Technical BIG 97 Stromberg help

I just installed 3-BIG97's on a SBC, 355" with AFR heads, 525 lift retro roller cam.
*** this main carb is running so rich it will barley run, I've messaged Uncle Max and Clive (no response yet), I want some0ne to talk to not this message crap, there is no-one in USA I can find for technical help.
****I;ve lowered float-tried different timing-fuel pressure is 1.5psi-checked for vacuum leak, in 10 minutes the plugs are coated with soot black, you can see from headers how rich it is, adjusted A/F screws but still have spitting coming from the passenger side emulsion tube, anyone have a referral I would be very appreciate it, I did not know there was NO technical support for these Stromberg's, I had speedway knock offs 9super7's had not problems, just needed more CFM, Thanks again.

***I can't e-mail Stromberg in ENGLAND can only use Gmail.

 

What’s the choke position?

Where is your throttle butterfly at idle in relation to the 2 idle discharge holes? With the choke off only the lower one should be in use.

PS why can’t you email England?

PPS I’m thinking that of the choke is closed you’ve got the butterfly open far enough that you’ve uncovered the 2nd hole.

 

Thanks Tim, I only see 1 hole when looking down carb, throttle plate is almost closed, have idle as low as I can.

 

You're running progressive linkage, yes?

 

Not my idea then.

 

yes, I unhooked the secondaries today, my headers after 10 minutes

 

That is drinking fuel! Do you know what jets you are running in the center carb? So, with the "SpeedBerg" carbs you were running, this rich run condition was not happening? No other changes than the carbs?

 

056 jets (came in main carb), no with speedways repops it didn't run anything like this-plugs were a little dark but not a problem, I can't even drive this like this, I'm trying to find what to do....ran down the road with no A/F thinking they were choking carbs, ran terrible (rich), Thanks for responding Billy, and I did open ports up on intake like stromberg says

 

Billy I might be wrong but the jets should not matter at idle...

 

Is the needle valve working properly ?

 

there is no needle and seat, grose ball valve.

 

I had exactly the same issue. When I fired up the new engine my o2 sensors were reading in the low 10's, I have one in each pipe. I tried everything including putting block off plates on the end carbs. They still poured fuel until I disconnected the fuel lines, told this was normal? I was told it was running rich because of the cam. I went as far as 46 jets in the center and 51's in the secondary's. Every time I pulled a carb the intake was drenched in fuel. I even changed cams with no luck. I probably have more jets than Summit . They ended up washing my cylinders on new engine. After 3 years and not many miles I gave up and went from 3x2's to 2x4's (Holley 450's), figured if I couldn't tune 6 lets try 8 , all on tunnel rams. I even re-installed the original cam and re-rung the engine. As a side note the pair of 450's were so close out of the box all I've done is increase the size of the idle feed restrictors and change the pump cams as they were lean down low as where the Strombergs were so fat every where. I did have plenty of emails back and forth with Clive so support was good, just didn't resolve the issue.

 

Well is that working then?
In other words is it flooding out when running and float not doing it's thing.

Also is the float actually floating.

 

Thanks, who said it was the cam? shit all mild builds have a cam about like mine, it's not radical at all, I'm getting not much help-hoping I didn't waste $2500. the china knockoffs ran pretty decent. were you useing the new BIG 97's ? They advertize that they made this setup just for the mild built SBC & SBF....

 

Clive

 

well if thats true then Clive should put in advertising that they are only for stock cams....I'm sure hoping that's not the case !!!!!!!!!

 

The float appears to be working? I lowered it a little just in case.

 

In all fairness it is a pretty radical cam but it was given to me years ago by an old friend. The car is pretty light, Camaro t5 and 4:11's. Not a knock on the Strombergs but it sure drives nice now with good afr's everywhere.

 

I can't see the cam causing it to run rich . . . it has to be dumping too much fuel at idle and maybe off of idle. The main jets do not influence idle and if you've checked to make sure the main venturi dumps aren't passing fuel, then it has to be the main idle circuits of the center carb.

If you don't see any fuel dumping into the main venturi area at idle (or out via the accel-pump shaft in the top), then the float should not be the issue either.

