Before/After grooved head pictures

[panic]

I'd be inclined to expect lesser effects on a 4 valve for 2 reasons:
1. newer design is more likely to have a chamber shape developed by testing rather than usual work-arounds based on 40 year old automotive stuff
2. smaller quench distances based on plug and valve locations

Do we more or less agree that each individual groove is immune to becoming a spontaneous ignition source, in that it has the same properties as quench-protected volume: very small number of molecules and close proximity to cool surfaces?
If this be true, it seems to me that more than one groove per quench surface would increase the amount of turbulence in all cases, and potentially induce or increase swirl (i.e., directional flow) if cut parallel to each other and tangential to the wall.
Grooves on opposing quench pads probably shouldn't point directly at each other, yes?

Please list mod vs. effect for any groove ideas you think are universal regardless of application?

[MadBill]

[quote="automotive breath...I will be providing controlled groove tests eventually. At the present I'm learning as much as I can to assure the tests are meaningful. At this point two ideas interest me most, determining if the groove allows more compression with out detonation and if maximum power is made at a leaner air/fuel ratio.[/quote]

Perhaps it's time to revisit potential procedures to maximize data (and minimize Monday morning quarter-backing ). Despite my motto below, I'm never short of opinions, so:

o Use high enough CR/DCR that some knock would be expected at MBT timing on 91 octane.
Muffle the engine and/or use stethoscope/electronics/whatever to allow knock detection.
o Baseline with high enough octane to run beyond MBT spark.
o Optimize spark and fuel on same.
o Repeat with 87 octane, tuning to borderline knock.
o Groove the heads and repeat.
o Compare power, spark requirements, optimum AFR, BFSC, minimum idle speed, idle vacuum, ?, ?,...

[automotive breath]

Do we more or less agree that each individual groove is immune to becoming a spontaneous ignition source, in that it has the same properties as quench-protected volume: very small number of molecules and close proximity to cool surfaces?

The one concern that I have is the sharp heat risers at the end of the groove becoming an ignition source. I have not witnessed pre-ignition in some extreme conditions. In only one instance I found signs of elevated temperature at the groove outlet. This was a high compression 355, iron head running very lean air fuel mixture and plenty of ignition advance. For this season I cut back the heat risers and asked the tuner to add more fuel.

Please list mod vs. effect for any groove ideas you think are universal regardless of application?

One aspect that I continue to try to understand is the fact that the oil in my modified engine remains clean. The grooved 40 year old engine design outperforms my modern 4 valve engine in this area.

[automotive breath]

Perhaps it's time to revisit potential procedures to maximize data (and minimize Monday morning quarter-backing ). Despite my motto below, I'm never short of opinions...

Thanks Bill,
This is the type of testing I have in mine, along with oil analysis and lean burn miss-fire limits. It's likely that the validity of formal data provided by me will be questioned.

[SWR]

I've done a 4-valver... (and a 5-valve). For the boosted 4-valver the result was being able to run borderline knock at 32 psi to boosting 35 psi,no knock registered whatsoever. Same gas,same everything. 5-valver is still under testing,seems to like less ignition now,as EGT's are down from before the grooves (2 per chamber) were added..

[MadBill]

For the lean limit/misfire tests, you would likely want a few manifold vacuum/RPM points representative of road load conditions, plus gas analysis capability to detect the rise in unburned hydrocarbons due to misfire.
Re oil analysis, I think it would take a lot of dyno time to generate meaningfully detectible levels of carbon, unburned fuel, etc. contamination. This might have to be left for on-road testing.

[automotive breath]

On the first page of this thread #84Dave described his findings when modifying his quench pads. In my opinion formal testing will realize similar results. Some of this could be related to improved wet flow, I think there’s more.

Dave, what other changes were noticed with your modified engine?

…. With the head gasket, I had .042" piston top-head clearance at the bore line. I sloped the quench areas in the chambers upward to where I had .060-.070 clearance from the piston top to the edge of the quench pad on the head. …I suspect the 'ditch' in the piston top accommodates some quench 'pump' and/or turbulence, that improves or allows quicker/better completion of the mass-fraction burn in the chamber…Dave

…. what causes a 'clean' piston top? So rich it won't burn, or so lean there is nothing to burn?

My opinion, either of the two mentioned can cause a clean piston top as well as excessive squish velocity or insufficient squish flow.

[BritishTurbo]

I've done a 4-valver... (and a 5-valve). For the boosted 4-valver the result was being able to run borderline knock at 32 psi to boosting 35 psi,no knock registered whatsoever. Same gas,same everything. 5-valver is still under testing,seems to like less ignition now,as EGT's are down from before the grooves (2 per chamber) were added..

Interesting... Boosted 4-Valve engines are what I mainly work with...
Do you have more specs on the engines?
For instance.... how much boost was run before the head work?

[SWR]

I've done a 4-valver... (and a 5-valve). For the boosted 4-valver the result was being able to run borderline knock at 32 psi to boosting 35 psi,no knock registered whatsoever. Same gas,same everything. 5-valver is still under testing,seems to like less ignition now,as EGT's are down from before the grooves (2 per chamber) were added..

Interesting... Boosted 4-Valve engines are what I mainly work with...
Do you have more specs on the engines?
For instance.... how much boost was run before the head work?

It's all in the last post you quoted. Mitsubishi 3000 GT '96. 7.6: 1 CR, BIG valves,rather big cams,huge turbo... If you want the specifics throw me a PM,as I won't clog the thread with the full build sheet of the engine..

[SchmidtMotorWorks]

Perhaps a quick, inexpensive and revealing way to look at this would be to make a clear head for a small flathead briggs and try some grooves in it.

Anyone have a briggs and a small dyno?
I'll machine some heads if somone knows what material to use.

[bc]

Would grooving the pistons have the same effect?

[Procision-Auto]

I would say, grooving the piston would cause issues with strength as well as
creating turbulence closer to the crown, as opposed to inside the chamber.

[timdog]

Has anyone tried dimples on the quench pads like a golf ball?

[Ape]

Yup,

on the spark plug side on hemisph. 2 Valvers in order to make the flow stay to the headside and perhaps make the turn upwards better, and on 4 valvers on the intake squish also on the heads side.
For the 4 Valver i can say that power output was great, but could have been the cam too!!

cheers

[Ed-vancedEngines]

I tried it with a BB Chevy years ago, but didn't see any differences.

Ed