planning on buying the holley hp mpi efi system. what distributor will get this system running for timing control and bank firing. what distributor will i need for seq injection ? or do i need a crank trigger setup also? for a bbc with 630 horse. i have a msd 8555 dist and blaster coil and 6al. can the 6al and the blaster coil be used with this ecu? ty

FAST p/n 305005 dual sync dist will do the trick.

FAST p/n 305005 dual sync dist will do the trick. - As said, will work on sequenital and requires your MSD box.

A GM small cap HEI would work fine if you don't want the cam sync for the sequential. But if you plan on going sequential, buy the FAST up front. You don't need to use the cam sync at first if you don't want to for whatever reason.

Something I recently read suggested running a basic mechanical distributor for initial EFI setup. Get the fuel mapped and tuned that way without having to also deal with the added complexity of ignition timing.

Later upgrade to the full computer control.

Makes some sense actually. Just something to think about.

thanks guys, i may use the small cap dist as i already have one and get it going. then get the fast dist and compare results. do can i use my msd 6al with the small cap dist? i do not have the connectors for the small cap dist. are they available somewhere or is it plug and play with the holley harness? again thanks to all

or i could just use the dist and stuff i have as steve suggested.

You need an HEI adapter harness which comes with some HP kits and a 2 pin coolant temp sensor metripak for the power/trigger on the HEI. A small cap HEI is about the simplest way to control timing. For a 10:1 N/A engine, you don't need the CD box, but if you have it, you might as well run it.

On one hand it might be simpler to use a non-computer controlled distributor first, but on the other hand most don't have good timing curves and going with a good ECU controlled timing map from the getgo might make the fuel tuning progress better. Personally the curves are so low in timing on most mech adv distributors, unless they have been modified, I'd want to control the timing right off the bat when using something as simple as the computer controlled HEI.

I cant possibly u/s not using a ECU-controlled distrib right from the get-go. Doesnt spark timing affect combustion, and ultimately the AFR? Seems to me you would have to tune 2x.

Well Vince it is complicated :D

Spark timing does not really change the fuel requirements in general because it has nothing to do with the volume/mass of air the engine takes in. So same volume/mass means the same amount of fuel.

Of course optimizing timing can change the effective power output of the engine. And since we often operate in constant power mode (read cruise) we automatically adjust our right foot and reduce manifold pressure. So fuel requirements change because we move to a different part of the map for that combination of speed and load.

Think of this another way: what do you do for a starting ignition timing map? If you do not have something provided you probably create a map that looks very much like what your old distributor had.

Not to say that computer controlled ignition timing is not a very cool and much more capable solution than weights/springs/diaphragms. Just explaining why one might want to walk before they run :beers:

Well Vince it is complicated :D

Spark timing does not really change the fuel requirements in general because it has nothing to do with the volume/mass of air the engine takes in. So same volume/mass means the same amount of fuel.

Of course optimizing timing can change the effective power output of the engine. And since we often operate in constant power mode (read cruise) we automatically adjust our right foot and reduce manifold pressure. So fuel requirements change because we move to a different part of the map for that combination of speed and load.

Think of this another way: what do you do for a starting ignition timing map? If you do not have something provided you probably create a map that looks very much like what your old distributor had.

Not to say that computer controlled ignition timing is not a very cool and much more capable solution than weights/springs/diaphragms. Just explaining why one might want to walk before they run :beers:

The Holley base tunes come with spark maps that pretty much mirror a performance distributor curve. I just tweaked a couple of areas on there to get the lowest MAP reading at idle, and kicked-up the cruise timing a bit. So its really not a big deal at all.

Spark timing does not really change the fuel requirements in general because it has nothing to do with the volume/mass of air the engine takes in. So same volume/mass means the same amount of fuel.

On the '730 controlled setups I have tuned I always have to adjust the VE tables with a timing change. More advance (until it already has enough or too much) will increase the VE.
Of course not all control schemes are the same. And I believe this effect is much more pronounced on a SD system than A MAF setup.

On the '730 controlled setups I have tuned I always have to adjust the VE tables with a timing change. More advance (until it already has enough or too much) will increase the VE.
Of course not all control schemes are the same. And I believe this effect is much more pronounced on a SD system than A MAF setup.

Ok I'll buy that you have seen this... but I would like to know if you can explain *how* a timing change changes the VE (which is merely a measure of how effectively the engine pumps air after all) of the engine?

I am also curious if there is a consistent adjustment of the VE table as you advance the ignition towards optimal?

I believe its because the VE is dynamic in nature and not merely mechanical. For example:
take a traditional carb engine and put a vacuum gauge on it. Then start changing the timing at idle by moving the distributor. You will see the vacuum changing and the engine runs better/worse. When the vacuum increases the engine is pumping more efficiently.

