platinum plugs 73 E

[cmcfaul]

What platinum plugs are recommended for a 73 911 E? Will colder plugs help my car run any cooler?

I Installed JE 9.5 /1 pistons with Nickacil (sp?) cylinders a while ago. Temps are fine except when run on a track. Stock 2.4 with MFI otherwise. Not sure if different plugs will have any effect.

Thanks,

Chris
73 911 E

[304065]

Platinum plugs don't work in the 911.

Use NGK copper. Heat range dependent on usage.

[cmcfaul]

Why?

I have been using platinum for years. Never know which one is correct however.

My thinking is that MFI's run rich. The more spark I can get the better.

Chris

73 911 E

[304065]

Modern self-cleaning platinum plugs work better in modern, watercooled cars, where the range of operating temperatures is narrower than in our ancient aircooled ones. There are a ton of threads on this here and at Pelican.

Also, platinums are a lot more expensive than NGK, last time I bought a box the NGK were about $1.50 each.

Worn-out or incorrectly adjusted MFI systems DO run rich, but installing platinum plugs doesn't help this issue. If you are experiencing high operating temperatures, there's a way to figure that out; if you are getting black smoke out the tailpipe, there's a pathway for that also. Let us know what the symptoms are and I'll point you in the right direction.

[cmcfaul]

no symptoms really. Just have not changed the plugs, cap and rotor in two years.

A perfectly tuned MFI will still run rich. It's the nature of the beast. When I pull the plugs I will determine if it's too rich (or lean) and make the minor adjustment.

Yes the platinum plugs are ridiculously expensive but what is not on our cars.

So, is the advice here that I will get the best performance from plain old NGK's

Chris

[cmcfaul]

I did a little research.

Interestingly there are several NGK plugs for a 73 E but only one for a 73 S.

My car is an E with more compression then a stock S.

NGK recommends BP6ES for the E and the bp8ES for the S. Based upon the search I did seem like folks like the BP7ES. Is this a good compromise for street and occosional track usage?

Thanks in advance.

Chris

[304065]

BP7ES for street use
BP8ES for track use

With NGK plugs, the higher the number the colder the plug, i.e. the shorter the ceramic insulator, which reduces the amount of heat buildup in the tip. For street use you want a longer tip i.e. hotter plug so deposits will burn off. Under sustained high load and high RPM the plug tip gets plenty hot to clean itself so you want a shorter insulator to carry more heat into the cylinder head.

While I agree with your basic premise, i.e. a fun to drive MFI engine is usually tuned to 5-6-7-8 (5-6% CO at idle, 7-8% at 3000 rpm and part-load) which is definitely richer than stochiometric, there is no inherent reason it has to run like that-- just that the transition and throttle response are a lot better when it's set up rich. With some patience, the internal adjustments of the pump can be set to flatten the fuel curve. See below:

http://forums.pelicanparts.com/showt...mfi+open+heart

I had mine tuned to a 14:1 or so AFR and it ran OK, but the throttle response was weak. A few clicks of the pump and it was back to that instant chainsaw-like response.

[cmcfaul]

Holy smoke, look at these. Thats per plug from Advanced Auto.




Part No.
BE1 Pulstar Pulstar Pulse Spark Plug
Pulstar Pulse Plug: 0.025


Ships in 1 day
$49.90

[J-P]

Platinum plugs don't work in the 911.

Use NGK copper. Heat range dependent on usage.

I know this discussion is mostly about MFI, but my understanding is that the 2.4 CIS are the ONE model that ARE supposed to use platinum plugs.

[304065]

Egad, "pulse" spark plugs. Has to put a smile on the face of the FTC.

NGK BP7ES are $1.69 from Rockauto (where I bought my last dozen). A replacement set of plugs are cheaper than the labor to have a mechanic clean them. (Although that makes me feel strange, coming from the aviation world where a REM40E costs $25!)