351 Windsor, which plugs...

[azfordman]

I have been trying to ID the motor set up in my car, a 90's era Contemporary....The motor in the car is a 351W, casting number E4AE-6015-FA7, which comes up as a 1984 block from a full size car/Galaxie. My problem currently is spark plugs....the heads use the old style "fat" base spark plugs not the new style skinny plugs, which according to the parts suppliers in town should not be used on a block this new (the fat base plugs), they were discontinued pre 70's. The plugs I recently put in the car seem to be too high of a temperature rating, Autolite 45's. Do I have to pull the heads off to ID them? Stamped on the top of the head with the valve cover off is "351", the ford symbol, and 4F5. The valve covers are a six bolt pattern, three on the top with the two outside ones just below the corners and the three on the bottom are more centered, two outside bolts not near the corners. Also it uses 7/8 bolts instead of the 1/2 bolts to hold the cover down. Any ideas? My only other choice on plugs is a much colder 124, which I think may be better, since a too cold plug will foul, but a too hot plug can damage the engine from pre-ignition. Thanks! Mark

[PANAVIA]

Have you checked compression ?

The heads could be anything / the 4F5 is a casting date which means ( if they have the large plugs ; "7/8 socket ) the heads were cast may 4th 1975 , as the small plugs came into production in 1977'

The ford part number on the Windsor ( and other 289-302 ) heads is under the intake surface on the deck side of the head, this is very difficult to read when the engine is assembled.

As for plug selection there are options , but it would be good to know where you are on timing and ignition

Steve

[azfordman]

Have yet to check the compression. I was told this engine does have higher compression, and have been running the highest octane gas I can get, 91, I believe. Timing seems to be best around 15 BTDC, but I have to plug the vacuum advance or it runs like crap. The motor always has good vacuum at the manifold, it will drop to around 5 lbs under hard acceleration, and the manifold has around 15-18 lbs while driving (watching a vacuum gauge hooked up and in the cockpit) and it idles at around the same reading. I do think I need to change the mechanical advance in the distributor somehow, since the car runs even better at a slightly more advanced timing, but it does pick up a slight ping at higher rpm's. The Autolite 124 plugs seems to be okay, but they may be a bit cold for every day driving. I will see over the next few days how fouled they get. Two weeks now of trying to tune this car and it is still not right.....FWIW`I am having to change to a lighter spring in the Holley vacuum advance, even under hard acceleration the secondaries are not kicking in until I get up to around 5500+ RPM.

[azfordman]

One more question....how critical is it to take a plug reading immediately after a hot run? I have to idle the car in 1st about 15 minutes down my driveway to get home. Will this slow drive affect the plug reading? Obviously I need to leave the car off and cool down to pull the plugs, so do I need to do this in town, say at a restaurant? Not too big of a deal, just curious if it really matters.

[Dwight]

yes, the 15 minutes of idling will affect the plug reading.

Dwight

link to a good site for plug reading
http://members.uia.net/pkelley2/sparkplugreading.html



How to Tune Your Holley Carburetor
http://www.bob2000.com/carb.htm

[azfordman]

Thanks Dwight, that's what I suspected. I will have to pull a couple of them next time I make a run into town.