Spark plugs???

**major_mitt** · 03-30-2008, 01:40 AM

Which spark plugs should I be using for my 430?
I have easy access to NGK so if anyone knows which NGK plugs will do the job. I don't think the ones in there are quite right due to the large amounts of black soot coming out the exhaust on start up and they are fouling in a matter of days. Would a hotter plug help?

**bobc455** · 03-30-2008, 03:31 AM

I think the stock plug is an AC Delco R44TS. You could try stepping up to the slightly hotter 45 plug, but you should be careful w/ detonation. I'd stick with the R44TS, and check the idle mixture on the carb for the cause of the black soot.

-BC

**sicksteve** · 03-30-2008, 08:54 PM

sounds like a mechanical or too-rich carb problem.

I know people don't like it, but I use 0.065" R45TSX with my igniion system, and it works wonderfully (except starting it aftering sitting out in the Winter for 6 months).

past two weeks, all I've been driving is my '73 Boat, and it starts/runs BETTER than stock!@
_____

In this other situation the plugs are usually an idication of something else--not the ignition system.

If they are so sooty, maybe you have a too rich carb.

You can have my too-lean emission's era Quad!!

**major_mitt** · 03-30-2008, 11:48 PM

I doubt very much its a mixture problem as 600 dollers at the dyno shop would suggest.

There is slight oil leak from the head down into the combustion chamber which i believe is the prime root of the problem hence the idea of going to a hotter spark plug to burn it off.

**BigRivy** · 03-31-2008, 03:48 AM

You gotta figure out what the real problem is. If it is for sure black smoke and soot it's a fuel problem. More on this in a bit. If it's BLUE smoke at start up then it is oil consumption in the combustion chamber. Whether it be loose valve guides or shot rings. Either way changing plugs is not really going to help much and may cause other problems. Either of these two conditions will usually show up after a period of extended idling also, not just at start up. Go get yourself a spark plug diagnostic chart. They are usually not to hard to come up with at any parts store or they are often in most repair manuals. They are a big help in diagnosing plug conditions. If it is oil problems I would suggest that you buy "non foulers" for the plugs that are affected. They look like an extra plug base that you screw your plugs into then install them in the engine. They cover the bottom of the plug and have a small hole in them to let the fuel mixture in and keep some of the oil off. They do not adversely effect performance. If all 8 plugs are affected equally by what ever is fouling them I would look back at the fuel system as oil problems rarely affect all cyls the same. It's usually one or two holes that foul the worst and the rest are acceptable. Back to fuel. There are several things to consider here using the limited info available here so I'll just throw them out. Engines tuned on a dyno for maximum power almost never have the correct jetting for everyday street use. There are 6 or 7 circuits in a carburetor depending on the carb. The circuits for this discussion are 1 choke, 2 idle, 3 main, 4 power. You can have any one of these messed up and cause your problem. The dyno tests will probably tune #4 and thats it. Dyno tests also will not show an actual mechanical problem, such as not working choke pull offs or a carb that leaks down when it is sitting, some Q-jets are bad about this, or a float problem. If you are using the original carb, which should be a Q-jet, than getting everything working like it should will likely fix any problems without much tuning needed as all existing jetting and settings should be what you need. If you have a modified engine and or a different type of carb then you have to start from scratch. Tune any circuit that isn't working right. A lot of off the shelf replacements are set up generically to work on about anything but seldom do they not need tuning in some respect. Especially the idle circuit. So get a sharp carb guy to look at it and forget the dyno stuff. There is pages more that can be written here but I hope you have a start. S-A Design sells an excellent book on the Q-jet carb that would help you or anyone else interested in Q-jets. So the long and short of it is forget messing with hotter plugs they ain't gonna help any, fix the problem. If it is fuel it shouldn't be tough or too pricey. Good luck, let us know what you find.

**major_mitt** · 03-31-2008, 11:10 PM

Yes its a mainly stock engine with what looks like a very recently rebuilt Q-jet. The guy who tuned it was recommended as someone who knew his stuff about these carbs and is Sure that its properly tuned. He did full diagnostics and found a couple of bad valve guides being the source of my oil leak,( number 8 cylinder only i belive).

Its not the biggest problem in the world as its only slightly annoying with the soot and occasional misfires under full power at high revs.

**dmfconsult** · 04-01-2008, 12:58 PM

To answer your question directly, the direct replacement in the stock heat range for the 430 in NGK plugs are the UR4's. If you want to run a colder heat range, try the UR5's. A lot of guys with 430/455 are running UR5 with good results, including me, just make sure your timing and advance is set up and working properly.

**Troys69GS** · 05-03-2008, 08:38 AM

NEVER BOSCH or a platinum plug. Only AC Delco or Motorcraft. Why, if you had a full shop scope in your garage you could see the spark discrepancy and how dirty it is.