The effect is really easy to see when tuning a Delco ecu and dataloging the BLM's on a spreadsheet. For example on the engine I was tuning the other day I added around 2 degrees timing to most of the main spark advance table. When I started it back up and logged for a while most of the areas that were running right at 128 BLM just 30 minutes ago, were now averaging around 129 to 129.5. Granted, that's only about 1 to 1.5 percent change, but it was consistently measurable across most of the generated graph.

So what was happening here (as best I understand it) is that with the additional timing the ecu had to add a little more fuel to maintain the exact same AFR. If the AFR is remaining constant but more fuel is being used then that means that more air is also being pumped.
I have no experience with the current generation of popular aftermarket ecu's, but the older stuff I used to mess with just didn't give enough good data back to see some of this stuff.

As far as additional advance causing VE to increase until the optimal point, I dont know if that method alone would be safe. Optimal timing settings seem so much more elusive than fuel to me. I believe this is an area where ION sensing has a lot of potential.

BTY, I'M really glad to finally see an EFI forum here (I usually only pop in to Chevelles once every couple of months). Chevelles performance forum was always the best big block knowledge repository, but EFI talk practically seemed taboo. This is a positive development.:)

I believe its because the VE is dynamic in nature and not merely mechanical. For example:
take a traditional carb engine and put a vacuum gauge on it. Then start changing the timing at idle by moving the distributor. You will see the vacuum changing and the engine runs better/worse. When the vacuum increases the engine is pumping more efficiently.
Not quite accurate because the pumping is the same. What is different is the energy conversion efficiency. The timing change allows more/less energy to be converted to motion (ie: more/less power). The vacuum change is a result of regulating the engine power to balance against internal mechanical friction and work. Otherwise the power change would create a speed change (which might change pumping as it relates to cam timing).

The effect is really easy to see when tuning a Delco ecu and dataloging the BLM's on a spreadsheet. For example on the engine I was tuning the other day I added around 2 degrees timing to most of the main spark advance table. When I started it back up and logged for a while most of the areas that were running right at 128 BLM just 30 minutes ago, were now averaging around 126.5 to 127. Granted, that's only about 1 to 1.5 percent change, but it was consistently measurable across most of the generated graph.

So what was happening here (as best I understand it) is that with the additional timing the ecu had to add a little more fuel to maintain the exact same AFR. If the AFR is remaining constant but more fuel is being used then that means that more air is also being pumped.
Hmmm... not familiar with the BLM acronym. It may not be possible to prove this one way or another. My thinking is for the same engine speed and MAP you get the same VE no matter what because it IS mechanical. The rub is as you affect the conversion efficiency with timing optimization either speed or MAP will always change.

I was not fishing for using VE to optimize ignition timing but more of the relationship of how VE changes with optimized ignition timing. You provided that. I agree that you need something more directly connected than VE to tune ignition timing. ION sensing may be the cheapest... would love to learn more about how *that* works :cool:

The Block Learn Multiplier (BLM) is a long term adjustment , which is stored permanently (unless you disconnect power to the ECM), to the fuel delivery calibration that results from the ECM "learning" the characteristics of your engine while you are driving around. A value of 128 is ideal, because it is the center point in a of range 0-255. Above 128, and the ECM is adding fuel to compensate for a lean condition at a particular load and RPM. Below 128, and it represents the opposite, a reduction of fuel to correct for a rich condition.

Thats a basic definition from a wiki.
OH, and it was late when I was typing the previous post last night, In my example the BLM's actually increased around 1 to 1.5 points NOT decreased like I posted, so it was like 129 to 129.5 or so.

The rub is as you affect the conversion efficiency with timing optimization either speed or MAP will always change. and thats why its so hard actually see it happening in realtime. But if you can log the readings and display the averaged results on a histogram table, using RPM and MAP along the two axis, you may be able to see changes (some aftermarket systems may not be able to provide this feedback). I prefer 21 cells wide for the MAP representing 0-100 in steps of 5 and RPM's on the vertical scale in 100 rpm increments. After 20 or minutes of logging I usually have most of the cells filled in in the area I'm interested in, and each cell's final number is averaged over many samples.

But anyhow this all may be going off topic a bit. My personal suggestion for the earlier question of using a non-computer controlled ignition and then upgrading later isnt necessarily a bad idea. Later on I would just consider the current fuel tuning to be a "rough-in" pass. Most of the TPI guys at TGO say they they go back and forth between adjusting fuel and spark, because one does effect the other (preferably never change both at once). I see it myself when I tune, its much more of a FINE tuning thing than a coarse one.

ION sensing may be the cheapest... would love to learn more about how *that* works
I looked into its development a few years ago, basically it applies a high voltage (but not enough to create a spark) to the spark plug AFTER the ignition sequence and somehow measure the ion flow (or possibly content)in the combustion chamber. Somehow that reading indicates the combustion quality as it relates to spark timing. Apparently SAAB has it all figured out, but a group of DIY guys have made some progress.

