planning an MS system for a Pontiac 455

[CaptainCaveman]

Hello

I'm planning on building an MS TBI setup for my 455 pontiac.

Engine details:
1975 block, +.060 bore, KRE heads
610 HP, 6700 RPM redline

Currently carbed, 850 cfm Holley (I can't make this thing idle well at all, part of my motivation here)
HEI distributor, MSD 6AL

Installed in a 1980 Trans Am, 700R4 transmission

I have two TBI units off 1995 Chevy 5.7 pickup trucks, that were in running order when parted out. I believe these are 480 CFM? I have the engine wiring harness from one of those trucks.
I'd like to run an Offenhauser 2x4 bbl intake with both of those TBI units. I want to run a 7 pin GM distributor and have MS control the timing as well, and ditch the MSD box. A large cap GM distributor will not work with this intake manifold, so I am a bit lost as to which distributor I can use here. However, having MS control timing is a non-negotiable requirement for my plan.

Why am I using these parts? because I already have them and I'd like to keep the cost down. If anyone sees reason why this would be a bad plan, let me know now and I can delay the start of this project and regroup. If I could find a single 4 bbl TBI unit that could support this horsepower for a reasonable price i'd much rather go that route, but I haven't found one for sale that wasn't part of a 2,000 USD kit from holley.

Does anyone have any advice on the distributor? On the intake manifold? ultimately sequential port fuel injection is what I want, but I can't afford it right now.

My plan in a short list:
1) design the fuel delivery system in a way that would be forward-compatible with E85 and sequential port fuel injection
2) purchase an MS kit
3) use the parts I currently have(intake manifold and TBI units, find a distributor) and just drive it, get used to tuning/troubleshooting the system
4) a year or two down the road if I am still driving this beast convert to port EFI.

I'm not in a giant rush to get done, This is just something I've been wanting to do for a LONG time.

[trakkies]

Unless you must keep the dizzy for cosmetic reasons, ditch it and fit EDIS.

[CaptainCaveman]

I will look into EDIS... only reason I was going to stay with a near-stock distributor config was because it would probably be easiest/quickest to get up and running.

[kjones6039]

Unless you must keep the dizzy for cosmetic reasons, ditch it and fit EDIS.

I have to totally agree with Dave on this, with only one exception.

My experience with EDIS8 on a ~500 hp sbc (in my sig below) was all good except at high rpm. EDIS more or less restricted me to ~6200 rpm, much like a rev limiter. That is far below your anticipated 6700 rpm limit!

My solution was to just ditch the EDIS module, install the JBPerformance 4 coil driver and go with wasted spark. With this setup I am able to pull ~7000 rpm (not something I do often) without any spark problem.

If I could find a single 4 bbl TBI unit that could support this horsepower for a reasonable price i'd much rather go that route, but I haven't found one for sale that wasn't part of a 2,000 USD kit from holley.

The Holley Pro-Jection systems are, as you know, very expensive and offer few of the features available in MS. (I wouldn't own one frankly) Having said that, I did buy their quite pricy 4 Bbl throttle body (Summit part # HLY-500-19) which I am very happy with. I have no idea where you might locate a 4Bbl TB that will support the kind of hp you are looking for, except to try finding a used Holley perhaps. Actually the dual tb's on the dual quad manifold kind of appeals to me because it would certainly be unique! (and very doable IMO)

My apologies for the long post.

Ken

EDIT:

I will look into EDIS... only reason I was going to stay with a near-stock distributor config was because it would probably be easiest/quickest to get up and running.

Probably no more work or time than getting a dizzy going. Wasted spark actually was easier (for me anyway) than fooling with HEI etc.

[CaptainCaveman]

Thanks for your input kjones6039, I think the dual TBI would look pretty nifty as well. Especially if I can fab a big oval air filter assembly. I have tons of space under the hood... I actually haven't heard of wasted spark, I will look into that as well. I don't actually plan on revving that high on a regular basis, but it might happen at the strip.

[kjones6039]

I actually haven't heard of wasted spark, I will look into that as well.

Evening Cap'n,

The matter of fact is, that EDIS is a wasted spark system using a 36-1 toothed wheel and vr sensor on the crank. The only difference between plain wasted spark and Ford EDIS8 (or 4 or 6) is that EDIS uses the Ford module to provide the tach pulse (pip) to MS and then MS sends a signal (saw) back to the module so MS can control the timing.

In my setup I just got rid of the Ford module.

The really good news is that EDIS parts (coils, sensors etc.) are easy to come by, in the US anyway!

I don't actually plan on revving that high on a regular basis, but it might happen at the strip.

I hate to be redundant but, there a lot of posts on the forums (here and Extra) regarding EDIS limiting rpm to 6000 or so. In my case the shutdown was violent and I didn't like that at all!

I think the dual TBI would look pretty nifty as well. Especially if I can fab a big oval air filter assembly. I have tons of space under the hood...

Here's a pic of one on my sbc. http://kandlservices.com/c3.html
Note the Ford coils and no dizzy!

Apologies for the long post.

Good luck,

Ken

Feel free to pm if I can help

[kjones6039]

Just a quick correction to that last post.....

The pic is of the high $$$ Holley.
I really like your dual quad idea!

