AC Delco Plugs? Or Bosch +4's

[atthacker]

Alright guys, help me out here. I've always bought Bosch +4 spark plugs for my 1990 GMC 3/4 ton pickup. I keep running across people who use the Delco Plugs. Can someone tell me what the difference. I'm assuming the Delco Plugs are cheaper than the +4's which is a butt-raping $60-$70 bucks for a set of 8. So what's so special about the Delco's. I want to hear from everyone. Because if I need to switch, I'll do it.

[2000CAYukon]

I have a 90 K1500 with the 5.7 that I bought new. They don't call for a platinum plug and I have been running AC Delco Rapid Fires in it with no problems.

I can tell you that I would never put the Bosch +4s in my 96 Impala SS (which requires a platinum plug). There are well known issues with the Bosch +4s. Only AC Delco Platinum in my SS! Of course, this is just my opinion (and preference).

The AC Delco Platinum is a very good plug. I have heard that the Bosch +4 foul easy but I have no experience with them. I have just read ton of posts (on an Impala forum) about problems with Bosch +4s.

//2000CAYukon

[atthacker]

awesome. well i'm replacing the head gaskets on my pickup this weekend, i'll throw out the +4 plugs. I know many prefer the ac delcos. I cannot imagine plugs doing that much damage other than mis-firing though.

[2000CAYukon]

Originally Posted by atthacker

awesome. well i'm replacing the head gaskets on my pickup this weekend, i'll throw out the +4 plugs. I know many prefer the ac delcos. I cannot imagine plugs doing that much damage other than mis-firing though.

I have only heard of driveablity issue due to the misfires with the Bosch +4. On the LT1 engine, the optispark is a problem area and is not easy to replace. Some people have ended up replacing the optispark only to find the Bosch plugs was the problem all along.

Does your 90 puff a little blue smoke when you start it? Mine does and I am replacing the valve seals in a couple of weeks (along with a timing chain). If you are pulling the heads, I would put some new valve seals in (or get a valve job). Just my 2 cents.

//2000CAYukon

[atthacker]

Well I'm not replacing the head gaskets because of the plugs by any means. I just thought since I'm buying a whole lot of other crap I would throw some AC delcos in. I had my engine rebuilt a few years ago because it would smoke at startups. We did replace the valve stem seals but it did not help the smoking at start up or the oil use. I wish you luck though, sounds like your weekend is going to be spent like mine.... under the hood. Thanks for the advice though, definitely going to pickup some ac delcos

[42adult]

Those SPLIT FIRE PLUGS SUCK! in a 3/4 ton 454/2500....

[jveik]

think about it, how could a plug with multiple electrodes help at all? Its not like the electric spart can split 2, 3, or God forbid 4 ways. its simple electrical theory here... the spark will pick whichever of the 4 electrodes poses the least resistance to the ground. basically, the 3 other electrodes are absolutely useless. I would just use conventional (single electrode) spark plugs and just make sure they are correctly gapped, because in my opinion, the other 3 electrodes would just get in the way and actually hinder combustion. plus, even if you get a slightly better mileage with those plugs, like maybe one hundreth of a mile per gallon, i would bet that the price difference would make you lose money anyway. just my 2 cents in not trying to tell you people you are wrong because God knows i havent done much research on the topic to tell people how to pick a spark plug.

by the way, the extra cost... why is it so much more? isnt it just a few extra electrodes? maybe they needed to make a whole new assembly line and needed to make em expensive until they break even on the cost of production

[Bullet[BS]]

As a 1990 K1500 5.7L owner I strongly recommend using the Delco plugs. They make all the difference in the world. One tip for you gap the plugs .05 bigger than what is called for on the gap and it will help it that much more. Don't forget to set your timing initially at 0 TDC and unplug the computer timing plug on the fire wall to check it. If you have any issues with a slight miss under load advance your time around 7 degrees.