Author Topic: crank trigger tach  (Read 873 times)

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427Fastback

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crank trigger tach
« on: March 13, 2018, 09:16:34 PM »
I have a MSD crank trigger tach on the 5.9 Cummins in my Grizzly Truck.
I didn't have access to work at the time so I drilled the balancer in 4 locations and installed small 1/4 nc jacking bolts.These have a 1/4 square head.Then I spun it in my lathed and trued them all to the same height.
The tach works but reads a little low at idle and then just gets worse.It does not read over 15 or 1600RPM.I checked my clearance the other day and it was at .035...
Anyone have some ideas ???I am getting close to pulling it off and milling the slots in the balancer...
Seems like I am not triggering it properly..
1968 Mustang Fastback...427 MR 5spd (owned since 1977)
1967 Mustang coupe...Trans Am replica
1936 Diamond T 212BD
1990 Grizzly pick-up

jayb

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Re: crank trigger tach
« Reply #1 on: March 13, 2018, 11:29:23 PM »
The MSD crank triggers I've seen use magnets for triggering, not just a ferrous target.  Are you sure that you don't need to use magnets to activate the sensor?
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

427Fastback

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Re: crank trigger tach
« Reply #2 on: March 13, 2018, 11:34:38 PM »
I have read the instructions 10 times and they require 4 posts like I have or four .500x.187 deep machined grooves...The only thing I can see is I am not 100% centered over the trigger.I am thinking I have one post not reading right...
1968 Mustang Fastback...427 MR 5spd (owned since 1977)
1967 Mustang coupe...Trans Am replica
1936 Diamond T 212BD
1990 Grizzly pick-up

jayb

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Re: crank trigger tach
« Reply #3 on: March 14, 2018, 08:48:48 AM »
Making sure you are centered over the targets is important, and also check for any potential vibration in the mounting of the sensor when the engine is running that could be causing an issue.  Also, is the airgap from the sensor to the targets the same on all four?  If the balancer is not quite concentric that could potentially cause a problem.
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

427Fastback

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Re: crank trigger tach
« Reply #4 on: March 14, 2018, 12:46:30 PM »
I spun the balancer on my lathe and all seems fine.The bracket is not very big and is made out of 3/8 aluminum and held on with three 1/2" bolts.I can see that I do not have the trigger perfectly centered tho...It is off enough to be noticeable to the eye...
1968 Mustang Fastback...427 MR 5spd (owned since 1977)
1967 Mustang coupe...Trans Am replica
1936 Diamond T 212BD
1990 Grizzly pick-up

jayb

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Re: crank trigger tach
« Reply #5 on: March 14, 2018, 08:31:35 PM »
If you get it centered up and you still have issues, you might have just gotten a defective sensor...
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

427Fastback

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Re: crank trigger tach
« Reply #6 on: March 14, 2018, 08:32:52 PM »
OK ..Thanks....I will adjust it on the weekend....
1968 Mustang Fastback...427 MR 5spd (owned since 1977)
1967 Mustang coupe...Trans Am replica
1936 Diamond T 212BD
1990 Grizzly pick-up

427Fastback

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Re: crank trigger tach
« Reply #7 on: May 14, 2018, 09:02:11 PM »
I took the balancer off and had four .500x.250 slots machined in it.It was done on a rotary head so I know they are accurate.Tach is nice and steady but reads very low.It is actually worse than before...I have contacted Autometer but haven't heard back...I will have to order a new sensor and try it.
1968 Mustang Fastback...427 MR 5spd (owned since 1977)
1967 Mustang coupe...Trans Am replica
1936 Diamond T 212BD
1990 Grizzly pick-up

TomP

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Re: crank trigger tach
« Reply #8 on: May 14, 2018, 10:05:12 PM »
Is the tach for certain diameter of trigger wheel? Or does that not matter.

427Fastback

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Re: crank trigger tach
« Reply #9 on: May 14, 2018, 10:54:32 PM »
No stipulation on diam or the number of cyl.It is built for diesel engines.It also cost $500.00 so I would like to get it working properly.
1968 Mustang Fastback...427 MR 5spd (owned since 1977)
1967 Mustang coupe...Trans Am replica
1936 Diamond T 212BD
1990 Grizzly pick-up

427Fastback

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Re: crank trigger tach
« Reply #10 on: May 15, 2018, 02:09:22 PM »
In my original post I said it was a MSD tach.It is actually a Autometer...My mistake.The sensor #5211 is indeed a magnetic sensor...I have a thick coat of enamel paint on the balancer..Could this be causing a weak signal.??
1968 Mustang Fastback...427 MR 5spd (owned since 1977)
1967 Mustang coupe...Trans Am replica
1936 Diamond T 212BD
1990 Grizzly pick-up

jayb

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Re: crank trigger tach
« Reply #11 on: May 15, 2018, 03:35:44 PM »
The paint should not affect the magnetic signal.
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

BattlestarGalactic

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Re: crank trigger tach
« Reply #12 on: May 16, 2018, 01:33:02 PM »
I thought most trigger wheels are alum with steel inserts.   Is the steel balancer making it fuzzy?

Those sensors are just like a distributor reluctor wheel/pickup and produce an electric pulse as two metals pass each other.  With not enough distance between the 4 points and the base wheel it might not be counting properly?  At a certain speed/rpm it might not be seeing the pulse if it is too weak.

I converted my Mack over from mechanical speedo to electronic.  I made a reluctor wheel that fit where the original gear was at on the output shaft.  Then machined 16 slots in it for the correct pulse/mile.  I then machined a hole in the tailhousing for a pickup coil and it works fine.  A buddy from the Mack site helped me design it and he is a Radar installation guy.  He talked about signal strength and how it skews with speed, which I know my speedo looses accurate over 65 mph(it looses a few mph from there up).  The cut of the tooth is critical to a point and must have a sharp enough bottom root so it reads it at faster speeds.
« Last Edit: May 16, 2018, 01:43:05 PM by BattlestarGalactic »

jayb

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Re: crank trigger tach
« Reply #13 on: May 16, 2018, 08:01:57 PM »
Factory Ford trigger wheels for new cars are all steel.  The ones I manufacture for EFI applications are also all steel.  The ones I've seen that are aluminum have magnets in the slots, not just steel inserts.
Jay Brown
- 1969 Mach 1, Drag Week 2005 Winner NA/BB, 511" FE (10.60s @ 129); Drag Week 2007 Runner-Up PA/BB, 490" Supercharged FE (9.35 @ 151)
- 1964 Ford Galaxie, Drag Week 2009 Winner Modified NA (9.50s @ 143), 585" SOHC
- 1969 Shelby Clone, Drag Week 2015 Winner Modified NA (Average 8.98 @ 149), 585" SOHC

   

427Fastback

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Re: crank trigger tach
« Reply #14 on: May 16, 2018, 08:04:12 PM »
Interesting....Autometer has said my signal is somehow getting corrupt and to install four 1/4 20 bolts instead of the groove.That is what I had before and it worked much better but I think the heads were to small...I m waiting for another reply but as I already have the slots machined in the balancer I could put 1/2 key stock in the slots and that would give me four posts .250 tall and the full width of the balancer.

The balancer does not require a puller and is easy to remove.The serp belt is more of a PIA...
1968 Mustang Fastback...427 MR 5spd (owned since 1977)
1967 Mustang coupe...Trans Am replica
1936 Diamond T 212BD
1990 Grizzly pick-up