Offy 3X1 - More ?'s than !'s.

[powerband]

I have been breaking in and tuning the Clifford built 250 and incrementally making progress. It has been running awesome with a Holley 2bbl and outer carbs blocked while I worked on ignition and other things. I am now re-visiting the Offy 3X1 setup. The engine came with three Holley 1904's rebuilt and clean - somewhat modified linkage, chokes removed and plugged, vac ports plugged. I used my '63 Falcon Wagon's excellent running 170' six for static and road testing the three Holley's after temporarily removing the OEM 1100 carb. The testing included hooking up vac advance and minimal idle A/F tweaking on the 170.

1) The FRONT Holley started, idled and revved well with static test on the 170. Drivability test revealed It stumbled mildly at mid throttle cruise and stumbled continually under load.
[ List 2245S / 11B (1-7/16) Base ]

2) The REAR carb started, idled and revved well static. Ran well on drive test except for leaky needle flooding episode which is minor repair concern.
[ 2?45S 803 / B35 (1-716") base ]

3) The CENTER Holley started but ran rough and only with mix needle all the way out - stalled and revved badly - ran better with finger partially choking venturi. I didn't attempt road test. [2245AS 0143 / E12 (1-9/16") base ]

Although these carbs are never used rebuilds, they had been sitting. I installed "jify" kits in them and got the EXACT same results other than eliminating the leaky float on # 2. I have taken them apart and compared the good running one with the other two for blockage, sealing and operation with no change to the problems with # 1 & #3.

Powerband 8)

 

[powerband]

Offy 3X1 cont'd - Comments welcome:

I suspended trying to get the clean , modified 1904's working and decided to try another set of carbs. I have a good YF from a '71 Maverick 170 and two good running 1908's from 60/61' s. I used the YF in center and the two 1908's front and rear.

This setup starts and runs but has a few "issues". Runs good under load and pulls well at WOT . If I punch it fast, it bogs and sputters which I believe is too much accel pump (the Clifford 1904's have the outer pumps in the leanest setting.)

Main problem currently > The idle setup is elusive. I have tried closing the throttle plates and idle mix needles on the outers and using just the center YF and it runs rough and fitful (seems to make the outers' essentially vac leaks at idle with needles shut). It idles better if I open the outer needles @ 1/2 to 1 turn but then the idle speed climbs to @ 1200 -1500 with outer plates closed and center almost shut. If I ignore fast idle, this is best running setup so far. I can turn in needles to slow rpm's but idles rough and fitful Can't find settings to get idle down and smooth to not stall and surge.

I'm running Duraspk diz to YF ported vac , progressive offy linkage. I get @ 18 on the vac guage at idle. I want to get a "Unisyn" type guage to help setup.

? > A few have mentioned that the spring loaded stud socket Offy linkages, to the front and rear carbs causes binding and return to idle problems. I would like to modify it with miniature "Heim" type linkage pieces if anyone knows a source.

Tinkering with a 3 carb setup makes me re-think the basic ideas I had set in my head about carbs, vacuum and A/F mixing.

Powerband

 

[Anonymous]

I run a 3carb set-up and while not completely glitch free it does perform well. My set-up is drastically different than the offy but end result should be similar. The linkage setup is the most crucial attempting to achive synchronised full throttle positions then adjusting backwards to the desired outboard carb initiation point. I have it now where the center carb does all till about 5/8' throttle then they all achive full throttle together. Since i am running a vac robbing cam and a 2100 (2bbl) in the center, idle characteristics are very different than yours. But I'll share my settings anyways. My best idle setup so far is outboards with throttle plates closed as far as possible without plate binding and a 1/4 turn out on the mix screw. It will idle down to 300-400 rpm and remain running but because of the cam i keep it at about 800rpm idle. I have the center carb (autolite 2100/108) running med adj. on accel pump but have disconnected the accel pumps on outboard (Weber ICT's) carbs. With the pump rods off the outboards it will take a stomp and romp. With the rods on it had a little better pull at 3/4 throttle but would hesitate when stomped so i figured if i get to that much pedal, stomping is more rewarding The return springs on the outboards can be felt in the pedal so when i feel tham starting to open i get a little quicker on the pedal or in a effort to save gas keep back a little. the center carb provides more than enough fuel to provide spirited response anyways even with out full throttle. The outboards are no more than secondaries on a 4 bbl. Rejetting the ICT's would probally achive a little better all around useage and alow me to use their accel pumps and someday when the Gods bless me with some spare time i may do this. But i use this as my daily driver and paint will get here first likely

