To make life easier for people to convert a Gen1 motor (2.8/3.1) to DIS, the harmonic damepner and stock pulley could be ditched. Then use a FWD pulley that has a dampener built in, and a DIS wheel could be fabricated to go in place of the dampener.

This would eliminate the need to shim out accessories.

Whatcha think? This would be an easy alternative to some of the other methods of getting a crank signal to the ECM.

I could make some up at the shop, and could even use a stock position sensor.

 

Which management system are you going with?

 

I'm going with MS1, but the ECM can be easily converted to DIS by re-pinning, and using a MEMCAL (chip) from a DIS equipped motor. The ECM sends the same signal to the ICM (ignition control module) as the distributor.

The problem is getting a crank signal since the 2.8/3.1 blocks don't have the provisions to use the center journal on the crank (DIS reluctor wheel). That and too much compression with RWD pistons is what holds a lot of people back from doing an aluminum top end on the 2.8/3.1 Gen1 motors, but that is also getting worked on to make a top end swap kit available that the avg mechanic will have no problem doing.

 

interesting

 

if you are going with spark and fuel control, the megasquirt guys recommend ford EDIS over GM DIS because of increased reliability. Just food for thought.

 

There's a few 4th gen guys using MS, and said the MS1 works fine with the GM DIS. Besides the GM ICM gets the same signal from the ECM as the HEI, so what seems to be the reliability issue? It was my understanding that the EDIS (Ford) was used because of it's availabilty and price in comparison to GM's stuff when doing a DIS conversion.

Thing is, I already have all the GM equipment for the conversion. I recently pyurchased a complete 3500 to work over the top end for a member of another board and is going in a 4thgen fbody (already equiped with DIS), and have the ICM and coil packs left over (along with a short block ).

 

Oh I didnt say it wouldnt work, just that they recommend the ford system.

If you already have all the equipment, go for it.

 

The 3500 DIS is VERY different than the eariler genII/3100,3400 DIS, and will not work the same. I also have a 3500 coil pack in the garage. I won't be using it, I will be using the earlier DIS.

The Ford EDIS will not work directly with the GM ECM, since the ICM is what converts the signals from the crank trigger and ECM to signals to drive the coils, where as the Ford EDIS is triggered directly from the ECM.

You won't be able to use the FWD crank pulley/harmonic balancer, because the FWD part, does not have a flat face for mounting agaianst AND it only has three bolt holes, where as the RWD parts (pulley) has 4 bolt holes.

 

yes, the ford will only work if you are using the MS to control spark as well.

 

The simplest way to switch to fwd heads w/ dis is to use a 3.4 block. Plus you get the extra cubes . Then you just need to fab up accesory brackets.

Someone should make some brackets for the conversion. But keep it simple. No billet crap, just like an oem setup. I bet whoever did would make a mint.

 

Getting brackets cast like that would not be that cost effective, the demand for these parts is pretty small.

Billet is actually the easiest way to do it, kit seems. There might be a way to make the parts out of mild steel, and weld a few pre-cut parts together, but everybody seems to want to use slightly different combination of belt driven accessories.

 

Yeah, I thought about it after going to work today, that the 3500 ignition is looking for a 56x trigger, so I'll still have to grab one.

I'm talking about replacing the balancer and pulley from the RWD and replacing it with the FWD unit - pressing only the FWD pulley/balancer to the crank, just like it would be on a 3500 crank.

 

Won't work, the FWD pulley and harmonic balancer is one unit, they are not seperable. The FWD belt groove/pulley is machined into the outside of the harmonic balancer ring.

 

That's my point. I'm saying to use a 3x00 pulley/balancer unit, and making a DIS wheel to go behind it.

 

RWD timing cover interferes with the FWD pulley/dampener.

 

And have no way to drive the belt driven accessories on top of not having space to install a trigger wheel behind the balancer?

 

I had an idea. What if you use the stock pickup on the distributor? Or make a reluctor wheel to mount in the dizzy and mount a pickup sensor through the cap? Then feed that to the computer and use the DIS for the spark. So you would have a dizzy behind the engine, but no wires going to it.

 

Because the dizzy won't even fit with the genIII (or II) intake, if it would, this wouldn't be an issue and people would be doing the gen III top end swap much more frequently.

 

Is the dizzy shaft in the way too? I know that the cap hits, but what if the unit was narrowed?

Wouldn't it be easier to drill the block to put in the crank position sensor that reads off the crank wheel? I know most of the 3.1's had the crank wheel, even in the RWD engines. Mine has one.

 

Some have the notches, some don't, but all the cranks have the journal after 86.

It's not just as easy as drilling a hloe for the sensor, there is extra webbing around the sensor location.
The LIM completely covers the dizzy hole.

 

No, the rear most runner covers a lot of the dizzy hole.

In addition to that the dizzy mounted trigger wheel would need to have twice the number of notches with two home notches, and to make it accurate the disc would need to be a fair size to have proper dwell and timing accuracy. Just won't fit, this was one option I looked at before deciding on an external balancer mounted trigger wheel.

Not at all, there is no boss or built up casting in the area that the sensor would need to be mounted, so an additional part would need to be machined and then somehow attached to the block, while at the same time you are weakening the webbing, causing a possible source for cracking to start. Yet another option I looked at before building my trigger wheel.