Inductive tach

[Tom-MI]

Amazon has a Runleader inductive tach for $13. The hook up seems easy especially for a flathead. Has anyone had any experience with one?

Thanks

Tom

[51 MERC-CT]

Used a similar one on a lawn tractor. It just had a wire that wrapped around a plug wire for the signal.
Unless you can determine it will work on an 8 cyl. engine, I would be suspect of it's capability to do so.

[tubman]

I had a Cirello magneto on the hemi in my race car. It wouldn't run a regular tach, so got one of those inductive senders and a very cheap digital tach from J.C. Whitney. I don't think the whole setup was even $50. It worked fine. I later got a magneto-specific sending unit from Autometer and hooked up a regular "4-wire" Mallory tachometer. The units read very close to each other.

The hemi, of course, had eight cylinders. These things will work on any 4-cycle engine from 1 to 28 cylinders because each individual cylinder only fires once every two revolutions. Well, their are some engines with "wasted spark" ignition systems, but I think we can ignore them here. And there goes my 6 volt tach driver business.

[JSeery]

Originally Posted by 51 MERC-CT

Used a similar one on a lawn tractor. It just had a wire that wrapped around a plug wire for the signal.
Unless you can determine it will work on an 8 cyl. engine, I would be suspect of it's capability to do so.

If it is just connecting to one wire the number of cylinders shouldn't matter. It is just counting the number of times per unit of time a current passes through a wire. 2-cycle vs 4-cycle would make a difference.

Nope, looks like they even take care of the number of cycles.

Runleader is proud to present the new RL-HM035LT LED Digital Multifunction Temp meter Tach/Hour meter. It can work on any 2 or 4 stroke gas engine up to 16 cylinders, 9 engine type setting. It has a powerful Temp system, RPM measuring system,timing system, as well as some other unique function design.

[JSeery]

Originally Posted by tubman

... And there goes my 6 volt tach driver business.

They are not exactly the period look! You should be ok.

[tubman]

Sponsored Links (Register now to hide all advertisements)

Originally Posted by JSeery

They are not exactly the period look! You should be ok.

Dodged a bullet.

[WBrown]

Well, gave one a try and ended up finessing it to get close to accurate reading.
Set it up for 8cyl 4 stroke reading as directed and got about half the RPM reading I should have compared to the reading on my timing light. Played with the settings till I got close to what the timing light was reading for idle RPM and ended up on 4cyl 4 stroke setting. Reasonably accurate through several throttle settings. This, on a 59AB with crab dual point dizzy 1947 vintage.
Any speculation as to why the 4cyl setting vs the 8cyl was more accurate??

[51 MERC-CT]

Originally Posted by WBrown

Well, gave one a try and ended up finessing it to get close to accurate reading.
Set it up for 8cyl 4 stroke reading as directed and got about half the RPM reading I should have compared to the reading on my timing light. Played with the settings till I got close to what the timing light was reading for idle RPM and ended up on 4cyl 4 stroke setting. Reasonably accurate through several throttle settings. This, on a 59AB with crab dual point dizzy 1947 vintage.
Any speculation as to why the 4cyl setting vs the 8cyl was more accurate??

What is the source of the inductive pulse?

[Newc]

Hi; My British vehicles had tachs that used a single coil of wire on the back of the tach. Found those in MGB and some British military vehicles. the tach sensed ign pulses or current in that single loop of wire. Newc

[Ggmac]

Originally Posted by WBrown

Well, gave one a try and ended up finessing it to get close to accurate reading.
Set it up for 8cyl 4 stroke reading as directed and got about half the RPM reading I should have compared to the reading on my timing light. Played with the settings till I got close to what the timing light was reading for idle RPM and ended up on 4cyl 4 stroke setting. Reasonably accurate through several throttle settings. This, on a 59AB with crab dual point dizzy 1947 vintage.
Any speculation as to why the 4cyl setting vs the 8cyl was more accurate??

Possibly having 2 sets of points

[WBrown]

Originally Posted by 51 MERC-CT

What is the source of the inductive pulse?

No. 8 plug wire closest to firewall driver's side (if I have my numbering right)

[banjoQ]

So I am curious, how accurate is “reasonably accurate”. Were you able to verify your readings with another source? Do you think attaching the sensor on the #1 cylinder would make a difference? They sound like a good option for those who just want to monitor the RPMs going down the road.

[1948F-1Pickup]

^ That would be good to know.
Used to see these types of tachs years ago on lawnmower engines, usually in gocarts.

[WBrown]

Originally Posted by banjoQ

So I am curious, how accurate is “reasonably accurate”. Were you able to verify your readings with another source? Do you think attaching the sensor on the #1 cylinder would make a difference? They sound like a good option for those who just want to monitor the RPMs going down the road.

Within 50-75 RPM. Used my timing light tach (which is accurate) as the benchmark. As mentioned, just looking for a guideline as to RPMs vs road speed.