gap for plugs - MSD box & dist.

-
So I got a set of Champion double platinum plugs (delivered to my door by O'reillys for about $50). Gapped them at .045 and installed them. According to my notes the old copper Champions had been in there since 2015. They looked pretty good, but erosion of the electrode had opened up the gap to .055 to .060. Its was time for them to be changed. With the new plugs in, I cranked it up and it ran significantly more smoothly. Hopefully these will be trouble free for a long time.
 
str12-340 said:
So I got a set of Champion double platinum plugs (delivered to my door by O'reillys for about $50). Gapped them at .045 and installed them. According to my notes the old copper Champions had been in there since 2015. They looked pretty good, but erosion of the electrode had opened up the gap to .055 to .060. Its was time for them to be changed. With the new plugs in, I cranked it up and it ran significantly more smoothly. Hopefully these will be trouble free for a long time.
Click to expand...


Just an FYI, gap erosion isn’t a bad thing.
 
Oh, the ignorance........

Gap erosion is a very bad thing because it leads to misfires. This is one of the reasons that Plat & Irid is used for electrodes. As well as having a very high melting point, they are also very hard metals. Erosion is slower, making for less misfires & therefore less emissions & better fuel economy.
 
STR-12,
What ign system? Electrons [ spark current ] jump the gap more easily from sharp surfaces. So your idle improvement could be because of a weak ign system, new sharp edged plug electrodes, the Plat plugs requiring less firing voltage....or a combination of the above.
 
For those who think 'spark plugs do not make a difference'......

Below is a D. Vizard test on a Mini engine that made 90 hp. Different plugs were tried & it lost as much as 30hp! As he says, all sounded the same on the dyno....
An extreme example no doubt, but there it is...

img330.jpg
 
Bewy said:
For those who think 'spark plugs do not make a difference'......

Below is a D. Vizard test on a Mini engine that made 90 hp. Different plugs were tried & it lost as much as 30hp! As he says, all sounded the same on the dyno....
An extreme example no doubt, but there it is...

View attachment 1716175537
Click to expand...
I haven't seen anyone say "spark plugs don't make a difference". I've seen people say, and rightfully so that snake oil plugs are just that. Snake oil. We all know a properly chosen plug can definitely make a difference and no one is arguing that. You always make the argument about somethin IT AIN'T in an effort just to keep arguin.
 
Last edited:
str12-340 said:
So I got a set of Champion double platinum plugs (delivered to my door by O'reillys for about $50). Gapped them at .045 and installed them. According to my notes the old copper Champions had been in there since 2015. They looked pretty good, but erosion of the electrode had opened up the gap to .055 to .060. Its was time for them to be changed. With the new plugs in, I cranked it up and it ran significantly more smoothly. Hopefully these will be trouble free for a long time.
Click to expand...
Thanks for taking the time to update us on your decision. So often we have someone ask a question, there is a lot of dialog and we never hear how it turned out. Thanks.
 
Bewy said:
STR-12,
What ign system? Electrons [ spark current ] jump the gap more easily from sharp surfaces. So your idle improvement could be because of a weak ign system, new sharp edged plug electrodes, the Plat plugs requiring less firing voltage....or a combination of the above.
Click to expand...
All that is laid out in the very first post...
 
Bewy said:
Oh, the ignorance........

Gap erosion is a very bad thing because it leads to misfires. This is one of the reasons that Plat & Irid is used for electrodes. As well as having a very high melting point, they are also very hard metals. Erosion is slower, making for less misfires & therefore less emissions & better fuel economy.
Click to expand...

Spark mark is real and it matters.

If you don’t check your plugs until they start missing that’s not a plug problem.
 
I just went to the annex and shot this pic. Back when i was running these I was jumping beer cans with the fronts, and no one could grab the $100.00 Bill off my dash

20231208_113711.jpg
 
A lot of people think the lowest resistance spark plug leads & non-resistor plugs always make more hp.

Nope, not on this 400 HP engine......
Highest HP was made with leads that had the second highest resistance out of 12 that were tested. [ #5 in the test ].
Test #6. The lowest HP. Test #6 used a non-resistor spark plug, as specified by the wire manufacturer. The remaining 11 tests all used the same resistor plug.

img331.jpg
 
In all my years of running and racking my 340, 383, and 426 Hemi, I never found any major difference between new plugs. As Rick Ehrenberg said, ignition does not make more power as long as it is properly functioning. Timing and tuning are far more important (except for maybe heat range if far off).
What no one brought up is the need for vacuum advance on street engines. There is much to be gained with vacuum advance on the street, and nothing at the track. But if you want an engine to be economical and last, vacuum advance is needed. 50-52° at cruise vacuum is ideal. Adjusting to maximize cylinder pressure at part throttle without knocking is needed though for some engines.
Properly set up with a mild cam, a 340 can get 22-24 MPG with the right advance curve. I did that in the late 70's when gas lines were horrendous.
 
