Drive it as usual, and in a couple of days, you will be able to see the result. In less than 50 miles, they will be teling you "what they think". Sometimes, city driving can delay the results if the plug is too hot, because the driving conditions can make the hotter plugs more tolerable by the engine. A good highway drive will show the truth.

Túlio Lazzaroni "FORD", Florianópolis SC Brasil.

'74 Ford Galaxie 500 292 V8

'82 Ford Galaxie Landau 302 V8

'98 Chevrolet S10 4.3 V6

'01 Ford Focus 1.8 Zetec

Give me a ball park for the number of miles to ensure I get a good read. I have a week to figure this out if I'm going to take it to Columbus; A few days will only allow 2 chances to check them. My house is only a few miles from the highway so i can put tome highway miles on them easily.


Lawrenceville, GA

This only adds to the data on Charlie's problem.  I just did a search to find out what a suppressor spark plug was exactly.  Champion's site came up and there was a blip on plug breakage.  Showed a pic similar to charlie's.  "Breakage is usually caused by thermal expansion and thermal shock due to sudden heating and cooling".  That's all folks .

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.

If you want to be sure Charlie, 100 miles would be enough. What Mike said just shows how much the plugs are heating. Heating enough, to break. I do a 180 Km trip every other week with my Galaxie, and it's very close to 100 miles. After that, the plugs always are the color they would be for a long time. You don't need to speed up a lot or anything, just drive like you always do.

Túlio Lazzaroni "FORD", Florianópolis SC Brasil.

'74 Ford Galaxie 500 292 V8

'82 Ford Galaxie Landau 302 V8

'98 Chevrolet S10 4.3 V6

'01 Ford Focus 1.8 Zetec

This is from another post by GREENBIRD-Here is why you want the limited distributor advance setting - the engine will only tolerate something like 36°-38° of total mechanical advance (that is the initial plus the distributor) under load (with low/no manifold vacuum). You want to put more initial on the bottom (10°-12°) without violating the upper limit. If you were to use the 18L slot - then the initial advance set point would have to be down at 0°-2°. When using the 13L slot, the initial can be 10°-12° (adding some nice low end torque) and not violate the advance limit as the engine gets into the higher rev's.

You mentioned your initial advance was 14. It would seem to me that you are advanced a little too much. I don't know which slot your distributor is set at but believe you should set back your initial to around 8 degrees. Here again I don't know your compression or the fuel you are using. As far as plugs go I have had the best luck with platium. GOOD LUCK

Ol'ford nutCentral Iowa

56 Vic w/292 & 4 spd.

My mechanical advance provides 20 degrees. I have 34 total. The heads are G's with polished chambers and compresion is about 9.35:1. I run premium.



I put a set of Autolite 45s in last night. Hopefully I can get enough readings between now and the 2nd.


Lawrenceville, GA

I think that Charlie's engine is a bit different than the average motor in our everyday drivers. It has some increased efficiency heads and a "real" compression ratio. Both of which allow the engine to run with decreased spark lead.

My 312 has some "C" heads of unmeasured chamber volume - and it has a composition head gasket - not the original steel shim style Ford put in there. It has nothing near the advertised compression ratio......and no head porting or valve upsizing - bone stock stuff. Because of its lower efficiency - the fire has to have a head start when trying to build cylinder pressure (make power).

Charlie's choice of the increased initial lead and a more reduced centrifugal advance - for a total of 34° is not at all unreasonable for the combination he has. Once he has chosen an advance set-up - he then goes about building a carburetor fuel curve to suit it. If it is dipping lean at some point in the "curve" - it could explain the plug situation.

 
 Steve Metzger       Tucson, Arizona

Charlie.  What carb are you running and what jets?  Are the jets the ‘as supplied’ jet sizes or have you changed them?  In regards to oxygen probes or sensors, I find some variability between them and sometimes as much as a full point so you have to give them some latitude when using the numbers generated by them.

Lorena, Texas (South of Waco)

It's a Holley Street Avenger 570. I have 60s in the primaries (richer), and changed the secondary diaphragm spring. Everything else is "out of the box".

My sensor has 3 lights. One for lean, one for rich, and one for just right. I erred on the safe side and jetted it until the rich light started to come on.


Lawrenceville, GA

Wise decision, with the kind of compression you have.

Túlio Lazzaroni "FORD", Florianópolis SC Brasil.

'74 Ford Galaxie 500 292 V8

'82 Ford Galaxie Landau 302 V8

'98 Chevrolet S10 4.3 V6

'01 Ford Focus 1.8 Zetec