colder plugs for LA with stock heads?

[scottlanes]

Hi all, I'm looking for a cooler running plug for a 318 with stock heads. I'm trying to reduce pinging and was told that colder plugs would help. I went through the NGK site to get more info but I cant seem to find any plugs anywhere that are cooler than normal

thanks!

-scott

 

[Cranky]

Might be worth a try but are you having pre-ignition or flame front problems. Is the fuel on the money or is it lean? What is the combination of the engine? From the NGK site....

The insulator nose length is the distance from the firing tip of the insulator to the point where insulator meets the metal shell. Since the insulator tip is the hottest part of the spark plug, the tip temperature is a primary factor in pre-ignition and fouling.

Whether the spark plugs are fitted in a lawnmower, boat, or a race car, the spark plug tip temperature must remain between 500C-850°C. If the tip temperature is lower than 500°C, the insulator area surrounding the centre electrode will not be hot enough to burn off carbon and combustion chamber deposits.

 

[scottlanes]

Might be worth a try but are you having pre-ignition or flame front problems. Is the fuel on the money or is it lean? What is the combination of the engine? From the NGK site....

Its a pretty stock 318 with an MSD 6AL instead of points. It has a 650 4bbl, dual plane manifold and headers.

I run on premium from a number of different vendors with about the same amount of ping so except for the overall decline of gas quality since 68 i dont think the fuel is tooo bad

 

[Cranky]

What's your initial timing, total advance at what rpm and what's the temp when it starts pinging?

 

[scottlanes]

i have it running at 160. Initial advance at 10 degrees, I cant remember total advance. It starts at about 2000 and is worse under load

 

[Ron Ward]

Thinking a colder heat range plug isn't going to fix your problem. If you had increased the cylinder pressure a bunch (via boost or nitrous), I'd say you need a colder plug, but it seems like you are either running too much total ignition timing or you are running very lean.

 

[67 coronet]

just for info...domestic plugs use lower #'s to get colder and import brands use a higher # to get colder.hows that for confusion.i agree with ron(above).i dont think plugs will solve an audible ping problem.try backing down the timing or add some octane boost,just to try it.how long has the motor been together?if old it could have some bad carbon build up inside retaining heat,causing pre ign.its what crankys post is talking about.

 

[lewtot184]

if that's a stock 318 it should have less than 9:1 compression, maybe as low as 8:1. i'd say you have a contamination problem with the intake charge. getting oil or water in the chambers will make the engine detonate. another thought could be the dampner has slipped.

 

[petieg383]

NGK has a reverse engineering site. Try it out:

http://www.ngk.com/Search.aspx?ptn=Spark+Plug

 

[wannadrag]

Or has a 67-69 318 with a newer style timing cover and pointer,which would put the timing way off if the damper wasn't marked for the drivers side pointer.

if that's a stock 318 it should have less than 9:1 compression, maybe as low as 8:1. i'd say you have a contamination problem with the intake charge. getting oil or water in the chambers will make the engine detonate. another thought could be the dampner has slipped.

 

[RJRENTON]

Scott,
You should investigate the cause of the detonation (pinging under load), is USUALLY caused by a lean mixture or too much spark advance (static and total) and perhaps too high coolant temp. Does the engine have EGR? EGR was introduced to reduce NOx formation by lowering the combustion chamber temp to less than 1650 degrees F . If you have eliminated EGR, you may have to richen the fuel mixture AND reducing the spark advance. In my old '67 Beleveder II, originally equipped the LA318 engine with a Stromberg WWC3 2bbl carb, and an agressively recurved distributor, I used to use Champion N-11Y plugs without any signs of detonation.
BTW...there is a distinct difference between detonation and preignition. I can explain the difference if you want. If you have any questions, PM me.
Cheers,
RJ Renton

 

[440roadrunner]

Before you get TOO carried away I would do a few things.

1....Numbaw Whone is to get / make a piston stop and verify the timing marks are actually correct. This is one I made in about 1975 and I've had it all these years.........

If you don't know how, post back, it's very easy

2....If you don't know what the advance curve in the dist. is find out, BUT FIRST

3....Be aware there's been some internet buzz about incorrect timing light triggering on MSD ignitions. This seems to be involving "dial up" or delay timing lights. I ain't sure, I don't use MSD

4....What do you have for a cam, and is there ANY chance it's worn enough the chain could have slipped, or INSTALLED INCORRECTLY from the getgo?

 

[mopar73dge]

go back to stock ignition parts. check your total timing with a light, no more than 38 degres total advance . Also take a distributor wrench with you go for a ride, adjust the timing back about 1/4 inch., drive it again same road conditions do this until the pre-ignition goes away. Advance a little at a time about 1/16 of an inch advance looking at your mark on your distributor and block that you made. stay with the stock plug heat range