Here’s another useful tidbit out of my archives, source unknown. Have a 60’s daily driver or cruiser, and want to eliminate points maintenance for very little cost, with easy to find, reliable parts? Install a Duraspark II system.
I won’t repeat the many good guides on installing the system. There’s plenty of information already handy on the web. This early wiring diagram is handy, though, and one of the clearest I’ve seen.
This scan has been floating around the internet for a while, and I honestly can’t remember where I found it. It’s a scan from a Ford publication showing the selection of cams used in the 302 from 1985 to 1995. Unfortunately it’s incomplete. However, I’ve found that accurate factory cam data and specifications are actually pretty hard to come by, so I tend to collect this info when I can get it.
Enjoy! Oh, and if you find more, or recognize the original source document – please let me know!
Please feel free to copy or download this calculator – like the rest of the site, it is shared under a Creative Commons license.
Supports up to six speeds, plus two ranges
Calculates speedometer drive gear for Fords, including speedometer error. (This will work for some other makes as well.)
Shows the RPM after shift for each gear shift
How to Get Your Copy:
If you’re already a Google Drive user, click the “File” menu, and “Make A Copy.” This will give you your own copy, which you can edit at will.
If you’re not a Drive user, you can click “File” > “Download As” to get a copy in the spreadsheet program of your choice. You might have to do a little cleanup work to make it pretty again, but everything should work.
Instructions for use:
Fill in the (yellow) blanks with your information. Vehicle and Trans fields are only there so you can keep track of your results if you choose to print this out.
Axle field should be obvious. If you’re using a portal axle (Unimog, H1, aftermarket, etc) you’ll need to put your total axle gearing here, not just your differential gears.
Range can be 0 for single range cars, or the ratio in your transfer case for four wheel drives or trucks with splitters.
Tire diameter is in inches. Your equivalent tire revs per mile will show on the right for the tire diameter you enter. If you are going primarily by a manufacturer’s rev/mi figures, I’d recommend guessing your diameter until you get Rev/Mi correct as the fastest method.
Enter your transmission’s gear ratios in rows 11-16. Unused gears can be left at “0”.
If you need revs at a specific road speed, you can easily change the speeds in row 10. Engine revs below will change to suit the speeds you’ve entered.
Entering your shift point in row 38 will show you your road speed for each shift, RPM before and after, and % drop in RPM.
I’ve found this spreadsheet very useful over the years, and hope you do, too! Please, feel free to leave any questions in the comments below.
Over the years, I’ve spent a lot of time on various online forums helping friends, acquaintances, and strangers sort out automotive problems. I tend to lean toward the more technical end of car modification and design, and over the years, I’ve found out that there really aren’t all that many good automotive resources online.
What about the mountain of automotive websites out there? Well, most of them don’t provide the sort of hardcore tech info I’m personally interested in. Also, I’ve seen a lot of information on very authoritative looking sites that’s just plain incorrect, too. I’ve looked at cars for years from the perspective of a designer who has to put numbers and tested data to everything, so maybe I just catch things that are below the level most people really worry about.
Either way, I’ve accumulated a fair amount of really detailed technical information (and some really useful tools, as well) over the years, and my goal is to gather the information I have and share it here for others to use. Really, I’m here trying to create the blog I wish I’d found five or ten years ago.
You might find the occasional stray post here about buildings and engineering, but let’s be honest – we’re all here for the cars!
Here’s hoping you find it as useful as I might have then.