We are having problems getting a tach to work with our mag. I have two different tachs and even with the special black kpart with the hole to run the feed line through, they don't work. And a call to Auto Meter gave me 'We don't service those tachs anymore" and not even a sorry. So a fellow member of the Rod Riders is lending me a cable driven tack off his coupe that he will not be using as the tach was set up for a SBC and he is running a banger. But there is a part missing. Here is what I got. Back of the tach Back of the drive. I am assume that there is suppose to be a part that bolts to the crank to drive the adapter to drive the cable to drive the tach. And I am also assuming that it has to be flexible to handle motor flex? I didn't get that part. Oh and here is a shot of the coupe Any help would be appreciated, as we race on the 13th of this month and Chick is allowing me to drive her roadster!
I take it yours is a 50% reduction on the angle drive? I had one on the SBC that came with mt roadster. I gave it to Bud Jones. It looked like a square drive cable from the crank to the angle drive. Pretty sure Buds engine was hard mounted. Maybe a part of a speedo cable? Is it a square drive in the angle drive? If so, could you take a harmonic damper bolt and drill it to accept the end you cut off a speedo cable? Then silver solder or drill from the side for a set screw to hold the cable in the bolt? Reinstall the bolt.
I was thinking something like that. Ill find a speedo shop, that has been around for awhile, and see what they have. Thanks
Went to the local marine shop, decent one, they sorta knew what it was and suggested wooden boat shop. The search goes on
Seems to me and I have no info on your drive exactly, but it seems to me that most of those that I have seen were driven by a spud off the cam and they were a doubler. Then a standard speedo cable ran though the cable housing from the drive to the tach.
This one was set up to drive off the crank, deep inside the 90 degree is the female end of a speedo drive. It looks like an old military or industrial part. The car it come off of had a lot of 'interesting' parts, just a couple of guys in a garage back in the 60's building with what they had.
If I had to set up your drive, I would perhaps, drill and tap the damper hold down for some smaller(10-32) bolt. I would take said bolt and drill it through to close fit with a speedo cable. Cut a speedo cable to length and slide it in the 10-32 bolt. Silver solder it on the threaded end into the hole. Screw that into the damper bolt. But that is just guessing without seeing what you are doing.
I probably get a little spoiled up here, with Steveston harbour 15 miles away, and us having had such a huge fishing industry for so long, a lot of the local old-time commercial marine shops are really on the ball when it comes to making up drive cables.
chuck up something (square?) in a cordless drill, that will engage the hole in the tach, and see how fast it thinks the drill is turning (use reverse direction on the drill)...compare to the rated speed of the drill. Some tachs are 2 to 1 The old Moroso tach and cable I have uses a normal 7/8" thread and small 0.1" square end at the distributor, and uses a larger 3/16" square end at the tach.
Rich, you are the closest to what I think needs to be done.. I eye balled it yesterday. When I switch to the GMC, I hope to find a mag with a cable drive, that will make life a lot easier, but who said land speed racing is easy??
If you can't find anyone closer, these guys can make the small cable you need: http://www.gaugeguys.com/home.html My tach drive on the crank of my '32 is similar. It is held out in mid air by a straddle mount from the tapped holes adjacent to the cam cover. There is a short flex cable with no housing that runs from the square insert I put in my crank bolt over to the square hole in the angle drive. The kicker will be finding the correct ends for YOUR flex cable, because there are about a dozen different sizes and configurations of ends (square of different sizes and round with tangs). Here's another source of parts: http://www.texasindustrialelectric.com/speedo.asp
Alchemy Can you shoot a photo or two, as the "mount" I have looks like it bolted to the frame and was attached to a solid mount motor. My motor has mount biscuits and I am worried about a solid mount with possible motor flex Thanks
When I sold the motor to George, it had a Vertex with a tach drive. You may need to mount the angle drive to the front cover somehow.
The drive on the back of your tach looks like the one on the back of my 5" face Jaeger. Its supposedly originally from an Alfa.
I can't get a pic soon, but the idea is simple. Just make standoffs from the front face of your block that will bolt to that crossbar the angle drive is attached to. You didn't say what engine you have, but most all have some tapped holes somewhere on the front face that are unused. My bracketry and angle drive was originally built for a Chrysler hemi, but the exact same brackets fit a flathead Ford with just a slight offset filing of the holes in the straddle strap. Some vintage flathead Ford angle drive mounts have a single-sided mount, so the drive hangs in mid air. But if you have room, I'd make it more solid and mount it on both sides of the crank. Another thing you might have difficulty sourcing is a crank bolt with a hole in it to drive the short flex cable. Finding a square drill bit to make the square hole is really difficult, so I dismantled a junk speedometer and took the input drive spud from the backend. I had my machinist turn it down so all that was left was the square hole and a little meat around it, about a half inch long. He then knurled the outside. We center-drilled the crank bolt slightly larger, smeared JB Weld on the knurls, and pushed the spud into the hole. It's been there for years and never given any trouble. Or, maybe the businesses I linked to above might have a spud to install in your crank bolt.
The Jalopy Journal
