Hey Folks,
I have a question (or two), but I also may be able to shed some light on some erratic tach issues.
My problems started when I upgraded to electronic ignition using the Crane Cam's XR700 optical module and a MSD HiPo coil. There is no "Multiple Spark Discharge" regardless of the name, so it isn't an issue. The tach would show 2x to 3x the normal RPM reading, and float around a lot. Frustrating.
Well, Crane Cam's recommends the use of part number 8-2050 (Tach Adapter) to remedy this situation, so after a long search, I find one at JEGS. It gets back-ordered.
At long last, it comes in, and with a wistful look on my face, I install it as per instructions (I'm a Master Electrician, so I'm no idiot), and my $100 (with shipping) solution only aggravates the issue! Now the needle barely moves!
So I call Crane Cam's, and the helpful tech says "you need a 10K Ohm resistor at 1/2 Watt in line with the signal ground."
"Is this in lieu of the tach adapter, or with it installed?" I asked...
"Oh no, remove the adapter." They say.
So, a 25 cent resistor from Radio Shack has solved the issue as far as I can tell. I think it's working great! It's reads a little less than usual though, compared to the readings when it had points.
JEGS won't take the adapter back since I've hacked it (as per instructions) and Crane Cam's more or less says "Sorry about your luck!" It would have been simple, easier, less stressful and saved time to have just set fire to a hundred dollar bill!
So, if you have a similar problem, try a 10K Ohm resistor first! They're really cheap! Heck, mine was free! I found it in an old Realistic brand receiver I had laying around.
Look for a resistor with the color code Brown Black Orange and Gold. Solder it in line with the signal ground ( the "usually" green wire connected to either the coil negative or the distributor ground). Don't forget to protect the resistor and joints with shrink wrap (real electricians rarely use tape).
Now my question(s).
To insure that my tach is working correctly, what RPM should I expect at, say, 55 or 60 mph? I have 4.10 gearing and 31" tires. According to my math, that's a shade under 2500 RPM for 55 and a shade over for 60, which is what I'm indicating now at those speeds (If I'm doing the math right...).
Before with points, it had hovered around an indicated 3000 RPM at those highway speeds.
Also, what kind of fuel mileage do you get? Mine gets 10 on good days, I've seen as low as 7.5 on bad. I would expect closer to 14 or so if all things were proper.
Gas is liquid gold these days!
One last Q...
Is this smilie of a Land Cruiser Newbie trying to maintain a straight line and who refuses to replace the idler arm?
-Virgil
I have a question (or two), but I also may be able to shed some light on some erratic tach issues.
My problems started when I upgraded to electronic ignition using the Crane Cam's XR700 optical module and a MSD HiPo coil. There is no "Multiple Spark Discharge" regardless of the name, so it isn't an issue. The tach would show 2x to 3x the normal RPM reading, and float around a lot. Frustrating.
Well, Crane Cam's recommends the use of part number 8-2050 (Tach Adapter) to remedy this situation, so after a long search, I find one at JEGS. It gets back-ordered.
At long last, it comes in, and with a wistful look on my face, I install it as per instructions (I'm a Master Electrician, so I'm no idiot), and my $100 (with shipping) solution only aggravates the issue! Now the needle barely moves!
So I call Crane Cam's, and the helpful tech says "you need a 10K Ohm resistor at 1/2 Watt in line with the signal ground."
"Is this in lieu of the tach adapter, or with it installed?" I asked...
"Oh no, remove the adapter." They say.
So, a 25 cent resistor from Radio Shack has solved the issue as far as I can tell. I think it's working great! It's reads a little less than usual though, compared to the readings when it had points.
JEGS won't take the adapter back since I've hacked it (as per instructions) and Crane Cam's more or less says "Sorry about your luck!" It would have been simple, easier, less stressful and saved time to have just set fire to a hundred dollar bill!
So, if you have a similar problem, try a 10K Ohm resistor first! They're really cheap! Heck, mine was free! I found it in an old Realistic brand receiver I had laying around.
Look for a resistor with the color code Brown Black Orange and Gold. Solder it in line with the signal ground ( the "usually" green wire connected to either the coil negative or the distributor ground). Don't forget to protect the resistor and joints with shrink wrap (real electricians rarely use tape).
Now my question(s).
To insure that my tach is working correctly, what RPM should I expect at, say, 55 or 60 mph? I have 4.10 gearing and 31" tires. According to my math, that's a shade under 2500 RPM for 55 and a shade over for 60, which is what I'm indicating now at those speeds (If I'm doing the math right...).
Before with points, it had hovered around an indicated 3000 RPM at those highway speeds.
Also, what kind of fuel mileage do you get? Mine gets 10 on good days, I've seen as low as 7.5 on bad. I would expect closer to 14 or so if all things were proper.
Gas is liquid gold these days!One last Q...
Is this smilie of a Land Cruiser Newbie trying to maintain a straight line and who refuses to replace the idler arm?
-Virgil