Carb question

s-o-s puller

New User
I know some of you here pull the four cylinder hundred and 01 series tractors. I have a 192 with some head work done on it, bigger valves, porting etc. has 190 lbs compression. It will run 2900 rpms unloaded but any load on it and it drops to around 2400 to 2500 and will pull at that with dropping very little rpm till it spins out. Have tried different carbs from different ford tractors and ind engines all the same results. Believe that it is running out of airflow, was wondering what carbs any of you might be running? Thanks in advance for any help.
 

A good friend has a nearly identical set-up. I believe that his is a four barrel with some fairly long manifold runners coming out to the side. The carb sits on top of the manifold.
 

suspect that the govenor adjustment might be holding it back,, but 2400 is close to the design speed...2900 is a bit over?
 
I have tried different govenor spings and settings with the same results and have watched the govenor work the linkage with no response from the carb. Did get better results about 200 rpms with a carb that had a larger thoat dia but still not what it needs. We are allowed 20% over on rpms and must use stock manifold and a carb of same style, 1 barrel updraft.
 
Ford 172 tractor engines as used in 8/9*1 and 4 cylinder 4000 tractors are governed at 2,100 RPM. 20% increase is 2520 RPM.

Valve shrouding will limit high RPM performance in these engines as the valves are badly shrouded.

Dean
 
As for the rpms NATPA list it at 2450 std., 2695 at 10% and 2940 at 20% for a 650 ford. The head is an early 134 that has bigger valves, port work and some relief to the shrouding and some milled off. It would run at 2600 with the stock head with a smaller zenith carb, after the head work it has higher compression and lugs better but really won't much run over 2400 on the track. going to drill manifold and install a vacum gauge to see waht is pulling vacum under a load. I was wondering if any other pullers were using a bigger carb from some other tractor or builder.
 
With all that work on the head to increase airflow, have you re-jetted the carb to get more fuel into it?
 
I am using a stock replacment manifold, the newer style with the elongated carb mount holes with the thoat bored out to 1.5". was using a zenith carb from another tractor puller that worked till I did the head work. With it I can open the fuel to make it run rich to blow black smoke but perfomnace is still the same no high rpm under even a slight load. Tried a MS carb from a 192 ind motor with bigger throat but it does not have an adjustable main jet in it and still behaves the same way.Tried to put an adj main jet in it and could not get it to seal and not leak gas, do not know the number on it as there is no tag on it. Many of the carb web sights that I have checked list the same carb for a 172 or 192.
 
NATPA is wrong regarding the governed speed of OEM 172 engines in farm tractors.

The 134 head is more shrouded than is the 172.

Dean
 
I have been told to use a carb off a D17 allis or other tractors, before I go through all of this I thought maybe somw of the pullers on here would have gone though the same thing and know which way to go. I read this forum a lot and gained quite a bit of knowledge from it and am thankful for all the help and answers. My next step is to try one of the speciality carb builders and if any one on here knows of one that has had luck with one for Fords any information would be helpful. Thanks for a great place to read and learn.
 
Well if you can make it blow black smoke with max enrichment then you are airflow limited (as you initially stated) somewhere in the induction system. (carb and/or manifold).I think it"s possible that your venturi is choking and limiting airflow. Can you get an increased area venturi for these carbs?
For 2800 rpm the limiting diameter of your venturi is ~0.8 inches in diameter (~13/16"). The venturi must be bigger than this in order for it to not limit your air flow. It should be roughly 1 inch in diameter.
 
I would tend to think that the cam profile is probably limiting it as much as anything at 2900 rpm... I mean... there is a limit to how much air you can suck through 190 inches of engine without pressurising the air...

Rod
 
That is my thinking on the venture, the carb I have off the 192 has the biggest venture of al that I have tried and is getting me the best rpms but still not what I need. I know there are fords out there with bigger motors and ag type carbs running those kind of rpms and thought maybe some body on here might know what they are using. Does any body on here know where you a supplier that you can get parts for MS carbs, that I might be able to get a larger butterfly and enlarge the throat on a carb I have several of the large MS carbs off of industrial ford motors. Or if someone has had a carb built from some of the puller places. I have tried to talk to Denny's Carb but did not get much of an answer if they could build one may have been busy and did not have time to talk. Again thanks for your answers and questions as they seem to be confirming what I have thought ois the problem.
 

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