***??? That grooved head looks like an extensively reworked head, re:ported. Again, no statistical conclusion can be pulled from this post as to the effectiveness of grooving based on my observation of before and after variables shown in those pics.

Welcome to the site

Interesting stuff but it would definately be interesting running some dyno comparisons with the groove being the only modification. Polishing chambers, valve jobs, milling heads, porting all, etc... add up to performance differences. It's hard to believe the car manufacturer's haven't caught on to this if it works.

I wonder what the difference might have been with increasing the comp ratio to 11:1 would have done WITHOUT the grooving, and then WITH the grooving. THAT would have made it a sensible test.

You can't test something by makine more than one change at a time.

tom

Tom,

One good way to test detonation resistance of a modification is to tune the
engine for maximum power with a compression ratio that is high enough
where mild detonation is present. This way you can control the detonation
by lowering the engine temperature, reducing ignition advance, adding fuel
or altering the IVC with valve lash.

Then perform the modification and get the compression ratio to the exact
same point before further testing. This way improvements are obvious,
meaningful and measurable.

It amazes me how such a simple mod can result in such benefits.

I like to compare it with the saw cuts in the leading edge of supersonic fighters like the Mirage or the Lightning. It's just a bloody notch, but the aerodynamic benefits from the turbulence it triggers for the wing are huge.





Even at the standard 10.0:1 this engine is on the edge of detonation. It's a mid-eighties design for family cars, conceived with economy and emissions in mind, more than performance. It even lacks knock sensor.

Open bathtub chambers + relatively high sCR is a tricky combination on pump fuel. As an example the scrap head I got had detonation pitting in the squish pads (gone with the milling). I know of adventurous people who had tried upping the sCR with this engine, but either they had to massively retard ignition, or dodge airborne con-rods.

However, I keep standard ignition timing, with no trace of detonation after 3K miles of really hard abuse. And I think the grooves are the key.



Stock valve timing (save for the slight retard due to milling), ignition timing and fuelling.




That it was. Once I had the engine disenboweled I pulled no punch in trying to improve every piece of it, as you would understand I hope.




Please notice scientific research or variable-controlled experimentation was neither my objective nor a practical possibility for me, an amateur backyard mechanic. I was just trying to improve the performance of my engine through simple & cheap ways. That I've achieved.

As the engine performs now better than before, I can say grooves definitely do not harm, and most probably they help.


To quote the words of another Singh grooves user: "There are 2 camps, those who have tried it and those who are against it."

in my opinion i think that if you dynoed those grooves alone, i don't think your going to see that big of a gain compared to a cam change or porting and installing bigger valves. if you look at some of the pictures on singh's web site the heads with the grooves in them the quench area there is black were the fuel was burnt in the quench area and on the heads were there was no grooves the quench area was clean and had hardly any burning on the head. i think that were you are going to see the gains alone is if by adding those grooves you would be able to raise the compression ratio or be able to run less squish clearance or if you are getting maximum street effort out of a engine that is running a radical cam and big carb. the channel's in the head allow the flame to travel to the squish area and to burn the fuel for a more efficient burn. there might be greater turbulence in the chamber but not enough to see big gain. but hell if you are trying to get more horespower out of an engine i don't think it well hurt!!

I think that many have missed the point that the grooves are not there to directly create higher hp at rpm, but to reduce detonation.

The grooves are claimed to reduce detonation to a degree that might allow lower octane fuel OR higher compression which in itself gives a power increase.

Detonation is most prevalent at high load lower rpm situations. High BMEP. Such as towing, etc. Which in some viewpoints is not all that different than an accelerating drag or circle track race engine.
I think we all understand that the higher the rpm is, the less octane is actually needed since the actual "clock time" available to burn the fuel is so short (milli seconds) that detonation doesn't have time to occur. So the effects of grooves is greatly reduced as rpms increase.

"Side" effects of speeding the burn and its resultant reduction of necessary ignition timing advance reduces the power loss of expanding gases before TDC, so the overall power output is increased. Exactly the effect heart shaped combustion chambers have created.

Many of us have discovered by trial and error that under a high-rpm high-load pull in high-gear that LESS ignition timing often produces more pull. And computerized engines are programmed this way. Also this is the situation that vacuum advance cans enhance. Less timing under heavy throttle.

Great pictures and storys guys...

Here's what I did to the heads on my 89 Nissan Maxima that is turbo charged.

The stock engine has 226,000miles now. It's been turbo charged for the last 60,000 with the grooves in heads. I did drive it for about 4000mi with no grooves but that's about all. When I pulled the heads I decided to do the grooves from the article in Popular Science.

It's very hard to detonate this engine. It's run a best of 13.40@107mph with pump gas on street tires. That's 181CID (3.0) with 12-13psi boost)
V6 for those who are not familiar with the engine.

I'll be doing this to the engine going in my Camaro (87 GN engine) with allum. heads. We'll see how well that does!

Thanks, Scott~

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I forgot to mention that this is the only car I can think of that I can hold my hand on the down pipe (just after the turbo) at Idle. It does not matter how long you let it idle it won't burn your hand. It's warm but not hot.
I've tried this on other cars with my exact engine and it'll scald your hand almost immediatly. Explain that to me if the grooves don't work
~Scott

The radiator fan in my grooved engine is in the unemployment now, never cuts-in even after long idling. As a matter of fact I had to keep it five minutes at 3000 rpm while static in the garage to force it to connect at 100 ºC (212 ºF), just to be sure it was still in working order.

I can now climb into a nearby 5500 ft. mountain pass two consecutive times, chastising it in third gear (just for the fun of it), and at the top the engine temp remains below 90 ºC (194 ºF).

Combustion is faster and more complete with the grooves + higher CR combo, hence less heat is dumped into the cooling system and EGTs are lowered.

http://www.theoldone.com/components/pistons/index.html

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A couple of years ago I did some testing on a mild 355 in my 67 Camaro.
Before grooves I would stage the car at the drags at 150 degrees, at the
finish line the engine temperature would be up to ~ 180.

I grooved the heads with no other changes made, at the track I would
leave the starting line at 150 degrees just like before, at the finish line
the engine temperature was 160 degrees. I knew something has very
different.

This is all about combustion efficiency, right?
I never thought about this again until UR50SLO and Telvm mentioned it.

Fall of 81 I bought an 80 Honda CVCC 1600 with 16,000 mi on it. The 3 valve statified charge engine, with a precombusion chamber like a tootsie pop. The burn begins in the little spherical chamber and squirts into the main chamber through the "stem" abruptly making burning turbulence for efficiency.

That car was cold natured. I drove it all winter and froze my buns off. I replaced the 195 thermostat 3 times and unless you exceeded 50 mph at 40-* ambient, it would NEVER make enough heat to keep my feet warm. At 30* F you could literally hold your hand on the exhaust and even the heater hose would be cool. It was too efficient in town. I bought a new 83 Accord 1800 non-cvcc and it was better, but not great. (Later I got a new 87 Horizon 2.3 that got much-much better gas mileage than either.)

Burn efficiency and coolant/exhaust temperature, mmmmmm????? There is something else we should be measuring.

Ignition advance, air/fuel for maximum power, lean burn misfire limits and
HC emissions to mention a few.