914 with SBC distributor question

[Emmerich]

I have an old conversion with an optical pickup MSD distributor. I sent it off to Ignition Engineering and tested it and said it was bad. Now they seemed to have disappeared. so plan b is find a distributor to fit. Not much luck so far, there is 7 inches of clearance from the intake to the top of the cap. Most new stuff is pretty tall. Crank fires have short distributors but that would be $$$.

My question, is what kind of distributors do you use? I have a new coil and ignition box so i hate to scrap them.

Any info appreciated
Fred Emmerich

[jadewombat]

Why not go crank-trigger? No clearance issues and would set you back about $350-400 and pick up 5-10hp.

https://www.autosportlabs.net/MegaJolt_Lite_Jr.

[Emmerich]

From the web page it looks like it works with Fords.

[jadewombat]

No, they're Ford parts but they will work on any 4, 6, or 8 cylinder engine. I used the Megajolt setup of my bug and felt the difference on the first drive in the lower gears right away. It eliminates the timing scatter. There's only one sensor to mount to pick up the signal from the crank wheel and use a port off of your carb for the vacuum signal to the Megajolt unit.

There's several crank wheels out there with the 36-1 mounted already for Chevy cranks. You'd just need a plug to put in the distributor hole and mounted the VR sensor on the block. You could install it in a weekend.

Shoptalkforums.com • View topic - Notes on EDIS--Megajolt install

https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=chevy%2036-1%20trigger%20wheel

[jadewombat]

Also, there's other crank-trigger systems out there for sale but they're more expensive. SDS, MSD, Electromotive, Holley, etc.


SDS EM-5: CPI

Home - Electromotive

MSD 8620 Chevy Big Block Crank Trigger Kit | eBay

[Emmerich]

What is the Ford EDIS?

[Emmerich]

I found this and it is even more expensive:

Compu-Tronix. Electronic Ignition Systems

[jadewombat]

EDIS is electronic distributor-less ignition system, I seem to remember. It's a wasted-spark system which fires twice per cycle--once on the compression stroke and once on the exhaust stroke. The exhaust stroke is considered the "wasted" spark, but it's burning the rest of the fuel that wasn't burned on the compression stroke.

In real terms, what you'll find is that the engine runs waaaay better with crank-trigger. You can run much more advance than a conventional distributor, the motor runs cooler because it's more efficient, and of course a little bump in mpg.

A mechanical distributor is really just a 2 dimensional device, with or without a MSD or Holley box added. The engine speeds up, distributor advances more. That doesn't meet the needs of what the engine needs though necessarily.

Consider 3,000 rpms. Are the demands of the engine the same at 3,000 rpms cruising down the road at top speed on the highway, as they are at 3,000 rpms launching off the line, or 3,000 rmps going up a hill? Of course not.

The "3rd" dimension of knowing where you're at on the map (by rpms) and what the engine needs (based on vacuum and MAP sensor signal) will better match the power output and the spark.

[jadewombat]

The Compu-Tronix would be an improvement, but not quite the same as crank-trigger. You're going to have a little bit of timing scatter because the play in the dist. gear.

Crank-trigger is a direct measurement. The ECU can sense RPM changes with change in speed of just a few teeth passing by the sensor.

[Emmerich]

What sort of equipment is needed for a crank trigger, and how difficult to install? Does it require engine removal?

I once had a mercedes with mechanical FI. It used a pump like a diesel. The diesel used a 2 dimensional cam inside and mine was 3D. I guess that is similar to what you talk about.

thanks
fred

[jadewombat]

It shouldn't require engine removal. Can you get at the crankshaft pulley in the 914 to remove the pulley temporarily?

Equipment with Megajolt/EDIS:

-Chevy cranshaft pulley with a 36-1 trigger wheel mounted on it (you can just pull your pulley off the engine, take it down to a machine shop and they'll charge you no more than 1 hour of shop labor time $50-75 to center, drill, and mount a universal trigger wheel on your OE pulley OR just buy one from SMI below) How to use DIYAutotune.Com's crank triggers
SMI Fab and CNC - Gallery
-Ford EDIS-8 module a few inches of the harness and plug
-2 EDIS-4 coilpacks
-EDIS spark plug wires
-1 VR sensor bracket
-Megajolt unit
-Some vacuum line from your carb. port to the Megajolt ECU

-You will need a 9 pin to RJ11 serial cable adapter https://www.autosportlabs.com/product/megajolt-serial-tuning-cable/
-You also "may" need a 9 pin to USB adapter for your laptop or computer to program the MJ unit (it depends if your computer already has a 9 pin serial port or not but it's easy to check)

I know it seems like a lot and maybe intimidating, but the software is free and if you have all of the above parts you can knock this out in a weekend and there's tons of people out there who can help if you get stumped https://www.autosportlabs.net/MegaJolt_Lite_Jr.

A couple of installs on SBC engines:
Megasquirt install on LTx engine, has anyone ever done it?? - Corvette Forum
Megajolt

[Emmerich]

My mechanic says we do not have clearance to remove the pulley, thus engine removal is necessary. No bueno....
Fred

[jadewombat]

Hmmm, I guess the CompuTronix would be the option then. Good luck with it! A few extra ponies and the smoothness of driveability are worth it.

[Emmerich]

Its looks like a choice of cheaper parts and more labor, or more expensive parts and little labor.

Renegade said they have used GM HEI distributors which is something I will look at.