Installed H.E.I. dizzy on my 79 f 100 351-400m
#1
11-16-2014, 06:47 PM
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Installed H.E.I. dizzy on my 79 f 100 351-400m
Well decided to install a hei distributor on my 79 f 100 shortbed. It actually just installed it out of the box and it actually worked great. Now before anyone says "you should of left the duraspark" lemme tell you guys why i did away with duraspark ignition. I bought this truck and immediately found that the wiring was hacked and my truck almost burn down to a crisp. So i bit the bullet and bought this dizzy and i like the way it works. Any suggestions on how to check if my curve is right any input is really appreciated it...
H.E.I dizzy on a 79 f 100 351-400m:
H.E.I dizzy on a 79 f 100 351-400m:
#3
11-16-2014, 07:10 PM
#5
11-16-2014, 09:39 PM
As a start on the "curve" did the distributor manufacturer provide information on total mechanical advance? You probably need around 12 degrees initial and 35 degrees total with vacuum disconnected (35-12=23 degrees mechanical advance). You can check with an adjustable or "dial back" timing light if needed.
If you can get initial or idle timing and full mechanical timing dialed in that is a good starting point.
If you can get initial or idle timing and full mechanical timing dialed in that is a good starting point.
#7
11-17-2014, 01:32 PM
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#9
11-17-2014, 09:03 PM
Once you get the mechanical advance dialed in it helps to get the vacuum advance hooked up and set up.
Why does it help?... vacuum advance improves MPG and gives cleaner burn while cruising to prolong engine and oil life.
Your carb should have a "ported vacuum" hook up. This provides near zero vacuum at idle and manifold vacuum when the throttle is open. Simply hook a vacuum line from the ported vacuum port to the distributor. Adjust vacuum advance as/if needed per instructions of the distributor supplier to avoid "ping".
Why does it help?... vacuum advance improves MPG and gives cleaner burn while cruising to prolong engine and oil life.
Your carb should have a "ported vacuum" hook up. This provides near zero vacuum at idle and manifold vacuum when the throttle is open. Simply hook a vacuum line from the ported vacuum port to the distributor. Adjust vacuum advance as/if needed per instructions of the distributor supplier to avoid "ping".
#10
11-17-2014, 09:27 PM
You have to see what it's doing now before doing anything else.
The mechanical advance is usually set up in a stock factory distributor as way "too much and way too late". There is roughly 50 (fifty) degrees of timing BTDC that is usable. Since Pickups are meant to haul heavy loads, this makes sense to delay. Usually the mechanical weights and springs won't get spooled up until 4500 RPM, say. When the mechanical advance comes in (RPM wise); and how much, is where you can really make the motor come alive.
The typical factory springs and curve limits the amount of crank or initial timing that can be advanced. If you just give the distributor a big ole twist, it's gonna ping, guaranteed.
Here's how to check what you gots: Verify that your crank damper is good condition. Depending on the motor, some have rubber sleeves that deteriorate and slip on axis, making the timing and TDC marks way off. Very common. Once that's out of the way, Summit and others sell handy fluorescent timing tape that reads out 50 degrees BTDC, this is handy. You don't need a fancy timing light particularly, standard is fine. A tach, yes.
Disconnect and plug the vacuum advance (for now) and check/verify the crank or initial timing at idle. Then staying out of the plane of the fan blades ... Watch the timing advance as you run the RPM up gradually from idle thru 4000-4500 and/or until there is no more advance. If you were to plot a graph with RPM and timing degrees on axis, you'd have a "curve". Ideally you will see the timing "all in" before 3000 RPM if you aren't ever planning on hauling gravel to Kansas City and want a little punch in your motor.
If timing keeps advancing past 4000, then you'll want to pull the dizzy and start replacing the springs with lighter ones to allow earlier advance. You'll also want to limit the maximum amount of mechanical advance as well. The idea is to end up with something like 14 deg of crank timing and 26 degrees of mechanical. Figure another 10 degrees of vacuum advance at hiway cruise speed for economy and driveability - there's 50. Depending on compression ratio and fuel quality you may want to dial things back a bit but that's the general idea.
The mechanical advance is usually set up in a stock factory distributor as way "too much and way too late". There is roughly 50 (fifty) degrees of timing BTDC that is usable. Since Pickups are meant to haul heavy loads, this makes sense to delay. Usually the mechanical weights and springs won't get spooled up until 4500 RPM, say. When the mechanical advance comes in (RPM wise); and how much, is where you can really make the motor come alive.
The typical factory springs and curve limits the amount of crank or initial timing that can be advanced. If you just give the distributor a big ole twist, it's gonna ping, guaranteed.
Here's how to check what you gots: Verify that your crank damper is good condition. Depending on the motor, some have rubber sleeves that deteriorate and slip on axis, making the timing and TDC marks way off. Very common. Once that's out of the way, Summit and others sell handy fluorescent timing tape that reads out 50 degrees BTDC, this is handy. You don't need a fancy timing light particularly, standard is fine. A tach, yes.
Disconnect and plug the vacuum advance (for now) and check/verify the crank or initial timing at idle. Then staying out of the plane of the fan blades ... Watch the timing advance as you run the RPM up gradually from idle thru 4000-4500 and/or until there is no more advance. If you were to plot a graph with RPM and timing degrees on axis, you'd have a "curve". Ideally you will see the timing "all in" before 3000 RPM if you aren't ever planning on hauling gravel to Kansas City and want a little punch in your motor.
If timing keeps advancing past 4000, then you'll want to pull the dizzy and start replacing the springs with lighter ones to allow earlier advance. You'll also want to limit the maximum amount of mechanical advance as well. The idea is to end up with something like 14 deg of crank timing and 26 degrees of mechanical. Figure another 10 degrees of vacuum advance at hiway cruise speed for economy and driveability - there's 50. Depending on compression ratio and fuel quality you may want to dial things back a bit but that's the general idea.
#11
11-17-2014, 09:39 PM
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#13
11-18-2014, 07:20 AM
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#15
11-18-2014, 08:35 AM
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You will not have an issue with the HEI on reliability. Set it and forget it. Especially that you go the one with the internal coil and it is self contained.
I wanted a little more adjustment so I went with the MSD 6AL box, external coil and dizzy. But it is still the same in theory.