spark plugs

[LuckyPenny]

I am in the process of doing a top end overhaul, and checking all the references pertaining to the right and wrong way of doing things.<br /><br />Anyway, I am running into a conflict regarding spark plugs. One reference said to use MR43T another said to use MR43TS I know the TS is a longer plug, I was wondering if the deeper reach would aid in total conbustion. (the engine is running rich no mater what I do)<br /><br />It is a 1977 Chevy 350 (5.7L) standard points ign.

 

[Silvertip]

Re: spark plugs

TS is tapered seat and requires no gasket. T is a regular plug with a gasket. They are not interchangeable.

 

[LuckyPenny]

Re: spark plugs

I have the two plugs side by side. both have a gasket (seal) but the TS has a bit longer tip.<br /><br />My question is what would happen if I use a TS instead of the T

 

[Bondo]

Re: spark plugs

The MR43TS plugs are being dropped I hear,........ We're back to the Good Ole MR43T plugs......<br />My NAPA Guys Can't even order them from AC......<br /><br />The Little bit of added length of the TS plugs is Supposed to promote combustion,+ is a Direct Interchange with the MR43T.........<br /><br />Now,..... There Is a Longer Plug for the Vortec heads,... It's the MR43LTS,... It will Not run in a Prevortec motor........<br /><br />I saw what Upinsmoke says in a post awhile back,+ Didn't bother to comment,.....<br /><br />I Believe AC's plug code would run,...<br />M = Marine.....<br />R = Risistor..... <br />43 = the heat range.....<br />T = Tapered....<br />S = Extended....<br />And the L for the Vortec Plugs is LONG arse.........

 

[LuckyPenny]

Re: spark plugs

My local NAPA has a ton of the TS. So if offered the option go with TS as long as they are available? Would that be the way to go? It just seems to be the longer tip would offer a cleaner burn; all things being equal.

 

[Bondo]

Re: spark plugs

Ayuh.........

 

[ron7000]

Re: spark plugs

one other thought, if your having problems with the plugs getting black and sooty, it may be because their heat range is too cold. Try going up one heat range or trying a different brand spark plug of equivalent heat range. Carb'd engines running 140-160 thermostats can do that.<br /><br />I believe the 'S' has a "projected tip".<br />The longer tip = cleaner/better combustion is just a school of thought. Just because the spark is more in the combustion chamber does not mean or guarantee better combustion and performance, it's largely based on overall cylinder design and flow and can be hit or miss. Another purpose of the projected tip is to help keep the plug cooler by being more in the flow of the intake charge.<br /><br />You can find some decent spark plug cross references at http://www.sparkplugs.com/. <br />NGK BR6FS and BR5FS(hotter) may work nicely and should be locally available at $2/plug.<br /><br />you also mentioned it's a 1977 with points ignition, so don't expect great combustion and clean looking spark plugs to begin with. The 'way to go' would be an upgrade to a high(er) power electronic ignition before swapping spark plugs in and out.

 

[Don S]

Re: spark plugs

one other thought, if your having problems with the plugs getting black and sooty, it may be because their heat range is too cold.

It could also be because the carb idle mixture is out of adjustment, or the choke is too tight or inop.<br />Dwell could be off, timing could be off. Even the compression could be off or a vacuum leak is present. <br />Just because the plugs are black and sooty doesn't mean adjusting the heat range is the cure.<br />It indicates a problem, and the root of the problem should be found, not just cover it up with a hotter plug.<br />The manufactures work to find the proper plug for a particular engine, if it doesn't work, there is a reason why.

 

[rodbolt]

Re: spark plugs

also its mostly a myth that electronic ign is "hotter" it may have more reserve but a well maintained points set up works and works well.<br /> in fact if you run the same plugs and electronics you will note about the same firing Kv.<br />electricity is lazy,like me and bass, and the fireing voltage will never be more than it takes to jump the gap. I dont care if you have electronic ign and a million jiggywatt chromey super duper coil.<br /> ya get only what is nessasary.<br /> if you were running alchohol at WOT and 13/1 compression then you would need a larger reserve capacity coil. compression pressure does alter firing voltage needed.<br /> however on a stock 350 motor of the 70's for marine use below 4500, points work fine they just require additional maint.<br /> I like electronic ign systems with dry coils cause I am lazy and they are basically maint free.<br />if I can afford it I may try using the coil in cap setup like yamaha uses on the F250. however at 160 or so a pop its pricey but simple.<br />it also develops a minimum of 34KV for fireing VS the normal 7-10 KV.

 

[LuckyPenny]

Re: spark plugs

I think we are getting off track, I never said the plugs were black and sooty. All I said was..<br />1-which is a better plug for a 250HP 350 CID engine.<br />2-I know she is running rich, which I intend to correct this week.<br /><br />Thanks

 

[Don S]

Re: spark plugs

The Mercruiser electronic parts catalog calls for an AC MR43T or NGK BR6FS

 

[ron7000]

Re: spark plugs

you started off with saying the engine was running rich no matter what you do and you were concerned with spark plugs. I was assuming you were getting black or fouled plugs because that's what typically happens when the engine runs rich.<br /><br />just an fyi, I repowered with a new ford 351 motor a while back and that came with motorcraft awsf32c plugs. I was never able to find those so I ended up using autolites, AC's, and NGK's over the years and they always ran black and sooty (dry fouled). But the engine always ran great so I figured it was just the carb running rich. Last year I ended up overhauling the carb and figured I'd fix everything, so after smaller jets, setting float levels and checking everything the only thing that fixed the sooty plugs was one heat range hotter plug. The cross reference for the original awsf's was ngk bpr6efs, a very common plug but turns out the ngk 5 plug is what was better. So just be aware that while you're running what's listed as a cross reference may not always be best especially if yong withu go to other brand plugs but since you have a chevy and your goi AC plugs it should be less of a problem. best of luck.<br /><br />not to p'off luckyp by getting off track,<br />hey bondo, i understand sort of how you explain firing voltage being the same between a points ignition vs electronic ignition when a points ignition is well maintained. But, on a points setup you have a resistor wire going to the coil limiting power through it, dropping ignition voltage down from 14v to 9v I think. With less 'power' to the coil there will be less power in the spark generated, resulting in poorer spark (or not as hot a spark) at the plug for a points ignition. While it may take only, say 10kv, to make a spark jump the plug gap, the total power leaving the coil is what determines whether the spark is a weak amber colored one or a hot blue one, no?