The old Splitfire ads said they first ran an engine on the dyno with copper plugs, then again with Splitfire and measured ~20% more max power (or such). They didn't relate that the engine was cold in the first run and warmed-up in the second. When ads state, "up to 20% more", that means, "no more than 20%". You could see a 10% drop and still match that claim.

Re gap, I had a bad misfire in our 1996 Plymouth 2.4L when flooring on a freeway onramp. High throttle at low rpm is the worst condition since cylinder pressure is highest. It is harder to throw a spark at higher air pressure. In contrast, sparks easily jump feet in a vacuum chamber. A Chrysler TSB for the turbo version of that engine suggested lowering the spark gap to fix misfires. I reduced mine from spec 60 mil to 50 mil and no more misfires. Judging from later engines, if using the GM HEI ignition module, or similar, you might run 60 mil gap, assuming your plug wires are thick enough to not arc to ground (view idling engine in complete dark, looking for "ghosts" around the plug wires).
 
RLF,
You might ask Ehrenberg what 'proper functioning' means??????
For those that still think there is no power in ign systems or spark plugs, why did some engines get two plugs per cyl?? I don't think it was because the manufacturer had left over plugs they wanted to get rid of....
 
There are designs, such as Hemi's, that benefit from 2-plugs/cyl due to emissions factors. I worked at Chevron Research for 18 years in the fuels and lubricants areas and never say meaningful data showing that plug type improved ignition materially. There was marginal data showing the plug indexing made a difference, but not enough to see in drag strip times in a stock 340.
Fuel combusts in milliseconds. The flame front travels from spark source across the cylinder and consumes fuel producing power. Multiple sparks may help a marginal design fire more reliably, but this does not increase power which is determined by the amount of fuel/air available and the ratio of each. Engines burn 99+% of available fuel or they would not meet emissions requirements and the cats/traps wouldn't work.
What does make power is proper Air/Fuel ratio and timing along with combustion chamber design and port flow (more air is better). Spark has no impact once the flame is initiated properly. Advanced plugs may be more reliable over time (Platinum, etc.), but cannot increase power as power is produced by fuel, not spark. So, if a new ignition system increases power, there was something deficient in the old system. Or it wasn't Fit For Purpose such as high compression ratio or high engine speed. Generally, Street Engines will not see a benefit for advanced ignition systems other than reliability.
And you still need vacuum advance under part-throttle conditions for maximum FE.
 
Years ago I was messing with Jacobs ignition systems. And along with the installation instructions they said to experiment with plug gaps. Open it 5-thou at a time til you felt performance fall off/ start to miss. Then go back to the last setting that didn't miss and that was your best setting.
 
I think that the differences in the value of plug types are not seen in comparing fresh plug sets (the premise of most tests), but in a comparison of plugs after 2000, 5000, 10,000 or 20,0000 miles. This is about plugs on cars that are driven, not plugs in race cars of cars that never see meaningful miles of use.
 
'65 V200 wagon with mostly '76 running gear and electrical, dual circuit brakes, sway bars: I put ~340K miles on a stock cast crank 225 Carter BBD Super Six with MSD 6A and Blaster coil, tweaked advance curve, A-833 overdrive, 3.23 rear end (the stock ratio for that trans). I always got about 25 mpg highway, and up to 27 mpg when I kept it under 55 mph on long trips (correcting for all of the above). I fooled around with plugs and gaps a lot and settled on NGK Platinum at 0.045" as the noticeably happiest setup. Going bigger gap didn't seem to help anything.
I was originally running the stock Mopar electronic ignition box and reluctor distributor, but my brother gave me a 6A so I put it on; a noticeable increase in power, and my gas mileage went up. That 6A has about 320K miles on it with no issues.

I met a retired Chrysler engineer who looked at my Valiant and said, "25 mpg, right?" He had worked on that cam design.

The machinist had screwed up the valve stem seals, so I had to rebuild the head at about 60K miles. This engine got a new cam timing chain set at about 225K miles. When I tore it down at 340K it had good compression and oil pressure; the machinist found less than 0.005" taper in the cylinders!

