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Old 03-04-2021, 12:29 AM   #21
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Originally Posted by Crown_Guy View Post
Very nice. BUT, You left out the only really critical information for those of us who'd like to try it for ourselves...... What's the site URL. This kind of resource never goes out of style, I can use it for my own and others who are looking for answers. I'll try to find it too but I like the look and layout of this site. The others that I've found are always lacking and/or just look bad. Thanks in advance.

You have to spend time figuring out how to set it up. You have to know the transmission ratios. You need to know tire circumference. You have to decide on your shift point. I have to confess I really enjoyed my time working with this tool.

I also came up with an Excel spreadsheet that calculated gradeability and startability which helped me a lot with understanding a lot of 'stuff' related to a bus.

https://www.blocklayer.com/rpm-gear.aspx

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Old 03-04-2021, 07:46 AM   #22
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I've got an excel spreadsheet as well that shows a dozen or so different auto and manual transmissions, their ratios, different rear axle ratios, mph-rpm correlation, driveshaft rpm(IT MATTERS).

Then that data is put on a line chart so I can see RPM drop between gears and speeds.

Big thing people have to realize/remember is that the torque converter gives you a variable ratio. That's how automatics can get away with steeper first gears then what one would ever see a manual transmission with. So comparing manuals to automatics isn't apples to apples.
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Old 03-04-2021, 08:13 AM   #23
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So.......thoughts on the 3126.
I have two 3126s and one 3116 at the moment and have had 3126s in the past. They are a very good engine. It is the owner maintenance that is the issue. Cat came up with the idea to use the engine oil at very high pressure to pressurize the fuel system and then use the ecm to electrically fire the injector. Hence "HEUI" on the fuel system description. Hydraulic Electric Unit Injector.

This system requires using very high quality engine oil that meets or exceeds Cat's specifications. Using Cat filters on both the engine oil and fuel system are a must. They are worth the money. They are not just marketing hype. Keeping the oil and fuel maintained and very clean will make your HEUI engine run a very long time.



Cat put out a few upgrades to the HEUI system over the years of production. You can find these upgrades described in a several places on the www. Look for them, and see if any upgrades have been done to any prospective purchase. Here is a link to one of the best known and respected Cat mechanics on youtube. Adept ape channel. He is very good, but not the only one and may also have differing opinions than some others about some aspects the Caterpillar line up.


Any "Cat mechanic" that says to run or pass on a 3126 is an employee that I would not want looking at any of my vehicles. A "Cat mechanic" would know better, and would be more willing to inform any prospective buyer.

For every individual that slams Cat or any other engine make, I can produce the same quantity of people that will slam their own engine of choice. This is the same old ford vs. chevy, vs. dodge etc., etc.



So.....my "thoughts" are do not fear the engine, fear the maintenance, or more particularly, the prior maintenance or lack thereof. If the engine appears upgraded or well maintained, and wow, would it ever be awesome to get ahold of records about said maintenance, the 3126 could very well be the most satisfying engine you will ever own. Or not.
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Old 03-04-2021, 08:36 AM   #24
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Originally Posted by Deezl Smoke View Post
... do not fear the engine, fear the maintenance, or more particularly, the prior maintenance or lack thereof.
With this, you win the succinct sage quote of the week award.
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Old 03-04-2021, 09:07 AM   #25
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Oldyeller, Thanks for posting. That is a nice resource. Please post your grad-ability exell as well.
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Old 03-04-2021, 09:56 AM   #26
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Oldyeller, Thanks for posting. That is a nice resource. Please post your grad-ability exell as well.
I tried to attach the spreadsheet and discovered I couldn't. Does this forum restrict the attachment of xls files? If you know how to attach them let me know.
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Old 03-04-2021, 12:50 PM   #27
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Best gear ratio calc ever!

I always used "grim jeeper" gear ratio calculator when planning out my (slow) bus rear end and tire/wheel swap. I thought it was pretty good... BUT...

