Upgrading ignition to MSD - worthwhile?

[SimonP]

I have a Chevy 350 small block, running a standard HEI system.
The engine was supplied by Repower - it's their mid range model, 355hp. I don't know exactly what's in it though, cam wise.

Idle is slightly rough, a little more so than I'd expected.

Would changing to an MSD system bring me any benefits regarding idle smoothness - and the feasibility of a stable idle below 1000rpm?

If so, the system I've been looking at is part# MSD-8500 which adapts the 6AL ignition box and Blaster2 coil to the HEI distributor.

A number of suppliers have this kit for $249.99, which seems better than buying a full new distributor.

Any advice or suggestions?

Simon.

[Philip]

Hi Simon,
I must confess I dont understand people who buy new distributors, unless their's is either faulty or they want to change the ignition curve quite a bit from the original. After all its just a switch, its the amp, leads, etc, that generates the quality of the spark. If you feel the ignition is where your problem is I would recommend an MSD, I would have thought a dissy was a complete waste of money unless yours is worn out or faulty or if its got points in it. Thats another thing, why do people replace a good electronic switch for a stupid points dissy? I must be missing something!
Phil

[SimonP]

Phil,
I'd looked at the MSD internal amp module and coil upgrades for the HEI distributor, but even though they carry the MSD brand name, these are not actually mutiple spark discharge ignition units!

I ruled these out because I didn't forsee any real benefit for low to mid rpm street driving.

My two options seem to be the complete MSD-8500 kit I mentioned previously, or just going for the 6AL unit, keeping the stock HEI internal coil.

Simon.

[Philip]

Hi,
I fitted the 6BTM amp to mine, couldn't keep the standard hall effect setup in the dissy, but the improvement was very good in low to mid range. I use a luminition system in the standard dissy to fire the amp, works very well for me, but I guess you could keep your dissy the same, I had a few problems which i thought was the hall effect pickup but it wasnt in the end. My websites got all the details on it,
Phil

[mikey]

Go for the multi spark, it cleans the Chevy pick up quite a bit and tickover is definately better.
Mike.

[SimonP]

Thanks

The biggest advantage I can see with the MSD 8500 kit is that it's all reversible - so if it ever fails, I can just go back to standard HEI to get on the move again.

Simon.

[graham]

Hi I have rebuilt my HEI (everything apart clean checked, new leads, coil,cap and rotor. amp module is original as is little condensor thingy) and works great from idle to 3500rpm at present. But when run in not sure whether it is meant to cope to 5500rpm or is then when we look at recurving it. I put new (advance curve kit) weights in purely for the new pivot bushes these maybe non std. But I did use the stock weights as using lighter one made it run bad. I guess this bit is left to rolling road time.

Graham

[SimonP]

Graham,
Mine is all new at the moment. When I went to visit Repower last month, Brian changed the vac advance can for an adjustable one and set it up with a dial-back timing light. Mech advance was left as standard.

The issue with HEI at high rpm, is that of insufficient dwell for the stock coil, so spark energy decreases over about 4500rpm. (but not THAT much)

The other thing I have to look at is the carb, which would now seem likely to be the main cause of my low-speed (idle-1500rpm) un-evenness, as I've done a bit more research.
What I've found out is that due to having a cam which gives low idle vacuum, the throttle stop has to be adjusted a fair way in, so then the primary butterflies are not over the idle progression slots when idling. This leaves a "hole" in the calibration of the carb off idle, where the idle circuit reaches its maximum fuelling, but the main jet has not started fuelling.

I've seen various means of achieving correct operation, but I don't really like the idea of drilling a 1/16inch hole in each primary butterfly.

Time for more research. Anyone had to have this done to their carb?

Simon.

[skid]

Hi Guys,

I have a Dave Brookes Cobra with the mid range '350' bhp output.

This ran a standard HEI dizzy/coil set up. As I'm over half way through setting up Nitrous I took advice from Russel Ram regarding the electronics.

The concern was that Nitrous would blow the spark out so up-rated to Jacobs Electronics Ulta Coil and Prostreet Pack.

Now I'm not an Auto Electrician and I had to learn a lot by fitting it myself and I'm very happy with the results. The Nitrous hasn't been switched on yet (another story and another black box to be fitted) but the car sounds and behaves so much more alive.

The wiring was essentially easy. A cap adapter goes on the top of the HEI dizzy and you remove the old coil and connectors. You tap into the red/brown wires that come out of the bottom of the dizzy and connect to the ignotion feed and tach cables. The coil is simple 2 cable job.

I promised DB I would forward him all the details and prices as think it's a worthwhile addition he should offer at build stage rather than retro fit like me. Will get round to it soon.

The set up feels much more responsive and quicker and the sound from the pipes has changed fantastically with much more pops and crackles.

The set up I estimate around £250 (not entirely sure as did a deal on other Nitrous stuff as well) and has the benefit of a built in programmable rev limiter plus an enhanced 'big spark' switch on WOT.

The Jacobs Prostreet is the top end pack for Nitrous and there are slightly cheaper units from Jacobs if you want normally aspirated running.

In brief, I'm chuffed, it's great!

If you are interested (hope it's ok to post this) give this chap a call. His name is Mark and he is the Importer for Jacobs in the UK. 07762456214. Mention the sale to me and you might get a bit of discount!

Regards
Mark

[callum]

One thing I learnt the hard way with my 350 (Edelbrock RPM Cam) with MSD 6A and MSD 8361 dizzy is to ignore/disconnect and cap the vacuum advance if you have a lumpy cam. It gives way too much advance when you floor the throttle and induces a bog. Otherwise, the MSD set up provides an easy 650 rpm tickover and, in a relatively light car (by US standards), clean, quick pick up from low rpm. Having tuned the car to full specified advance/rpm spec, then if you do not have this then it will be more to do with the cam than the ignition system.