Sparkplugs for '74 2.7 CIS? Catalog lists 2
 

I wondering which plugs to buy. The pelican catalog lists two Bosch plugs: WR4CC and WR-5-DC-S

My car is new to me but has been upgraded to S-spec rebuild with a '79 fuel distributor. I'm not sure if that makes a difference.

Since I'm at work right now (goofing off) I can't pull the existing plugs to check.

Any advice would be great....I can always order later but since I'm placing an order now, I thought I would add plugs to it.

Thanks........Vern

NGK BP6ES. not on the list, but pretty universally used. not much of a bosch fan.

I went with ngk BP5ES...not to mistaken with...NGK BP5ES..with a R in it.(advice I got from mechanic)

Mixer - re-read your post and ask yourself - "Why don't I reread my posts before I hit the post reply icon?"

Tidybouy, Autozone lists this for your car but I would go with what JW says.

Ngk Standard Copper/Spark Plug (5534) | 1974 Porsche 911 6 Cylinders 1 2.7L FI | AutoZone.com

uh.oh I think I've go 7's in mine

I used to use the 7s (BP7ES) in my '76 2.7. That was the NGK recommendation.

NGK numbers go smaller for hotter. bosch is opposite. i figure that a bit hotter for the older engines helps keep the plugs cleaner. colors are normal at replacement time. if you have higher compression than 8.5, a bit colder is good. C2/C4 still uses a 5. if you run carbs or MFI and the plugs are always dark, go hotter. race conditions are different than street of course.

These questions are just because I am ignorant - not critical that I get an answer.

Is higher compression easier on the plugs regarding fouling since there is a more powerful explosion?

The C2/C4 have 11.4 compression and you put 5's in them. Why do the higher compression engines require a hotter plug - does it have to do with the twin plug set up?

That is two heat ranges lower than "stock" but the 2.7 runs 8.0-1 compression and if the engine is a "little tired" I think I see where your mechanic is going.

Don't forget about the Denso IW22 iridium plug. I run these in my 2.7 CIS with "E" cams and 8.5:1. They are virtually maint free, when I check them at oil changes. Here is a quote from the Denso site for their heat ranges in case you need to move up or down due to your particular application.

"DENSO heat ranges move up as they get colder; 16 would be our hottest Iridium Power plug, 34 would be our coldest (ranges; 16,20,22,24,27,31,34)"

As you can see I run towards the hotter end but when checked they are always spotless. I am very happy with these in spite of the cost (approx $11 each). They have performed flawlessly at DE days when at or near red line.

Sláinte

another thing to ponder; is your sparkplug chart recent, or from the days of real gas?

thankyou bob
 

Mixer - re-read your post and ask yourself - "Why don't I reread my posts before I hit the post reply icon?


Sorry Bob I dont think my post ...was crazy or out of line....
Bob I have alot of respect for you....ya I joke ...sometimes my posts might be off the wall...its humor...get over it..you are a wealth of info...(understandable,,naming next child after you on hold...lol)

Young Skywalker,

Post was great and I am not upset with you or the content. Not even upset with your feeble, as well as pathetic and sorrowful attempts at humor. I think you are a righteous dude.

Just take a few moments and read your posts out loud and tweak them so they read like you talk.

Y

Copy Teamleader

...I'll ponder your points...
As for my humor.. ya ..Its not great
Not trying to steal Tidybouy's post
But my new injectors are coming this week.
I might need some advice.
BY the way Tidybouy their for a 74 2.7 as well..30 bucks a piece..Bosch