Wrong Heat Range- Bentley Got Me!

[hank911]

Changed my spark plugs a couple of weeks ago.Went to a set of Bosch wr7dp's on my 83SC Targa per my Bentley manual.The car seemed to run fine for about a week,then it dropped down to an idle of about 600-650rpm.After seeing recent post I've relized I have the wrong plugs in my motor.I have a set of wr5dc's comming in today,hope that clear's up the idle,but did I possibly cause any damage by running these "hotter" plugs in my motor.The motor went through a top end rebuild this winter with new cams,I do run it hard.If I'm taking the 911 out it usually see's 5000-6500 rpm's.The motor only has 56k on it but I'm wondering if my new valve job could have been compromised with the wrong plugs?What do you guy's think? Thanks in advance, hank911..

[Bo]

Interesting thread - since I'm about to change plugs in my engine for the first time (it has Bosch platinum plugs), I'm interested in knowing what plugs everyone has for their SC-engines (I have an 82 RoW).

Thanks!


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1972 911S Targa
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My project!

[hank911]

Any Idea's guys??

[nhromyak]

There MAY be damage ONLY if you heard pinging on acceleration. I doubt it though. Even if there was light pinging there should be no damage.

However, if there was excessive PINGING for extended periods of time, the rings can shatter, and the pistons can shatter where they hold the rings (ask me how I know). Then even more carnage can happen after the rings shatter.

I doubt anything has happened to your motor in that short of time.

Did you feel any loss of power?

Change plugs and all should be well.


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Nick Hromyak
'85 Carrera 7 & 9 Fuchs
Havin' Fun in Sacramento

[Wayne 962]

Unfortunately, almost all books have errors in them. We've found a few in the Bentley manuals, the Haynes manuals, and even the Factory Workshop Manuals.

One way to double-check is to have a few books (I personally purchase ever old manual or book I can find) that you can refer to, just to make sure that everything is correct. Even the Porsche factory spec book for the 356 has some known glaring errors.

On a side note, for my upcoming book, 101 Projects for your Porsche 911, <- subtle plug, I had five different technical editors review it and correct it to make sure that it contained no mistakes...

The moral of the story is to make sure that you verify just about everything - even the factory literature can be rife with mistakes...

-Wayne

[82sctarga]

I to bought the Bosch W7 plug because of the "Bentley mistake" for my 82SC which I now find calls for a W5 plug. Because of the difficulty I had in installing these, I only had one of these in my engine when I found out about the error. I had run the car only 23 miles and hit 6000rpm 4 times. I pulled this plug and observed that it was clean and had not turned the electrode blue which is the first sign of an incorrect heat range. Also this plug is used in a 3.2 engine w/ 9.5 to l comp. (which is higher than the SC @ 9.3) In short I don't believe there was any damage done to your engine.

[hank911]

Thanks for all the feedback guys.The car hasn't lost any power,infact it runs great aside from the lower idle.If anybody has a 3.2 e-mail me your address and I'll send you these plugs.I'm getting pretty good at the plug change thing,I guess I'll never like doing #6 though. Thanks again guys, hank911..

[82sctarga]

hank911,......on #6 use a thorensen 4-/2" extension 3/8" or better yet,if you can find one a 4-1/2" long "WOBBLE" extension, I understand it is made, maybe snapon. I'm still looking....in the mean time I jury rigged my thorensen with 2 turns of black elec tape between extension and 13/16, then when you pull up plug until you get interference, you then pull extension out of socket, the tape creates a "hinge" allowing you to pull 13/16 w/plug straight up.

[Doug Zielke]

Yeah, Bentley has a "few" mistakes in it.
My list has grown to 14, as a matter of fact.
(These verified by the Factory workshop manuals, Spec book, Technical parts book, and Factory update bulletins.)

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'81 SC Coupe (aka: "Blue Bomber")
Canada West Region PCA
The Blue Bomber's Website

[This message has been edited by Doug Zielke (edited 08-24-2001).]