FAST p/n 305005 dual sync dist will do the trick.

I have had nothing but problems with this one. Yuck!

I have had nothing but problems with this one. Yuck!

Jason, what kind of problems?

Mark

Jason, what kind of problems?

Mark

Well for one, I can't even get my motor to fire. I bought the entire kit from Prodigy last year March. Figure it would be safe to just bite the bullet and buy the entire kit to avoid any issues.

I'm on my 2nd dist module now that appears to have the same problem as the first one. Works fine for setting 50 reference angle, then eventually just craps out when I get ready to try to fire it. LED's are both lit up but not getting any crank/cam signal. I have spent countless hours trying to trace all the wires and get this running, still no luck. There are 4 wire that connect to the distibutor: 12v, cam, crank signal, and pickup return. Nothing is shorting out or blowing fuses, so I'm really stumped here. Engine cranks over fine.

The initial problem is there is 'noise' coming from somewhere that is interfering with the signal from the distributor. It won't change from cranking to run mode until the ECU senses the RPM. Well, when the RPM spikes up from 2000 to 12000rpm, the fuel will shut off because it senses it's well above the fuel cutoff. Initially i thought it was the MSD, but I found it falsley triggering on the dash from the purple/green pigtail.

I'm going to order a new ignition box today and see if that's possibly what's causing this *)*#@%ing problem.

Anyone else out there have suggestions?

I'm going to order a new ignition box today and see if that's possibly what's causing this *)*#@%ing problem.



Do you need to run the ignition box?

Mark

Do you need to run the ignition box?

Mark

Yes, the FAST XFI has no ignition. I'm debating between a digital 6 box and a 6al. Not sure if the digital circuitry will reduce the noise issue.

Yes, the FAST XFI has no ignition. I'm debating between a digital 6 box and a 6al. Not sure if the digital circuitry will reduce the noise issue.
Do you really mean that the FAST XFI has no ignition driver?

I presume it still has ignition control and mapping tables for ignition timing. The difference is the output control signal is a basic logic level signal without any real horsepower behind it electrically. So it needs an amplifier so to speak to drive the ignition coils. This was something GM built into the 7 and 8 pin computer controlled HEI distributor pickup modules.

Does the FAST have anything in it to configure dwell?

Where are you getting power for the hall sensor from? Been using these with our new EFI and have had good luck so far.

Where are you getting power for the hall sensor from? Been using these with our new EFI and have had good luck so far.

Where should I be getting it from?

I was tapping off the switched pink wire that feeds through the passthrough connection from the FAST harness. This connection also provides power to the MSD. Wondering if this is what causing it to crap out. This is hot in both key/run position.

edit: I just checked and it's the coil wire coming from the fuse box, this connects to the passthrough for the FAST(pink wire) and the MSD. This is a brand new Pain(inthe@ss)less harness.

What ignition module have you been using?

Where should I be getting it from?

I was tapping off the switched pink wire that feeds through the passthrough connection from the FAST harness. This connection also provides power to the MSD. Wondering if this is what causing it to crap out. This is hot in both key/run position.

What ignition module have you been using?

I'd get it off the MSD power.

When you say ignition module I assume you mean CD box. We've tested with several as to understand their characteristics, digital and analog. Most MSD boxes aren't very "clean", especially the cheaper analog boxes. I always say to run the power and grounds for MSD boxes seperately than anything that feeds EFI.

I'd get it off the MSD power.

When you say ignition module I assume you mean CD box. We've tested with several as to understand their characteristics, digital and analog. Most MSD boxes aren't very "clean", especially the cheaper analog boxes. I always say to run the power and grounds for MSD boxes seperately than anything that feeds EFI.

Yep.. sorry. My brain is focused on that damn module burning up.Pisses me off to no end...

Msd power and grounds run direct to battery the same as the XFI box. I thought someone said these had to go direct on the battery. This could be part of the noise issue i'm having.

For the Cam hall 12v, this needs switched 12v. MSD also needs 12v switched. So you are saying to run these separate from the same connection?

Tempted to just remove the MSD from the equation(pull the power/ground/coil wire), and see if I'm getting a clean cranking signal in the XFI dashboard.

I'm afraid to do anything again at this point, every time I turn the key its more money up in smoke.

Stories like this scare the hell out of me......Maybe I will hold off till next month to start my efi conversion.

Stories like this scare the hell out of me......Maybe I will hold off till next month to start my efi conversion.

Well, there are a few things that could be designed better so they have some sort of built-in protection. I never had one issue with my MSD 6al and HEI trigger. That was bulletproof and never had anything to fail. EFI w/SFI is a bit more complicated.

Start now and maybe you'll have it running by end of winter... ;>) hehehe