Blocklayer takes it to an entirely new level!

The guages are so fun!.. and I appreciated the fact that I could change the Tach. to a 4000 RPM version just like I have in my bus so that the sweep was similar to what I see when in the bus.

I have no need for a 5000 redline version running IH gas motor 304..
If an old binder motor sees 5000 RPM... It will be the last time...

Getting off topic here, but before you buy anything - Bus, ring/pinion, tires..
Get the numbers... Engine RPM sweet spot, Tranny high gear ratio, tire size.

Run it through one of these calculators. It was so satisfying on my project to have it all on paper and know what to expect rather than an expensive version of trial and error...

I changed rear ratio (6.68 to 5.29) and tire size to get speeds and ratios I wanted. Using gear calc. I didn't spend money on things that didn't "pencil out" first... Just for the record, still slow.. but great on the 2 lanes!

Diesel with a stick shift? DO IT!... You almost never hear about a stick shift bus anymore, but you do hear people wishing they had one.
Just not common anymore, even the military doesn't expect people to drive a stick. Kind of a bummer really.
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Old 03-04-2021, 02:39 PM   #28
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Quote:
Originally Posted by crowcreekcabin View Post
I always used "grim jeeper" gear ratio calculator when planning out my (slow) bus rear end and tire/wheel swap. I thought it was pretty good... BUT...

Blocklayer takes it to an entirely new level!

The guages are so fun!.. and I appreciated the fact that I could change the Tach. to a 4000 RPM version just like I have in my bus so that the sweep was similar to what I see when in the bus.

I have no need for a 5000 redline version running IH gas motor 304..
If an old binder motor sees 5000 RPM... It will be the last time...

Getting off topic here, but before you buy anything - Bus, ring/pinion, tires..
Get the numbers... Engine RPM sweet spot, Tranny high gear ratio, tire size.

Run it through one of these calculators. It was so satisfying on my project to have it all on paper and know what to expect rather than an expensive version of trial and error...

I changed rear ratio (6.68 to 5.29) and tire size to get speeds and ratios I wanted. Using gear calc. I didn't spend money on things that didn't "pencil out" first... Just for the record, still slow.. but great on the 2 lanes!

Diesel with a stick shift? DO IT!... You almost never hear about a stick shift bus anymore, but you do hear people wishing they had one.
Just not common anymore, even the military doesn't expect people to drive a stick. Kind of a bummer really.
One thing I noticed using the gradeability calculator was increasing the tire size effectively decreased the 'final drive' ratio. In many cases that's a good thing but you have to consider the impact on gradeability. Having said that I expect you'd (whoever you might be) have to be on the line for it to hurt you and most buses probably aren't that close to being geared so low increasing tire diameter would hurt them. When I was looking at the short bus with the manual I was torn between going with a 3.42 vs. 3.73. In fact my indecision probably led me to missing getting that bus because by the time I went back with the intention of buying it I was told it had sold the day before. Trials of a newb. LOL, I'm still dealing with them.
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Old 03-04-2021, 02:49 PM   #29
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The math is actually quite fun to do and is very simple. No special calculator needed.
Basically the only conversion you'll need is remembering to convert hours to minutes, which is a simple division by 60.


Tire diameter x 3.14. Now you have inches of circumference. Divide by 12 if you want feet. A mile is 5280 feet. How many rotations of the tire does it take to get 1 mile. How many miles per hour is the target? Multiply the target by 5280, divide by the tire circumference, and you have the revolutions needed in one hour to reach the target speed. Divide by 60 and the revolutions per minute. Same rating measure as the engine specs are listed in.


