Pro Systems Carb Users.

[jhv48]

I recently called Patrick at ProSystems and ordered a carb for spirited street use for my SPF with a Roush 427 SRTW.

The engine came with a Street Avenger 770 with vacuum secondaries and an electric choke. Needless to say, the car ran lean and had the normal slight stumble off idle that seems to be the norm with this carb.

I have the large headers and 3 inch inside diameter sidepipes to open up the breathing somewhat.

He recommended a Holley HP 950 with .45 squirters and 80 primary mains and 86 secondary mains. My Street Avenger had .37 squirters and 73/76 main jets. I have it installed and set up and it seems to be slightly rich based on the plugs but I'm wondering if the overall setup is too rich for my engine. Especially based on the difference in settings from one carb to another.

Was the Street Avenger that far off what this engine needs? And if so, why does Roush install it at the factory?

So, what specs did you guys end up with on your carbs and what size engines are you running. Just give me your engine size, carb size, squirter size, main jet sizes and your altitude please.

Just want to make sure this thing is not too much for my engine.

[cdnus]

I have a 408W, air gap manifold
I have a pro systems 950HP,76 pri.-86 sec. 45/45squirters, 50ccpri 30ccsec pumps. I am about 200ft. ASL
Those are what it came with. I have had to make quite a few changes to achieve as close to optimal performance for my application.
Note:
I was under the impression it was a 950cfm carb going by the model # & paper work when he sent it to me, but in fact Patrick later informed me it is a 830cfm. Don't know if yours is the same.

Craig

[Zoom This]

No matter who's carb you're using, 950 cfm seems awfully big for 427 ci. Unless you're running 93% + volumetric efficiency and spinning the motor in to the 7k rpm range I'd stick with a 750-850 cfm carb. So much better throttle response, torque and economy. I had an 850 Holley DP on my 418W for 2 years before I just gave up on trying to dial it in for street use. Went to a 650 Mighty Demon. Gave up 15 HP at the top end but made up for it with 19 lbs. of mid range torque and way better throttle response.

[209]

Hello Jim,
What number of Roush's 427 is yours? Mine is 795(rebuilt once) and it has the 770Holley vacuum with electric choke and mine is way rich at the bottom and nice at the mid and top. I haven't a clue what jets are where and what size. Cliff

[greg schroeder]

Originally Posted by jhv48

Was the Street Avenger that far off what this engine needs? And if so, why does Roush install it at the factory?

So, what specs did you guys end up with on your carbs and what size engines are you running. Just give me your engine size, carb size, squirter size, main jet sizes and your altitude please.

Just want to make sure this thing is not too much for my engine.

My engine was the 427R with single plane intake, TKO 600 .64 5th, 3.73 rear gear and usually 28 inch tall rear tires. I had the 1060 CFM mechanical secondary from Pro-Systems. Absolutly not too big for the engine I had. Out of the box with stock Superformance side pipes it hammered perfect. When I bought new 3" ID side pipes I went up 2 jet sizes all the way around for summer and 3 jet sizes all the way around for winter. I forgot the jet sizes, but they were in the 90s. The car hammered from just about any RPM or drove like a cream puff farting around too. There were zero street drivablity issues and power was like a light switch when desired.

Here's my air fuel, HP and TQ at the rear tires


You could drop down one jet size for both primaries and secondaries. You'll know if you're to lean if the top RPM of 3rd or 4th gear stumbles on hard acceleration before your rev limit.

Vacuum secondary carbs and dual plane intakes are are nice for heavy cars with auto transmisions and lug around rear gears. That Avenger 770 is sort of goofy for a stick shift 2450 lb car with driver in my opinion, but hey the Superformance dealer here talked me into one so I could find out it didn't work too.

[ACademic]

Originally Posted by greg schroeder

You'll know if you're to lean if the top RPM of 3rd or 4th gear stumbles on hard acceleration before your rev limit.

Good advice if you don't have access to a dyno or A/F meter. But in those gears at top end/WOT just make sure you have enough runway to work with.

[jhv48]

I've got engine number 808.

It sounds like I'm in the ballpark with his settings. I was afraid it would be a big dog with such a drastic difference between the Avenger and the HP. And yes, I think mine is an 830 HP with a 950 base????

