Good idea or bad idea....MSD unit for 67S?

[ThomasWilkinson]

Sherwood,

A few points:
The Crane breakerless unit was on a different car (see my other posts).
The coil used on the 914-6 motor during all dyno. runs was the OE Bosch CDI unit.
Two runs were done with the OE ignition and came out within a few tenths of a horsepower. Both MSD runs (using two separate units) were both off by 5-6 peak hp. The final run with the stock ignition was again back to the original power level +/- a few tenths. So no, it was not the dyno error range.
Perhaps it was a CDI/coil (transformer) issue.
Given that the motor is now installed in the car and runs great I have no reason to replicate this experiment.
My intent was simply to relay my personal experiences as requested by the initial poster. I replied to a similar post on Pelican in the last year and got some replies from a few that really like the OE Bosch unit.
They did not seem skeptical of the results.
I would however recommend a healthy dose of skepticism regarding any blanket claims touting power gains from most manufacturers of performance parts
unless they can produce documentation substantiating the gains after testing an otherwise identical motor without their part. Then make sure that the specification of motor tested is also the same motor you have in your car.
Buyer beware.
Regardless, I have nothing against MSD.
If I was looking for a replacement CD unit, I'd probably buy one.
Until that time, I'll keep my 2 OE Bosch units.

Tom Wilkinson
R Gruppe #130

[Steve@Rennsport]

Hi:

This is a great thread but deserves some context.

I was there during some of those dyno runs on Tom's motor.

For the record, the dyno's (Superflow 800 HP) resolution is 2 HP. All runs are totally automated so no operator errors are a factor.

I've seen this happen several times where the MSD is substituted for the Bosch or Permatune (retaining the stock coil) and results in a small loss in HP.

Coil impedance (load) is VERY VERY important to the MSD and Crane series of CD ignitions and both manufacturers optimize their ignition amplifiers to the coil impedance.

When the MSD (and Crane) ignitions are used with the appropriate MSD (or Crane) coils, one sees the same HP as stock; no losses at all. When the plug gaps are opened up to optimize what these ignitions are capable of (.040-045), one sees HP gains of 5HP to 10HP, depending on the configuration engine under testing. In this case, the dyno doesn't lie as long as one follows the manufacturer's recommendations to match ignition systems to the coils. Further, the idle quality and low-speed drivability is much improved.

IMHO, its inaccurate to make any conclusions without all the facts,...

On a personal level, I've used all sorts of MSD's on different cars over the years as well as on 3.0 RSR, 935, 917/10 engines and in all cases, the car started, accelerated and performed better with the MSD, rather than the OEM Bosch units. MSD's and their matching coils make a big difference on engines with imperfect air/fuel ratios,....MFI & carbureted ones.

[Sacto S]

'67 S, 2.O, Webers..........

[Steve@Rennsport]

'67 S, 2.O, Webers..........

I use Bosch Silver plugs in these things as they are very foul resistant and last a long time. A 2.0 litre "S" can use the 5's for street use and 4's for track work if the car has its original ignition system.

[pwd72s]

Justin, you might wish to do a search on this topic over on Pelican...search word would be MSD and early_s_man. His other name is Warren Hall. I value his opinion highly. Especially when it comes to early 911 electrical and ignitions systems. In an earlier life he was an electronics specialist for NASA...he has some opinions about MSD vs. Bosch CD units, and the personal test data to back up his opinions. My opinion is that both systems work well, but I'm an original phreak, and I see no reason to go to MSD...not now that rebuilt Bosch units are affordable. Here's a link to one of the Pelican threads on this subject:
http://forums.pelicanparts.com/showt...d&pagenumber=1

[Fritz A. Ficke]

I have a 67S I brought from a fellow who had it since 1970. I wanted a CD unit for the car since stock it came with none and there was no fuel inriching device on the car. MSD was a cheap track proven systom that worked great for me, I opeoned the plugs up like Steve and MSD suggests and changed coil. Lean misfire when cold is almost nonexistent, fouled plugs I have not had since instalition and I feel passing AZ. emission should be easery . Bosch Cd would most likley have the same results but for alot more money. Fritz

[911pcars]

Increasing the gap increases the voltage requirements to fire the spark. The bigger the potential (voltage), the bigger the spark, and a better chance of firing the A/F mixture. However, if the ignition system isn't capable of producing the needed voltage, the result is a misfire. Normal voltage during cruising is perhaps 5,000 volts. However, under load, the voltage requirements climb much higher. The better ignition systems can produce a high voltage spark across the entire rpm range (if needed).

Sherwood

[Eric911S]

Just a small note that I found out the hard way about MSD units, it's spark is so intense that it will melt the resister spring inside the stock rotor. I use a rotor with a solid brass plate on top and that does work very well.I also use the MSD coil as well.I've used the Crane units and they work great too. One last note is to run a plug gap of 0.040".

[mjmoran]

Not only does the MSD with matching blaster coil a great performance upgrade, the soft rev limiter v. the stock rotor limiter is very nice to have with track work or sporty driving. The only other thing I would recommend is using a pertronix igniter. Pertronix now manufacters a kit for the early cast iron distributors -- call them as it is not listed in their catalog. These along with the MSD system and widened gaps gives a much more enjoyable performance. Quicker start-up, stronger idle, and powerfull accelleration. Not to mention fewer fouled plugs. Its no wonder the factory installed CDs in the 69 cars. With the cost of the Bosch unit costing twice the MSD and with neither unit being correct for the 67/68 esses, go with the MSD. I can think of no reason (unless your a concourse junkie) to not go with the upgrade.