Vroom Vroom...Who am I kidding

I have a 59' CJ6 with a rebulit Hurricane and rebuilt stock T90 Transmission. The drive shafts have new ujoints as well. She runs very well and is a blast to drive however top speed seems to be around 30Mph.

I have the transfer case in high gear, the front drive shaft is disengaged and she has 31" tires. The D44 rear and D25 front axles have not been refurbished yet however they seem to be ok. There is no whining or binding, the wheels seem to spin freely on the axle.

I would appreciate any ideas on this, she runs great after she warms up. She is just not going to win any speed awards.

Petho

 

The F-Head should handle the 31 inch tires ok with 5.38:1 gears in the differentials ( I dont know what you have ).

A Few things you can check assuming a YF carb and clean air filter would include,
1. make sure the throttle linkage is properly adjusted so the throttle plate in the carb will fully open when the accelerator pedal is held on the floor.
2. Double check your timing
3. Check for a plugged fuel filter.
4. Check fuel pump pressure and output volume.
5. Double check the float level in the carb.
6. While checking float level make sure the metering rod has not fallen off the rod arm into the main jet.
7. Make sure the choke is staying fully off.

Also if the above all check out make sure the points are gaped properly and the reluctor in the distributor is not siezed or stuck to the shaft ( are advance weights working)

 

Thanks for the quick response and ideas:
1 Rebuilt Carter YF, yes the metering rod did fall off when it was shipped back from being rebushed and the float is set to about 7/16" with the spring needle valve.
2 The choke seems to be set properly, its manual and wide open when the engine is warm and running.
3 Fuel Pressure is 3.5PSI, I had a flooding problem so I checked it.
4 I have checked the dwell and timing but not recently. It seems to run well when it warms up, no backfiring however it does stumble a bit when it is cold.
5 The speedo says 30 and I checked it against one of thoes speeding signs that gives your speed on the display.
6 I did engage low gear last weekend and it crawls
7 It has fresh fuel in the tank, the filter is a bit dirty but the fuel is flowing. It is a new see through filter.
8 The brakes are adjusted and not binding while driving.
9 The distributor is rebuilt and seems to be happy however I will check that everything is freed up.


I am going to check that the accelerator linkage is set properly today, I have not checked that. I am also going to clean the spark plugs, they got fouled when it ran rich due to the metering rod debacle.
It feels like it needs a 4th gear, the engine rpm increases but it still putts along. Even on a down slope, it just will not pick up speed.

Thanks for the advice guys and to the fellow with the cool Willys collection in Chula Vista that turned me on to this site.

 

The spring loaded steel fuel valve ( resilient tipped needles are another story ) should be intially set to 5/16.............The 7/16 setting will likely result in a low wet fuel level that may have an effect on fuel delivery at the booster nozzel. A quick check that has worked well for me over the years on the 938 series YF is to remove the carb top again after float adjustment and a few minutes of running and quickly measure the fuel level in the bowl. I have found that a wet fuel level with carb top & float removed thats between 1.140 and 1.190 will yield good performance. Adjust your float accordingly.

A jeep with 5.38:1 gears will top out quickly, 30 to 40 is a comfortable cruising range with 50+ getting the revs up there. once over 40 it takes lots of revs to get more speed.

There may not be much wrong............its a jeep thing

 

"the engine rpm increases but it still putts along".............are you saying in 3rd gear you can increase the rpms but the speed stays the same? How's your clutch?

 

Are your brakes dragging? When I had my 4 banger I could hit 50 with 32" tires rather easily on level ground. I didn't have an OD either.

 

I'm not much of a mechanic but if the engine revs in 3rd. but speed does not increase it sounds to me like the clutch is slipping.
Tommy

 

Thanks for all of the thoughts, the brakes are not draging and the clutch plate is new. I am going to investigate the carb setup again. I have a feeling that it may be a combination of gearing and carb set up. I am going to take Brians advice and remeasure the carb fuel level.
Otherwise, I may just be experiencing a 50 year old jeep thing!

 

I agree with most of the suggestions above. In 4th gear on my f-head powered jeep, (same ratio as 3rd for you), I can comfortably hold 50 mph at about 3100 rpm, and still have plenty of throttle response, (though I am not brave enough to take it much above 3200 rpm). The only thing that I would add to check is the gear ratio in the differentials. Seems to me that if someone stuck too high of gears in it that it would run out of power and not be able to get up to speed, (although I don't think that would explain the downhill problem).