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#1
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AFB Carb Tuning Help needed
OK I use two AFB's on my Pontiac powered altered and they work great. Now on to my problem. I just installed a Edelbrock dual quad air gap manifold on my 1960 Ford Falcon and I am using 2 3895s AFB's the same that I use on my Pontiac 400. I can tune them in great at idle and it snaps the throttle nice and crisp. When I do a burn out everything seems good, but when I launch the car it takes off good on the accerlerator pump / squirt and then falls on it face and I have to let off and roll back in to the gas but I can never go all the way into it or it starts breaking up. My fuel presure never drop below 4.5 and I have a brand new Holley blue pump installed with -8 line running from my tank to the pump to the regulator where I go to -6 off the regulator and go to the carbs. I have the regulator set at 6.5 psi at idle. The plugs look lean and I have been all over the place with rods and jets. I thought the floats were set to low but they are fine. I know this is a Ford but alot of Pontiac guys use AFB's and I am in need of some help. I am sure I have left something out so please let me know if there is any other information that could help. Thanks for any help.
Jon Tomkins |
#2
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Are the secondary air valves still in the carbs?
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#3
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Ditto...my thoughts too Joe...
What about carb mounting angle....?? Max was given to me as 11 degrees...mines borderline but it still responds great !!
__________________
ECM member. 2008 Outlaw Pontiac Drag Series Champion MANDRA Do it now fool! Life is short. 69 Grand Prix/3163lbs / IAII 535 w/ Tiger heads by Gaydosh....9.35@ 144 so far.. through mufflers. 1.26 60'. Going back to track with pump gas engine.... My 60 Ventura retired to street/strip duty.. |
#4
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First off I would get rid of that lousy Holley Blue Pump. A terrible pump for a drag race application and this is coming from a former Holley Employee. (30 years ago).
The pump cannot keep up under acceleration. Same deal for the little blue regulator. Get a proper fuel pump like a Mallory 140 or similar and then buy the large Holley regulator that has the 7/16" diameter orifice ball in the regulator. If you have a old Fram Canister fuel filter between the tank and the pump get rid of that deal too. Buy a 20 micron screen pancake type fuel filter from Holley (The large one - They make two sizes) and use that. It comes threaded with both AN or pipe threads in the screen filter housing. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#5
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Air valve
We did pull them out for a run and it made no difference, we thought it might have stumble to it with them gone and then it would pick it up but there was no change.
thanks for the thought Jon |
#6
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Agree with Tom. However, try the carbs off your altered just to see if the problem isnt in the carbs. I had a sticking air valve(not fully opening) on the front carb on my wifes car when I was first sorting the dual quad setup. It would go very rich and breakup badly. Stuck open or missing would be a bog.
A few months ago Mike Davis had a metering rod piston stuck in the down position causing it to run too lean. Some needle seat assemblies have a very small opening that could possibly lean you out. Last thought, while your float height may be fine, if your float doesnt drop the needle sufficiently (float drop setting) you can starve for fuel.(I've been there once) Too much drop can cause flooding from needle binding and not seating.(been there too) FWIW, I've been using Edelbrock "off road" spring loaded needle and seat assemblies for a while now and havent had any float related issues since. I have installed them in several other peoples carbs with no more float issues for them either. Just be sure float height and drop are correct. |
#7
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thanks for the info.
Quote:
I am going to try the altereds carbs, maybe on Sunday it looks like I will be able to fit it in and I am only 4 miles from the track. As far as the fuel pump I have never had a issue with the Holleys, I use a red unit on my Bantam with dual quads and never had a issue. I also use two of them on my SCCA GT-1 road race car and it make about 600 h.p. and never had a issue, but this also does not mean that something else might be better, and Tom seems to know his stuff so his input is really great but this does not seem to be the issue that I having. This car is a high 11 second type car. I am going to check the angle of the carbs in the mornig to make sure this is not an issue. Thanks for the info everyone. Jon |
#8
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tom is correct, run the biggest pumps and lines you can afford..no such animal as "too much fuel to the regulators"..does anyone else modify their afb style carbs for dual feed anymore?..my mentor use to port his fuel bowls also, saying every bit helps..and in my experience, getting the pump shot right is the biggest problem..
i bet 2 really nice q-jets would kick the afbs butt.. |
#9
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Bantam, some very smart guys in here giving the answere's ! take note, I agree with Tom, under acceleration is where you have the problem, sounds like fuel delivery issues to me too
__________________
D.S.R.E. Your NW Pontiac Street/Strip Engine Builder, Specializing in Cylinder Head,Intake Manifold,and Exhaust Manifold Porting services and Building the Most Efficient stock rebuilds to Hi HP Pump Gas and Race Combinations for Pontiac,Buicks,Olds,FE Fords,385 Series and HP Gen 3 and 4 LS engines! 2006 silvy Z71 4X4,383 LS 600+hp NA Shared Toy-66 Lemans 470cid by me 537hp 580tq-manifolds, 570hp 590tq-2"headers,custom cam,rpm intake, mild e-heads, Looks stock ;-} |
#10
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Great Help
Quote:
thanks agian Jon |
#11
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Agree with Tom on the Black Holly 140 pump and large regulator...
