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I am referring to the copper core side gapped style ones an I am curious. Could these be ran on a lightly modified 305 (daily driver) and if so which ones would I want to get?
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I just run the normal NGK race plugs and index them so that the ground electrode is at the top of the cylinder, away from the piston.
A taper seat plug to use is R5674-7. The higher the last number, the colder the plug. 7 is about average. For high compression, boost etc, use a colder plug.
For a head that uses gasket seat plugs, R5671-7.
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87 IROC-Z
All engine, no power adders! Bests: 9.348@144.71
That particular picture is a gasket seat. Factory GM heads have used tapered seats since the late 60's. Even Jegs only shows that picture to represent all the NGK plugs.
You won't make any more power with that plug than a regular plug. I buy my NGK race plugs at the local Napa. They're cheap and they work.
This is a taper seat plug
The only time you need a plug with a cut back ground strap like that is if you're running a huge dome piston. Even then, you can index the plugs to clear the dome or cut off the ground strap from a regular plug. My plugs are all indexed.
Last edited by Stephen 87 IROC; 05-25-2009 at 06:16 PM.
The part that is confusing me is that the picture indicates they have a side happed style ground strap like the one I was referring to, but when you mentioned those plugs I was getting the impression that they have a standard style ground strap.
So, you say that the R5674-7 plug should be ideal for a 305 TPI with exhaust, a few intake modifications and (I regret to inform you, done by a PO) a JET stage 2 'performance' chip?. Everything else on the engine is relatively stock, at least not enough to make a difference in plugs IE no high compression, supercharger or nitrous.
The R5674-7 will be fine. I doubt you need to go to the colder -8 plug and the -6 is probably too hot. Plug temperature refers to the tip temperature.
No matter what engine the plugs are installed in, be it a lawnmower, a boat, your daily driver or your race car, the spark plug tip temperature must remain between 450°C to 850°C. If the tip temperature is lower than 450°C, the insulator area surrounding the center electrode will not be hot enough to deter fouling and carbon deposit build-ups, thus causing misfires. If the tip temperature exceeds 850°C, the spark plug will overheat which can cause the ceramic around the the center electrode to blister as well as the electrodes will begin to melt. This may lead to pre-ignition/detonation and expensive engine damage.
Always run the coldest plug possible that doesn't foul. Changing timing and jetting will change the tip temperature.
DIY to your plugs. If it doesn't work you're just out the cost of a standard set of plugs. Which, you were going to change anyway, (right? rhetorical question.) Think, once you un-shroud the electrode it makes it possible for the spark to misfire if the gap is too wide.
Look in your owners manual and buy some factory recommended AC Delco plugs or upgrade to any brand of platinum plug and put them in. You won't notice any performance difference by using some fancy trick plug since it's still just in a daily driver. Don't believe all the marketing hype about fancy plugs. If they were as good as they claim, they would be a factory installation.
The advantage of a platinum plug is that it won't wear out as fast. Regular plugs should be replaced every few years. Plugs are cheap and are not worth cleaning and regapping as they wear. Platinum plugs will just last a lot longer which is good on engines that the plugs are difficult to replace.
Stephen, can you please clear the air for me on the deal with plugs made with "fancy" materials.
The general concensus I am gathering from people here is that copper plugs are the best fit for our cars. Platinum and Iridium plugs offer no benenfits except for the fact that they last longer between servicing, but also tend to foul out alot easier and generally are more susceptible to harsh conditions than copper.
The Iridium plugs in the engine now went FUBAR after about 3 months.
I don't mind paying $100 few years to have the plugs changed out if going with copper. Doesn't seem to be too bad a deal.
If your platinum plugs are fouling, you normally have the wrong heat range. If one or 2 foul, you have something wrong with that cylinder such as valve guides or seals, rings etc. I had all the RH plugs in my daily driver foul up every 6 months. I changed the valve seals in that head and they don't foul up any more.
If your platinum plugs are fouling, you normally have the wrong heat range. If one or 2 foul, you have something wrong with that cylinder such as valve guides or seals, rings etc. I had all the RH plugs in my daily driver foul up every 6 months. I changed the valve seals in that head and they don't foul up any more.
Stepehen,
I ordered the set of plugs you recommended and they got here today. Should the stock gap be good for my application or should I go buy a gapping tool?
