Spark Plug Gap w/ w/o Pertronix/Flamethrower

[350SL4spd]

I'm getting ready to upgrade my M116.982 euro 350SL to a Pertonix set-up with a Flamethrower coil.

I was wondering what everyone using this set-up is running for a spark plug gap. Is anyone running a larger than stock plug gap? If so, what have been your results?

Anyone out there w/ ANY ignition set-up on a euro 3.5: What are you running for a plug gap, stock or not, on the higher compression euro?

I'm planning on running NGK BP6ES's if that factors into anyone's thinking.

Thanks.

Mahalo.

[jas2wa]

Mahalo,

I just bought the same car, but a euro delivery 71. 350SL, 4 speed. I have plenty of work to do to get it up to speed, including a pertronix conversion. I'm curious to hear how you make out with the process- our cars are rare to say the least, and so I'd really appreciate learning how yours turns out!

Cheers,

Justin

[350SL4spd]

Hey Justin,

Mine's also a euro 4spd w/ a 12/71 birthday. Good choice.

I've already got about 40hrs into her chasing down old D-jet ghosts due to the poor thing being ignored for the last five years. The best thing you can do is buy a copy of "How to Tune & Modify Bosch F.I." by Ben Watson. Awesome step by steps for dealing with 30yr old/hi-mi finicky Bosch injection systems. In a week mine gets the full work-up to see if I can get rid of a pesky bucking/surging issue.

Good luck & I'll keep you posted.

-M-

[350SL4spd]

Oh Yeah.

Bump.

Still curious what anyone is running for plug gap with their pertronix set up.



Thanks!

[dillonkbase]

my cars running fine with the preset gap whatever that is

[WINGAS]

Dont open it up much over stock. My expereince is from big block Chevies with the older Pertronix I. Good unit, although the reluctor wobbled loose after many trips past 7000 rpm.

Anyway, it DOES NOT boost output to the plug. Therefore by gapping them too wide, it taxes the coil unnecessarily. I would gap them only a few thou over stock. Only with a CD ignition would you gap them much wider. I use .043-.045 in a 10.5:1 compression engine with an MSD unti. I would use .035-.038 for a stock Pertronix app.

Dont be fooled by "high voltage" coils. Recall that amps are the horsepower of electric current, voltage is potential. High voltage coils typically ahve a faster slew rate ( but not anywhere near a CD ignition box) , and can handle higher rpms better, BUT, and its a BIG BUT for a MBz driver, you lose some lower rpm amperage in the process.

I.e. a stock coil will provide better spark at normal driving rpms.

[350SL4spd]

That the kind of info I was hoping to hear.

Thanks 427L88 for putting it in the proper perspective.

[jas2wa]

M,

Have you gotten the old girl to stop bucking and surging? I'm going to order the "How to Tune & Modify Bosch F.I." by Ben Watson- thanks for the citation. I'm starting with brakes and a tune-up, plan to do the Pertronix. Did you have to give them the number on your distributor?

Here's mine, I have done NOTHING to it yet, other than driving it home. These are even pics from when I first looked at it.

Cheers,

J

[350SL4spd]

J,

Got my Pertronix in and she idles phenominal.

Still have the bucking problem, though.

Pulled off the valve covers yesterday and saw enough chain strech (like, gouging the head @ revs) that she's sidelined until I have time to pull the front cover and do the chain & all the guides. Then I'll see where we stand with bucking. I think I'll upgrade to a Megasquirt as well. Someone's had my ECU apart and I don't know if that's contributing to my bucking or not, but a used ECU is way more than a Megasquirt kit (man hrs not inc.) and it's way more reliable & tune-able than the ancient D-Jet ECU. (Maybe even squeeze out a few more MPG's...)

Anyway, let me know before you do the Pertronix. On these Earthed-coil D-Jets, setting up the Pertronix is as per the instructions and takes a few extra steps.

[t walgamuth]

i am not sure what you mean by bucking.

i had a 74 saab with the djet injection. it was almost new back then. it never would run at a steady speed around town. it either cut out or accelerated. i got in the habit of accelerating a little then letting off around town. on the highway it was fine, and it ran perfectly in every other way.

i decided it was just how it was built.

tom w

[350SL4spd]

T,

By bucking I mean that when you try to accelerate, it'll accelerate for just a sec then cut (well, either fuel or spark) abruptly & unceremoniously stopping all forwrd progress, then a sec later it willl dive back in @ whatever throttle you have your foot at rev hard for a sec and then cut out again (the cut-out is not a stall, the car just returns to idle, I got it to stick once and it just settle back into an idle before it took off again).

