Doug,

Sounds like a tough motor!  I am curious what cam specs did they grind for you?  I currently still have the Cuise-0, but plan on putting a t-5 in soon to help with my 4:10 gears.

On the Autolite carbs, You are correct about the throttle shaft spring.  The great thing about the majority of the Autolites is that you can bend the accelerator pump linkage to get full stroke of the diaphram in most cases.  I haven't tinkered with trying a modified squirter for my issues, simply because the mixture issues I have are more at moderate throttle opening vs poping the throttle quickly.  It is a signal to the booster cluster issue.  I wish I could pick the pony carb people's brains to see what they do to make this carb compatible with a bone stock 289.. I know that they have to do some air bleed calibration, just not sure weather or not it is in the booster cluster, Or the carb body.  Looking at my 1.08 I have two 1/16" or so holes that are directly in front of where the booster cluster goes in. These are not in either of the 1.12's I have.  These holes I belive go into the area where the cluster sits.  If I remember the siphoning process these "bleeds" calibrate the pressure difference between the venturi & the chamber that the cluster goes into.  Also, the holes on the sides of the brass tubes from the cluster vary from carb to carb...

The 2100's are great.  I experimented alot on the motor before rebuild.  I ended up with the stock 2100 with the throttle shaft slimmed, hand pollished venturi, & some misc. fileing on the upper carb body. 

Kevin 

This has been a very interesting topic and I wish I had seen it a couple months ago.  I am just finishing up a 301" 292, ported G heads with big ex valves, Ported iron I manifold, Rams Horns and 2 1/4" exhaust, Racer Brown cam for my Ford o matic '56 truck.  I have a 1.12 carb for this setup which I had hoped wouldn't be too much for this motor.  The old 2100 on a stock tired '58 292 had a pretty bad off idle sag but I put that down to the old motor.  The 2100 carb was a 1.02 I think.

One other thing to think about with these carbs is the accel pump linkage is driven by the spring coiled around the throttle shaft boss.  This has to be tight against the drive link so that the pump squirt has no lag.

Doug T

(I am NOT a newbe)

Doug T

The Highlands, Louisville, Ky.

Ok, so I do have to admit that this topic got me thinking again & so with the wife & son out of town & too much time on my hands I began to tinker... (not like I didn't have other projects to finish! -OOPS)

I found some reducer ends of 3/4 pvc that I happen to have & cut them up. I experimented & cut a groove in the wanna be venturi reducer to fit around the brass tube that sits in the primary side. (I think it is an equalization tube.)  I cut these pvc pieces short enough to clear the throttle blades on the bottom & to barely stick up on the top.

I measured them right at 3/4" ID.  The booster cluster fit nicely & the veturi piesces were snug.  I couldn't get the stupid fragil holley jets out of this particualr carb that I have had sitting since 2004 so I just put it together & tried it.

Of course imediatly the acccelerator pump was shooting out the side of it's housing so I found an un-opend kit & replaced it & the power valve.

when I fired it up, it idled real smoothly, just a bit high.  as soon as I craced the throttle it responded, but imediatly started to roll a rich coughing blurb, blurb, blurb,.  I reached back & with my left hand opend the secondarys while opperating the primary's with  my right.  I cleared the rich  mixture by rapping it a couple of times. still the same . Way too rich! 

off with the carb!   A quick trip to the local parts house revealed that you can not always find Holley jets on the shelf any longer.  I did find a wide tipped screwdriver to try to get the stuck ones out.  Moments later I scrounged & found a pair of 46's  to replace the 57's that were  previously stuck.    While there I decided to replace the needle & seats .  Back on the truck it fired up & idles a bit lean.. A good sighn! I adjusted the idle screws  & reved it a bit.. Definetly alot smoother. With an idle that sounded crisp.  I took it for a quick drive... Still a mosquito killer. !! good only once the secondary comes in.  I took it off, & removed the pvc inserts. I found in my box of carb stuff that little tin piece that bolts to the booster cluster that blocks a portion of the venturi.  (came factory on some 2100's & some 4100's)  I hoped that it would make the carb think the primary's were smaller, & gibe a sronger signal to the booster cluster. I put the bigger jets back in, & tried again....

