lots of problems

[crane_guy]

i have purchased a performance q-jet from jet performance and i am having nothing but troubles the number of the carb is 17057584. this carb is modified and advertised to work with a 400 hp small block. i have a fresh rebuilt 454 9:1 compression with a comp cams extreme 4x4  cam (idle to 5000 rpm) the motor makes  20 hgs of vacuum at idle if it means anything the elevation of where I live is 3700 ft
. the crab has 74 jets 41 metering rods da secondary rods and they set the float at 1/4 inch. i am  also using a large style mechanical fuel pump. The first problem I had was too much fuel pressure it was leaking out of the air horn gasket and flooding the engine bad enough that I ended up with fuel in my oil. the filter that came in the carb was open at one end with a cork gasket, when I installed a filter with the rubber end  that has a check valve, this helped my problem. But did not fix it. Now I have not yet installed a fuel pressure regulator but I am going to tomorrow, right now I am running the carb at the recommended 15/32 float hight (as per rebuild kit sheet specs). The manufacturer says that this carb will not work with a big block and I am not sure why? I also dont understand why they have blocked the idle bypass air by plugging the holes in the void beside the primaries in the main body ( the holes that you show on page 29 on the bottom right corner in your book) I do believe that the system is complete except for the epoxy plugged holes. If I were to remove that epoxy what gaskets do I need to make it work ? At present the truck idles smooth except for a surge lets say it occurs every 10 seconds at idle. It feels sluggish and bogs put at full throttle it just have that clean sound.

I am going to install the regulator and gage, what fuel pressure should I have ? What is ideal ?  Should just set it so it will work with a ¼ inch float hight? And what do you think I am going to need to do to make it work with my 454 and by the way this engine is in a 4x4. Any help would be appreciated love the book thanks !

Thad 

[Cliff Ruggles]

Not sure where to start, all that I can say is that we get a LOT of carburetors in here built by other sources for custom calibration and performance mods, etc.....Cliff

[crane_guy]

ok so  i drilled 3/32" holes in the primary throttle plates  raised the float to 5/16ths and she has a great idle no nozzle drip! i am not sure if its correct my mixture screw are about 4 turns out idling at about 900 rpm. i hate a moderate bog of idle, so i pulled the accelerator pump linkage, and that made things worse so i turned the apt screw out to three turns( was 2 turns out)A now i just had a slight hesitation hooked the accelerator pump back up and it runs not bad
i guess i should start by measuring all of the idle circuit ? is using drill bits a satisfactory way of doing this ?
 what are you thoughts on the fuel pressure fluctuations ?  plugged return line ??

[Cliff Ruggles]

Any particular reason you didn't unplug the blocked off idle bypass air passages?  More effective than drilling small holes in the throttle plates, but if it helps that's a good thing.

I'm not familiar with that carburetor part number.  What size are the main airbleeds?....Cliff

[crane_guy]

acctually i have 2 of these carbs from jet with the same q jet # the first one i used before the rebuild, it had a bit of an accident while the motor was being rebuilt i just simply drilled the throttle plates from the first one to use on the second one just as an experiment and it seems to have worked.  but really i do not know enough to remove the blockage i didn't want to solve one problem and create another. i still think i have a fuel pressure issue i dont like how i have a steady 5.5 psi at idle and then when i rev the engine the pressure drops to 3 and jumps up and down between 3 and 5  i am going to get a new fuel pump before i do any more tuning

[crane_guy]

OK cliff id like to start over  I am confused and I could use some advice and clarification.
The carb is still the same 17057584.  I now have an Edelbrock mechanical pump and a Holley pressure regulator. I still have a few remaining problems. 
 Engine details
454 9:1 or could be as high as 9.75:1 compression, the cam is a comp cams ENERGY 4X4 X4 254H CAM, Camshaft, Hydraulic Flat Tappet, Advertised Duration 254/262, Lift .505/.505,
 if I understand things correctly my carb specs are as follows all measurements were taken by go and no go using # bits

idle tube:0465”
idle down channel: .043''
upper idle air bleed:.116''
lower idle air bleed: .076''
idle air bypass: blocked off
holes under idle mixture screws: .0995''
holes in throttle plate: .089''
jetting is 74 and 41k
this carb has an external adjustable apt screw

I do live in Calgary, Alberta at 3900 ft barometric pressure can be anywhere from 99 to 104 kpa

the tuck runs and starts great, but I believe I should have better performance, and throttle response that what I have. I ran the truck with 76 and 49 k rods but it was too rich. Right now with the 74/41k,I have a lean crackle on hard engine braking, but a much better throttle response and a cleaner sound at mid range. But it has a foul smelling exhaust on idle, smells lean and not rich. I can stall the motor when I close of the idle mixture screws.  Right now the mixture screws are at 4 ½ turns out.

Some questions
can the idle channel and idle tubes be drilled with out removing them ? Is the restriction the whole tube ? Or is it just the end ?
What length of bit do I need ?
What is the max size I can go on mixture screw hole ? That is the hole perpendicular to the mixture screw ?
The picture I have seen of main air bleeds have a brass insert in the hole, are mine missing ?
Do you think I should install un-drilled primary plates and re activate the idle by pass air.
Should I just find a new carb ?

Thanks

[crane_guy]

here are some pics

[Cliff Ruggles]

I see the problem, thanks for the pics.

You are working with a large main airbleed carburetor.  They are the most difficult to set-up.  I would suggest contacting us for a complete recalibration package, which includes new main airbleeds.  Those carburetors simply let in too much emulsion air to ever get a good clean fuel curve with them....Cliff

[crane_guy]

ok well thats good news...i think whats involved with the recalibration kit ? from the pics what else do you suggest ? jetting, where do you think i should start ? how do i get order calibration kit ? what sort of lead time do you have for this ? what forms of payment do you have ?

[Cliff Ruggles]

Open up the bypass air system in the main casting.

Install main airbleeds.

Install new jets, and metering rods.

I would also get one of our HP needle/seat assemblies, and the correct accellerator pump and springs.  Most of the time they put used pumps in them, with the wrong spring that coil binds before the pump completely compresses.

One of our fastener kits would also be a good idea, with black oxide coated screws and they are long enough to stake them on the shaft(s), etc.

Call the shop for parts, 8am-5pm M-F EST.....Cliff