I'm looking to add an MSD distributor & 6AL or 6AL-2 box when I build our 351w. I don't know much about the ignition system yet. What MSD distributor should I go with? Been told it should still have a vacuum advance on it since it should help with fuel mileage.. this true? Whats the advantage of HEI?

I'm putting together an engine build and besides the pistons this is the next biggest pain I'm finding.

 

form what i have been told
hei will put out more spark more accurately than a point distributor. also it is more reliable and will not need points filed down every so often.

 

Ok.. and is a coil still needed or is there one inside the HEI unit?

 

inside

 

HEI is a GM term and the coil is mounted in the distributor cap. Vacuum advance works by advancing your timing when engine vacuum is high (steady cruise, decelerating) and the load on the engine is light. When vacuum drops (acceleration), advance is reduced keeping the engine from detonating. Many people don't run vacuum advance thinking it is an emission provision (race cars don't use it). Actually, it is helpful to fuel mileage (racers don't use it as it is one more thing to break).

Your distributor choice is based on several things. Do you have a roller cam? If yes, you need a steel gear. MSD offers a distributor with a steel gear or they sell one separately you can change or have changed (must be precisely installed). Do you want vacuum advance? If yes, select one that includes the vacuum canister. Do you want a ready to run or will you run an MSD box? If using the box, get one that provides a magnetic trigger. Here are some that fit a 351w:

http://store.summitracing.com/egnsea...115+4294889096

 

I like the ready to run small base dizzys. Thats what I have, and its small size allows much more room for things such as an air cleaner. They can be run as is, or an ignition box can be added as well. I don't like the HEI style units because they are big, bulky, and ugly, and they also take up a lot of space due to their size.

 

Here is my take.

I bought a ready to run MSD with ignition box. When i bought mine MSD only had out the old version of the 6al box. It uses small chips to control the rev limiter. So, I bought the Street Fire box. (made by MSD) this box is a digital control that provides higher volytage and has two dials to set the rev limiter.

Where i believe i went wrong is by using a mechanical advance dizzy instead of vacuum advance. I do like the tuning aspect of the mechanical advance but it is just one more thing to screw with. go with the mechanical advance.

Here is the one that i bought:

http://www.msdignition.com/Products/...stributor.aspx

As you ca see it is a large body. It gets in the way of my air filter. THE PART NUMBER IS DIFFERENT FOR A 351.

Here is the one that i would recommend for you.

http://www.msdignition.com/Products/...stributor.aspx

 

Is there a noticable performance gain with the MSD setup?
Or is it just more reliable with slight hp gain?
I already have the Pertronix kit to replace the points but everything
else is OEM style ignition.

 

i noticed that the msd will help smooth out your idle a little so you dont have to 2 foot it if you have a lumpy cam, due to it firing each plug multiple times at lower rpm. dont know about the power, although i think they claim it helps.

 

Mark, I'll be going with Comp Cams Hydraulic Roller Cam & Lifter setup (CL35-424-8) and Retro-Fit Kit (31-1000). Yes, the guy at Comp Cams told me I'd need a steel gear on the distributor but thanks for adding this information.

Thanks for the vacuum advance explanation and yes I do want it. Are there any pros/cons between going with vac/mech, mech or elec advancing?

Regarding the box... I do plan on using a box, most likely the 6AL-2 (MSD-6421) and having it under the dash. Going with the programmable box (MSD-6530) which "give you the ability to tune an ignition curve or boost timing map from a PC" costs another 130.00 bucks and I don't know if this is worth the extra cash or not. I'm looking at mileage per dollar here. Any idea if this tuning would give me another mpg or so? Not so much a question on weekend drivers / show cars but as a daily driver I'm thinking mid & long term fuel savings.


tyler72.. got a part number for your small base distributor and know if they have one for a 351w? I'd like a low distributor since I'd like to have an oval air filter but it looks like most of my options are the higher HEI units.

MonsterBilly.. I'm guessing you meant to say "go with the vacuum advance". Thanks for your recommendation however that is for a 351c and will not fit the 351w.

1971mach1.. From what I've gathered doing with a newer ignition setup like the MSD and box will allow you to gain not only a bit more HP but also greater throttle response, smoother idle, cleaner valves, better mileage (high on my priority list) and an easier more reliable start especially on those damp and cold mornings.


Thanks for everyone's replies so far.