Will turning the idle screws in influence the idle speed? If you can turn the idle screws in all the way and it is still running, then it is pulling fuel from someplace else.

I've not worked on these carbs, but I've worked on plenty of others and have not had the issues you're talking about.

 

Thanks, idle screws are not very responsive and even at low idle it spits out passenger side venture a little, the accel pump shaft are real tight like it could be putting pressure on pump, on the knock off's that accel shaft was not that tight-had tiny bit of play? I can't see how the CAM could cause it??

 

Air bleeds to small?
Not trying to add disappointment,
I tried 3 set up , sound wicked when all 3 opened up , went from running
high 7:60s to 8:70s , made a adaptor & put a single big Rochester 2 barrel off a 455 , caped ends off went 8:20s , then tried Ram with 2 Holleys 2 barrels back to 7:60s with more mph

 

Brother I just want it to IDLE and cruise town correctly, Thanks Tho.

 

Testing my short memory but there's only idle jets that were above my paygrade to modify. I even bought a second primary carb to try. I think my problem was the secondary's as I don't understand them peeing fuel with block off plates. The first cam only pulls 6-7" vacuum at an idle, up to 12-15 by 12-1300 rpm. It's been a while and my memory doesn't work so well. Running 2 broadband sensors sure does help to see what is happening.

 

Never touched a Stromberg, admittedly, but what's your idle set at? Used to build some gnarly drag bikes and some carbs (Lectrons come to mind) wouldn't run right until the engine was idling 500 rpm more than a Miki or Keihen. 100% sure the fuel pressure gauge is accurate?...big cam lowers your vacuum signal at idle, it gets less obvious the higher in rpm you go, wfo is wfo. Which can make things in a carb wonky on the bottom. The shake of a big lumpy idle can also bounce the floats, and release the valve, letting too much fuel in.

 

I'm running about 12" vac @ idle

 

ya believe psi is 2psi fuel, 12" vac at idle, cam is not radical.

 

Can you tune the idle circuits of the two outside carbs completely off, so it only idles off the center carb? Might take a bit of tuning to get tip in right, but might be necessary if its running on all 3 at idle...Like I said, never touched one of those but just bouncing off ideas from a different set of eyes.

 

First things to check: float setting, Grose valve operating properly, and fuel pressure is set correctly.

Next: disconnect the linkage and wind the idle screws on all three carbs out until the butterflies all close completely. Then, adjust all the air/fuel screws all the way in, then out 1 1/2 turns. Now, concentrate on getting it to idle on only the center carb. Might not hurt to disconnect the accelerator pump linkages as well at this point to get those out of the picture as well.

Once the center carb seems happy, install the accel pump linkage on that carb only and see how it responds. Do a couple plug chops and make adjustments to the air/fuel screws on that carb only as needed.

Next, you need to sync the other two with a Uni-syn by adjusting the idle screws until they all pull the same vacuum. Then, without moving any of the throttle shafts, the progressive linkage can be installed and adjusted depending on when you want the two outer secondary carbs to "come in".

With the carbs synced and the car idling nicely, reinstall the accel pumps and do another plug chop and see where that gets you.

I'm assuming you have a primary carb in the middle and secondary carbs on the outside and not 3 primary carbs, correct? Good luck, multiple carburetion can be a finicky mistress.

You're on the right track by using an Air/Fuel Meter and O2 sensors. Takes out the guess work when tuning!

 

Of not already done what @PotvinV8
Recommended, if not try recommendations...
my self have been there on things driving me / us nuts..
Then If still having isues , Take a different approach, Me I do not like feeling defeated ! Some thing simple like what you are dealing with ,,
Try this , if you have a extra single carb
4 barrel intake , wip up / make a adapter
Install the primary , & see if same Issue
If not ,& issue solved , @ least you know carb issue or not, maybe that particular 3 carb intake with you engine combo just not a good balance /match , Yes maybe another set of gaskets & a 2 hrs or So , trial and error , feel your anger many of us have been there one time or another,,
From my DD to over 200 mph drag car

 

Thanks, was gonna try that in morning..

 

Thanks for noticing I'm looseing my mind, if I pull this intake and carbs-they will be for sale...(brand new)