C4 1987 Owners Manual - Spark Plugs Alloy Heads.

[Vettech]

I would assume that most Vette owners in Oz would not have an Owners Manual esp if your car is a C4 between 84 & 92.
Google shows free downloads for OM's from early to 82 - then a big void - then 93 thru to now available one way or another.
Also I can see some differing opinions on the type of plugs to be used, since my 87 has alloy heads (not cast iron), it requires a different plug c/w a sealing washer.

The 87 was ready for rego in Dec'20, but it threw the P/S Pump, now thats fixed its running like a dog, throwing codes 33, then 34, then 33, also missing on a least one cylinder.

I can see at least one lead (#2) cross firing at the dissy boot to manifold, the leads hang everywhere with no rhythm or reason, so it may be time to shout the ole jalopy a new set of leads, plugs and wire retainers ?.

Any info greatly appreciated. I'll try Ponti World and/or Chev Parts on Monday.

So! - does any one out there know the correct type (pn#) for plugs for L98 c/w Alloy heads.

Also another point of interest is the positioning of the Dissy, the net, youtubes, googles and sales brochures show the top of the Dissy sitting square at right angles across the manifold, but my 87 (and 90 as well) have the dissy offset, I can only assume this positioing is in-correct, even though the timing seems to be ok !?!?!?.. This puts strain on the leads and causes them to be sandwiched in positions that rub, chaff and crossfire (like #2 cyl).

Any info welcome.

[Vettech]

Further to below - I believe the AC-Delco type FR3LS SUPERCEDED BY 41-629  Or NGK#5155 V power.
The AC is the basic plug at US$1.39, But these have been superseded by Platinum then Iridium, each supposedly better than its redecessor. (Of course they are a lot dearer here by over 10 fold.)

Whilst the AC-Delco R45TS, is for use in a Cast Iron Head engine.

Here's a Question - removing plugs whilst engine HOT or COLD, which is better ????.

[MY081]

Doug that is obvious if hot you will burn your fingers !!!!

[Kenobe]

  With the low melting temperature of Aluminium at 660 degrees I would remove them when cold to avoid causing any thread damage.
You don't want to have to remove the head to fit a helicoil now do you?
Threads bind up more often when they are hot and cause more damage so go and either boil the billy or grab a coldie and let it cool down a little. 

[Vettech]

Now I'm worried.

It seams that 2, 4, 6, 3, 5, 7 come out fairly easily, as long as they are not grown into the metal.

But 1 & 8 are an issue, I heard a quick mention on a forum that you remove RHF wheel, inner guard skirt and with multi bendy tools you can just get into #1, and eight may be better from under the car.

Any way its Canberra time, plugs can waite.   

[87Z51]

As you say the original plug was Delco FR5LS (discontinued) which cross references from this chart

https://www.sparkplug-crossreference.com/convert/AC_DELCO/FR5LS

to a Champion RC12YC

I ran the colder RC9YC in my '87- perfect plug colour on the open road or WOT at the strip with a proper tune.

https://www.sparesbox.com.au/part/champion-copper-plus-spark-plug-oe005-rc9yc

or Repco for twice the price
https://www.repco.com.au/en/parts-service/fuel-ignition-exhaust/spark-plugs/champion-copper-plus-spark-plug-rc9yc/p/A7122195
Have also used NGK BCPR6ES

FWIW : the pre made plug lead sets will only fit PROPERLY if the dizzy is in the correct orientation .
Need to set the engine to TDC on No 1 cyl  ,pull the dizzy out and reinstall it back in correct orientation

[Vettech]

Well thank you for telling me that, I've seen pics, video's etc which shows exactly that, but when I've pointed this out to people they have said I'm drinking too much. I dropped it, thinking that when I  got the car, it's paperwork included a spec sheet from some mob called "CROW", maybe that causes a change or was it when I threw the Harmonic Balancer. This was repaired, but is it in the correct position, esp since the timing mark is on it. But my 90 definitely picks up and goes like a rocket sled, so maybe a combination of tied plugs, leads and timing, coupled to #8 firing past the plug, yes I got it out along with Alloy, a deformed sealing washer, and a sooty plug.

I just revisited the 90, and its as you say, the dizzy is located at 90° exactly across the intake. But now I have a plug hole to get fixed, to get this car out of the garage, as the wife wants the 3000 tiles laid asap.

The old plug was NGK BCPR5ES-11 same as new ones - see pic below - note the seal washed was bitten or crimped or cross threaded by the last mechanic, destroying the plug hole, allowing blow by.