The Dodge Challenger Message Board

Hi
What sparks plugs could you suggest me to my 440?
I have compression ratio 11.1:1 and when the engine is hot I can hear the pinging between 2000 and 2500rpm.
Timing is 10 advance, vacum is almost "disconected" from distributor and I using only 98 octane fuel.
Maybe colder sparks can cure a little bit this problem?
Yaro

11:1 compression is your problem if you have iron heads. Not the spark plugs. Plus the timing curve must be out.

If you are sure the air/fuel mixture is correct at idle and all through the rpm range then select a plug temp that gives you a nice tan colour on the plug.

The next problem is your distributor timing curve. If you only have pinging at those rpms the timing curve is not right.

Try blocking off the vacuum advance completely first of all. Then work on your distributor so that you have at least 14 degrees initial (idle) advance but no more than 32-34 degrees total advance at 3000-3200rpm with no further advance after that.
Try to get about half the total advance in by 2000-2300 rpm.

Once you have no pinging at any rpm you can try adding a bit of vacuum advance if you like.

Just to add to this (I didn't have time before) the lower the duration of your cam the higher cylinder pressure will be. So if you are using 11:1 compression with iron heads and a mild cam you will be lucky if you can get rid of any pinging.

If you have alloy heads and a hot cam you should be able to run 34 degrees total timing.

There is one sure way to find out how many degrees advance you need for any rpm. It is a long process with lots of driving though.

What you do is you drive in second gear up a steep hill and see if you have pinging at 2000rpm. Adust the timing until you just start to get the pinging at 2000rpm on that hill. Then back off two degrees and note what the timing now is at 2000rpm.

Then you do the same for 2500rpm and 3000rpm. You don't take any notice of pinking at other rpms. Just the rpm you are working on.

You should end up with a timing curve of four points to aim for from idle, 2000, 2500 and 3000rpm. Remember you want 14 degrees at idle and no more timing advance after 3000rpm.

Adjusting the timing curve in a stock or Mopar performance distributor is a pain in the arse. You need to take it apart completely to adjust the weights and replace the springs. But it is worth it in the end.

Much easier is the MSD system which comes with everything you need to adjust the curve and all the bits are just under the rotor arm.

Hi
You are right - I have iron heads and quite mild cam from Hughes (duration 223, 230 at 0.05") and also stock distributor.
I modified timing curve from stock and I spend one day on a dyno to set distributor and timing for max output of the engine, but with vacum advance conected is not possible to get rid of pinging. Without I do not have any problem except one - fuel consumption.
I am thinking about thicker head gasket, to lower the compresion to 10,5.

On dyno I checked also AFR and iy seems to be a little to lean (but plugs are nice and tan) and lean conditions also can cause pinging.
I have Edelbrock carb, I went one step richer, but pinging is still there, so maybe I have to go one more?

Also although mild cam my engine is rough on idle and produce a lot of noice (not from exhaust, just engine itself). When I compared it to another big blocks my engine produces such a big amount of noise, almost like diesel. Could it be caused by compression ratio?

I can't see that compression ratio doing you any good without high octane racing fuel. It may even be damaging the engine.

You really need to either get the compression down to 10:1 OR fit Edelbrock heads if you can afford them. Try contacting these guys http://www.six-packspeedshop.be/ and get a price from them. I have heard they are not too expensive from there.

11:1 will work great with Edelbrock heads. Keep your engine temp down to 180F (82C) and you should have no pinking at all.

I have to stay with iron heads (money, money, money), so I will lower the CR to 10:5 and I hope it will hepl.
Thanks