Need advice on which spark plugs to use

[DMC Fanatic]

I've been searching around the forum and it seems that most people are using the oem silver bosch hr6ds plugs and some are using the bosch hr6dp platinum tipped plugs. I heard that the silver plugs aren't great if you do a lot of city driving and short trips which is what I do. Would I be better off with using the platinum tipped plugs? I read that platinum plugs are not necessarily good to use in our engines especially the bosch +4's, which I don't intend to use anyway, but it seems like some are now recommending the hr6dp plugs.

[NightFlyer]

Silver electrodes are going to give you the best electrical conductivity, period.

As to your hearing that they're not ideal for short trips - where did you hear that from? Drag cars commonly use silver plugs, and there's no shorter / more wearing trips on a cold engine than flat out down the 1/4 mile that I'm aware of. Thus, me thinks that you were fed some BAD advice on that front.

If the silvers are hard to source, too expensive, or you don't see the benefit of running silvers because you're not using your car in a performance fashion, then the copper electrode version of the same Bosch plug is your next best option, not to mention the most affordable option available.

The only advantage to platinum plugs are longevity - they wear slower than either silver or copper electrode plugs.

Others have had success with other brands, but unless you're looking for a cross reference, I'll conclude my post here, other than to say don't buy into the 'snake oil' plugs, as they're all BS and a waste of money - that includes multi-pronged plugs, split-fires, e3, etc.

[DMCMW Dave]

The +4s are crap. I can't figure out how Bosch still sells them, I've heard bad things about them in many different makes of engine and rarely anything good, and I have seen them make DeLorean engines run poorly.

HR6DS (silver) is OEM. The work well and last a good long time. HR6DC (copper) or HR6DP (platinum) are good alternatives.

There are others but I prefer to stick with the Bosch series listed. Stick with the factory plug gap too. This engine, at least in stock configuration, does not have any ignition issues.

But I can say that I've seen otherwise good running engines really get messed up by the Bosch +4 or, even worse, Champions.

[DMC Fanatic]

Thanks for the replies. I'll go with the oem silver plugs. I read about the "not ideal for short trips" from John Hervey's website and a real old post from the DML to answer your question.

[dmc6960]

If all you do is really short trips and never let the engine warm up, that'll be bad for it no matter what spark plug you use. Get the silvers, and be sure to drive long enough to let the engine warm up.

[NightFlyer]

Thanks for the replies. I'll go with the oem silver plugs. I read about the "not ideal for short trips" from John Hervey's website and a real old post from the DML to answer your question.

Actually, I think the concern was more or so related to the heat range/rating of the plug (the '6' designation in the plug number HR6DS), rather than the composition of the electrode material. But what they (Hervey/DML/whomever) fail to account for is the FACT that a silver electrode plug also has the best thermal conductivity, thus the density of the insulator really doesn't affect the heat range/rating on silver plugs all that much (at least when compared to other electrode materials).

But you don't have to take my word for it (because I sure as hell wouldn't)...

http://i636.photobucket.com/albums/uu88/czarnaduska/P1000704.jpg

[Chris 16409]

I was thumbing through the owners manual the other day and for spark plugs it says to use "Platinum Tipped" plugs. Was that an error, because I know Dave said his first choice was the silver plugs (HR6DS). By the way, RockAuto has the HR6DS plugs for like $5.60 each. It seems to me that the HR6DP plugs are usually cheaper than the Silver plugs.

[AugustneverEnds]

+1 for HR6DS Silver Plugs

You have to figure engineers who design an engine must spend a fair amount of time, research and money to determine what spark plug is best. I for one have no business questioning their choice.

[NightFlyer]

I was thumbing through the owners manual the other day and for spark plugs it says to use "Platinum Tipped" plugs. Was that an error, because I know Dave said his first choice was the silver plugs (HR6DS). By the way, RockAuto has the HR6DS plugs for like $5.60 each. It seems to me that the HR6DP plugs are usually cheaper than the Silver plugs.

Owner's manual says Bosch HR6DS (Platinum Tipped). I still have my Dunmurry spark plugs, but don't know how to tell if they're platinum tipped or not. Visually, they appear identical to German made modern Bosch HR6DS plugs, which are advertised as having a silver (or silber) electrode.

Silver's have a shorter wear life but a higher performance, typically only used in high-end sports cars, performance cars, and race cars, thus they aren't as mass produced in today's world, which translates to higher prices on silver electrode plugs, even though as a metal, silver is significantly cheaper than platinum.

Platinums have a longer wear life but reduced performance, but with the efficiency of today's ignition systems and AFR controls, such is preferred by a majority of motorists, thus they're produced in greater volumes, which translate to lower consumer prices, even though the price of platinum is significantly higher than silver.

Chances are, the platinum being used by most if not all manufacturers is derived from recycled catalytic converter core material.

[Chris 16409]

Anyone have experience changing out spark plugs with the intake manifold in place. I've only done it with the manifold removed. I know it's possible to do, just that it's a pain. Anyone got any tips/tricks they've discovered?

[DMCMW Dave]

Anyone have experience changing out spark plugs with the intake manifold in place. I've only done it with the manifold removed. I know it's possible to do, just that it's a pain. Anyone got any tips/tricks they've discovered?

4 of them are easy. You may want to move the pipe of agony for the back 2 on the driver side. DO NOT thread them in with a socket and extension or you will cross thread them as the extension will hit the manifold and they won't go in straight. Get them started by hand with the socket only.

[DMC Fanatic]

Just installed the silver spark plugs a few weeks ago with the manifold in place. All you have to remove is the air box and idle speed motor and it's pretty easy after that. I think it took me about 45 minutes for the entire job.

[Chris 16409]

I got the spark plugs changed out. I've included a picture of what the old plugs looked like. I also made an "apparatus" to help push the plug wires down when I could not get my hand close enough to do it. The old plugs look a bit toasty.

29261

29262

[AugustneverEnds]

I got the spark plugs changed out. I've included a picture of what the old plugs looked like. I also made an "apparatus" to help push the plug wires down when I could not get my hand close enough to do it. The old plugs look a bit toasty.

29261

29262

Good work, MacGyver! That's a neat tool you came up with :thumbup:

Recently was checking out a D that's been parked since 1991 and the spark plugs are covered in dried coolant residue :sad30: Guessing a blown head gasket was the reason the car was parked