Spark Plugs

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14 Nov 2012 10:00 #12550 by wallyp
Spark Plugs was created by wallyp
If you have not done any research, you might jump to the conclusion that the best spark plugs for your 928 would be Bosch, and that the best Bosch plugs would be the platinum or the multi-electrode ones.

Wrong.

The best Bosch plugs would be the standard copper version. The 928 does not like the platinum or multi-electrode versions.

My wife's Cadillac STS with the Northstar all-aluminum, quad-cam V-8 started running very poorly. I removed the Bosch Platinums that I installed about 20,000 miles ago, and installed ACDelco Platinum Pro plugs. Problem solved. I did absolutely nothing else, and the engine now runs strongly and smoothly. GM engines don't like the Bosch platinums either...

Wally Plumley
928 Specialists
www.928gt.com

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14 Nov 2012 20:05 #12552 by ROG100
Replied by ROG100 on topic Spark Plugs
I had the same experience in my early days of 928 ownership with Platinum 4 prong plugs.
Wally is right as always - stick with the plugs that Porsche put in the cars from the factory or their direct equivalent - nothing else.

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14 Nov 2012 20:52 #12557 by mm928
Replied by mm928 on topic Spark Plugs
Good advice....sometimes what seems logical, is not always! I tend to lean towards Porsche engineers knowing what they are doing (did :)

1983 928S - 16v 4.7L L-Jetronic
Dark Grey w/ Blue Leather
85/86 exhaust manifolds
Y-Pipe
SS Hi-perf Cat
S4 springs
Bilstein shocks
Air pump delete
VIN: WP0JB0926DS861180
- - Isn't Life great? - -

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14 Nov 2012 22:05 #12560 by 928mac
Replied by 928mac on topic Spark Plugs
I dont remember what I put in it but I wonder if it was the bosch

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21 Nov 2012 18:52 #12612 by ROG100
Replied by ROG100 on topic Spark Plugs
Bosch is fine as long as it is the correct plug. Rule of thumb ----
WR8DC+ - Copper - 77 to 80
WR8DS - 80 to 84
WR7DC+ - Copper was 999 170 119 90 - 83 to 91
WR7 DTC 92 to 95 (alternative is NGK BP6ET)

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23 Nov 2012 12:24 #12627 by pcar928fan
Replied by pcar928fan on topic Spark Plugs
That is some good info there! Thanks Rog!

James
78 Silver / Black-white #295
84 Ruby Red / Black AO84
88 Dark Blue / Linen-Black
92 Polar Silver / Dark Blue 92EURO
93 Arrow Blue / Black

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24 Nov 2012 15:28 #12638 by linderpat
Replied by linderpat on topic Spark Plugs
great; I bought the platinums this past summer. Frig it; I'll run them until the car tells me it doesn't like them. I assume that we can't damage anything by running platinums?

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27 Nov 2012 22:18 #12684 by 928mac
Replied by 928mac on topic Spark Plugs

great; I bought the platinums this past summer. Frig it; I'll run them until the car tells me it doesn't like them. I assume that we can't damage anything by running platinums?


No I dont think you will hurt anything unless they are missing so bad that you get carbon deposits.

It would have to run really shitty all summer

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27 Nov 2012 22:38 #12687 by Kiln_Red
Replied by Kiln_Red on topic Spark Plugs

No I dont think you will hurt anything unless they are missing so bad that you get carbon deposits.

It would have to run really shitty all summer


I agree that there is probably no imminent threat. I would just change them at my earliest convenience. If there is any detonation, the knock sensors will want to correct the condition and your car will run far less efficiently. I think that is the extent of the concern though.

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28 Nov 2012 12:02 #12697 by linderpat
Replied by linderpat on topic Spark Plugs
no knock sensors on a 78.

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28 Nov 2012 19:44 #12703 by Kiln_Red
Replied by Kiln_Red on topic Spark Plugs

no knock sensors on a 78.


Correct. I apologize for not looking closer at your signature. I guess I have gotten myself into a bad habit of assuming everyone is driving '87+ EZK cars. :rolleyes:

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