2.25 Max RPM?

[Tim Smith]

Just because people can build an engine that rev's to 9 grand doesn't mean that it lives long there or gets its best fuel mileage there.

Yes, and reading the gauge that goes up to 6 grand means absolutely nothing about whether the motor will do it. Heck the speedo goes up to 125 in that old 300D and I think you would have to be absolutely mad to think that means the car will do it.

As a side note, I once had a FIAT X 1/9 that would cruse at about 4700 rpm to hold 60-65. It would do it all day long and did once on a 1100 mile long trip to FL. Deciding to cruse at 75-80 was more of a leap of faith in that thing...

OK, I just took pity on you.

Oh, thank god!

... and spent 5 minutes doing a web search for Mercedes 300TD gear ratios & stock tyre diameter then ran the numbers. The Mercedes factory engineers gear the 617 engine to turn 3000 RPM at 65 MPH. That should be your target RPM for top gear.

A quick look at the gear charts and the perfect set up would be the drive train from a early US spec V8 Discovery. Find a LT77S with its LT230 from a mid '90's Disco I, grab the 3.54 R&P, order a pair of CV joint Series front axles from HEYSTEE Automotive Components (Netherlands) and you are in business with full time 4WD and Mercedes factory top gearing.

Stock Series ratios wil have you running about 700 RPM too high. Stock with 4.1:1 R&P has you running about 200 RPM too high (but is ball park enough to work if you don't mind the higher low range ratios). An Ashcroft kit in a stock drivetrain is about 300 RPM too low. The engine will be more sluggish below about 75 MPH (!).

Thank you so much, I just get flustered when I'm trying to figure that stuff out. I guess I just haven't really sat down and though about the numbers.

As always, thanks TeriAnn!

You know I really need to add a chart for Roverdrive ratios. I just ran the numbers for a Roverdrive. A Roverdrive will put a 617 engine in the sweet spot at 65 MPH with a stock series drive train. You ARE installing 24 spline rear axles, right?

OK so you have 2 choices for best gearing for the 617 engine.

1. Stock Series drivetrain and a Roverdrive
2. Stock V8 Discovery LT77S drivetrain with CV front axles.

The LT77S is the stronger gearbox and you just have a single lever to shift. A Roverdive is your easiest & cheapest solution assuming Roverdrives are in stock.

I guess I forgot to mention... I'm running a Roverdrive right now! No wonder my previous story about NJ scared you so much. LOL

I know, I know. The brakes, steering etc... were only designed for 55 or so but when it feels right, it just feels right!

Thanks for all the info.

Cheers,
Tim

[graniterover]

Tim, when are you going to get going on the swap? Did you get an adaptor from Jim?

Mark

[Tim Smith]

Tim, when are you going to get going on the swap? Did you get an adaptor from Jim?

Mark

I've got to finish this house of mine first... Hopefully I'll be able to get back to the 109 at the end of the summer. The Merc 300D has it's taxes paid up till July, so I'll drive it till then and then start going over the motor to make her nice and ready for this. I'm probably not going to do a full rebuild as I don't want to over stress the series 3 gearbox I've got for this. So mostly going to check the top end, change some leaky gaskets and the like and just give it a good shine.

TA has been super helpful with figuring out the numbers and I think that with the rover-drive, I'll be able to use the old transmission and go easy on it for a year or two until I get a new 5 speed to throw in there.

I've talked to Jim about the adapter and got a chance to see his truck up close and personal. I have to say that I'm very impressed and will be getting an adapter once I start all this up. I'm sure I'll have lots of questions for him once this is underway.

The last adaption is for the WVO conversion. Luckily I found a guy local to me in CT as well who does these conversions with the Elsbett system. This just happens to be the system I was looking for too. He says he is ready to install at any time but I want to wait till I have the motor in the rover and all is running well before I spend the cash on that conversion. His website is: http://ctbiodzl.freeshell.org/votdi.html

I'll also have to make some kind of website of my own to document the project but that should be easy. The hard part will be removing all the expletives in my notes.

Cheers,
Tim