Spark Plug and Gap recomendations for MSD Streetfire

Kemo · 10-07-2021, 08:56 AM

All,

i recently have installed an MSD Streetfire to replace my questionable unit. Is there a recommended spark plug type and is there a magic plug gap that should be set?

thanks for the input!

Reiver · 10-08-2021, 08:35 AM

You should use the recommended plug range for your 911...you can open the gap a tad (technical term)
I do not use Bosch plugs anymore as too many are made elsewhere and not in Germany.

I have great results with NGK's....I use cooler plugs as I have a 930-10 Euro with 9.8-1 comp. so no need to give you that number...I believe you should use BRP5 ES plugs in the US model SC and you can find a cross ref for the NGK's....but look at your ref manual.

btw, you should tell us what model 911 you have when asking specifics... fyi.

kent olsen · kent olsen's Garage

Check a little further, with a MSD you use a larger gap. Sorry I can't remember mine, I've been running MSD for nearly 20 years, but it is quite a bit more than with a stock ignition.

gssereik · gssereik's Garage

I installed an MSD Streetfire a couple years ago and ran it a few hundred miles with old plugs gapped at original spec and crusty old (original to the car) plug wires and it worked great! But I was already planning to freshen up the rest of my ignition…. Now, my engine is out of the car for rebuild (due to broken dilaver studs). I searched and read a lot of old posts on this forum and saw various recommendations. One guy on this forum (tirwin) seems very knowledgeable and he has the same year car as me - he recommended .045” plug gap. So that is what I am going with, at least for starters. I also have a new set of Clewett Engineering wires, NGK plugs, a new Bosch cap and a special (and cheap) resistorless rotor that was also recommended on this board (By John Walker, I think). The rotor I got at o’Reilly’s is part number 12-0101. But I think this was based on a cross-check lookup of some other part number I had found on Pelican message board. Anyway, the O’reillys auto 12-0101 rotor works great.

Reiver · 10-08-2021, 04:28 PM

Yes on the non resistor rotor ...and clewetts are great...some still use the solid copper but MSD suggests you should not (resistance)...a nice MSD coil too, the hvy duty one that can be mounted upside down.

Kemo · 10-08-2021, 07:06 PM

All...thanks for the input...my motor is a 1978 big port with 9.8:1 compression, GT racing headers and a dansk gt3 center out muffler, interesting about the rotor, does pelican sell them?

Reiver · 08:10 PM

Quote:

Originally Posted by Kemo

All...thanks for the input...my motor is a 1978 big port with 9.8:1 compression, GT racing headers and a dansk gt3 center out muffler, interesting about the rotor, does pelican sell them?

No they don't. I use a NAPA Echlin made rotor EP 407...it looks exactly like the stock rotor minus the glued in resistor...it has a solid transfer bar.

If you take another look at your MSD inst. they say max perf. comes with the least resistance.

Some using MSD have had the original resistor style rotor melt/deform. Some others seem to have no issue...depends upon the MSD box type I suspect.

Did you modify/change your piston profiles? Oh yeah....track it. If you are running 9.8: 1 then a colder plug should be in order too I use an NGK BRP9 ES stock number 7788. This is also the range Porsche recommends for that compression in the 930-10 Euro. Especially with anything under 93 Octane US. Hotter and you could have detonation as you know.

Tyson Schmidt · 10-09-2021, 06:20 AM

MSD Streetfire is only a marginal increase in output over the stock CDI.

It’s the MSD 6AL that is about double the power, and requires upgrading the wires, non resistor rotor, and increasing plug gap.

With the Streetfire version, it’s basically a direct replacement, and doesn’t necessitate any changes.

Reiver · 10-09-2021, 07:46 AM

I'll go with the manual recommendations etc..and reduce resistance in the rotor

Note. Solid Core spark plug wires cannot be used with the Street Fire Ignition.

Kemo · 10-11-2021, 12:40 PM

thanks again for all the input. i currently have a set of magnecore wires that are a good 8 years old, does anyone know if those are solid or not? if i were to purchase some non-solid core, what would be a good recommendation?

i just have a few misses and pops here and there and would like to rule out any hardware issues. i was at the track this weekend and noticed that it starts really good cold, and once the idle settles down it starts to miss here and there until it warms up. Also, between 5-6K under full load, it feels like its missing there, seems like it got progressively worse as engine temps climbed. coming off track engine hot, just an occasional miss at idle.

Reiver · 10-11-2021, 08:16 PM

Those wires are spiral wound but at 8 years I'd replace them....Magnecore or Clewetts are good choices and old wires can cause a miss like that.
I'd start with a tune up..rotor/cap/plugs/timing/valves set and wires and go from there.
What is your AFR? With that compression I'd want a 3.5 to 14 (it moves) but with most of the activity in the 3.5/3.7 range and a stomped WOT in the 11's.
I'd also want cooler plugs with the fatter AFR....
The best onboard tool I have is an AFR gauge in place of the clock...I can monitor 'health' and fuel delivery in real time..... for a track car I'd consider that a must.

Kemo · 10-12-2021, 06:36 AM

ok...so here is what i have in there...new cap and rotor but not the solid rotor,8 yr old magnecores and old plugs.

Timing is set to 30 deg at WOT, AFR is set to 12.75-13 as it tends to bounce around with my gauge. I will mount this permanently. i tend to just use it and then pack it all back up till i need it again.

so ill give it a shot with the new rotor, new cooler plugs. i actually talked with MSD/Holley technical support and they recommended 40-45 thousands for the gap and the MSD-Iridium plug number 37334. Not sure how that compares to the NGK, but i have used NGK before with good results, i have the BOSCH units in there now. just recently got a new engine harness from Timmy2 just for this MSD unit and im running the black MSD Blaster coil

also, i Ohm'd out my wires and the shorter wires were in the 3K Ohm range while the longer ones on 4,5,6 were in the 6K-7K range. And the little wire from Coil to Cap was 1.4K Ohms. not sure if these are acceptable numbers but if the plugs and rotor doesnt help...

thanks again for the input

Reiver · 10-12-2021, 08:35 AM

That's a pretty fat AFR and I've found that checking thru the tail pipe (exhaust) to be a bit off...right behind the collectors in the straight pipe to the exhaust seems to give a more honest reading...if you mount one that's where they will recommend.
Too rich at idle will cause surging but should be no issue at WOT.
I'd just change the wires right now....(not sure about your test fig. tho if good/bad) and do one item at a time so you can isolate the issue.

Kemo · 10-12-2021, 10:39 AM

https://www.napaonline.com/en/search?text=EP407%20rotor&referer=v2

here is the results at napa...seems to be two, the brown one or the red one?

thanks!!

Reiver · 10-12-2021, 02:35 PM

Quote:

Originally Posted by Kemo

https://www.napaonline.com/en/search?text=EP407%20rotor&referer=v2

here is the results at napa...seems to be two, the brown one or the red one?

thanks!!

Brown top one...the lower red one is the stock resistor style. The Brown one (I use them) is exactly like the stock resistor rotor except for no resistor....perfect fit.

gamin · 10-13-2021, 04:03 AM

Thank you Reiver for the heads up regards the rotor. Just installed the brown rotor and just seat of the pants seems to run better. Purchased at O'Reilly. Added bonus is that it is made in the USA.
'70 has '79 ROW 3.0 MSD 6al blaster coil Clewett wires solex cams 9.5 JE's PMO 46's. Since this is
about plugs I'm using NGK BPR5ES at 35 gap.