Classic Hifi Care

Gents,

I'm currently running modern AC R45S spark plugs in my '70's original 307 V-8. I've got an opportunity to buy some genuine N.O.S. AC 45S spark plugs.

Will these work okay?

My understanding the lack of "R" in the number means it has no internal resistance in the plug itself. Is this correct?

The original owner's manual spec's an "R" in the spark plug number........

Any thoughts?

You may get some noise in the radio, but othewise they will work just fine. If you put on a set of "resistance" plug wires, that may take the place of the missing resistors in the spark plugs. If you run the radio antenna fully extended, you may not hear much noise from the spark plugs in the radio. My Buick runs 44-S spark plugs with no resistors. They started using resistance plugs about the same time they started using radio antennae buried in the windshield. AC/Delco no longer makes plugs, air filter or oil filters for my Buick. I put a NOS set of spark plugs in the Buick in 1995. I have no idea what I'll do if I have one foul. I'll have to replace the wires as well, because they are long ago stuck to the spark plugs.

Thanks Greg.

Maybe I'll pass on this purchase.

I am running radio/tv suppression plug wires (they are reproduction with the 'correct' date codes), but.....

I have the "hidden" antenna. (Factory style radio antenna inside the windshield).....

Then, in that case, you may want to pass on the non-resistor plugs. You might get some ignition noise in the radio from the windshield antenna.

Hello, On my MG 1100 the plugs were all non resistor type . But for the radio there was a wire from the coil to a condenser mounted/grounded on the top of the alternator, for years I didn't even know what it was for. But I wonder if you had non resistor plugs could you rig up some wiring like that.

My Buick has a capacitor on the alternator to eliminate radio noise. Delco-Remy generators also had them. Ford put the caps on the voltage regulator for a time, I'm not sure when that stopped. The front wheel bearing caps on GM cars had little coils that grounded the wheel to the car suspension for radio noise suppression. I think GM started using resistor plugs when they put the radio antenna into the windshield glass. This put the antenna closer to the distributor.

"my MG 1100"... ah so that's where "Hydrolastic" comes from.
I've had a ton of MGBs and MGBGTs, but never one of those little Alec Issigonis inspired sedans... fun to drive I bet.

As to plugs I use only NGK anymore.

What's the functional difference between resistor plugs and resistor plug wires? Same effect, right, although maybe the wires are more subject to deterioration.

Chris Campbell

GM specified resistor wires with resistor spark plugs. I don't know for sure just why. Radio interference elimination was the goal, but why both was required I don't know.

TC Chris wrote: ↑Sat May 20, 2023 3:56 pm What's the functional difference between resistor plugs and resistor plug wires? Same effect, right, although maybe the wires are more subject to deterioration.

Chris Campbell

I think they were just trying to choke off as much RFI as possible.

With more and more resistance, you get more and more current limiting, thus less likelihood of RFI being transmitted. However, the trade off is, you're going to hurt your performance as you keep adding resistance since you won't have that "super super hot" spark. That's why all the racer types swear by their non resistance solid core plug wires.

Hello guys, last year I was working on AJ'mini at the track. Got zapped by the coil while adjusting the distributer. Took a while to recover.
firedome yes its mostly Hydrolastic in the garage. with a 1966 New Zealand mini, 1963 MG1100 (first car) and the 1969 Austin 1800 Land crab. All are hydrolastic. But there are also others like a MK1 mgb project and the 1100 race car. I wonder... is Fire dome referring to the red ram or the hemispherical decendants. Hydro

Actually "firedome" refers to 3 DeSotos I had, 2 '58s and a '59. It's my name on all the various Mopar sites I visit too.

Not Hydrolastic suspension, but one BL (Leyland) car I always kind of wanted was this one; I'm sure most here have never heard of it. Rather thin on the ground in the US being produced and sold in Australia only, the Leyland P76 had the ex-Buick/Rover aluminium V8 in an enlarged form mounted longitudinally in a RWD configuration and had IRS. Even using the ex-Buick "odd-fire" V6 as well was originally contemplated, however an existing BL "E-series" 6 cyl from the Australian Austin Tasman was used instead. The coupe was particularly pretty but few were made, 18k sedans were produced in 3 years. An intriguing and rare car, I'd love one as I like stuff that's out of the ordinary. Aluminium US derived V8, RWD, pretty lines, IRS, and nice interiors... what's not to like?!