dimented24x7

iTrader: (2)

Desided to pull the plugs out last night and have a look, bosch platinums, btw. I took them straight out of my old 305 and they where completly crusted up w/ carbon deposits and oil and all i did was gap them and throw them in my new motor. When i pulled them out, the plugs looked like they went through a time warp and came back to the day i got them. Aside from the tannish brown patch on the side of the plug that faces toward the inside of the cyl, the rest of the plug was clean and it looked like i had just bought them. I mean, id expect that the whole plug would be clean but they still have a normal colored patch of deposits on them. The blms look good and it doenst run lean at WOT so does this mean i need a cooler plug? If so, what is the usual stock heat range on a plug so i know where to start. It just struck me as odd to see them in that good shape after 10k or so .

92RSFivePointSlow

If you read the box on the bosch platnums it talks about getting up to temperature so it can "self-clean". I like those plugs because they have such a small tip that they will never foul. Platnum plugs can also run hotter because of the material, so if you have that brownish tint then you've got the right plug. By running a plug thats too hot you can detonate or actually burn holes in your pistons(in bikes anyway). I use the bosch #7's because they are so short that I can change them without taking my headers off. Shorter than the accell "header" plugs actually, and much cheaper. The shorter you go though, the hotter plug you end up with, so be careful.

kevinc

Ya know, I just saw the same thing on mine last weekend. I pulled a set of NGK TR-4 plugs that I've been running for ~2K miles, they were like new. I switched back to Bosch platinum FR8DPX plugs, same model I ran since the engine went in, because the throttle felt just a tad lazy. No noticeable improvement with the Bosch plugs.

Super clean plugs, slightly lazy throttle...I'm thinking they've switched to blended ethanol/gas early this year, and maybe with more ethanol than usual.

I reburned a chip with 2deg extra spark advance across the board, and that pretty much got the throttle response back without introducing spark knock.

lbrohez

i thought you werent supposed to gap the plantinum plugs because it caused them to have problem.

kevinc

What kind of problem does gapping cause? If you have actual data from Bosch that's good to know, but if this is another "I heard about a guy whose brothers-friends-dads-cousin said he heard gapping platinum plugs causes problems" I wouldn't give it much credibility.

lbrohez

It causes the plantnum to get stress fractures in the platnium. The fractures cause it not to spark to its full potential. It is actually from bosh that says it, i dont remember if the paper came in the spark plug box or if we had to ask for a paper on it from the parts house, but it says do not gap them. IF you dont believe me see if you can get ahold of bosh and ask them.

92RSFivePointSlow

while I agree with the statement about gapping causing fractures in the porcelin, bosch advises you to gap your plugs. Buy a box and look on the inside of it, there's directions on how to gap it. I didn't gap mine because I didnt want to crack the porcelin, but I did check them, they were gapped apropriatly already.

bigblue

i guess its jus because i have a new motor and im not used to having an engine run clean. Even my almost new honda with <20k didnt run as clean as my new 350 does. The engine itslef is really good. Has excelent throttle response. Smokes the tires when ever i try to giv ein more then 1/2 WOT from a standing start. It even gets around 23 mpg in city. And i gaped mine when i first got them, as a matter of fact, if i too remember correctly, the box even says to gap the plugs. Oh well... guess its notig to sweat about.

oh.. as for the issue of chaning them, just used a 5/8 box end wrench. Manages to get around quite nicely.
-dimented24x7

HIL87TA

I have bosch plat+ 4 was told already gapped[not have to mess with] runs o.k.[around 4,500miles ago]

kevinc

Yes, the Bosch +2 and +4 plugs are a different animal than conventional design. Gapping them would be tough. The conventional-design Bosch platinums have instructions printed inside the box as stated above, basically don't contact or exert force on the center conductor or it's insulator.

This is how I gapped mine (0.045") for both sets I've used.

Adding 2deg spark advance to the entire table woke my engine back up from it's ethanol-induced slumber, and the extra bump of PE fuel got the WOT O2 readings back into the 890-910mV range. Back to normal, but it likes 93 octane gas where during the non-blended fuel months I can run 89 happily.