The Stovebolt Site Forums The Shop Area Driveline Need for speed

Heh Folks,
I have a 51 3100 fully restored. The engine is a 235 and the numbers say it's a 58-62 block. I have an SM420 bolted behind it, torque tube rear with the 3.55 setup. The truck has 15 inch wheels with P225x75 tires in the rear. She runs like a dream....up to 50 mph. It would be nice to at least go 55-60 if I get on the highway to go somewhere. If I bump up to 16 inch wheels and tires is that gonna give me 5-10 mph more? Should I go with a "regular" 4 speed, open rear end with lower gears? If so, what easily swapped 4 speed and rear end would you graduates of Truckology recommend? Thanks for any and all ideas.
Bodini

With the tires and gears mentioned, you should be able to cruise 60mph at 25-2600 rpm. That's well within stovebolt capabilities.

Here's a spreadsheet if you'd like to play with tires, gears, rpm
https://drive.google.com/file/d/1tOJj5vmPHfJh61G5QV4-8iIjQ8WBDCB_/view?usp=sharing

Is the rear end actually 3.55?

I can cruise for hours at 60-65 mph for hours with 16” truck radials.

MPG gets lower as you go faster.

15-16 mpg at lower speeds.
10-12 mpg at higher speeds.

Here is another RPM calculator (I use the calculator at the bottom)
http://www.csgnetwork.com/multi rpm alc.html

Thanks guys. Yeah, I had the rearend rebuilt and the Patrick's 3.55 set up was used. But over 50 mph I feel like I'm pushing it.

Bodini,
Do you have a tach? If so, what RPM are you running at 50 mph?

Regards
Craig

These engines are supposed to scream at highway speed. They are supposed to scream before each gear shift.
They are high torque, low horsepower engines by design. In order to get them to do work, you need to make them scream.
Once you get over the fear of the screaming, you will begin to enjoy them for what they are.
If you baby these engines, the combustion chamber becomes clogged with carbon. That's why you need to drive it like you stole it from time to time.
If it blows up, it means something was wrong with it to begin with.

I ran a 1958 Chevy DelRay coupe with a bone-stock 235, 3.55 gears, a 3 speed column shift, and 14 INCH WHEELS anywhere from 65 to 80 MPH routinely back when I was in college. Yes, it screamed, but it stayed together. If I'd had 16" wheels and a long enough straightaway (or a slight downhill run) I could have gotten it up to 100+ MPH!
Jerry

Switch to 16 inch wheels and TALL tires. I can easily cruise my 53 truck with 235 with stock driveline at 60 mph and have pushed it to 70 mph plus on occasion with pedal to spare... 15 inch tires are just too small for these trucks in my opinion.

My 51 flys down the highway with traffic without issues!

Engine:216
Rearend: 3.55
Trans: 3 speed
Wheels: 15” (not a tall tire)
RPMs: roughly 3200-3400
Speed: roughly 70-75 (speedo doesn’t work, so using GPS)

If I haven’t driven my 1 ton (261, sm420, 4.10 rear with 215/85/16s) for a while, I feel like she is screaming down the highway too. After about 15 minutes, my foot gets heavier, the speed increases, and the noise seems to fade away as you get reaccustomed to it! Then, I drive imthat engine properly. Haha!

Fox nailed it. The reason your truck isn’t going faster has nothing to do with the truck but rather the driver. At 60 it can be louder than you’re used to. Just keep going.

I’ve taken trucks of your similar setup well beyond speed limits once determined all driveline components are sound and operating as required to safely go faster.

One important thing to remember is we're spoiled to QUITE vehicle cabins these days. So isolated from the normal mechanical noises our vehicles make that they could be electric and often times not be much quieter. AD trucks are not like that. You hear every little tick and tock, clank and possibly knock (hopefully not a knock).

The above said, if the valves are not properly adjusted, a 216 or 235 can be a lot noisier than it should be. So, make sure everything is as it should be and then check out a rpm/speed calculator to determine how many rpm you're turning at a given speed and don't worry about how things sound. If another stock AD truck is in your part of the world it might help to ask a ride just to broaden your experience base.

Also, check your engine tune. Minor adjustments can make big differences.

"The above said, if the valves are not properly adjusted, a 216 or 235 can be a lot noisier than it should be."

When you next plan to adjust the valves, take off the rocker-arm assembly and inspect the surfaces on the tappets that contact the top of the valve stem. They might have wear-indentations in the contact-surface. This produces noise and also results in incorrect valve lash/gap settings (most likely affecting gas mileage and performance?)

These surfaces can be carefully resurfaced/smoothed. If that is needed, you will have excessive noise when the engine is running. (there are other "wear areas" in that assembly (the two "pipes"), but those indentations on the tappets/rocker-arms are the most most common wear areas)

If/when you ever visit northeastern NC, please stop by my house for a ride. You can sit in the rear seat of my Suburban and we will be able to easily talk with each other at 60-65 mph.

