I had Lamey refurbish and replace all needed parts for my 77 GMC when he did
the rest of the mechanical work. I had the GMC tuned on a Dyno at the Dyno
shop before taking off on a 9,000 mile summer trip. I got 9.6 mpg average. I
replaced the ignition with Jacobs ignition and took off on another 17,000
mile summer trip. I got 9.7 mpg. The latest trip had some extended time
above 4,000 feet in the west, but 0.1 mpg is within the error of driving
habits and speed changes. I have them tune it for 87 gas.
The people at the Dyno shop tune GMC's and the owner has one. They said that
they do not see any improvements in power, if the standard ignition system
was is good shape to start with. The GMC motor never gets to high enough
rpms to use the wonderful stuff that the ignition is supposed to do for you.
They also recommend that I carry the removed good parts because if the
Jacobs ignition every goes out on the road, very few mechanics will be able
to do anything with it.
The reason I put it in was to get the motor to start easier. Using the
battery boost when starting does more than the Jacobs ignition.
I would not recommend that you spend any money on it.
Chuck Botts, San Diego
the rest of the mechanical work. I had the GMC tuned on a Dyno at the Dyno
shop before taking off on a 9,000 mile summer trip. I got 9.6 mpg average. I
replaced the ignition with Jacobs ignition and took off on another 17,000
mile summer trip. I got 9.7 mpg. The latest trip had some extended time
above 4,000 feet in the west, but 0.1 mpg is within the error of driving
habits and speed changes. I have them tune it for 87 gas.
The people at the Dyno shop tune GMC's and the owner has one. They said that
they do not see any improvements in power, if the standard ignition system
was is good shape to start with. The GMC motor never gets to high enough
rpms to use the wonderful stuff that the ignition is supposed to do for you.
They also recommend that I carry the removed good parts because if the
Jacobs ignition every goes out on the road, very few mechanics will be able
to do anything with it.
The reason I put it in was to get the motor to start easier. Using the
battery boost when starting does more than the Jacobs ignition.
I would not recommend that you spend any money on it.
Chuck Botts, San Diego
