1986 4.9 Distributor questions

[thelastkeg]

The factory GM HEI coil in the distributor cap is a power hog. GM cars used a 10ga wire to feed the system. To use one on a Ford (not on mine ever!) first you need to bypass the ballast resistor for the DS-II. This isn't needed if you are replacing a computer controlled system as the resistor is bypassed in the harness. The second item I recommend is using a Bosch relay to tap the main power feed underhood to go directly to the HEI system.

One more thing I have seen with these Chinese made units, the shaft is sometimes a two part item and the Chinesium is either soft as butter or so hard it is brittle, either one can break and leave you stranded.

So I've been doing a lot of reading about this. Electrical stuff is not my cup of tea so I'm a little nervous about this. Never have installed a distributor either. I'm confident I have the engine at TDC after removing the #1 spark plug and rotating the engine by hand. I've located and painted the timing mark on the crank pulley, which is sitting at zero on the gauge too.

For the 30 amp relay, it looks like I'll need to have a fused (30 amp?) 10 ga wire coming from the battery to the relay at terminal 30. Then a 10 ga wire from terminal 87 to the distributor. The stock W/LB wire to the relay terminal 86. And a ground wire to terminal 85. Is that it? And that'll provide the needed voltage in both run and start conditions?

My truck does have a tach, and I'm thinking the tach wire from the HEI distributor will go to the DG/Y wire.

Thanks again guys. I appreciate the help in keeping this old truck going.

[85lebaront2]

So I've been doing a lot of reading about this. Electrical stuff is not my cup of tea so I'm a little nervous about this. Never have installed a distributor either. I'm confident I have the engine at TDC after removing the #1 spark plug and rotating the engine by hand. I've located and painted the timing mark on the crank pulley, which is sitting at zero on the gauge too.

For the 30 amp relay, it looks like I'll need to have a fused (30 amp?) 10 ga wire coming from the battery to the relay at terminal 30. Then a 10 ga wire from terminal 87 to the distributor. The stock W/LB wire to the relay terminal 86. And a ground wire to terminal 85. Is that it? And that'll provide the needed voltage in both run and start conditions?

My truck does have a tach, and I'm thinking the tach wire from the HEI distributor will go to the DG/Y wire.

Thanks again guys. I appreciate the help in keeping this old truck going.

That sounds right. Should work just fine.

[Gary Lewis]

So I've been doing a lot of reading about this. Electrical stuff is not my cup of tea so I'm a little nervous about this. Never have installed a distributor either. I'm confident I have the engine at TDC after removing the #1 spark plug and rotating the engine by hand. I've located and painted the timing mark on the crank pulley, which is sitting at zero on the gauge too.

For the 30 amp relay, it looks like I'll need to have a fused (30 amp?) 10 ga wire coming from the battery to the relay at terminal 30. Then a 10 ga wire from terminal 87 to the distributor. The stock W/LB wire to the relay terminal 86. And a ground wire to terminal 85. Is that it? And that'll provide the needed voltage in both run and start conditions?

My truck does have a tach, and I'm thinking the tach wire from the HEI distributor will go to the DG/Y wire.

Thanks again guys. I appreciate the help in keeping this old truck going.

You have it figured out correctly. And the 30A fuse is correct as you fuse for the ampacity of the wire and #10 can carry 30 amps for 10' with only about a 2% drop in voltage.

EDIT: Bill beat me, but just barely.

[thelastkeg]

You have it figured out correctly. And the 30A fuse is correct as you fuse for the ampacity of the wire and #10 can carry 30 amps for 10' with only about a 2% drop in voltage.

EDIT: Bill beat me, but just barely.

Fellas thanks for all the help. The 86 is back up and running, better than ever now. The HEI looks a little strange in there but it’s not a show truck and never will be. There’s a lot of wiring I could remove now, but I’ll save that for some other day. Thanks!

[Gary Lewis]

Fellas thanks for all the help. The 86 is back up and running, better than ever now. The HEI looks a little strange in there but it’s not a show truck and never will be. There’s a lot of wiring I could remove now, but I’ll save that for some other day. Thanks!

Glad it is going. And I'm sure it is running better than ever since you should now have both vacuum and centrifugal advance. Should make a huge difference.