No more smoke, had to open the idle screws about two more turns from previous.  .. Out on the road, noticebly less throttle application to maintain speed.  Great once in wot.  however, when stopped & take off audiable pre-ignition. This is with 57's on the primary side, & 63's on the secondary.  Back to square one... The Airflow in the primary's at low speed does not suffice on my 301 y-Block with e-4 cam, Cite Heads.  Sadly, I don't think it will work properly without alot more cubes.  It works great above 2000.  The y block could really scream with an engineered spreadbore like Pony Carbs sells.  I put the old 1.08 back on, after freshening it's accelerator pump, power valve, & Needle & seats. Once the plugs get nice & hot, It will be back to it's old self. 

Once again, my rudementary tests do not show the 1.12 working on a y block without running improperly.  I imagine that with a specific booster cluster & jet I could find a medium.  Not sure what the trade off might be though.

Kevin

Hmm... I would be curious just what they did. It seems to me that they either jetted the crap out of it, or did some other mods to help pull the fuel down easier.  I have seen on other types of carbs & combos in Magazines where the throttle plates would be drilled with a small bit to attempt to help the trasition from idle to off idle.. I don't know if it would apply to the 1.12 on a small engine.  I think the theory here is to have a signal already present in the booster cluster in which once you pop the blades open the fuel is already partially siphoning & the effects of the low pressure from the big venturi & sudden throttle opening are supposedly reduced..

Like I said, I think that is the theory. 

Anyone?

I believe they do leave the butterflies the same size. Reducing the venturies doesn't neccesarily reduce the amount of air going in, it makes the air flowing through go faster, thus giving a different vacuum signal for different idle circuit and tuning caracteristics.

I ordered a 1.08 from a rebuilder other than Pony for a lot cheaper and what they sent me was a 1.12. when I recieved it I called them and told them it was not what I ordered and wanted the 1.08 and they said they tuned the 1.12 to work on my motor so I decided I would try it. I have been running it all summer and it appears to work great. No black smoke out the exhaust so it is not too rich. maybe I should check the plugs and make sure it is not too lean like you ended up with.

55 Vicky & customline

58 Rack Dump, 55 F350 yard truck, 57 F100

59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?

ok, so I have a further question then, does anyone know what the proper, or ideal percentage of butterfly size to venturi diameter is??  Would shrinking up a 1.12 venturi in theory require a smaller butterfly? I would think for ideal throttle response of course.  But for adequate throttle response?

I personally have successfully increased the secondarry venturi on my 1.08.  I know the stone I used is right at 2.0.   With the transitioning work I did to clean them up, (more on the bottom) it could be a fraction more.  The trottle plates for the secondary's are obviously too small for that size venturi. 

Pony carbs claims they reduce the primary venturi on their 1.12 spreadbore to 1".  Do they leave the throttle plates?

Kevin

After thinking a little more about it,you and John are right of course.So, for now I guess I'll stay with my stumbling Holley.

And the tall spacer fooling the card into thinking it's a larger engine is right also.I ran into that on a circle track car when the rules required a two barrel for the limited late models.I bought a C&S carb that flowed 925 CFM and it was too much carb for my 383 until I put a 1.25" two hole spacer under it.With that spacer that thing came off the corners like a rocket.

 

Paul,

Boonville,MO

Paul,

      Re the question on the restrictor plate. Like John said the issue is the air flow at low RPM. The Restrictor plate won't change that. All it'll do is restrict the amount of air at higher RPM. You have to have enough airflow through the primary side of the carb to create a signal for the fuel circuits to work accurately. If you don't have that because the carb is too big, nothing short of fuel injection is going to help.

Frank/Rebop

Bristol, In ( by Elkhart) 

This would be the Holley model 4100.  Basically a good carb but never really caught on with the aftermarket crowd.

Lorena, Texas (South of Waco)

Didn't Holley make a version of the Autolite carb for a while? I think it was the same basic design with a removable top cover and annular discharge boosters.

Best regards,



Paul Menten

Meridian, Idaho