Spark plug gap for stock L81

[PokerJoker]

Hey guys,

Just getting started on this tune up and I can't find the spark plug gap info anywhere.

What is the recommneded gap for stock AcDelco plugs?

Many thanks,

Jeff

 

[GerryLP]

0.045"

 

[GerryLP]

Initial timing = 6 deg

curb idles = 700 (manual) 500 (auto)

fast idle = 2200 (manual) 2200 (auto)

fuel pressure = 7.5 to 9.0 psi fuel volume = 1 pint every 30 seconds

spark plugs = R45TS

Are you missing the emissions label?

 

[PokerJoker]

THANKS

Yes, I'm missing the label.

Thanks for your help Gerry

 

[dap220]

I also thank you for your help Gerry. I to an just getting back into the world of working on a car for pleasure!
Just picked up a 1981 Corvette and feel I will be visiting this forum regularly!

 

[dirtypants]

81 4 spd

81 4 spd, here..All the smog chocked up Calif stuff is gone..Installed are Edelbrock intake, carb and cam, Hypertech chip.
The AC Delco R45TS, is a tapered seat, no washer, thus no washer to compress..be careful on torque..when it is tight it is tight. Gap .045. Good luck getting to them. Be careful not to crack an insulator on the tight installs..try a rubber heater hose that fits tightly on the plug to get it in and turned in until final tightening.
Before doing the work, try to have a good drive, keeping decent revs until shut down so you can inspect the plugs coming out..which will tell you a lot about your tune and engine. Since plugs are such a PITA..I try to do plug wires at the same time. The exhaust manifolds cook the wires.
Nick

 

[dap220]

Thanks for the hints. I did get the plugs changed, used a 5/8" open end wrnch to get 1 & 2 out! The other s I was able to get to with a spark plug socket.
Tomorrow I'll finish up the cap, coil, rotor and wires then try to remember how to set the timing! Mine also has the emissions anchors removed. Has headers with dual exhaust. Just starting to get familiar with this but am enjoying the new challenges.

 

[dirtypants]

L81 pluts and tune

Gerry LP correctly says "initial" timing. An "initial" timing set, in this case 6 deg BTDC can be used to get an engine runniing, but optimal timing is best set using dwell meters, and exhaust / tune analyzers. so if not in your bag of tricks, after installing your plugs it is not a bad idea to have a good shop that does hot rods and older cars for the classic car guys..do your final tune set up..and note for you what that set up is. This may include some tweaking of the carb. Be sure to have a fresh clean airfilter in place, and good quality fresh gas. ( I prefer no ethanol with added Octane improver and Techron or similar) By the way the AC Delco Rapidfire plug #2 is on shelves in two mfg generations.. one a serrated tip. the other a small non adjustable pre-set tip..be sure you have all 8 of the same type..I just got delivery on a set that was a mix of both, or simply use the R45TS. R=resistor, 4= 14mm; 5 is the heat range, T means tapered seat with no washer, S means extended tip.

The 80, 81, 82 got the worst of the Federal and Californian mileage and smog rules so the good ol 350 was all detuned and bottled up. I have the all smog removed, including no catalytic, (over 30 yr old cars here do not need state or county smog checks..find out what is required in your area) and have the Edelbrock Performer series of cam, intake manifold and carb. Intake manifold polished Edelbrock Performance: EDL 21011; torque sequence see per Edelbrock, 25ft lb.
Edelbrock carb: Edelbrock Weber 1406 1734,
Edelbrock Performer cam kit SBC, EDL 2102 , cam specs see PerformerPlus #2102. Use only sure seat valve spgs #5802 or 5809, use stock ratio rocker arms only. Use only link timing chain gear set #7800, Do not use late model sets.
timing set EDL 7802 ;cam chnge kit MRG-4400 from Summit Racing.
Intake gskt EDL7201 Gasgacinch 4oz EDL9300
Edelbrock (made by K&N) aircleaner, tri-angle, 2.5 deep, 13.125 Across, can be cleaned, oiled. Check clearance carefully to hood, use a flat nut to secure. You can use clay or weathersrip with sticky side up on top of the aircleaner in about 6 places..if the hood contacts the wxstrip it will stick to the hood..if not it stays where it is on top of the aircleaner.
Accel distrib and 8.8mm plug wires.
After much research and asking this is what I have learned..but as in all web posts do some checking for yourself to verify. For your new to you C3, 4 wheel alignment is critical to good handling, but only after bushings in all suspension parts, front and rear are checked or replaced and wheel bearings replaced, packed, and properly adjusted. Suspension bushings especially in the trailing arms, and the wheel bearings are weak points in the later C3. Use ONLY Timken wheel bearings and set the very minimal (almost none....001) clearance carefully. It's a good idea to replace the "rag" coupler in the steering column as well. It will take some web research to learn about the alignment specs and what you will want on your car, but the original factory specs should NOT be used. You will want near max caster, some toe in of all 4, and some negative camber..all 4 (top of tire "inward" from the bottom). Various sites will discuss settings depending on driving and astrology. I like 2.75 to 3 deg caster (set to max the A arms will allow..about 3), .5 deg camber front and rear, and 1/8" total front toe (1/16 per side) , rear is also 1/8" total, but if the car is darty on some pavement up to 1/4" total front toe in. First Set rear camber then toe to establish thrust, set front toe last, after caster and camber.

 

[dirtypants]

Caution the AC Delco spark plug Rapidfire #2 option for R45TS 3 different of same

For the later C3 where the AC Delco R45TS is specified, you might consider the newer Rapidfire AC Delco. It is the number 2, but look out as there are at least 3 different versions of this same plug..so it is the same but is not the same. Seems they made plug changes along the way and some older ones are out there on shelves. The first is in a Red box and has a ribbed insulator and a serrated electrode and this box does not say platinum, then there is a white/blue box that can have either a smaller platinum tipped electrode, or a larger electrode. Box looks the same, no says "platinum" but has different bar code numbers for the two types of #2 spark plugs. You decide which one you want, if any..but they need to be 8 of the same.
I opted out of this yard sale of plugs and went with the Autolite double platinum #APP25 (the APP26 is the direct cross, but the Delco R45TS is a hot heat range plug..the hottest in that series and it is a safe bet to be a little colder. Too hot a plug can cause serious piston problems. Too cold can merely foul, but one range lower will not be a problem.) This plug has platinum on both tip and electrode. The earlier C3 call for a Delco R43TS..a colder plug than the 45. Of course you can still use the orig spec AC Delco R45TS: Note that for any tapered seat, no washer plug, you tighten to firm FINGER tight, and then go ONLY ONE FLAT tighter, that is about 1/32 if a turn..not much. When the seat contacts the head it is seated and tight..no washer to crush. Gap for all later R45TS remains at .045.

 

[dap220]

i did use the AC Delco R45TS plugs so I made one right decision!!
Thanks for taking the time to post these great tips.
This forum rocks!!

 

[Peer81]

Thanks for the heads up! Make it a habbit to always check the gap even out of the box ones my differ

Greetings Peter