tuning for booster-ring removal

[magicrat56]

cliff, i've been chasing my tail trying to getting a q-jet that has had the rings removed for increaced cfm,put seem to have lost most of my low speed drivabilty compared to my 750 quad that i have set-up to your 3'rd recipe. the q-jet in question out performs mine from about 2000 and up,pulls very hard but seems to have no control in low speed metering, is this just nature of the modification? do i try running it without rods,seems i have to run them way out of the jets anyway to get any kind of low speed drivabilty. bottom line is i think i out-smarted myself on this one. thanks,joe

[Cliff Ruggles]

I would need a carburetor number to provide any insight at all?

Once I know which carb you have modified, no problem at all setting you up with the correct jets and metering rods to make it work.

Single ring carburetors require special tuning, to get them to be smooth right off idle and at low throttle openings.

They never do work quite as well as the two ring carbs, but we've built quite a few of them over the years with great results.....Cliff

[magicrat56]

cliff, the carb # is 17056502, i ended up with it on some trades. as i got it the jetting was 78's with 43k rods.surprisingly it ran without idle tubes. no were near right but it did. low speed responce was more like an on&off switch. the car actually was "porpoising" when i just rolled into it. took it off and installed idle tubes set at .042,with.063 idle feeds. jetting is at .077's &.043k rods. think i'm on the rich side still. i installed bushings in both bleeds both @.069. idle mixture holes are .103,idle by-pass is .120". on top of this the primary plates are drilled with .125" holes. what seems odd is that they are in the back side of the blades; thought they went towards the transfer slots? with all this the car idles fine pulls very strong but you cant pull it down in high gear as my 750. with that carb i can go as low as 1200rpm in 4th and pull away fine. this carb just wont go below 1500rpm without bucking.can this be worked out or is it just nature of the mods? i have another clean main body17054922 without mods.straight casting big bore primaries. how far off is the metering with what i"ve done? carb sits on a 468 9:1 ovalport motor,.238/.248-.540/.540 @114lsa.4speed car with 3:73's thanks for your time.

[Cliff Ruggles]

Ditch the "K" series metering rods, they only have a .005" taper on the upper section, and are stepped between sections.  They offer very little control for part throttle adjustment.

Not sure why all the idle bypass air, it shouldn't need any additional holes in the throttle plates beyond the .120 bypass holes in the throttle body.

Jetting is too much for the smaller airbleed set-up.  When you get time, contact the shop and we can set you up with some parts that will be much closer, and provide full tuning from rich to lean for part throttle fuel.....Cliff

[magicrat56]

thanks cliff,i'm dropping the jetting to 74/.044 rods. after my last post i read thru some other problems with low speed metering and discovered the K-rod issue. i'll during the week. thanks again,joe.

[magicrat56]

last nite i was taking measurements in the air -horn and found the accell. discharge ports are drilled out to .039"! can this bushing be resized? if not i have one here. could you use a roll-pin punch to peen the face shut and redrill them? i'm determinded to get this one right! thanks again,joe 

[Cliff Ruggles]

The holes can be carefully peened down some an re-sized.  We have also installed threaded brass set screws in them and re-drilled them, but only to save valuable/rare airhorns....Cliff

[leroy]

Just on the Accel discharge holes in the air horn it is the hole that shoots into the barrels yeah?

 there is not a smaller hole that should be present within that passage?

The reason for asking is my  accel discharge pump holes are also huge and I wondered if I was missing something

[Cliff Ruggles]

The actual restriction is in the second partition deeper in the casting, not the large outer hole....Cliff

[leroy]

but still in the air horn yeah not the main body?

[Cliff Ruggles]

If we are talking about the primary side accellerator pump discharge holes, they are in the airhorn, in the second partition, not the larger outer holes where the fuel comes out......Cliff

[leroy]

Hi Cliff yes talking about the primary accel pump holes

Thanks for perservering with me

 soo should I be able to put a a 63 thou drill bit inserted from the discharge straight through and see the end of the bit from the underside of the air horn

Just not sure what you mean by in the second partition
Thanks

Leroy

[Cliff Ruggles]

The inner hole, not the outer hole....Cliff

[leroy]

Righto starting to feel pretty dumb here but need to clarify it because I think my inner hole is non exsistant and has been drilled out

The restriction hole which should be 26-28 thou   is inside the discharge hole yeah?

[Cliff Ruggles]

If there is no restriction in the inner partition, it can be tapped for a small 4-40 brass set screw, and drilled back to a smaller size....Cliff