327/365 spark plugs

[Richard M.]

I have been researching spark plugs for 327/365 driver that I recently purchased for street use. It has a set of Champion J8Cs in it now that need replaced. Was going to use same plug or AC Delco 45s. Would appreciate suggestions. This is a confusing subject for some of us. Thanks.

[William C.]

Re: 327/365 spark plugs

The 45S is an extended tip plug and NOT recommended for the 11.0 to 1 engines due to possible interference with the piston domes at high rpm. I would use a regular 45 and be very happy for "cruise nights" or a 44 for highway driving. I have personal experience with the ac 45S and high rpm (7000) in my early years and it was not a real good mix.

[Duke W.]

Re: 327/365 spark plugs

J8C is too cold for normal road use. If you're not concerned about judging, the best non-resistor plugs are the NGK B4 and Denso W14-U. They are equivalent to AC 45, which are no longer manufactured.

If you have your car judged and don't want to spend a fortune looking for NOS AC 44 plugs, use the AC R45, which is a resistor version of the AC 45.

Duke

[Dan H.]

Re: 327/365 spark plugs

[QUOTE=Duke Williams (22045);618083]J8C is too cold for normal road use. If you're not concerned about judging, the best non-resistor plugs are the NGK B4 and Denso W14-U. They are equivalent to AC 45, which are no longer manufactured.

If you have your car judged and don't want to spend a fortune looking for NOS AC 44 plugs, use the AC R45, which is a resistor version of the AC 45.

Agree with Duke. I have run the R45 AC for over 18K miles now, radio is clear too! Using 91 octane tree hugger gas here in Ca., they last and come out clean in my L84 motor.

[Richard M.]

Re: 327/365 spark plugs

Thanks. The Champion Y8C in the car when I purchased are also burning black. I believe the hotter AC R45 will help with this. If not I assume I should turn to the carb.

[William C.]

Re: 327/365 spark plugs

Somewhat depends on your driving cycle, may need work on carb and plugs.

[Jerry B.]

Re: 327/365 spark plugs

I use AC 44 in my 69 L46. The tail pipes carry a light brown color which i was told is good. Thoughts?

[Duke W.]

Re: 327/365 spark plugs

AC heat range 5 or equivalent is best for all Corvette engines that see normal road use, which includes extended freeway cruise speeds up to 80-85 MPH.

Unleaded fuels usually leave a black residue in the exhaust pipes. Leaded fuels can leave a brown to off-white residue.

What fuel are you using?

Duke

[Richard M.]

Re: 327/365 spark plugs

Unleaded. Also using Joe Gibbs motor oil HR-2 10W-30. Any thoughts re this oil (and Gibbs HR-1 15W-50)?

[William F.]

Re: 327/365 spark plugs

Any experience with the AC "Rapid Fire" plugs?-#7 said to cover all heat ranges for SB.

[Duke W.]

Re: 327/365 spark plugs

I know nothing about them. Do they carry an API service category?

If your engine has relatively high oil consumption, some additive in the oil could be coloring the pipes.

Duke

[Duke W.]

Re: 327/365 spark plugs

No experience other than recognizing marketing hype. There is no way a single plug can cover all heat ranges.

The basic design of spark plugs had not changed for over 100 years. The shape/thickness of the insulator determines how quickly the plug sheds heat to the cooling system, which is why different heat ranges are required for different service - like road use vs. road racing.

There have been incremental improvments in electrode design - particularly small platinum center electrodes, which offer a smaller heat sink to incipient combustion and longer life.

But those mulitple ground electrode plugs are a joke. The spark will only jump to one of them and the rest are just a heat sink which can pull heat energy out of the incipient combustion process, and potentially quench it.

The Denso U-groove on the ground electrode and V-center electrode on NGKs are good technical features and don't add to the price. Sparks typically jump better from sharp corners, so those are good features since they add more sharp corners without adding heat sinks.

That's why old plugs with a lot of miles have rounded electrodes.

Duke