carb guys point me in the right direction

rubberneck · Dec 16, 2004

I have an 86 coupe with a stock 1990 bottom end, edelbrock 60379's, victor jr, f303, and longtubes

on the dyno it put 275.6 hp to the wheels (no torque reading for some reason ) flat as a board almost from 3500 to 6500

the air fuel from the dyno was richer than 10.0/1 , operator said it was almost off the chart.

the carb is a 650 holley mechanical secondary. i think the front jets are 72 and the rears 84 squirters are 31's.

do i have too much fuel or not enough air?

i have a proform main body that suspposed to be good for 780cfm.

im not opposed to buying another carb either, what ever it takes to go faster

thanks in advance for your help

EMW150 · Dec 16, 2004

It's definately a fuel problem. Check float levels. If all ok there start pulling out jetting. For an idea, I'm running 70/78 jetting in my combo (carb flows around 850) and my powerband is from 4800 to 7600 rpms.In your case, I wouldn't be afraid to knock 4 jet sizes out of primary and secondary and then try it. It would be great if you could tune it on the dyno cause it'll show you your air fuel exactly. That's how I always dial mine in.

rubberneck · Dec 16, 2004

EMW150 said:
It's definately a fuel problem. Check float levels. If all ok there start pulling out jetting. For an idea, I'm running 70/78 jetting in my combo (carb flows around 850) and my powerband is from 4800 to 7600 rpms.In your case, I wouldn't be afraid to knock 4 jet sizes out of primary and secondary and then try it. It would be great if you could tune it on the dyno cause it'll show you your air fuel exactly. That's how I always dial mine in.

your the second person to reccomend 4 jet sizes on carb. so im definately doing that right away.

do you think the i should play with the squirters too, or should i save messing with those for later to avoid changing a bunch of things and complicating what seems to be a simple fix.

do you think my combo could benefit from the proform carb main body thats been riding around in my trunk with me?

EMW150 · Dec 16, 2004

The squirters really don't mean much in the whole scheme of things except driveability really. If you get a hesitation when you start leaning it out you may need to up the squirter a bit. Really the squirter only effects things when you first open the throttle. If you experience poor throttle response or black smoke when you first give it throttle you could back out on the squirter size till it clears up for you. As far as the Proform body, I don't think it would be worth much to you yet but when and if you up that cam and the combo gets a little wilder you might see a gain with it.

rubberneck · Dec 16, 2004

EMW150 said:
The squirters really don't mean much in the whole scheme of things except driveability really. If you get a hesitation when you start leaning it out you may need to up the squirter a bit. Really the squirter only effects things when you first open the throttle. If you experience poor throttle response or black smoke when you first give it throttle you could back out on the squirter size till it clears up for you. As far as the Proform body, I don't think it would be worth much to you yet but when and if you up that cam and the combo gets a little wilder you might see a gain with it.

no hesitation when i stand on it, actually im pretty impressed with how it runs to be honest, but when theres more in it, ill certainly try to chase every extra little bit there is.

im going to leave the proform body in the trunk for now and save it for when i need it.

thanks for your help, ill report back with what happens for anyone curious

what kind of increases do you think ill see when i get this thing tuned in a little better?

EMW150 · Dec 16, 2004

rubberneck said:
no hesitation when i stand on it, actually im pretty impressed with how it runs to be honest, but when theres more in it, ill certainly try to chase every extra little bit there is.

im going to leave the proform body in the trunk for now and save it for when i need it.

thanks for your help, ill report back with what happens for anyone curious

what kind of increases do you think ill see when i get this thing tuned in a little better?

It's hard to judge how much you'll get. You could get as much as 15 or so to the wheels if it was that fat. What I meant about the squirter is, when you lean it out, you may develop a hesitation. It won't now because it's so rich. I'd get the jetting where it needs to be and go from there and yes the horsepower #s are looking good for what you have in it. You're going to be close to 300 rear wheel tuned in.

rubberneck · Dec 16, 2004

EMW150 said:
It's hard to judge how much you'll get. You could get as much as 15 or so to the wheels if it was that fat. What I meant about the squirter is, when you lean it out, you may develop a hesitation. It won't now because it's so rich. I'd get the jetting where it needs to be and go from there and yes the horsepower #s are looking good for what you have in it. You're going to be close to 300 rear wheel tuned in.

awesome!!, thats right where i wanted to be n/a!

once i get it running properly ill hook up the big shot kit to a 175 hp shot to start

thanks for your quick replys, ive always gone to the corral.net for advice, but now im a converted stangnet'er you guys have a top notch site, keep up the good work!!!

rubberneck · Dec 16, 2004

ok, checked a few things

my fuel pressure was at 11psi

pulled the plugs, a little sooty

drove it and still had slight hesitation at wot.

getting a whole jet kit tomorrow, ill go down four sizes to start and try to get more dyno time in order to get it right, thanks for all the help!!

EMW150 · Dec 17, 2004

Definately get the fuel pressure back to 6-7 lbs. That could have been a big part of your problem. Keep us posted.

rubberneck · Dec 18, 2004

EMW150 said:
Definately get the fuel pressure back to 6-7 lbs. That could have been a big part of your problem. Keep us posted.

ok went down on jets, looks like were heading in the right direction. i understand what the squirters do now, there is a slight hesitation when you first romp on it, then it goes. i have 31's in now, im going to get 35's and 37's and tryit again. it may not be bad to jet down more, it still isnt smooth past 5000-5800 then it clears back up.

any other tips or pointers would be appreciated.

once again, thank you for all your help

EMW150 · Dec 19, 2004

rubberneck said:
ok went down on jets, looks like were heading in the right direction. i understand what the squirters do now, there is a slight hesitation when you first romp on it, then it goes. i have 31's in now, im going to get 35's and 37's and tryit again. it may not be bad to jet down more, it still isnt smooth past 5000-5800 then it clears back up.

any other tips or pointers would be appreciated.

once again, thank you for all your help

Is the hesitation from idle or if you romp it at say 3k or so? Does it feel like it's pulling harder? If there's only a hesitation when you put it to the floor, you could fatten the pump shot just on the secondaries. If you're also getting a hesitation during part throttle then up the shot on the primaries also. For idle and idle to part throttle transition you'll also want to readjust your mixture screws if you haven't already.

rubberneck · Dec 19, 2004

EMW150 said:
Is the hesitation from idle or if you romp it at say 3k or so? Does it feel like it's pulling harder? If there's only a hesitation when you put it to the floor, you could fatten the pump shot just on the secondaries. If you're also getting a hesitation during part throttle then up the shot on the primaries also. For idle and idle to part throttle transition you'll also want to readjust your mixture screws if you haven't already.

man, thanks you so much for the help, the car is running way better now.

it has to be close.

heres where i ended up

front squirter 28
rear squirter 31
front jet 67
rear 76

there is still a small hiccup from 5000-5200, but i think its spark plug related at this point as it doesnt hesitate or stop pulling just makes a different sound for that 200 rpm.

now i have a really good starting point for more dyno tuning, and all the pieces i need to dial in, ie jet kit, different squirters etc.

ill post some numbers up after the holidays when i can sneak to the dyno

EMW150 · Dec 20, 2004

Once you get it on the dyno you can see exactly where the air/fuel is at and then dial it in even more. If it's close but still rich, you may want to take some jetting out of the secondary and leave the primary alone. You don't need to keep 8 jet sizes of stagger. I've had different combo's that were within 4 or 6 primary to secondary.

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