It runs great so far, have been fiddling with the floats and air screws before I nail it through the gears. It also seems to want to percolate a bit after hot shut down so I am installing a phenolic spacer tomorrow. Then back to the test strip.

Keep the numbers coming. I need more reassurance I didn't end up with a road race carb.

[cdnus]

If yours is the same as mine it has a 750 main body with a 1&3/4" (looks like a Quick Fuel) throttle plate, with Patrick's tweaking ends up flowing about 830cfm.
The first carb he sent me looked the same but had a 1&11/16 throttle plate & flowed 800cfm.

Craig

[Karl Bebout]

Jim, you'll be hared pressed to find a better carb, specifically for your application than Pro Systems. Patrick really has his act together and has a great knowledge of setting up carbs.

[jhv48]

Thanks, I am resting easier today!

[351windsorsnake]

Why not talk to Patrick about your concerns,he will be better qualified to answer your questions,particularly as he supplied the carb and he has a good rep for after sales service

[Ant]

I am using a Pro Systems 950 on my 373 nascar based engine, this would be the nicest carb engine my dyno guy has come across his comments were it runs like an injected engine all through the rev range. This 600hp + engine pulls real hard from under 4000rpm with max torque at 5000rpm 530ft Ibs.

I was under the impression the road race 950 I have is based on a 750cfm base plate etc and can flow up to 950......!!!

[StanJ]

While technically, Pro Systems is a business competitor of ours (although our markets don't actually overlap all that much), the simple fact is that Patrick is on the money with his recommendation here. Holley's marketing department is far more responsible for the #80496 HP 950's claimed airflow capacity than anyone in their engineering department. It's sad these days just how many fuel system companies prefer to do their product development R&D with a word-processor rather than a flow bench and dyno. The 950 HP carbs share the 1.375" venturi diameter with the 750 cfm family of Holley 4150 series double pumpers (HP and otherwise), differing only in their 1.750" throttle bore diameter as opposed to the 750's 1.6875" TB diameter. In many applications, the 950 HP is in fact slightly more responsive than it's 750 HP sibling due to the main circuit coming online a bit quicker, making the carb less dependent on accelerator pump discharge...the main exception to this being applications that by nature really dependent on transfer slot length.

Anyway, we've also built many, many carburetors for street-driven 400+ cu. in. Windsor applications in the this general power range and when properly prepared and calibrated, the 1.375V/1.750TB "950 HP" platform is by far the best starting point in Holley's product line for these engines.

Stan Justus
Stallion Racing Components

[vector1]

i had a pro systems carb built for a 375ci engine and here is the sheet:

950hp main body--822cfm
p/s-pump 50/30
p/s-sqrtr 45/45
pri jet 78 sec jet 86
hi air 36
idle air p76 s73
idle feed 35p
pv feed 55
pv 6.5 plugged sec

it ran pretty rich and i couldn't do anything with it. if you compare it to a bg there is quite a bit of difference. i am using a bg carb on a similiar engine with a few adjustments and it works pretty good, it is an 850 cfm rr carb, probably flows 900+cfm.

[cdnus]

vector1
Identical to mine for a 408W-HP950--except

pri jet 76
pv feed 60

Craig

[vector1]

on the bg 850 carb, i ended up with 78p 86s mains on the 383 9-1 engine with dual plane intake 244/244.620 110. pvcr .070. afr wot in 5th pulling from 3g+ is 13.5 and could probably be fattened some but i think i need to check the other gears first.

[WardL]

I have the Roush 427 SRTW #460. I got the Cobra used and it came with a Bigs Performance Products 750 Stage 5 Carb. The primary jets are 75, secondary: 82, primary power valve is 4.5, there is no secondary power valve, the primary & secondary shooters are both 0.035, the idle feeds are 0.033, the idle bleed is 0.073 and the main bleed is 0.036. I wonder what all that means! I get about 13 MPG. The engine seems to run perfectly. I don't think it has ever stumbled. The original owner did not like the carb that came with the Roush. Made me wonder how could that be??

[RET_COP]

I have a 357ci 465hp, Patrick made me a 780mechanical sec. P/S pump 30/30, P/S Squirter 40/40 Jets 74/84
The primary throttle plates drilled 3/32.
I had a BG 650vs. I bolted this carb on and adjusted idle while balancing the primary and secondary throttle plate positions. Adjusted the idle mixture screws and done. The carb was spot and the car felt like a new animal.
Lou