Box Stock

Ignition timing

I posted a couple of my observations about compression timing and such in a couple of threads hoping someone would argue with me set me straight on what is happening inside a GX motor.

No luck.....

I know some of the wiser and older fellows guard their engines and secrets.
I would love to learn from some of that wisdom
 
So detonation can cause the marks on piston and head that he discribed? Im asking because marks im used to seeing are not well defined. More like pock marks where metal was burned or melted out.
 
Winston what you said about diminishing return is correct. Gasoline is not a very accurate fuel to depend upon, the formulation varies, from region to region ans season to season. You are dealing with a fuel that is retail and versatile for many situations. When you get to the upper levels of compression ratio tuning is much more critical, the air fuel ratio has to be precise, and as Al will tell us the air density, temperature and moisture content will play an extremely important role. Imagine the variation of compression pressures and how each factor plays a role, this will affect how the fuel reacts.

Improper conditions in the chamber will cause pitting, of aluminum parts, often careful inspection of the spark plug will show aluminum deposits on the steel.
 
Kart43 said:
…….. and as Al will tell us the air density, temperature and moisture content will play an extremely important role.
Click to expand...
good post kart43, but you need to be careful when you start quoting what other people would say. The, “moisture content” of the air is of little importance, and I would never say otherwise. An engineer friend of mine gave me a chart, when I first built my dyno, showing the correction factor for humidity. We were both surprised at how small the correction factor was. I lost that chart and I’ve spent no small amount of time trying to find another. It’s easy to find charts showing the correction factor for temperature and barometric pressure, but not humidity.
No harm done, just wanted to set the record straight.

comments compliments criticisms and questions always welcome.
If the data does not support the theory, get a new theory.
 
OK give me credit for that, as humidity level will cause a difference in compression pressures. Water is noncompressable so takes space
 
From what I'm reading into this it was a brand new engine you ran for a few minutes then tore down correct? If so since the marks match on the piston and head that there was possibly debris left over in the machining process at the factory.
 
Yes, that's correct. Engine was ran very little prior to my building of it. That's a definite possibility, yea. Thanks!
 
W Lindsey said:
Ho Ce Min the air hose operator may have been asleep or absent that day
Click to expand...

Awesomeness!! That's great!
I was pretty meticulous cleaning engine prior to operation, and pulled it apart again, prior to modding it. Bore is in excellent shape, rod is fine, and that one spot on piston, and spot on head are the only indicators of anything "wrong".

Planning on getting it back on the kart here soon, start tuning from there.
 
I once watched a guy at a dealership I worked at once Blow a 2 liter twin cam Mitsubishi engine that he had just put a head on because he hadn't cleaned the debris out of the intake from the previous failure.
It had broke a timing belt and swallowed a valve. He replaced a piston and head cranked it up and revved it a little about 6K and sucked pieces of piston that had blown back into the intake thru the head propping intake valves on all 4 cyls open and when the pistons hit the open valves it snapped the heads off of the valves . This time it wasn't repairable because it got head, block, pistons and the turbo. about $9200.00 back in 1994.

Lesson learned from this by me watching it take place Air is cheap. And using an air blower pays off.
 
In some places its still common practice to paint all the parts you can with Glyptal just to be sure you did not miss anything in the cleaning stage.
Or rather I should say it was expected you would miss something and the paint would seal it in place to keep it from moving around.

I blow out, wash and sometimes even paint things to this day.
 
Yea, I used an air compressor, reg'd at 60 psi to clean out case, bore, etc.
Sprayed everything down with WD-40 and wiped it all off/out prior to assembly.
 
You must log in or register to reply here.
Back
Top