Maximum torque value engine rpm? Multiply by transmission gear of your choice. Direct? OD? If direct, the engine rpm will be the same as the driveshaft rpm. If OD, then multiply engine rpm by the OD ratio to get driveshaft rpm. Now you can determine your ring and pinion ratio needed to achieve your goal.
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Old 03-04-2021, 06:44 PM   #30
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Quote:
Originally Posted by Deezl Smoke View Post
The math is actually quite fun to do and is very simple. No special calculator needed.
Basically the only conversion you'll need is remembering to convert hours to minutes, which is a simple division by 60.


Tire diameter x 3.14. Now you have inches of circumference. Divide by 12 if you want feet. A mile is 5280 feet. How many rotations of the tire does it take to get 1 mile. How many miles per hour is the target? Multiply the target by 5280, divide by the tire circumference, and you have the revolutions needed in one hour to reach the target speed. Divide by 60 and the revolutions per minute. Same rating measure as the engine specs are listed in.


Maximum torque value engine rpm? Multiply by transmission gear of your choice. Direct? OD? If direct, the engine rpm will be the same as the driveshaft rpm. If OD, then multiply engine rpm by the OD ratio to get driveshaft rpm. Now you can determine your ring and pinion ratio needed to achieve your goal.
Fortunately for my math challenged mind I setup the spreadsheet to do all the calculations. I put the tables I needed in the spreadsheet so it's pretty easy to use I simply plug in the correct variables. Too bad I can't share it here.
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Old 03-09-2021, 07:39 AM   #31
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Well we did it. It has the 230hp version of the 3126. At 65MPH the engine is at 2250 RPM so I'm guessing the rear is geared a little low. Runs great easy to drive and the sticks gift works smooth. Super happy we found it. Any guess on the gas tank size?
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Old 03-09-2021, 08:12 AM   #32
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Congratulations - You did it!!!
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Old 03-09-2021, 08:48 AM   #33
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Awesome. No idea on tank size, but 45 gallon is a popular class 6/7 truck size so.... Grab a picture of it and an approximate length, width and height. Then multiply the length and width, take that and multiply by the height to get cubic inches, then divide by 231 to get gallons as there are 231 cubic inches per gallon.


Now that you own the 3126, buy Caterpillar fuel and oil filters and get them changed soon. The fuel cleanliness is very important to the HEUI system as is the quality of, and cleanliness of the engine oil. Very important that the oil specs meet or exceed Cat's specifications. Coolant maintenance is also very important in all diesel engines. Once you get the maintenance in check, it will be good for a long time and many miles. It may sound expensive up front, but trust this one statement if you never trust anything else I ever say, the curative costs will far exceed the preventative costs by many, many times.


Please keep us up to date with your progress. If you want to put a faster ring and pinion in it someday, start now on places like craigslist or offerup etc., looking to trade your ratio for something lower numerical. Get the specs off of the rear axle to list with it. Sometimes you get lucky and someone has a truck that they want to use off road and need higher numerical ratios.
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Old 03-09-2021, 09:00 AM   #34
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Quote:
Originally Posted by Moto955 View Post
Well we did it. It has the 230hp version of the 3126. At 65MPH the engine is at 2250 RPM so I'm guessing the rear is geared a little low. Runs great easy to drive and the sticks gift works smooth. Super happy we found it. Any guess on the gas tank size?
I'd consider that bus to be nearly unicorn status!
Welcome to the bus world, ya done REAL good gettin that one!
Fuel tank is probably around 60 gal, but they came in all sorts of sizes. Mine's 35 gal.

Like mentioned- only use CAT filters. they cost the same as the store brand stuff if you shop around a little. So far in my 3126 owning experience everythings been affordable and easy to get at.
One thing to check that goes unnoticed a lot is the water pump belt. Make sure its in good shape and properly adjusted. Its easy to do but most folks don't even know its there.
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Old 03-09-2021, 09:45 AM   #35
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Engine: 6.9 International
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I recognize the bus, and know of the owner, it's local to me. Did he tell you why he was selling it?
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Old 03-09-2021, 10:47 AM   #36
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Congrats on your new bus, let the games begin.

You should start a conversion thread when you start on it.
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