Spark Plug

[scotch1]

Can some one please tell me, the spark plug cat. number of the Bosch Platinum plugs for my L 98, 1990 coupe? I was asked if I had an aluminum head or a cast head.
Tom.

 

[gmboileau]

Hi Tom

You have the aluminum head. The plug is quite a bit longer than for the cast iron.

Cheers
Gary

 

[scotch1]

Thanks for your reply.
I tried to do a simple thing like replacing my spark plugs, which started this barrage of questions.
Upon ordering spark plugs the counter person in “Pep Boys” asked me if I had aluminum heads or cast iron? I thought that it was an interesting question, so before I replaced my plugs with wrong ones, I consulted my book, “ Cor-Vette Specs” by Mike Antonick which is a very good and valuable reference.
In it, it says that I my L98 has cast iron heads.???
That’s interesting, but, after that I consulted my GM Service Manual, and that says that I have Aluminum heads in my L98.
Consequently, and you are in agreement, I will install new Bosch Platinum, number. 4202, plugs for aluminum heads.
Thanks Again.
Tom.

 

[gmboileau]

Hi Tom
The standard plug for your car is AC Delco FR5LS. I have used this plug in my vette and it works just fine. It is quite a bit cheaper than the platinum plug and if originality is an issue it's what the car started with. My understanding for the use of platinum plugs is a longer life in terms of mileage which makes sense for a commuter car. Most vettes however, are low mileage vehicles and besides you should really remove the plugs every couple of years so they don't get seized in the head. I'm not sure that the platinum plugs have any particular advantage for your application. What is your thinking for your choice? Anyone else have data that verifies the use of a different plug other than the standard?

Cheers
Gary