Zz383 crate 500 miles new holley 770 Vac sec, untouched. New gmpp hei 14 initial 33 at 3500.

Ground strap color concerns me. Local 9 second guy says no big deal, it's the ethanol in pump gas that does that, put in a fresh set make a pull and check. Not sure I buy it. No signs of detonation on the insulator. Tiny wet spot on ground strap of all plugs. 1 thread dry. CAR pulls good, lots of heat under hood but haven't seen 220 coolant temp in 90 degree humid weather.

My initial thoughts were lean or timing issue, I was always under assumption good timing will show a color change on the apex of the strap.

Thoughts?

 

Back in the old days when installing chambers and re-jetting two-smoke Yamahas, I'd install new plugs, make a WOT run and then clutch and cut the ignition. Read the plugs by looking at the insulator down inside the plug. Never really cared what the ground looked like.

 

I barely read plugs any more. Running alcohol makes them hard to read anyway. As mentioned above, you need to do a full throttle run then kill the engine to get a good plug reading. Also, the best way to read plugs is with new plugs.

So many things can change the plug readings. Timing, jetting etc all change how a plug reads. You may have some plugs that look bad but changing the ignition timing a few degrees may make them look good.

When I first built my engine, I was more concerned about the heat range. You need the spark plug at a specific range the generate good power. On the ground strap, you'll find a heat line. It's a blue discoloration line.

Changing the timing can move the plugs heat range so you need to have your timing set properly first. You want the blue dividing line half way up the ground strap. The edge of the blue area towards the tip is the base timing end. The edge farthest away from the tip is total advance. Once the best timing is set, you can see where the heat range is. Changing the plugs heat range can move that blue line around on the ground strap. Too cold a plug and it will foul up. Too hot a plug and it will melt the tip off. Best rule of thumb is to run the coldest plug possible without it fouling up.

My race car uses NGK copper race plugs. With NGK plugs, the higher the number, the colder the plugs. #5 is a base average. My engine runs a #9 plug.

For a lot more information on reading plugs, read through all of this.
http://www.crankshaftcoalition.com/w...ng_spark_plugs

I'd be with your local 9 second guy and say no big deal. They're not damaged. They're not fouled. I may suggest going 1 heat range hotter from looking at the ground strap since you probably don't want to advance the timing. Your base timing is probably close enough for that camshaft (never checked the specs of the cam) but your total timing could probably be bumped up a few degrees. 33 degrees total timing is low to me but it all depends where the engine likes it's timing. A few pulls on the dyno while changing the total is the best way to determine where the engine likes it. Once you figure out where the engine makes the best power from timing changes, you never change it.

 

Alky, thankyou. Speaking of heat range. I have been told the number of dry threads is a good indicator of that, do you know any truth of it.

On the timing. I'd say it's actually a touch to much. Gm recommends the total no more than 32. It is a question whether they want everything in by 3500 or 4000 as they have been caught documenting it both ways. A select few will tell you they are conservative with timing in efforts to help on their end with the warranty they offer.

Do you recommend a fresh set of plugs and do a pull or not worth it? I can't see an a/f gauge being in this car anytime soon.

 

As far as timing goes, you want it fully advanced as earlier as possible as long as it is not causing any detonation.

Where and when a motor (ideally) reaches full advance can vary with fuel & air quality.

 

Doesn't matter what GM says. You don't have an OEM engine. How much total timing an engine likes depends on the engine. Two identical engines but they have a slightly different cam and they'll probably want different total timing.

How much total you need is going to be trial and error unless you can get some dyno time. 32-33* is for a factory production car. As mentioned above, you also want to get to full advance as quick as possible. You should be at full advance by 3000 rpm.

If your HEI is a large cap then you can play around with it. Changing the weights and center cam can change the mechanical advance. Mix and match weights to get the proper amount of advance. The springs control how quickly the timing advances. Light springs will advance the timing sooner and you can mix and match a light, medium and heavy spring etc to get the proper curve.

Looking at a ZZ383 from Summit to see some cam specs, the base timing should be in the 14-16 range so you could bump it up another degree or 2 which will also bump up your total the same amount. If you need more or less total timing, it will have to be done with the weights.

The nice thing about ignition timing, once you determine where the best initial and total needs to be, you never touch it again no matter what other type of engine tuning you do. Changing jetting, plugs etc won't change where the engine wants the timing.

 

ok thanks for your advice, the timing specs from gm are are from the book that gmpp provides with this crate motor. I guess their claiming the fast burn head likes a lot less timing, I'm **** with this thing, dumped a lot of money into it, just being cautious.