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MG MGB Technical - Will Tach work with XR3000?

I was just given the Crane XR3000 ignition along with the turbo boost controller/timing controller/ rev limiter from Rich Wasman's 1972 turbo GT. He said the stock tach would not function with the Crane but I wonder if it will drive the one in my negative ground converted '66. Anyone have any info? The folks at Crane haven't a clue.
David

David; I have a XR700 and the manual also covers the XR3000. According to their instructions the tach should work with a negative ground system. They do say it may cause eratic tach operation. The manual suggests removing one loop of the tach sensing wire and recalibrating the tach at around 4000 rpm. That said, I had problems with the tach in a 68 GT when I installed an XR700. I tried removing a loop but the loops were inside the tach and I couldn't work the wire around all the components to remove a loop. Your tach probably has external loops and it should be much easier to remove a loop. You have to make sure the remaining loop isn't reversed. If that fails they do or did make a tach adapter for use on vehicles with erratic tachs. It's a motorcycle item but they say it will solve most tach problems. Clifton
Clifton Gordon

Thanks Clifton. I have been running an Allison which I believe became the XR700. I had to fiddle with the pot in the back of my tach after I installed it but it works OK. I'll give the 3000 a whirl. I'm not sure, but I think the tach in the '72 used a signal directly from the coil. Maybe that's why his didn't work? I appreciate the tip on the adapter too. I wasn't aware of those.
David
David

David; I looked at the adapter hook-up again and I'm not sure it would work with the early tach. It takes the tach signal off the negative coil post. Clifton
Clifton Gordon

David, I have the XR3000 in my '71. The tach works fine. Crane actually has a digram on their website on how to modify the Smiths to work with their ignition. It's part of the owner's manual.
Jeff Schlemmer

You should throw the Crane system away and go with a better pertronix kit. I have seen nothing but failed Crane systems. The kicker is, you dont need to modify your tach, itll just work
Jarrod Hills

Jarrod - what part have you seen fail on the Crane system? I can understand having the optical sensor go bad from placing it into a filthy distributor, but I have had nothing but good luck with all the Crane systems I have installed. I believe that since they have less dwell than the pertronix, they actually make your engine run better! Please tell me in detail what problems you have encountered that cause you to say - across the board - to never use a Crane ignition conversion kit.
Jeff.

By the way, my tach worked with no modifications using the Crane system.
Jeff Schlemmer

I have been using allison/crane units since Allison brought there unit out. I have only had one failure and that was do to the flexing from a vac advance. I have had two pertronix units cause missfire. I won't by choice install the pertronix system. Take the Crane cut with a grain of salt. Bob thompson/International Auto
Bob Thompson

Bob, there are a lot of us who like the Crane system. I'm just wondering what possible causes there are for failure. I know most failures are due to improper installation - wires being cut from the rotating points plate, or the timing disc rubbing on the sensor.
Jeff.
Jeff Schlemmer

Jarrod-
I've been using the Crane systems since back in the days when they were known as the Allison system. I've put them into other people's cars, too. I've never known one to fail. Just exactly why do you recommend against them?
Steve S.

hello ive got a crane xr600 fitted to my b ,the best mod up to yet. im going touring to france next year but worried that it may go wrong .is it easy to swopback to points on the side of the road ,or do you think ive got nothing to worry about daren
daren parker

This thread was discussed between 12/01/2005 and 15/01/2005

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