 

[mustang652]

Currently going through the same problems with mine and I'm using the round log head (5205) with autolite carbs. Following Addo's advice, I removed the check ball valve from the outboard carbs in an attempt to disable the accelerator pumps last night. Based upon the bench test it appears to have done the trick. Will not have a chance to fire it up until later this afternoon. I don't think that I am going to be able to settle all the issues until I get the problems with the lousy Offy supplied spring loaded carb rods addressed. Got one original style comming from a forum member, will take nearly a week to get here, but still got to locate another one. I'll post the results of the running without the ball check after I get back this morning.

 

[woodbutcher]

For the small Heim joints that you are looking for,check out a hobby shop that sells radio controlled model aircraft supplies.They have that type of thing or can order it for the giant scale aircraft.These are very good quality pieces,and should do the job for you.
Leo

 

[mustang652]

Thanks for that imput. In addition to trying to obtain the originals, I'll check that out. I had used the smallest heim joints I coud find at a speed shop to build the connecting rod from the center Offy progressive arm to the accelerator rod. I have found a listing for what appears to be an original style rod in the NPD catalogue. Page 96 of the 2006 edition. It can be found on line also at www.npdlink.com/ under Fuel systems, page 96. It's in a pdf format and is a pain in the neck to use. At 29.95 a piece they must be at least gold plated.

 

[powerband]

I run a 3carb set-up and while not completely glitch free it does perform well ... .... running a vac robbing cam and a 2100 (2bbl) in the center, idle characteristics are very different than yours. But I'll share my settings anyways. My best idle setup so far is outboards with throttle plates closed as far as possible without plate binding and a 1/4 turn out on the mix screw. It will idle down to 300-400 rpm and remain running but because of the cam i keep it at about 800rpm idle. I have the center carb (autolite 2100/108) running med adj. on accel pump.,......... and someday when the Gods bless me with some spare time i may do this. But i use this as my daily driver and paint will get here first likely

Interesting, I was running a 350CFM 2300 in center and had outers blocked. I thought it would be too much but I might re-visit that.


I need to re-think my Idle setup understanding. The current YF ran well in center position with outers blocked but I can't keep idle down with outers working. There doesn't seem to be any vacuum leaks other than the carbs themselves and those were tested individually as well.. The idle needles all affect idle significantly so individual lly they are OK. Rich due to too much fuel or Lean due to closed needles and minor leakage through plates etc - That is the question - (I think). .

Thanks for the info and food for thought

Powerband

 

[powerband]

Currently going through the same problems with mine and I'm using the round log head (5205) with autolite carbs. I removed the check ball valve from the outboard carbs.... .... until I get the problems with the lousy Offy supplied spring loaded carb rods addressed. .... I'll post the results of the running without the ball check after I get back this morning.

Thanks for the info, I thought the original linkages only have the socket on one end of the link. I am interested in modifying the current ball and socket links with something ball bearing or at least minimally binding. I checked out some multi-carb linkages on tri-power muscle cars, they use longer throttle arms for leverage for less pedal effort.

I was real intested in your idle setup. How's your idle speed and what's your setup. ,,,, The Accel pump mod seems needed as well but the road testing is gonna' get me in trouble - if ya know what I mean ' ...

 

[Anonymous]

Hop-up kits for older VW's came with some nice linkage pieces with heim joints on both ends with 1 end left hand thread. The ICT's ,manifolds, runners and linkages on my wagon are a dune buugy dual port head VW kit(with extensive modifications). another place to check is 'Go-Kart World'

 

[nitrousnick]

the holley 1904s are great carbs there is only one small problem with your -you cant take the choke out-its part of the venturei(or how ever you spell it) look at it real close ,if you take the choke out you will loose the signal to the carb and it will be super lean(how do i know? I done it) to fix your carbs just take a piece of hard line (fuel line )and put it in where the choke shaft was.