Need for Speed

So I am looking at Flatties (3As & Bs). I spent a lot of time in a 55 CJ5. I like this stock set up including the whiny gears, frame mounted pedals, offset diffs. I can even handle the Ross steering when it's in good shape, no front locker. Problem is I need to drive 60 highway miles to the wheeling spot. The CJ5 seemed that it would maintain about 45-50 without an OD and maybe 55 with it. Hills were slow here in KY. It was the 5.13 axles.

So I got to looking at a torque chart on the F134. You are probably around 90 ft# & 70 HP at 4K/max speed & really too much RPM for this motor. It would seem that the 4.27 ratio might be better on the road since at the same speed you would be higher on the torque curve with the lower RPM. But you'd loose crawl which is never a good option IMHO.

So my questions.
1. On road, 4.27 to 5.13....more drivable? With or without OD?
2. Swap in a V6...better acceleration how much faster do you really go? BTW...I will do the 1 1/4 intermediate shaft if I am going fast.
3. Flat towing....I could drag it behind my F250.

 

Yep, mistyped the gear ratio (I am actually trying to think what I was thinking has 5.13s). Figured bigger intermediate shaft=bigger bearings=less chance of heat up. Probably not a big deal. I am looking at a couple of 3Bs in various states of repair/modification. Nice 2A with a fiberglass tub and V6. We'll see. I am really just trying to get my ducks in a row.

 

With the Ross box, 2 piece tie rod and stock brakes, how fast do you really want to go? I think 65 would be really pushing one's luck and it doesn't really matter how conservative you drive because there are a lot of idiots out there that make very poor decisions. With the F head, I certainly would not go any higher than 4.88 and suspect I would stay with the 5.38's. With the OD and motor in good condition, something near 60 mph is obtainable-just not on any notable uphill grade. The factory V6 and 4.88's worked well, especially with the OD. That combo will go about as fast as you will ever want to drive one.

 

Yes, I would disk the front for sure. Sounds like V6 will be the thing for me. Would a modern 4 like an GM Iron Duke do well? I just want to be able to not get run over on the highway. I really don't want to tow it. What's the fun in that and hard to hear a wheel bearing from the tow vehicle. Thanks for the input.

 

Virtually any modern 4 banger will allow the Jeep to maintain 70-75mph.

 

The 3B's Hurricane is a huge plus over the 3A's Go-Devil.

Even though it provides double the HP;
the Dauntless only provides a 10% increase of crankshaft velocity over the Hurricane at maximum torque output.
Crankshaft velocity is critical to speed.

Trust me on this one....The 5.38 geared 3B with O.D is a great setup.
It will cruise all day long at 62 MPH.

If you don't trust me maybe I can dig up my old article titled ...
Everything You Ever Wanted to Know About CJ-3B Speed and Then Some

 

Not meaning to be a butt head about this, but what you posted is very misleading if its even true. With better than double the hp and double the torque the v6 will run 90+ mph without 3.73 gears and will get there faster than the Hurricane can get to 50. There is no comparing the power and acceleration of the Dauntless to the Hurricane or Go Devil.
My Dauntless will pull a 8% grade without downshifting and accelerate from 45mph, the Hurricane would definetly be slowing down and downshifting at the same 45mph.

 

The big attraction of the I4 over the V6 would be the under the hood space. I like the in line engines for that. I know the V6 is shorter but it is also wider. Just doing a little creative thinking right now. I have a 3B I have some interest in. It is on a 62 CJ5 frome with a 343 AMC V8/T15/D20/D44 center/D30 front. I would sell the old AMX motor (this should be worth some $) and probably the rest of the drive train, maybe keep the D30 front. Then use the proceeds to buy a more typical drive train. All on the back burner but who knows.

 

Mcruff's take on the 225 versus either of the 134's is absolutely correct, whatever the crankshaft velocity issue may be. There is no comparrision in the overall drivability, 225 wins hands down. As noted, there really is no space issue putting the 225 in a 3B-not much different than in the 5. I do not know about the 3.73's as I have never used them, but a factory 225/4.88 with OD in my CJ5 will also hit 90.

 

4.27s are not the way to go. I had a '63 CJ-5 with the F-head, 55ish was about the top end maybe 60 downhill with a tail wind. Also power was a noticable difference with the hardtop on.

If you start doing the math (30" tires):
5.38 x .75 = 4.04 rpm @60 - 2708
4.27 x 1.0 = 4.27 rpm @60 - 2869
4.27 x .75 = 3.20, rpm @60 - 2150

At 3.20 gear ratio, you will be hating life with the 4 cyl.

 

As far as room for motor swaps, the easiest is the 3b hands down. The 3b grill is much easier to take the shroud off and get the radiator tight to the grill.

 

There is actually enough space to put a ps or engine cooler (or both) in front of the radiator in a 3B, even with a V8. I just tilted the radiator back to match the plane of the fan and it worked great. You can also get the standard size 19x26" gm radiator in there.

 

We probably have wheeled in some of the same areas. Don't screw around with changes that make it go faster on the road. Tow it. Get home safely. Tow it!

 

What I stated is absolutely true. And it was certainly not intended to mislead.

The maximum torque output for the F-134 is approximately 114 ft lbs @ 2200 rpm.
The maximum torque output for the Dauntless is approximately 235 ft lbs @ 2400 rpm.
That is roughly a 10% difference of crankshaft velocity.
What does that mean ?
The maximum efficient speed for the Hurricane powered jeep is only 10% slower than
the maximum efficient speed of the Dauntless powered jeep. PERIOD.

I NEVER EVER stated that the output of the F-134 was more powerful than the Dauntless in any way.

The viable top speed for any short wheelbased Jeep is a matter that takes in a multitude of factors.
The bottom line is: Speed is a measure of unidirectional time and linear space. PERIOD.

As for 4.27 gearing.... I fully agree with bobracing, 5.38 and O.D. wins everytime for the low powered Hurricane.

 

You'll love a 225 V6 on the road and off, this is my first one and I've driven quite a few different engines from a 258 I-6 to a Chevy V8 to a 400hp 800lb/ft Cummins 5.9 and the V6 is my favorite.

 

a well built f-head will do 4,000 RPM all day long. I have seen a mud racing Jeep with the f-head, running 5,000 RPM going around the track. Loud. But help together just fine, and the owner said all he did was very carefully build it.

OD is useless it you live in a hilly curvy area like I do. They are best suited for the flat lands and down hill. NOT UP HILL.

The 225 is a great engine, but I will stick with my straight engines, I like those better, less that could go wrong.

 

Thanks for all the input. It's a matter of horsepower versus hills. Plan moving forward...V6 & OD.