no power f-head

Today was the first off-road test for my '67. And by off-road, I mean very loose/rough sand at the beach. This is the kind of sand that swallows all 2 wheel drive vehicles. The CJ did pretty good. The 4x4 definitely works, but it seems the engine is always bogged down. I know the f-head is not a muscle machine but, this was sad. I have 31.5 tires on it so that doesn't help with the gearing but it just seemed like the motor was gasping for air the entire time. The f-head is completely stock except for a cone air cleaner instead of the oil bath. The worst part was going over the bridge across the intracoastal river. I had to stay in 2nd and wind it out to go 30 mph up that thing and its not a huge bridge. If I put in in 3rd, it felt like I was going to coast to a stop. What are some pointers to make sure that the f-head is performing like it should and putting out all 72 horsepower?

 

sounds to me like it was running rather well if you were able to use 2nd gear in sand. Get used to it cause it don't get much better.

JB

 

If these items haven't been checked in a while, might be worth checking:
timing and dist advance weights
carb bowl for sediment
fuel filter (can you blow thru it?)
what gear ratio, 4.27 or 5.38 ?
mine with 5.38s ran pretty strong
my 0.2 worth

 

the compression isn't good when they are brand new.......you very well might be able to improve it slightly but don't get your hopes up. If you have 4.27's you are in trouble. I drove one for 20 years, new rebuild, wore out, milled heads, clean fuel filter, dirty fuel filter, good valves, burnt valves, new carb, carter carb, solex carb, rochester carb, header, they are not power houses and never will be.

No offense sparky but as far as I'm concerned they are best on the end of a chain hanging from a boat.

JB

 

My 56 Willy's with the F134 handles the hills great in East Texas. It will easily pull a 30 degree grade in 3 rd gear without any problems.

Have you checked your brakes? After these older jeeps set up for a while the rubber hose on the front has a tendency not to let the brake fluid return to the master cylinder. This will cause symptoms like you are describing with not having any power. It keeps pressure on the brakes.

I have had 3 jeeps with the F134. And 2 of them had a problem with the front brakes not releasing all the way. Replaced those rubber hoses, and it was like I had a new motor.

An easy way to check to see if they are indeed dragging , is to touch the outer hub with the back of your hand to see if it hot. If the brakes are dragging, it will be almost impossible to push it by hand. Another way is when on a flat surface, see if you can push your jeep.

That little F134 motor puts out 72 HP. Next time you are in the sand, try shifting the transfer case into low range. You will then have plenty of power.

 

Sparky,

I was just having a little fun and you are right, they are lots better on hard ground. I have always thought that the L-head flatfenders felt stronger. Low compression is the biggest problem, being that they start off at 7.5:1, when you loose a little of that they will NOT lug. If madmax has less than 5.38's it will be hard to make better. I hate to see these old jeeps chopped up. I always tell guys that don't like the F-heads to keep it in the shed and get a cut jeep to modify.

JB

 

Is there a simple way to tell what gear ratio it has? I had a previous post and most people guessed it should be a 5.38. But, now I'm not so sure. I'm going to do the compression test and see if thats a prob. Also, I posted some new pics here www.matanzasjeepclub.com/cj5.html

 

Well, I know next to nothing about darned near everything, but can't you get pretty close to figuring ratios by jacking one wheel up, marking the driveshaft, and counting revolutions while you rotate the rear wheel? Just a thought. Oh, great, hope I didn't waste my thought for today. That happens quite a bit.

 

Yep, on the stamp, except I don't think my ratio was on the tag, instead I have 41-11 stamped on the axle housing (Pumpkin). 41 divided by 11 equals 3.73 and some change. That's 41 teeth on the ring gear and 11 on the pinion gear.

If there's no tag, look on the flange of the pumpkin for this stamping. Don't know what the figures are for 5.38 or 4.27 but if you find the stamped numbers and do the math it should be one or the other.

 

John that was not done by the factory that way unless it was a Canadian thing, if you have a dana axle in a new vehicle it still has the tag on it even today, that is dana's standard way of doing business. They will have the tooth count and the ratio and I think a serial number.

 

Here's how to tell the ratio.

Vehicle in neutral, tires blocked, transfer in neutral, one wheel off the ground

mark the 1200 position on the tire with some chalk, or you could turn the wheel 'till the valve stem is at 1200.

Mark a line from the diff housing to the drive shaft with some chalk or paint or something.

Rotate the wheel TWO - yes, count 'em TWO full turns and count the number of revolutions of the drive shaft. It will turn either 5.38 times or 4.27 times. You don't have to worry about calculating to the hundredths; there are only two ratios that it could be.

3.73 and 4.88 were used in the V6 jeeps, so they are most likely not involved here.

I had a low power problem with a jeep engine that I rebuilt and the solution was not the engine, but the gas pedal. It was maladjusted to the point where flooring it gave only, maybe a third of the range of the carb. I fixed that and I've got plenty of throttle.

Timing could be off and that would affect it too.

good luck

kamel

 

If I could ever get a day off from work, I could make some more progress on this project. But the more I think about kamel's gas pedal suggestion, I might just end up dragging the flood light into the carport to check it out. I do remember feeling like I had the pedal all the way to the floor, so it could be possible that there is some binding or adjustment problem there. I'll post an update when I figure it out.