c4 plug options

[purple charlie]

looking to put a parts order in
the spark plugs fitted are AC FR3LS, are AC5 an option or how do NGK get on as I prefer them on bikes?
NGK 2685 (FR4GP)
thanks

 

[BigVet]

What year C4?

 

[purple charlie]

1987 ally heads

 

[purple charlie]

as confused now.
the owners handbook says AC FR3CLS ally heads and Haynes say AC FR5LS for ally heads
Rockauto dont list the FR3CLS and only have 2 of FR3LS left, they do have FR5LS but not on the list for an 87.

 

[Chevrolet]

as confused now.
the owners handbook says AC FR3CLS ally heads and Haynes say AC FR5LS for ally heads
Rockauto dont list the FR3CLS and only have 2 of FR3LS left, they do have FR5LS but not on the list for an 87.

Look at the US websites, they are saying FR3LS for an '87. According to this, there are 142 equivalent non AC Delco plugs you can use. But somewhere else it says the Bosch part number is 0242229775 for an '87 Vette. So stick with the AC Delcos?

spark plug cross reference

www.sparkplug-crossreference.com

These AC Delco ones should be them?

https://www.corvettecentral.com/c4-84-96/ignition-distributor/spark-plugs-tune-up-kits/86-87-spark-plugs-set-ac-delco-with-aluminum-heads-304757