The plug issue ! Hot versus Cold

[Haans]

from what I understand now,......the range of the plug does not reduce engine temp,......??
You can use a colder / hotter plug to reduce plug temp ? In order to controll the temp of the plug to ensure "decent" combustion ?

Is this about right ?

Haans

[retrovan]

Yes to a point.

The combustion is not effected by the hot and cold due to spark intensity.

The spark plug has a perfect working temp. and that is why most manufacturers specify mid range.

The most have mid-range at 5 or 6 and go hotter up scale to 7 and 8

NGK, is the only one I know that goes the other way, and 7 is colder and 4 is hotter.

The more off standard you engine is the colder you should go with your plug, as this will allow the plug to cool faster between fires, and in this way prevent per-ignition.

So the hotter the combustion, the colder the plug, and the more colder the engine, (low octain) the hotter the plug.

VW beetle engines normally use a 6 NGK, but if you run twin carbs, you should go for the 7 plugs, if more mods, then the risistor (R)series and a number 8

I run the R7 NGK series with great results. thats because I have twin carbs and light modified engine.

You can change the spark plugs to NGK BP7HS or NGK BPR7HS

Herman

[Tony Z]

Haans, do yourself a favour and go to the NGK website. They have a lot of info there and you should get your answers.
Then you can update this post and share your findings

[Haans]

Thanks gents,...will do that and see if it makes sense

Haans

[retrovan]

Here you go, from a technical sheet..

..............In most cases, it is not until the engine is modified, or the compression is raised significantly, that stock ignition systems and spark plugs begin to show signs of being inadequate. At this point, a variety of factors determine which spark plug will be best suited for a particular configuration. In these modified engines, specific electrode/tip combinations, electrode materials and colder heat ranges can provide measurable gains in power. If your vehicle has had extensive modifications, it would be best to seek the advice of the manufacturer of your vehicle, the aftermarket supplier who manufactured your modifications, or your mechanic............

Herman

[Haans]

All,...am currently embarking on a "Masters"in plug understanding !!!!! Some of it is still "greek" to me but i've got time onmy side,........I hope

But in the mean time enjoy this with me,......will definately go for the 7's plug for the 1641,....and probably go for a hotter "5" for the TP in the '70 single cab asit is running short distances.

[Tony Z]

All,...am currently embarking on a "Masters"in plug understanding !!!!! Some of it is still "greek" to me but i've got time onmy side,........I hope

But in the mean time enjoy this with me,......will definately go for the 7's plug for the 1641,....and probably go for a hotter "5" for the TP in the '70 single cab asit is running short distances.

keep it stock.
A 1641 doesnt need 7's. I run stock 6's in my 2110 pushing my bus and it runs perfectly.

[slak]

1600 Stock non modified engine original plugs were

Bosch W8AC
Champion L87Y
NGK B5HS

so The B = 14mm thread with 20.8mm hexagon
The 5 = heat rating
The H = 12.7mm reach
The S = Standard type end construction

[Terry Phillips]

The wrong plug heat range can burn holes in the piston.

[Tony Z]

The wrong plug heat range can burn holes in the piston.

thats from the plug being too hot and causing detonation.
A plug thats too cold will foul up and not spark anymore.

[Haans]

Yip,.....we are on the same page,....
Reasoning for the "hotter" plug on the single cab is it has fouled up a plug or 2 already,....... if it does it again ,.....I will chance it with a "5" and drive it for a week or two,...then check the condition of plugs

Thank you all,......your responses is exactly why I joined this forum,"..............get informed education,..then decide on action.
If you foul up,....then you did'nt listen well!!!!

Haans

[Tony Z]

now to add confusion, there is another means of tuning the plug heat range. I havent found much info on it but in all honesty, I need to look into it again.
This involves driving at wide open throttle and then cutting off all spark and fuel and pulling out the plugs to see where their "temperature line" is. If this line is close to the tip, the plug is too cold, if it is too close to the threads, then its too hot. It is supposed to be somewhere in the middle, but I am not sure exactly where.





Those pics came off Angrrr after I destroyed the gearbox when flatout in 4th around 4500rpm
And yes, I am still unsure of exactly which plug I need to use in that engine - I'm on NGK 8s at the moment. If they foul up again, I'll try 8P's before going to 7s

[retrovan]

Haans,

Do what I do, fit the plugs you think are right, drive at your normal top speed for 20 Km, and pull into a Hiway Quick stop, have lunch while the car cools down, Take out the plugs and see what they like, then decide if you need to go colder or hotter. (do not take vw plugs out when hot, you can damage the threads) Repeat till you happy, rather cold plugs then hot, because cold only fouls up, hot can burn pistons

OMO

Herman

[Haans]

Herman,....makes sense ,.......

Bay had 7' in previously,......can't quite remember whats in now? Will check tomorrow or this afternoon when cold

Haans