So I finally got my GM style (HEI coil in the cap) distributor on order for my 86 F-150 ... 300 six.

I also ordered some new wires.

Now what to do for plugs????

I have been reading all night and am more confused than ever.

I was going to go with Motorcraft SP-459 ... a bit expensive but I only put less than 5K a year on the truck and they may be the last set of plugs I put in it.

Then I got to thinking .... "fine wire platinum" .... will the HEI coil kill these plugs?

Should I go with a more standard plug like a SP-549?

Then I started reading about gap and erosion and ..... wow ....

So any advice on plugs. I don't mind spending money on the fine wire ones if I know the GM coil won't kill them in 10K miles.

Honestly, I don't even know why the fine wire platinum are any better.

I can go other brands, I just have always stuck to motorcraft in my fords and have hand no problems ... yet.

Thanks ..... Mike

 

My .02 go with the normal plug and gap it a little wider than stock.
When HEI first came out the plugs were gapped at something like 60 and they found it would burn out the modules as it had to work harder to jump that BIG gap.
Dave ----

 

There are three motorcraft plugs listed for my truck ... copper, platinum and thin wire platinum.

Which of the three are you calling normal?

Thanks so much again!

Mike

 

I run the Motorcraft SP450 Standard Copper plug @ .044 gap with Motorcraft WR3946C ignition wires on my 302 HEI. I imagine i could've opened the gap a bit but it runs great as is so i didn't bother.
Copper is "regular/standard".

 

The platinum will last longer. I would stay with the stock gap. That will make them last even longer also.

 

I would also go copper don't think I would go much more than say .050 on gap.

I hear some motors don't like platinum plugs. Beside for the amount of miles that would be put on any plug and they are easy to get to to change out I would not spend the extra $ on them myself.


Remember when the HEI came out motors were run as lean as they could to meet GOV specs. It is hard to ignite a lean mixture and why the wider gap to expose more spark face to the mixture.
In our case it will ignite more of the mixture for more power.
Dave ----

 

The gap is a compromise. You do get more performance from a larger gap, but as the plug wears it becomes harder and harder to the spark to jump the gap, till there is a miss-fire.

So if you run a wider gap, you should change the plugs more often. Compromise on performance a little bit by using the stock gap, and you can run the plugs longer before they miss-fire.

Platinum's should be the same as the regular plugs, only they use the better metal which does not erode away as quickly. You can get regular platinum which only has the good metal on the center electrode, and double platinum which has the good metal on the ground electrode also.

True, if the plugs are easy to get to, you can just change them more often and not use the platinum. Some newer cars and trucks require the platinum because the plugs are so hard to get to. My daughter had a car where I had to take the upper dog bone mounts loose, take the radiator overflow bottle off, and take a come-along and pull the engine forward in the car to get the back plugs out. It's called "rolling the engine".

 

Agreed..HEI or not,
Most engines running on pump gas (87 octane) do not tolerate much more than a .048 gap regardless of platinum, splitfire, or thinwire plugs in stock engine form as it is a wasted spark curve. It's one thing to choose a plug for a newly rebuilt engine vs. choosing a plug for an engine in stock form with veteran mileage.

 

I did a bunch more reading ... I should have just stopped while I was ahead.

This is off a web page I found (actually found the same thing on private pages ..... pages like AutoZone don't mention this).

"Copper spark plugs are generally considered to have the best performance of any spark plug type. This is potentially different from what advertising companies suggest, but the other metals are, unfortunately, not as conductive in general as copper is. Platinum and iridium plugs are more likely to overheat, which causes damage to the plug components and can compromise the delivery of the spark to the engine block."

On the other hand, I got this off the Advanced Auto page:

"You guessed it: iridium is harder than platinum. In most cases, iridium spark plugs last about 25 percent longer than comparable platinum spark plugs. Because iridium is costly, iridium spark plug manufacturers reduce the diameter of the center electrode to as little as .4mm. In addition to saving money, the “fine wire” center electrode of iridium spark plugs increases firing efficiency."

Now I realize that on my 30 year old carbonated straight six, this probably makes no difference. I am sure I could use just about anything and it would work.

Still it would be nice to know ... are copper plugs better for performance?

In this case, changing all the plugs takes about 15 min. Me and three other people can stand in the engine area of my truck.

In my RV ... well, lets just say changing 10 plugs takes me at least 4 hours if everything goes right. I can see why I want platinum plugs there.

I question everything but for some reason, I just never asked about plugs. The parts stores just say ... copper, plat, double plat then iridium ... good, better, better yet, best.

Do they just want the quick cash? In the long run, I would spend more on say four sets of copper plugs in the long run then 1 set of platinum plugs ... and I have no problem with that.

Thanks .... Mike

 

Mike...You answered your own question without knowing it. It boils down to what your truck was originally equipped with. It was designed that way for a reason....design reason. It stands to reason.

 

The standard copper plugs were what our engines were designed with. I'm not sure what you are surfing for ?

 

I'm inclined to think that you are reading too much into this.

 

Yes! I read way way way toooooo much!

This is why it took me 6 months to buy a drill. I read reviews and personal stories and ratings and .....

In the end, I know on my poor old tired truck, anything will work. I have always been the guy that want to know "why". Why is one better or worse?

I do appreciate you guys putting up with me.

If you look at my postings, they are always questions on why and how.

On the other hand, the truck and RV are both still running ... truck 30 years old and RV 17 years old.

Thanks again!

Mike

 

Copper has been, the most economical, cost efficient, contravene of electricity known.

 

We are glad to have you here Mike ! The FTE Family is broad and You are certainly a part of it !