Very rough on the neck (and the image, if you worry about that sort of thing). Kinda looks like and feels like you let the clutch out wrong and it jerks forward. just over & over.

J,

I did give them my dizzy #, but it didn't help. The euro wasn't in their computer. You want a Perrtronix Ignitor I #1885 & a 1.5ohm coil. I got mine here: http://www.vintageperformance.com/retrorockets/mercedes.htm. Great guys.

[jas2wa]

Hey-

Yeah, they asked for my dizzy # too, at a different supplier (car shop.com)- is there a number on the housing or does the number on the cap suffice? Probably not. It is the 91885 model- the 1.5 ohm coil must be the extra spec I need- thanks. I will check out the guys you bought from.

The limited records I have for my car show the timing chain was done, so I am hoping I don't have to deal with that for awhile. She fired up right away last night when I went to move it- good sign! She just needs a full tune-up and brakes. The parts are starting to arrive- I am going to get to know my UPS guy- I'll keep you posted when I get her on the road.

Cheers, Justin

[jas2wa]

I just checked out the site you bought from- so you got the Ignitor I, correct? Evidently the II is not compatible with 'solid core wires' but I am not sure what that means- simply the spark plug wires? I will be changing them as well, so I wonder if I might be able to go with the II.

Maybe I am misunderstanding what they mean... -J

[WINGAS]

350Sl, gee my "new" diesel experiment is doing that.

BTW, my "experiment" was an Ebay purchase with 220K on the clock. ( try adn find a deisl MBz up here in WNY is useless) And its one of the tightest cars I have ever driven, a true testimony to the design..

Loose chains mean that cam timing is actually moving around continuously as the chain tightens and slackens. Gotta feel funny.

Myself, I got lazy and didnt do a compression check on the 220K 606.910 engine I bought, and should have. Why? I have some modest bucking as well. Could be the flappers in the intake track ( new tech to me!) OR it could be indicative of a bad valve somewhere. a CP would have found the leak if there is one. Suspect its a fouled up prechamber anyhow.

Just saying, if you havent done a compression test, you might consider it. Will give you an indication of cylinder seal. Wet test will eliminate rings and see if valves are holding comrpession. If you;re doing chains, now is the time to know. IF you need to freshen the valve job, now is the time.

Once drove home from college with a frat bro and did a valve job, only to find that the ingition wires were shot. We finished up at night and fired it in the dark in my parenet driveway. Pinball machine light show. Bad valves and bad wires can both give you an "off/on" feeling under power, as well as generally sluggish performance.

A vacuum guage can also help diagnose bad valve seal.

Check the wires with a VOM. I've gotten to be anal about that since my expereince over 20 yrs ago. If you havent done that, ( even on NEW wires!), I'd bet you a pint of Guiness, you have a bad wire or a dead plug.

Recall that the voltage required increases as the load develops. So , while the errant plug/wire will spark at idle, when you throw some more mixture into the cylinder and ask it to spark it, , it fails. It's almost as if resistance in the system increases as load/rpm increases, so the faults show up under load, and will eventuall show up at idle.

Solid core wires put up one hecuva "b" field, or magnetic field. In close proximity, they mess up chips, etc. ( the old Am radio in my Chevelle actually worked BETTER with solid cores in! but use of an MSD precludes them).

The Pertronix II has a chip inside ( and a starting delay - which I dont care for). Hence you an sue magnetic field gerating solid cores.

Other than the CD ignition giving the hot spark I needed to ignite an oil contaminated mixture at 10.75:1 at 7000 rpm, the Taylor solid core wires, Pertronix I system worked FLAWLESSLY. If you dont mind the radio noise, solid cores are EXTREMEMY durable and the resistnace thorugh them is infitesmal as compared to modern spiral cores. Taylor wire makes a great wire btw. I use the universal "roll your own" sets , so you can make any installation look stock.

Of course, I wont be using them on my Benz.

Good luck!

[350SL4spd]

427,

I've had several cars give me the 'bucking' sensation and two of them were just plug wires. Neither condition was as severe as what I am experiencing now. And I'm on my second set of new plug wires in a month, so that SHOULD rule it out.

I've been vaguely looking for an E300D for a few years. It's hard to find one that's drive-able under 10 large, much less around WNY. Good luck with her.

J,

You want the Ignitor I. The II is unnecessarily complicated for you application. All you need to do w/ the I is put an in-line fuse in or remember to disconnect the unit from the ignition switch if you need to leave the ignition on for several minutes at a time (if you're diagnosing an accessory isssue or whatever).

Just go to the site I gave you and get the Ignitor I and the Flamethower coil. Let meknow when it gets there and I'll shoot you over teh wiring diagrams you'll need.

Cheers.