Jacobs Ignition System

[tfowler9]

I installed a Jacobs ignition system and Mallory # 4756701 distributor way back in 1990. I have a 351 Cleveland with two barrel heads. Installed englebrock intake with Holly 4 barrel carb.
The car has always performed well. May frustration is the tach will not register over 1300 rpm.
They (jacob ignition) back then claimed to have a fix and sent me a jumper- didn't work.
Anyone seen this? Any solution?
If not, I am thinking its time to replace ignition system. Any suggestions?
I read the forum almost everyday - best Mustang forum out there.
Any suggestions / help would be appreciated.
Tom

 

[Hemikiller]

Jacobs made a slew of different ignition systems. Which one do you have? I have the book they published somewhere.

 

[Steve McMahan]

Hemikiller, is there a book or info you don’t have? My friend, you are a treasure to this forum.

 

[Dave66]

I installed a Jacobs ignition system and Mallory # 4756701 distributor way back in 1990. I have a 351 Cleveland with two barrel heads. Installed englebrock intake with Holly 4 barrel carb.
The car has always performed well. May frustration is the tach will not register over 1300 rpm.
They (jacob ignition) back then claimed to have a fix and sent me a jumper- didn't work.
Anyone seen this? Any solution?
If not, I am thinking its time to replace ignition system. Any suggestions?
I read the forum almost everyday - best Mustang forum out there.
Any suggestions / help would be appreciated.
Tom

I had a similar issue when I recently upgraded to a Pertronix billet distributor - bought an Ignitor III and matching coil, and then was told by Pertronix that the Ignitor II was compatible with the stock tach and that the III was not, so I ordered the II and matching coil, installed it and tach didn’t work.
So I pulled all the gauges, and sent them to RCC Innovations and had the tach and volt meters reworked, and also had the needles repainted on the other gauges. I did take advantage of having the gauges out and replaced the bulbs with blue LED bulbs, replaced the ribbon circuit, voltage regulator, and the plastic lens.
Unfortunately for me, I waited too long and couldn’t return my Ignitor III billet distributor and Flamethrower III, so if interested, its for a 351C/429 (won’t fix your tach issue though!).

If you decide to rework the tach - RCC Innovations did a fantastic job and had a quick turnaround (couple of weeks).

Good luck!

 

[tfowler9]

I had a similar issue when I recently upgraded to a Pertronix billet distributor - bought an Ignitor III and matching coil, and then was told by Pertronix that the Ignitor II was compatible with the stock tach and that the III was not, so I ordered the II and matching coil, installed it and tach didn’t work.
So I pulled all the gauges, and sent them to RCC Innovations and had the tach and volt meters reworked, and also had the needles repainted on the other gauges. I did take advantage of having the gauges out and replaced the bulbs with blue LED bulbs, replaced the ribbon circuit, voltage regulator, and the plastic lens.
Unfortunately for me, I waited too long and couldn’t return my Ignitor III billet distributor and Flamethrower III, so if interested, its for a 351C/429 (won’t fix your tach issue though!).

If you decide to rework the tach - RCC Innovations did a fantastic job and had a quick turnaround (couple of weeks).

Good luck!

Thanks Dave, the Jacobs iginition box has an on off . If you turn the high voltage off, the tach works. So, I believe its something to do with he Jacobs ignition system.

 

[tfowler9]

Jacobs made a slew of different ignition systems. Which one do you have? I have the book they published somewhere.

I'll see if I can find it. Thanks for responding. Tom

 

[c9zx]

I found an old Jacobs troubleshooting guide. It says if you a a series tach (mentions 70s Ford and 240Z), use a series tach drive . Jacobs PN 380228. How you find one I don't know. Chuck

 

[tfowler9]

I did purchased and installed the adapter part # 380228. It didn't work. I also took to a good friend who's is a mechanic and races ford mustangs. He couldn't get it to work.
The Ignition system I purchased is part #370416

 

[tfowler9]

Jacobs made a slew of different ignition systems. Which one do you have? I have the book they published somewhere.

Ignition System part # is 370416 and the tach drive adapter (the fix) is part # 380228

 

[MaddMike]

I installed a Jacobs ignition system and Mallory # 4756701 distributor way back in 1990. I have a 351 Cleveland with two barrel heads. Installed englebrock intake with Holly 4 barrel carb.
The car has always performed well. May frustration is the tach will not register over 1300 rpm.
They (jacob ignition) back then claimed to have a fix and sent me a jumper- didn't work.
Anyone seen this? Any solution?
If not, I am thinking its time to replace ignition system. Any suggestions?
I read the forum almost everyday - best Mustang forum out there.
Any suggestions / help would be appreciated.
Tom

My problem is that the tach doesn't move until I rev it or get the idle up when the car is in motion. And when it begins to work it bobs/pulsates until the R's come up then it is fine. I ALSO have a Jacobs unit I installed in 1998 during my Resto. Fast forward to today - my car was in storage since 2001 until December when it shipped to me. So I have again been re-acquainted with the problem. I concluded that back then those Jacobs units were pretty good - I got mine directly from the Jacob's Sls & Mkg VP at that time. But today they are big and bulky and obsolete so this winter I am going to toss mine and go with a Pertronix unit.

 

[tfowler9]

My problem is that the tach doesn't move until I rev it or get the idle up when the car is in motion. And when it begins to work it bobs/pulsates until the R's come up then it is fine. I ALSO have a Jacobs unit I installed in 1998 during my Resto. Fast forward to today - my car was in storage since 2001 until December when it shipped to me. So I have again been re-acquainted with the problem. I concluded that back then those Jacobs units were pretty good - I got mine directly from the Jacob's Sls & Mkg VP at that time. But today they are big and bulky and obsolete so this winter I am going to toss mine and go with a Pertronix unit.

Thinking of doing the same!

 

[c9zx]

Fowler and Mike, I suggest doing a deep dive on Pertronix before you pull the trigger. I'd do a hidden Duraspark I conversion before any of the Pertronix parts. Chuck

 

[tfowler9]

Fowler and Mike, I suggest doing a deep dive on Pertronix before you pull the trigger. I'd do a hidden Duraspark I conversion before any of the Pertronix parts. Chuck

Thanks Will do that!