Have you tried moving the pump rod location to some different holes in the link ?? I would at least try the larger regulator if you don't want to spring for pump now.. I had a high speed lay down on my car at 1,000' and going to a black pump & large regulator cured it..however it did launch OK..I ran a Perma-cool filter set up as it way out flows the junk Fram set up ....IMO...think they are made for lawn mowers.. Fram rated at 1.5gpm and the Perma-cool is 25gpm....no brainer.. I just moved the fuel system from under car to inside trunk now to make room for coilovers...I went with a 40 MC inline filter over the Perma-cool....guess I should heed Tom V.'s advice....He's the one with the Engineer degree....and head to use it ! CYA at Norwalk Tom.. BTW: As per class rules I run dual AFB Comp.series 750's with the choke horns removed on mine You didn't say what size your Ford engine is ?? Good luck..
__________________
ECM member. 2008 Outlaw Pontiac Drag Series Champion MANDRA Do it now fool! Life is short. 69 Grand Prix/3163lbs / IAII 535 w/ Tiger heads by Gaydosh....9.35@ 144 so far.. through mufflers. 1.26 60'. Going back to track with pump gas engine.... My 60 Ventura retired to street/strip duty.. Last edited by 60man; 08-03-2008 at 09:15 AM. |
#12
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Whoops..Forgot to mention. Check all the linkage screws on pass.side of carbs. I had one back out enough that secondary did not open on front carb....!!!!
Just for kicks here's a pic
__________________
ECM member. 2008 Outlaw Pontiac Drag Series Champion MANDRA Do it now fool! Life is short. 69 Grand Prix/3163lbs / IAII 535 w/ Tiger heads by Gaydosh....9.35@ 144 so far.. through mufflers. 1.26 60'. Going back to track with pump gas engine.... My 60 Ventura retired to street/strip duty.. |
#13
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Quote:
"I use a red unit on my Bantam with dual quads and never had a issue. I also use two of them on my SCCA GT-1 road race car and it make about 600 h.p. and never had a issue," I did the Tech Inspector deal/Corner worked deal for SCCA for 13 years. A lot of TRANS AM and GT-1 background. have seen a LOT of GT-1 cars built with a pair of Holley BLUE pumps (sometimes the 2nd one was a back-up) that would run well on the track at over 600 hp. Deal was the engines are on and off the gas which allows the pump(s) to catch up. Drag racing is a different deal with a severe high demand load on the pump immediately, no chance to recover from a weak pump rate. Why the carb basically runs out of fuel in third gear under load. Quote:"Agree with Tom on the Black Holly 140 pump and large regulator..." I was recommending the MALLORY 140 pump, not the Holley Black pump. I would not put a Holley pump on my car. Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#14
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Another thing to look at as you sort through these deals if the secondary is OK do you have too soft a power piston spring not allowing it to pull the metering rod out to enrich it.
__________________
Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
#15
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Tom V. quote: I was recommending the MALLORY 140 pump, not the Holley Black pump. I would not put a Holley pump on my car
Sorry 'bout that Tom...I screwed that up !! So far Holley Black "seems" to be OK but I'm looking to upgrade this winter,to something with more capicity/flow...... May I ask about your poor assesment of Holley pumps...what should I be on the look out for ??
__________________
ECM member. 2008 Outlaw Pontiac Drag Series Champion MANDRA Do it now fool! Life is short. 69 Grand Prix/3163lbs / IAII 535 w/ Tiger heads by Gaydosh....9.35@ 144 so far.. through mufflers. 1.26 60'. Going back to track with pump gas engine.... My 60 Ventura retired to street/strip duty.. |
#16
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Quote:
__________________
D.S.R.E. Your NW Pontiac Street/Strip Engine Builder, Specializing in Cylinder Head,Intake Manifold,and Exhaust Manifold Porting services and Building the Most Efficient stock rebuilds to Hi HP Pump Gas and Race Combinations for Pontiac,Buicks,Olds,FE Fords,385 Series and HP Gen 3 and 4 LS engines! 2006 silvy Z71 4X4,383 LS 600+hp NA Shared Toy-66 Lemans 470cid by me 537hp 580tq-manifolds, 570hp 590tq-2"headers,custom cam,rpm intake, mild e-heads, Looks stock ;-} |
#17
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Quote: "May I ask about your poor assesment of Holley pumps...what should I be on the look out for ??"
The pumps (red and blue) were from the old days 40+ years ago. Bill Jenkins and a lot of racers QUICKLY figured out that they needed at least two blue pumps and maybe three to get the job done. Same deal for the little blue regulator. Look at any of the jenkins pictures and you will see that they are feeding two regulators with two fuel lines and then putting a pipe coupling between the regulators to balance the flow. Regulators were too small. Holley fixed the regulator issue with the large ball regulator. I like the Mallory 140 and 2X0 (240 or 250, I forget) because as soon as we put one on Jim Brady's 64 GTO Steel car we picked up 3 tenths. Obviously a lot better than his dual Blue Pump deal. I would not mess with the BG pumps either. Aeromotive, Magnaflow, Mallory, all make quality pumps. JMO Tom V.
__________________
"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#18
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Thanks Tom...3 tenths is a lot of ponies......
__________________
ECM member. 2008 Outlaw Pontiac Drag Series Champion MANDRA Do it now fool! Life is short. 69 Grand Prix/3163lbs / IAII 535 w/ Tiger heads by Gaydosh....9.35@ 144 so far.. through mufflers. 1.26 60'. Going back to track with pump gas engine.... My 60 Ventura retired to street/strip duty.. |
#19
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alot of knowledge here. listen to what these guys say. but i would swap the other carbs too.
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