Ken

[trakkies]

I too started with dizzy ignition but ran the MS fuel only. Most dizzys provide both the trigger and advance mechanism. If you want to use that trigger and map via MS, it means locking the advance - and on a eight cylinder you can have problems with rotor arm to plug output phasing, as it not longer tracks the trigger point. Especially since I found I could use more advance with MS than standard.
Other thing is a dizzy trigger - no matter of what type - isn't going to be as accurate as a crank one due to 'slop' in the drive path. And a dizzy may well have problems (rotor arm and cap) handing a high energy spark.

EDIS is cheap secondhand and very reliable. Its rev limit wasn't a problem on my engine as is limited by other things anyway. But if this can be solved by changing the EDIS ECU to another make, it still makes sense. As you could get things up and running before changing this module.

COP is the other alternative, but is in a different ball park cost wise.

[8974Ollie]

One answer to the distributor problem is to obtain an early points type distributor and convert it to an electronic distributor.
Conversion kits that come to mind are the Pertronix Electronic Points Ignition and Mallory Unilite.
On other thing to remember when converting to sequential ignition is, there still needs to be a cam signal and a drive for the oil pump.

There is Dave's small body HEI's. Dave converts the early points distributor to use standard HEI electronics.
Link to Dave's web site.
http://www.davessmallbodyheis.com/

[trakkies]

Even with the most accurate trigger ever made fitted to a dizzy, you still have the problem of the drive to that dizzy Most commonly it will be gear driven off the cam, and that cam driven by a chain. And that's before there's any wear in the dizzy itself. A crank driven trigger will give a much more accurately timed signal.
And a mechanical advance mechanism is a *very* crude device. Even when in good condition, they rarely are to spec, and even then simply can't produce the ideal curve for the engine due to the limitations of the mechanics. And a vacuum advance is even worse...

So unless you need to retain a dizzy for cosmetic reasons, don't. EDIS just works and is cheaper and quick to install.

Other point is most fitting MS will do so to an engine which is modified from standard in other ways. Which can mean a different advance curve. The petrol today is also likely different from that when the engine was designed which also alters the ideal advance curve.

[kjones6039]

On other thing to remember when converting to sequential ignition

Not a huge consideration with TBI I suspect......

and a drive for the oil pump.

I cut the top off my large cap HEI and with a small amount of machine work at my local shop, voila!!! No dizzy! Just a small stub and still drives the oil pump. I will post a pic if anyone wants to see it.

Even with the most accurate trigger ever made fitted to a dizzy, you still have the problem of the drive to that dizzy Most commonly it will be gear driven off the cam, and that cam driven by a chain. And that's before there's any wear in the dizzy itself. A crank driven trigger will give a much more accurately timed signal.
And a mechanical advance mechanism is a *very* crude device. Even when in good condition, they rarely are to spec, and even then simply can't produce the ideal curve for the engine due to the limitations of the mechanics. And a vacuum advance is even worse...

So unless you need to retain a dizzy for cosmetic reasons, don't. EDIS just works and is cheaper and quick to install.

Other point is most fitting MS will do so to an engine which is modified from standard in other ways. Which can mean a different advance curve. The petrol today is also likely different from that when the engine was designed which also alters the ideal advance curve.

AMEN!!

Ken

[8974Ollie]

and a drive for the oil pump.

I cut the top off my large cap HEI and with a small amount of machine work at my local shop, voila!!! No dizzy! Just a small stub and still drives the oil pump. I will post a pic if anyone wants to see it.

Yes, that is what I did too. I used a distributor from a Pontiac computer controlled 301ci. No mechanical or vacuum advance.

Please post a photo of your distributor, I would like to see how you did yours. I a looking for a photo of the distributor I did.

[kjones6039]

Please post a photo of your distributor, I would like to see how you did yours. I a looking for a photo of the distributor I did.

Instead of taking up space here, I put up a quick page (with pics) on my website.

http://kandlservices.com/dizzy.html

Hope this helps. I could send more if you need them.

Ken

[8974Ollie]

Thanks Ken,

That is basically how I modified the distributor for the Pontiac 455. Only I didn't cut it down that far.
Fabricated a cover out of 2 inch tubing.
Still looking for the photos. May have to dig out the distributor and take more photos.

[trakkies]

With RV8 dizzies, it's common not to bother with anything to stop the shaft moving down, as all the thrust when running is upwards. I thought this bad practice when I first saw it - but it apparently doesn't do any harm and is much easier to make.

[kjones6039]

I just do that stuff 'cause I'm anal retentive, Dave!

The thrust on the shaft is upward which is handled by the lower thrust washer. Meaning that my addition of the upper washer is probably not necessary.

Ken

[8974Ollie]

OK, This is the link to some photo.
http://i361.photobucket.com/albums/oo60 ... ion096.jpg
http://i361.photobucket.com/albums/oo60 ... edArea.jpg
http://i361.photobucket.com/albums/oo60 ... 0_1063.jpg
http://i361.photobucket.com/albums/oo60 ... 0_1061.jpg

[trakkies]

I just do that stuff 'cause I'm anal retentive, Dave!

Nothing wrong in doing things correctly.

The thrust on the shaft is upward which is handled by the lower thrust washer. Meaning that my addition of the upper washer is probably not necessary.

Ken

The Lucas dizzy on the RV8 has only a very small plastic washer to take any downward movement of the shaft, so obviously doesn't do much.

[kjones6039]

OK, This is the link to some photo.

You see Ollie, great minds think alike!

Nice work!

Ken

[8974Ollie]

thanks Ken,
I have some other Ideas too.
Involving a Mallory Unilite distributor and Accel duel point