MSD Ingition

pablop · #1 (**permalink**) 02-24-2009, 06:40 AM

Hello,
I've a 351W on my BDR Cobra that is working still fine. I have a lot of power and torque at hight RPMs but the engine response at low speed is not so fast... I'm actually using the car only for street driving and crusing.

So I'm looking for some tips to improve the engine throttle response. I've now an MSD billet distributor with a MSD coil. I'm wondering if I will be able to have a better engine response upgrading my ingnition system with a MSD 6AL system.

Alternativelly I suppose that I've to work on the carburetor tuning.

Any feedback will be appreciated.

thanks.

Ron61 · #2 (**permalink**) 02-24-2009, 06:58 AM

What gear ratio do you have in the rear end? The higher spark from the ignition module might help a little at low end but they are mostly a big help at high RPM. I used to disconnect mine once in a while to see if I could tell much difference and just driving around town I hardly noticed it and probably wouldn't have if I didn't know I had it disconnected. But I sure did notice it when I started getting up into the higher RPM range. And as you said, maybe have a good mechanic set up your carb and timing for what you want to do.

Ron

jwd · #3 (**permalink**) 02-24-2009, 07:34 AM

I doubt the 6AL would make a noticable difference. Does your current dizzy have vacuum advance and if so, is it connected to a constant vacuum source (vs. a ported source)? I would optimize my timing curve before I tried anything else. It can make a big difference in how your engine runs.

Jim

madmaxx · #4 (**permalink**) 02-24-2009, 08:50 AM

It will do nothing. I changed from a duraspark to MSD and realized zero gain. True the msd has a rev limiter but that is it. The MSD also buzzes which can be annoying. Look elsewhere for your gain.

On a side note the MSD only fires multiple sparks at rpm's below 3000.

vettestr · #5 (**permalink**) 02-24-2009, 08:51 AM

Your best bet would be to optimize your tune up. With help from buddies or a shop the goal of a performance tune will verify everything is working to its abilities and has the right settings for stock and then a little more.

A couple of very generic things I see causing lazy response is carb float settings wrong, low to way low initial timing settings, over carb'd with larger CFM than ideal, mechanical secondaries opening too fast, no or too little accelerator pump discharge and system vac. leaks.

No better way to learn than jump in and try. If you record what settings you have you can always go back to them. Use a hot engine spec from the late 60's muscle car as a direction.

Rick Parker · #6 (**permalink**) 02-24-2009, 10:30 AM

If you are running a mild or stock camshaft the error that is often done is to install a carburetor that has a too large CFM potential for the application (IE 700+ CFM) and by design has throttle plates that are also too large for your application. If this is the case try a carburetor with smaller bores such as Holly 600 or 650. A smaller carb will always have a crisper throttle response, as long as the sizing is not too small for your engines RPM and top end breathing potential.

pablop · #7 (**permalink**) 02-24-2009, 04:07 PM

thanks guys for your help.

Let's me recap: I'm understanding that I should work more on the carburator than on the ignition system.

I've a Demon 650 carburator; what do you think about changing secondary linkage to a progressive opening configuration ? I'm wondering if this could improve drivability al low RPMs.

jwd · #8 (**permalink**) 02-24-2009, 05:15 PM

A 650 CFM on a 351 is fine. The easiest and cheapest to start with is your timing/advance curve. Like I asked before, do you have a vacuum advance unit?

Jim

gt500bill · #9 (**permalink**) 02-24-2009, 05:24 PM

Probably your best bet would be money spent on a dyno Tune ($100-$150) to maximize
your setup.

bubbagump · #10 (**permalink**) 02-24-2009, 05:52 PM

My input would be the intake manifold, camshaft combination. This dictates the engines torque curve much more than the ignition system.
A Victor Junior, single plane, only makes 6 more HP over a Performer RPM, 180 degree (dual plane), on the big end. However, the HP and torque on the low end is FAR superior. And similiar results could be quoted on camshaft of different durations.
And, the MSD 6 fires the coil 5 times below 5500 rpm then over 5500 fires the plug twice.

DAVID GAGNARD · #11 (**permalink**) 02-24-2009, 07:53 PM

According to MSD, it will fire the plug three times at low rpms, according to my 20+ year old Sears timing light, that is exactly correct....My timing at idle is 10 degrees and on my timing light it will show 30 degrees as it counts the times the plug is firing, somewhere bewteen 2,000 and 2,500 rpms, the MSD on both my cars will begin firing the plugs only once as noted by the timing light....

My total timing is 32 degrees and that's what I read at 2,500rpms.....

As for the original question, a chasis dyno session will give you more results for your money than anything at your stage right now....

David

Rick Parker · #12 (**permalink**) 02-24-2009, 08:32 PM

If you do not have progresive linkage, what type do you have? With a mild motor a vacuum secondary would be highly recomended.

pablop · #13 (**permalink**) 02-25-2009, 06:41 AM

Quote:

Originally Posted by bubbagump

My input would be the intake manifold, camshaft combination. This dictates the engines torque curve much more than the ignition system.
A Victor Junior, single plane, only makes 6 more HP over a Performer RPM, 180 degree (dual plane), on the big end. However, the HP and torque on the low end is FAR superior. And similiar results could be quoted on camshaft of different durations.
And, the MSD 6 fires the coil 5 times below 5500 rpm then over 5500 fires the plug twice.

I totally agree. I'm realizing just now that (probably) I've a Victor jr single plane manifold.
But getting a Performer dual plane is too much "invasive" for the moment... I guess more easy to work on the carb tuning. I'm checking if I've a vacuum secondary or not.

Anyway, I understood that you have had a positive feedback about MSD 6. Isn't it ?

DAVID GAGNARD · #14 (**permalink**) 02-25-2009, 01:04 PM

Quote:

I totally agree. I'm realizing just now that (probably) I've a Victor jr single plane manifold.
But getting a Performer dual plane is too much "invasive" for the moment... I guess more easy to work on the carb tuning. I'm checking if I've a vacuum secondary or not.

If your running a Victor Jr. intake, that is going to kill your off idle/low end responce quite a bit...You may check around and find someone looking for a Victor Jr. intake and swap him for the Performer RPM... On my 65 Fastback, 351-W, about 350hp, I'm running a Performer RPM intake and a 20+ year old Holley 600 double pumper and if you stand on the throttle from idle (800rpms) it will haul the mail thru 5500 rpms with no hesitation....

On the other end, I'm running a Victor Jr. intake on my race car (331 stroker,13.3 to 1 compression), it never sees less than 3500 rpms under race conditions and I run it up to the 7000 rpm rev limiter.....

The MSD ignition is a definte upgrade to any stock ignition set-up,but I don't think you'll see any performance difference with it in your current set-up.....
Your Demon carb is a very good carb and sized right for the 351-W, maybe changing your jetting might help a little, but I think your biggest problem is the intake....

David

HighPlainsDrifter · #15 (**permalink**) 03-01-2009, 01:57 PM

Hi,
Don't waste time and money on bandaging the main problem.
Change out the victor intake to a performer manifold.
The open plenum victor will not give a proper signal to the carbs vacuum at idle so don't even try.
the dual plane intake will pick up huge amounts of torque for you.
Also add 2* to your initial timing to 12*BTDC , set with vacuum advance disconneted.
Good luck,
Perry.