72 LS5 Posted September 30, 2013 Share Posted September 30, 2013 I put a second hand MSD6AL box in ol Blue a few months ago and it had a 6000 pill in it. A few times the tires broke loose and the tach swung past 6 grand and I didn't feel the limiter kick in. I've been real careful not to over-rev it and figured the MSD may not be working 100%. So this weekend I bought the set of 5000 rpm pills and stuck a 5600 in there, again the needle went past 6k. Finally, with the 5200 pill, the limiter kicks in just shy of 6000. Dang - my tach must be waaaaaaaay off. Like almost 600 rpms off. It's a VDO that I've had in the car for probably over 20 years. My question is this: Can I be confident that the MSD box is giving me the correct rpm for the limiter? Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted October 1, 2013 Share Posted October 1, 2013 hook your tach to the negative side of the coil and try it again Quote Link to comment Share on other sites More sharing options...
Mike 57 Posted October 1, 2013 Share Posted October 1, 2013 I have a Auto Meter play back tach. When I down load my run I see the exact rpm that I choose for my launch on my MSD. I also have hit the the high limit chip a few times and it has never gone over 7000. I still have the factory tach and it is slow to respond and then swings past the RPMs that the Auto Meter shows. Quote Link to comment Share on other sites More sharing options...
72 LS5 Posted October 1, 2013 Author Share Posted October 1, 2013 Mike - so your MSD is spot-on from your download, that's good. I'm going to have a factory style tach when I install the gauge package in the future, so I won't be putting too much stock in the accuracy. As long as I trust the 6AL box, I'm good. Sam - with the HEI gutted and MSD hooked up, I wasn't sure you could still use the negative side of the coil. I have the tach hooked to the port on the box. Quote Link to comment Share on other sites More sharing options...
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