I ran various full synthetic oils from BiMart for about 150K miles, then got creative since I figured I would be rebuilding soon; I started mixing synthetic and petroleum in the engine but always at least 50% synthetic, and changed with a new filter @ 3-4K miles. I also ran top cylinder lubes of various brands in the gas for most of these 340K miles. Ethos (methylated vegetable oil) was noticeably the best top cylinder lube I used; the mpg went up and the engine got smoother somehow.

This '65 rusted out in 2015 after 50 years as a daily driver. All of the modified '65 parts are now transferred to a '64 V200 with no rust. This modified parts set was originally driven about 40K miles in a '76 Valiant that rusted out in '94. This 8.25" rear end has only had synthetic fluid changes since I put it in the '76 body! I keep a notebook and recorded every ounce of gas and mileage that went into all of these cars. I was doing energy efficiency projects in Oregon, Washington, Idaho, and Montana, and lived near Eugene.

65 Valiant w-mags (1).jpg


2021 March24 033.JPG


2021 March24 025.JPG


64 V200.jpg
 
When formulating Chevron engine oils, I did a field test of a API SF oil (current classification in 1970's) vs SH oils including Mobil 1 Synthetic. The SF oil had half the additives of the modern formulations. The field test was in NY City Taxi Cabs for 100,000 miles. The SH oils used extended drains of 10,000 to stress the oil and see differences. The SF oil used a 3,000 mile drain. At the end of 100K, the engines were disassembled and rated for wear, sludge, varnish and deposits. The SF oil with shorter drain interval showed less than halv the wear and deposits of the modern oils including Mobil 1. This showed that it is far more important to change oil than worry about the quality of the oil used.
Synthetics don't actually have better wear and deposit control than modern API SN oils as all use high quality base oil to formulate the finished lubricant.
But this is an Ignition thread, not a lubricant thread. Sorry for the diversion.
 
Bewy said:
The statement in post #2 is completely wrong, there is NEW technology. The writing mannerisms remind me of someone that has been banned from this site at least twice before....


Platinum, Iridium are just two of the new boys on the block.
The plug you are using is a hott-ish plug which is a good idea. NGK equivalent is a 5.

If you go to a Plat or Irid plug, you get two major benefits: long term reliability & higher spark energy which allows you to run a bigger gap. The smaller electrodes of P & I plugs require less firing voltage, which means they can run bigger gaps. The benefit of a bigger gap, exposing more spark to the mixture should be obvious. With a canister coil, I would use 0.055" gap, 0.060" gap with a an E core ign coil. MSD actually recommends 0.060" gaps up to 10.5:1 CR with the 6A box, & that is with stock coils & stock spark plugs.
Click to expand...
Stock plugs on a 68-71 340, 10.5 compression is a Champion N9Y. Add a C for the newer plugs (copper). With your 9.5 compression you should be correct. A platinum plug would be a step up as you state, in Quilty. I use the Axcell distributor, duel point with the added Super Coil and the stock N9YC plugs, everything works fine. In believe, "if it is not broke, don't fix it". BTW, this motor is in my van, not car. Car is all stock.
 
Dual plug cylinder heads are typically something you can benefit from if the engine has slow flame front travel speeds, which is a common issue with Hemis. The two plugs are set at least an inch apart and start separate flame fronts. A common tip-off if an engine design may benefit from this is if it needs a lot of timing; you'll often see timing requirements drop a lot on a dual plug Hemi.
 
RLF Cuda said:
When formulating Chevron engine oils, I did a field test of a API SF oil (current classification in 1970's) vs SH oils including Mobil 1 Synthetic. The SF oil had half the additives of the modern formulations. The field test was in NY City Taxi Cabs for 100,000 miles. The SH oils used extended drains of 10,000 to stress the oil and see differences. The SF oil used a 3,000 mile drain. At the end of 100K, the engines were disassembled and rated for wear, sludge, varnish and deposits. The SF oil with shorter drain interval showed less than halv the wear and deposits of the modern oils including Mobil 1. This showed that it is far more important to change oil than worry about the quality of the oil used.
Synthetics don't actually have better wear and deposit control than modern API SN oils as all use high quality base oil to formulate the finished lubricant.
But this is an Ignition thread, not a lubricant thread. Sorry for the diversion.
Click to expand...
All well-done new information is useful and relevant, especially about making the car last longer. Thanks for kicking in.
OK, how about some research on oil filter designs? I would love to go back to my old toilet paper oil filter!
 
You must log in or register to reply here.
-

Back
Top