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-   -   Spark plug no longer aval . ac 43N (http://www.hotrodders.com/forum/spark-plug-no-longer-aval-ac-43n-141461.html)

Tommy B 07-04-2008 08:32 PM

Spark plug no longer aval . ac 43N
 
Thats the plug heads orignally took . I heard to use delco r43xls now . Do i need to go up or down in heat range since i'am 30 over now and added a bigger cam and about .5 point compression , gears and a convertor . I don't drive the car on the street , its just a toy at the track . I tried NGK bpr4es but the plugs stay very white and i get a pop now and then at idle ,more so when engine is not to operating temp . ( I think that means the plug is too hot correct ? ) i have msd ing and 6al box if that matters . I gapped the plugs at .35 also .

carsavvycook 07-04-2008 09:51 PM

Quote:

Originally Posted by Tommy B
Thats the plug heads orignally took . I heard to use delco r43xls now . Do i need to go up or down in heat range since i'am 30 over now and added a bigger cam and about .5 point compression , gears and a convertor . I don't drive the car on the street , its just a toy at the track . I tried NGK bpr4es but the plugs stay very white and i get a pop now and then at idle ,more so when engine is not to operating temp . ( I think that means the plug is too hot correct ? ) i have msd ing and 6al box if that matters . I gapped the plugs at .35 also .

It looks like you have problems other than just spark plug heat range.

You went bigger on the camshaft, and just a touch on compression. You will need to re-jet the carb richer, by a couple jet sizes, at least. The "very white plugs" says you are running too lean now. The "pop now and then at idle", says you might have a real lean mixture at idle.(possible vacuum leak) Also MSD recommends a plug gap starting at .050 to no more than .060, for their products to operate best. The fuel you are using will play a part in your tune.

A spark plugs "heat range" is determined by the engines cylinder temperature. In other words, a "hotter plug" is designed to perform best in higher temperature's, as in a "lean mixture". and "colder plug" would perform better with a richer mixture. The plug does not "burn" hotter, it will just dissipate the heat slower, keeping the plug "hotter".

You also changed gears, and converter which is going to have to be close, rpm wise, to the "grind" of the camshaft.

Tommy B 07-04-2008 10:38 PM

Thanks carsavvycook ,

compression is 11.5 so i could up the gap to .040 to .050 as msd says for 10.5 to 13 compression ratios

I did try re jetting the carb also : 84 /82 , when i removed the rear power valve i went to 90 in back ( 850 dp ).

i checked for vac leak and exhaust leaks as well .. none were found , car dies very quickly if i cover the choke area .

Iam using 110 oct. fuel . I had a couple people at the track tell me the pop could be a vac leak as you mentioned or something about the fuel igniting with a plug to hot and is creating a hot spot in the combustion chamber and some fuel is unburnt creating that pop , cold fuel , hot exhaust .

I just know it don't sound good but yet yet the car runs quite well as long as iam not idle or just slightly above it . I will check the air mixture screws again with the vac gauge but was sure i did it right . I can only think of plugs after i check that , I guess since the plug now is a hot plug i could try one or two steps colder . The being lean iam afraid will hurt something .

carsavvycook 07-04-2008 10:58 PM

I forgot to add. Everything on your "tune-up" is going to change with the air temp, and humidity,= barometric pressure, at the time you run. On a cool evening you may have to drop a "heat range", or possibly a "jet" size or 2.

What you need to find is a "happy medium" to start with, with this new engine. Good luck, and Gods speed. Go get em!

carsavvycook 07-04-2008 11:29 PM

Check your exhaust temps at the header ports of each cylinder. An infrared hand held unit with a lazer pointer works good. You will be OK between 650 and 850 at hot idle with your set-up. At higher rpms you would want it no more than 1350.

66bowtie 07-05-2008 08:35 AM

sparkplug no longer available
 
Here is a pretty good site on plugs. It May help you pick a heat range for your engine.
http://www.autohausaz.com/html/spark...lug-wires.html

dawg 07-05-2008 11:07 AM

heres a cross reference for your plug
http://www.sparkplugs.com/results_cr...CrossWarning=1

DENCOUCH 07-05-2008 11:41 AM

Question..
 
Quote:

Originally Posted by carsavvycook
It looks like you have problems other than just spark plug heat range.

You went bigger on the camshaft, and just a touch on compression. You will need to re-jet the carb richer, by a couple jet sizes, at least. The "very white plugs" says you are running too lean now. The "pop now and then at idle", says you might have a real lean mixture at idle.(possible vacuum leak) Also MSD recommends a plug gap starting at .050 to no more than .060, for their products to operate best. The fuel you are using will play a part in your tune.

A spark plugs "heat range" is determined by the engines cylinder temperature. In other words, a "hotter plug" is designed to perform best in higher temperature's, as in a "lean mixture". and "colder plug" would perform better with a richer mixture. The plug does not "burn" hotter, it will just dissipate the heat slower, keeping the plug "hotter".

You also changed gears, and converter which is going to have to be close, rpm wise, to the "grind" of the camshaft.

Perhaps I learned the wrong lesson sometime ago, but it has been my held belief that the opposite is true.

A hotter plug than required is detrimental in that it retains heat which can lead to expensive problems in a motor. A plug that is in the too cold heat range fouls easier as the heat from the plug is transferred too quickly to the cylinder head.

With this reasoning, I would believe that it would be worse to have a "too hot" plug in a lean condition than it would be to have a "too cold" plug.

carsavvycook 07-05-2008 01:22 PM

Quote:

Originally Posted by DENCOUCH
Perhaps I learned the wrong lesson sometime ago, but it has been my held belief that the opposite is true.

A hotter plug than required is detrimental in that it retains heat which can lead to expensive problems in a motor. A plug that is in the too cold heat range fouls easier as the heat from the plug is transferred too quickly to the cylinder head.

With this reasoning, I would believe that it would be worse to have a "too hot" plug in a lean condition than it would be to have a "too cold" plug.

You are correct. I should have "proof read", not just "Spell Check".


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