Ultra 950 Holley HP tuning - Team Camaro Tech
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  #1  
Old Aug 7th, 10, 06:46 PM
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Default Ultra 950 Holley HP tuning

I have had this carb for almost a year and it still isn't where I want it to be.
I got idle and WOT fine. I just cannot cruise without being way to fat. Usually in the 11's and 12's afr.
I have had the idle mixture screws at best idle , best vacuum,best AFR and even up to 15.0. Played with IFR's, idle bleeds. Tried different timing #'s. Different powervalves, no powervalves .I could go on and on.
I basically have a near race engine for a street application.
496bb cam 248 252 @50 650 lift 110 solid roller.
Present timing 20 initial 32 total
9.5" vg @950rpm
15-16 vg at cruise (2200)
78 jets in front 6.5pv 73 iab 28 hsab
86 jets in rear no pv 73 iab 28 hsab
I think IFR's are around 30

I am open to any suggestions that may have worked for you .
Would opening up emulsion bleeds or changing from blocked to 028 help lean me out at cruise?
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  #2  
Old Aug 8th, 10, 08:00 AM
built4spd built4spd is offline
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Default Re: Ultra 950 Holley HP tuning

I would first try locking the timing out,then carb tune from there

in the summer months,its not uncommon to jet down 3 sizes to compensate for lack of good air

also its best to powervalve at 50% of the vacuum at idle reading,you can use a 4.5 p/v
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  #3  
Old Aug 8th, 10, 09:02 AM
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Default Re: Ultra 950 Holley HP tuning

I can feel a surge if I use 76 jets.
I have high vacuum at cruise so I don't think my powervalve is opening causing it to go fat.
I need to borrow a street carb for a few months till I get my fuel injection!
But I have to make due for now and I have a long roadtrip ahead with this carb.
I have a 850dp I can play with as well. It is just about as fat. It is a little tougher to move things around.
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  #4  
Old Aug 9th, 10, 01:26 PM
Z15CAM Z15CAM is offline
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Default Re: Ultra 950 Holley HP tuning

Your getting 15 Hg Manifold Vacuum at Idle thats incredible I'm use to working with 454 Solid Rollers with Idle Vacuum around 10 to 12 Hgs with 850 Carbs.

Anyway Surging at Cruise. You didn't mention whether you are running a Vacuum advance distributer. If not I would recommend it. They really settle down a 460 SR at cruise. The Hg of the Power Valve and Distributer Vacuum Pod should be approx 1.5 to 2 points below your Manifold Vacuum at Idle. I still find that 15 Hg Manifold Vacuum incredible.

If the Distributors Vacuum Pod is rated to High for the Idle Manifold Vacuum the Timing will Haunt at Idle and Cruise.

Another thing that might help is if you are running Vacuum Advance is to "T" in a 1 Quart Vacuum Canister into the Vacuum advance Hose between the Distributors Vacuum Pod and the Intake Manifold Vacuum Source. Do not use the Carbs Port Vacuum if you have one - Plug it off.

You may also have a Vacuum leak. I would plug all vacuum sources including the Power Brakes and the Auto-Trans-SX Module to see if this makes a difference.

Do you have a Steady Vacuum Gauge Reading ?

Are the throttle Plates on the Secondary set per Specs and Carb Floats Set - check you Distributor Mechanical Advance Springs?
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Last edited by Z15CAM; Aug 9th, 10 at 01:38 PM.
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  #5  
Old Aug 9th, 10, 01:44 PM
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Default Re: Ultra 950 Holley HP tuning

Try some slightly larger high speed air bleeds. Just one or two sizes bigger. This will lean out the fuel curve in the middle.
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  #6  
Old Aug 9th, 10, 01:45 PM
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Default Re: Ultra 950 Holley HP tuning

9.5 hg at idle
15 cruise
I am about to try another vac adv dist. I didn't have much luck with the last custom one I had built. Vac guage is pretty steady at idle ...maybe fluctuates .1-.2.
Throttle blades are covering the transfer slots. Idle is too high if they are exposed.
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  #7  
Old Aug 9th, 10, 01:47 PM
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Default Re: Ultra 950 Holley HP tuning

I went as high as 56 on hsab's! No effect. Surprising ....minimal effect on WOT.
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  #8  
Old Aug 9th, 10, 01:52 PM
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Default Re: Ultra 950 Holley HP tuning

Quote:
Originally Posted by trackman View Post
I went as high as 56 on hsab's! No effect. Surprising ....minimal effect on WOT.
You went from 28 to 56 on the high speed air bleeds and it did not affect the AFR at cruise?

You did change the 4 inner air bleeds, not the outer? Just making sure you changed the correct ones.

What is the AFR at WOT?
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  #9  
Old Aug 9th, 10, 01:55 PM
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Default Re: Ultra 950 Holley HP tuning

Correct. Very very minimal effect.
Outer are for idle.
I presently have the carb jetted for WOT AFR around 12.5-12.9ish
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  #10  
Old Aug 9th, 10, 02:00 PM
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Default Re: Ultra 950 Holley HP tuning

Quote:
Originally Posted by trackman View Post
Correct. Very very minimal effect.
Outer are for idle.
I presently have the carb jetted for WOT AFR around 12.5-12.9ish
I would lean the main jets out a tad, 12.5 is a little fat. After you do that try the HSAB's again.
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  #11  
Old Aug 9th, 10, 03:52 PM
camaro434 camaro434 is offline
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Default Re: Ultra 950 Holley HP tuning

IMO that is way to small of a carb. I am running a ProSystems 1000HP that wet flows 982cfm & dry flows 1040cfm on a 434 SBC.
Call Patrick & he can help you get the right set-up.
http://www.prosystemsracing.com/index1.html
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  #12  
Old Aug 10th, 10, 08:46 PM
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Default Re: Ultra 950 Holley HP tuning

I tried Patrick's carb but he/we were unable to get a very large lean stumble out of it with my engine combination.

I was able to lean cruise today by opening up one blocked emulsion bleed on each side of the metering blocks. Driveability was reduced and I didn't get a long enough test in to confirm my results.
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  #13  
Old Aug 15th, 10, 01:27 PM
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Default Re: Ultra 950 Holley HP tuning

Did a good test today. I was very happy again with the cruise @ around 14.0. At very light throttle it crept up to 15-16 and I started to feel some missing. I am going to try a little smaller emusions bleed and see if it improves. I am going to try to get a mpg tour in and see what my milage is. I have never been able to do a mpg test. I want to nail it every time I get in it.
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  #14  
Old Aug 15th, 10, 07:41 PM
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Default Re: Ultra 950 Holley HP tuning

Well my mpg test didn't go so well. I just couldn't keep my foot out of it. I changed the 3rd emulsion bleed from 031 to 020. It didn't change a thing. So I will try to fatten it up with smaller idle bleeds.
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  #15  
Old Aug 28th, 10, 10:34 AM
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Default Re: Ultra 950 Holley HP tuning

Smaller idle bleeds helped a lot. Low end drive-ability really improved.I am going to go a few sizes more .
My wideband readings:
13.5ish at idle
14 inching to 15 as I cruise at the same speed.
12.4-12.9 WOT
I'm happy with this . Pretty stable and no rich or lean spikes.

Case closed.
Now I need to see if I can make headway with my vacuum advance dist.
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