Topped Out at 65 mph

Today, I decided that my timing could not possibly be correct. I figured the F 134 that I had built and put the 2-bbl Weber on, had to have more to it than what I was getting. I had read earlier in here where people were trusting their hearing and their experience when it came to timing their vehicle and not so much the elusive timing mark on the crankshaft pulley. So I did just that today, and decided to go for broke to see what the actual top end was for my '62 Willys. Since I have 31" tires on the Jeep, I decided that the only way I could get an accurate reading was to use my GPS. So I hooked it up and went for a ride. The first thing I noticed, after changing the timing, is that the engine had a lot more "life" to it than it did before. That was a good thing to experience. So I found a long, level stretch of road close to where I live and hit it. The 2-bbl seemed to do what I wanted it to. It took the Jeep close to 65 mph and it was topped out, both in rpm and breath. So now I (we) know what to expect in the end. This is a freshly rebuilt engine, using 10W-40, a T-98 tranny and 31" Baja Claws. No need to run it that hard, as that is not what it is built for. I will be trailering it behind my Xterra Pro-4X and keep my Pro-4X nice for winter trips to Tahoe, etc., and use the Jeep for the hills.

By the way, the power brakes work well. I tested them and found that the Jeep was pulling to the right. So I figured out how to adjust the shoes and now it is perfect. I really like the adjustment mechanism. So easy to use. You all have a good Superbowl tomorrow. I plan on doing so.

Thanks to all of you who helped me get to this point. I am very glad to have found this forum and hope I have helped a few of you along the way, too.

 

Glenn, I was watching my tach, and it was a bit over 4K, and that is all she wrote. Just had to see what would happen. I am going to play with my timing some more, and I want to try changing one more jet in the Weber and see if that gives me more "around town" driveability. I am getting it dialed in.

 

What ratio are your axles? 4:27,4:88, or 5:38? It makes a big difference on speed.
I remember as a kid being able to edge just over 75 indicated with my old Tux. F134 with stock carb, 4:27 axles, and h78-15 tires, and about 5 miles of straight road.
A week later ended up breaking the crankshaft due to an over-rev going from 1st to 2nd in deep sand. I don't know if my speed run contributed.
-Donny

 

31" tall tires 3rd gear 5.38 no OD 65mph is 3800 rpm
29" tall tires 3rd gear 5.38 no OD 65mph is 4055 rpm

If your tach was showing over 4000 rpm it might not be real accurate.

Speed Calculator

 

That's right, Glenn. Good point. But the tach may not be totally accurate, too.

 

See my signature. 4.27:1

 

What does the tach read at 50 mph?

 

OK changing to the 4.27-1 gears his tach is WAY OFF

31" tall tires 3rd gear 4.27 no OD 65mph is 3000 rpm

Also why on earth would you have a 150cfm The Weber 32/36 and Holley Weber 5200 is rated at 230, 280 or 320 CFM depending on the pressure drop used. (1.5, 1.84, 3.0"Hg).

What progressive Weber do you have that's that small?

I'm currently working on modifying a MG aluminum manifold to fit my 134L running a 32/36 DGV Weber.

 

Disagree on the tach reading 3K at 65 mph. Maybe with 3.3 gearing. Mine reads 3.2K at 50 mph, and just under 3.5K at 55 mph with 5.38. 4.27 should give him somewhere around 2.8k at 50 or 55. 65 mph would be hanging around the 4K mark.

 

One can play with the numbers on "paper" here-- Speed Calculator

 

What size tires were you running?

 

The Weber is a 150 cfm K-553. If you do the calcs,

134 in^3 volume (“134” is the cubic inch displacement of my 4-banger)
2 revolutions/volume (4 –stroke engine)
4000 revolutions/minute ( I used the redline value for the F-134 engine for max possible air usage by the engine)
1 foot / 12 inches (at least it did last time I looked – this is just to make the units end up at CFM)

Now put what you know together so that the dimensions give the result that you want - CFM, or feet^3/minute

134 in^3 / volume * 1 volume / 2 revolutions * 4000 revolutions / minute * [1 foot / 12 inches]^3 = 155 CFM.

This assumes 100% volumetric efficiency, that is, that the intake path is so smooth and large that the cylinder fills completely. We know this isn't true, but we can conclude that I should not need more than 155 CFM to get everything out of the F134 that is possible without forced induction.

The formula was given to me by Timgr. I had seen it before when I was younger, but couldn't readily find it, so being the Jeep nerd that he is, he jumped right on it. (Thanks again, Tim!!)

I know when I was a kid, building engines, I couldn't believe how people screwed up by totally "overcarbureting" their engines. It was like they were thinking that if 650 CFM was good, a 1000 cfm must be that much better. The jeep runs great with this carb. Since 134 c.i. is a little less than 2.2 liters, I think this carb is an excellent match.

Don't forget, I also have a T-98 tranny. I don't know how the gearing compares to others like the T-90, etc., but I do know it is different. I certainly like that first gear. In low and low, I can get out and walk faster than the jeep rolls at an idle speed of 800 rpm.

I once took a Karmann Ghia engine and took it from 1600 cc to a little over 2300 cc with dual port heads, a snake package and modified the intake manifold to put a Holley 5200 which was close to 150 cfm with a mechanical, progressive secondary setup. This is the same carb that was used on the ill-fated Vega engine, but it was an excellent carb. The Vega was a 2.3 liter engine and this carb worked well on it. I can only tell you what I have been told and have experienced in my engine build-ups. Let me know if I can help you with any info.

 

Thanks for the input. One can tell a lot just by listening to the F-134.

 

True.
But that can also be more risky at speed, versus wind noise, transmission whine, tire howl, and the sensation that your jeep is holding up traffic.

 

LMAO!!! Thanks for the (truthful) humor. All I know is I am satisfied with what I have done so far. I really like the carburetor. My friend has a CJ-5 and mine is much quicker than his. I take him off the line and all the way down the road from there.

 

So you guys are saying the Speed Calculator is incorrect (that's where I got my numbers)

Speed Calculator


I have to wonder what the heck is wrong with your engines? Or are your tachs screwed up?

If eti engineer has 31" tall tires is in high gear (which is straight through on any but an OD tranny) with 4.27- gears in his rear axle his engine at 65mph would be mathematically turning 3010rpm Sorry I rounded it off to 3000

K-553 is the manufacturer (Redline) of the carb kit your using the carb is a Weber 32/36 DGV that will have depending on how its measured between 230 and 330 CFM No matter what your math problem says the engine requires. Sure it might only draw 155cfm but the Carb will flow at least 230 cfm at 1.5" of Hg I have two of the same carbs sitting on my bench right now (ok one of them is in a whole bunch of parts as I am modifying it).

Myself I will stick with the math I learned as a Auto tech Major in college (which matched the Speed Calculator I linked to) and have been using to build hot rods and performance cars for the last 40 years.