Today's engines are barely above idle speed at highway cruise. No wonder they're quiet! I actually went to smaller wheels on my daily driver (04 Ram 1500) because the engine RPM was too low. By the time the little V8 and the OD transmission worked its way through all the gears, got into overdrive, and locked up the torque converter, the thing was running 75 MPH at 2000 RPM. Any attempt to run slower resulted in constant toggling in and out of converter lockup, and/or shifting out of overdrive at the slightest hint of a hill. Cruise control? "Fuggedaboutit!" To keep the transmission from eating itself, I changed from 17" wheels to 16". Now I can run 65 or a little less at 2K, which is the place the engine likes to cruise.

If you're not running a stovebolt engine 3K RPM at highway cruise, you're lugging it.
Jerry

I concur with Sweet!
For it was he whom had my truck with a 216cu up to 77mph! There is a picture out there somewhere of the recorded speed! He also broke the land speed record for a 53 3804 with original power plant!
Jim

Install a tack and judge rpm by that as opposed to sound .
A number of years ago I did a 600 mile day trip at 60 mph at 3000 rpm . The truck ran fine and required no down shifting on the larger hills as it did when I had an over drive trans. I even had a little better gas millage than when doing 60 mph at 2200 rpm . In time I realized that the motor seems to come alive at about 2500 rpm and starts to drop of at around 3000. I'm not a mechanic and any tuning I do is by ear and I sure guess a real mechanic could get it to perform better , but they still need to rev.

John

Good post. Makes me think more about maybe I'm babying my truck a little too much when I start worrying about driving faster than 2500 rpm with 3.55 gears.

Ditto on the 16" rims and tall tires. That's what I did to my 49' 3600 with a Dana 60 rear end geared 3.73. I took her out today and ran her 60 mph at 2600 RPM.

Thanks for the real-world report, bztguy

Remember Boys .... it's not "screaming" .... it's "singing"

That picture makes me smile.

Thank you

One picture is worth a kazillion words !!!!

Chris,
Do you have my 77mph picture. I can’t find it

I should. What year was that? I’d have to search.

I found this pic from 2016, if you enter the coordinates on the top, is on the speeding grounds......

I think it was singing a good tune John

Very true, John Especially if you look closer at the picture to see the rain on the windshield (vacuum wipers) ... And remember that my truck has its original steering (Oh look, I'm steering with one hand that isn't in a death grip ...) ... original springs/suspension ... bias ply tires ... Huck brakes ... gas tank still in the cab ... Shoot, it is even running the 216 dizzy and valve cover (which, in retrospect and considering all the engine oil coating my engine these days, was a poor decision on my part ... )

But, in the spirit of full disclosure, I *do* have a group-built (Hotrod Lincoln directed) 261 with an 848 head (but stock manifold and exhaust), 4.11 gears in the otherwise original HO72 axle and ... seatbelts (The Juliano's kit).

Jus sayin' ... for the record ... that one needs not go bat guano crazy with modifications to get safe speed and cruise ability for modern roads.

If, having considered all this, one decides one *wants* to modify ... well, that's an entirely different matter

When men were men!

OK, who and what truck did the 86 MPH in the photo posted by Sweet? John was looking fir a photo of him doing 77.

John ,I agree . As you know I have managed to accumulate a fair bit of highway miles with a stock tired 235 , no power steering or brakes with the only concessions being after market rims and an o/d transmission and still have a fairly dependable truck .
That being said I admire the guys that have improved performance with cams , carbs , and manifolds but alas I lack the funds and the know how to do the same .
I did find a 261 out of a 2 ton that I installed over the winter but it too will retain the stock manifolds and carb . I am anxious to see how it performs later this season .

John

Phak1

Who was driving and what? We may never know.

However, if I had to guess, I’d guess either DJ or I was driving either his truck or mine.

I know they can move like that. Been tested.

Is it possible to over-rev a stock 235?

My 1962 235 has stock intake, exhaust, ignition and a Rochestor model B carb. I think I could floor it in 2nd gear and it would never blow up. Correct?

Dj's truck can certainly exercise the speedo to its full potential , and as a side note , it's a fairly good cure for constipation !!

John

Some of the really low-geared big rigs had governors on them to prevent over-revving in the lower gears, but it was probably sort of redundant once the first few shifts got accomplished. The gas flow through the cylinder head is so convoluted that it's unlikely a stock 235 would hurt itself once it's out of 1st. or 2nd. gear on a SM-420. Maybe downhill with a heavy load, wide open in granny gear might make one over-rev, but it would take a real doofus to try that!
Jerry

Jerry -- you, of all people, should know better than to underestimate our doofusness ...

Play with this for a while.. I have a set up that most scoff at. It is 54 235 with a T5 trans and 2.73 Nova rear end. It is great on moderate Indiana roads and I have had it in the Smokie mountains. I cruise all day long at 65-70 mph at less than 2000 rpm. Mpg around 15.

It's like a built in governor.

So, I won't bother with a tach. I have a cheap one but it doesn't work well. It's powered by a button battery and you wrap the sense wire around a spark plug lead.

When we cruze on I-95, with the 54'-3100 I set the throttle cable at 70. It goes for hours at that speed. I will have to check what my ratio is both with the transmission and rear end. Doc