Had a lil miss so desided to change the older plugs. Picked up some Motorcraft plugs,, replacing the autolite ( which found one was cracked)..Now have a lil backfire at times and not the exceleration responce did have..Does the 302 typically like a certian brand name plug ?

 

i might get kicked in the nuts for saying this but here goes..... i bought motorcraft plugs for my 88' 302 and it too started to backfire. i took them back and got a set of AC Delco plugs for it. ran like a champ afterwards. part number CR43TS to be exact. sorry if putting chevy parts in a ford is wrong. it just works good

 

I have not had much luck with motorcraft Plugs myself. I have been using Bosch or AC Delco in my stuff.

I just wonder how well the AC Delco parts will be seeing how its Government Motors now?

 

Simply put, Autolite & Motorcraft plugs are what your engine should be running.

300/302/460 all take autolite 25's
351 takes 24's.

Also, you will generally have better luck with copper electrodes. I've seen many people have trouble with platinums. I had a set of platinums (AP24) that worked fine until I widened their gap. Once I replaced them with the plain coppers (24), the truck ran great.

Did you change your wires? If not, moving them around to change the plugs could have cracked the old insulation, allowing the spark to leak out. You may find a big decrease in low end torque if this happens, because the spark will jump the gap at the plug easily until you start adding more air/fuel and increasing cylinder pressure. The electricity will always take the path of least resistance and if it finds an easier way, it will take it. Also, you should double check that all you still have the firing order correct.

One other thing is that if the wires got moved, you could be experiencing cross fire, a condition where the magnetic field generated by the current in one wire, will induce a current in another wire. Make sure that your spark plugs wires are not running too close or crossing over each other.

 

I'll second what Skyfox said. Bosch may make alot of good parts, but their plugs are a joke. The Delco plugs are probably ok, but I would stick with Motorcraft or Autolite. Thats all I run in our Fords, and we have never really had any issues with them. Once I had a problem, but I think it was my fault. The ceramic part on one of them cracked.

There is nothing wrong with mentioning Chevy parts. I have a retractable under hood work light from a 95 2500 on my truck.

 

Thx for the input guys,,will put some autolite 25's back in it see what happens,,should not have crossfire issue or bad wires for they were replaced 8 months ago,,but never know,,

 

never hurts to double check their routing to make sure they aren't crossing over each other.

Check out this link for more info on crossfiring.
Spark Plug Wire Cross-Firing - BumpWiki

 

I might get kicked in the nuts as well for this one but you double checked the spark-plug gaps right? I have seen it all too often turning wrenches for a living where the owner put all new plugs and wires then complained of a skip or something not feeling right. Plugs are usually pregapped but alot of times will get bumped around and the gaps can change. I've seen brand new plugs with no gaps. I agree in double checking the spark-plug wires. If there is any cross fire you will see a whitish tint around the spot where the plug wires are touching. or where the spark can be jumping to metal. Valve covers, etc...

 

I know what you mean,, called for .044 gap,,,some out the box were .047 - .048

 

Good points on plug wire routing and plug gap. What year did the gap change. I think mine is .056 ish. I bet its the same year that the 302 adopted the 351 firing order.

 

could also have to do with having a push to start or a cumputer controlled dwell ICM. Both my 95 SD truck and 96 MAF stated a gap of .042 - .044

 

Couldn't agree more. Also, Motorcrafts where specifically designed for your Ford. (The copper cores are actually designed to fail before piston damage occurs/ Double Plats couldn't if they wanted to. They'll keep going till the pistons toast!)

Re: Double platinums for your truck, other than their anti fowling characteristics (not necessarily a good thing/ masking potential engine problems) & duration between changes (at the expense of poor thermal transfer property's, which contribute to higher combustion chamber temp, knocking on the door of the ping threshold). What's to like? Poor choice for timing advance further than stock, gap stretching or sidegap. They require more resistance to be overcome to initiate spark & produce extra heat when they do.

If you'd mentioned the year that would help. The correct gap for you truck depends on the year. Could be .042-.046 or .052-.056. That falls under "mechanic's error, no fault of the engine or plug!

Then there's the firing sequence & plug wire routing. Also dependent on the year. However whichever of the two possibilities it is, either require there own specific routing method be follow to avoid cross fire. Once again, if I knew the year, I'd post the diagram!!!!!

If you really want to run a double platinum, before I upgraded my ignition system & started side gapping copper cores, AC/Delco Double Platinum Finewire Rapidfires ran great. Mororcraft also came out w/ there own D/P Finewire.

 

I'm leaning towards that too. That would be 94' I think. For the 302. Not really sure. I alway's default to the Factory's permanent stocker under the hood (mines on the top of the air filter box cover), that shows the correct Gap & plug wire route for that truck. I'll see what I can find.

I haven't heard "Might get kicked in the nutz" for a long time. Mentioned twice in the same thread, cracks me up! Is this Forum well known for such transgressions between members?

 

Again,,thx for the input guys,, seems the autolites did the trick,,running like a champ (for now),,its a 89 F250 44k original miles,,,hood sticker called for .042-.046 so i split the differance and went with .044

 

glad to hear she's running good.

I'd say if everything is working good for now, leave it alone. However, if you want to go a little bit further to improve performance and gas mileage, you can try increasing the gap a bit to around .055 or so. This does put more demands on the ignition system though, so it's best to replace the coil, wires, cap, and rotor so you eliminate any weak links.

Like I was saying though, if you main concern is reliability, leave her right where she is.