about 8 sizes smaller.

Well I ran it today and with the idle screws at 1 1/2turns it won't idle AT ALL! cold, warm, running after 10 minutes, doesn't matter I have to keep feathering the throttle to keep it running. Think I'm gonna try What Dragula said with the #70 air bleeds on the idle circuit and give it another try.

70 Idle bleeds work well in several gas applications.

Here's a pic of my ProSystems 950HP 4150 build sheet.
Idles mixture screws are 1 1/4 turns out, power valve in the front only. I have 2 light weight springs in my distributor, I even stretched them a little so my timing is pretty much locked out, idles around 30 degrees and goes to 34 total when I rev it.
Runs great on the street and idles nice in gear.

UPDATE;

I ended up going to #63 idle air bleeds in the front ans #55 idle air bleeds in the rear and 2 turns out on the idle mixture screws. The truck idles WAY! better now and it isn't rich at idle anymore. Cold start I still have to hold the throttle open some for it to idle but only ofr a minute then it idles fine on it own. I also have the idle at 1,200-1,100 in park or neutral and the timing at 38*.

good result
I did find this thought it may help - even if a little late

Tex

Way too rich...Please square them at #70....from 76 to 55 is a ton and not needed.

You made it more rich if you went from 76's to 63f and 55r rear.

It had #65's in it and I went down to #63's front and #55's rear. It idles the best it ever has and isn't rich at idle anymore as I'm not having to work the throttle to keep it running. Patrick had put #65's in it last time I sent it in for the same complaint. he says because I have such huge heads and carb on such small cubes the velocity at idle is very low. I need the carb though as this is a nitrous motor and runs its best times with this 1000 versus the 950hp i had on it.