This is a piece of one of the email's I sent the guy who's done the most R&D on it Randy.

Why it helps tame big cams...

....Ignition timing doesn’t vary much with RPM partly because the velocity of the flame front is roughly proportional to RPM. One of the main reasons of this is the increase in chamber turbulence. Which is caused by “high piston speed combined w/ squish reagons” right? Ignition timing is also influence by the density of the air/fuel mix. That’s why at low RPM combustion velocity is quite slow, b/c the low density & high manifold pressure.  And that explains why the grooves help the car idle better b/c it speeds up the flame, at low RPM...
-b

 

Hi All,
I recognized a few of the user names so I signed up. I have been cutting grooves in cylinder heads for some time now; I can answer some of these questions if you’re interested.

Idle quality? 13:1 compression 383 with 280+ degrees duration at 0.050”; idles at 600 RPM, lower if you desire, no bull.

Anyone going to the division 4 bracket finals in Dallas this weekend, ask the 2006 NoProblremRaceway foot brake champ in the 65 Vette, he'll be happy to tell you all about it. The team is bringing at least a half dozen or more grooved bracket cars.

 

Here's a picture of one of my current projects, 062 vortec heads...

 

A-B

What's the difference between cutting the grooves in the head verses cutting them in the piston?

AND - What do you use to cut those grooves?

Denny

 

Denny,
I have grooved dozens of engines, I modified the cylinder heads similar to what was shown. Have you ever been involved with something like this?

I cut the initial grooves parallel with the deck surface with a 1/6” ball end mill. The groove is then widened and deepened at the chamber with a file. Here’s a picture that shows the end results at the chamber.

 

A-B

No!

But I read all the material that has been posted and went to the other sites. I also looked at the EMC engines and found one winner that had the pistons groved. I understand the principles there, now all I have to do is convince one of my customers to try it. But my truck has over 200K miles on it and probably could use a valve job - could I find a better way to test it out?

I saw some with 3 grooves on both sides in sort of a triangle shape - does it make any difference?

Could I use a ZIZ Wheel to cut the grooves?

Denny

 

Find someone that wants to extend engine design limitations like detonation. A good candidate is the guy that is convinced that he can run his compression a little higher than you recommend. With one groove in each chamber, take what you consider the highest you would safely go with the static compression ratio for the combination and fuel in use and build the engine 0.5 higher.


Testing on an engine with over 200K miles on the rings is not ideal. If you decide to do it tell me more about the engine, what’s the squish to bore ratio?


I don’t see any advantage for this type of groove layout, I haven’t tried it. I know someone that did this to a high HP LT1, he’s pleased.


With skill this is the quickest way to cut the grooves. Be careful, one slip could ruin the gasket surface.

Cheers,
AB

 

One question, why don't you make the grooves a little shorter so they don't go into the deck and sealing surface? I like trying new things and I like to get away with compression&n20 on pumpgas so I may have to try this on my new heads. later

 

The groves DO NOT go into/through the gasket sealing circle.

 

If it works, why haven't I seen it on aftermarket heads?

 

...possibly because it works best with flat top pistons. The head manufacturor would not know what pistons are going to be used. That's my story and I'm sticking to it.

 

Actually it works best with high compression domed pistons especially when the piston interferes with flame travel. Directing squish flow into the roof of the chamber has a very positive impact on combustion.

Flat top pistons works great also. With a dish piston the squish to bore ratio is very low, the grooves work but the effect is less pronounced.

As for why the cylinder head manufacturers don't use this idea, I suppose it's because the idea has not been widely accepted.

1racerdude is absolutely correct, if you cut a slot through the gasket surface the gasket wont seal at all, I stay 0.080" to 0.125" away from the sealing area.

 

i can remember a time whem multi layer head gaskets and plastic intakes were stupid. now they are the norm. it sounds like a lot of good theory and sounds like it may work. just need to provide good solid proof. as for the mpg and efficiency increase. i think nascar is one sport that would really care. i drive my car and if i can get better fuel mileage and more power that is a double bonus

 

Does anyone know of someone running an LT1 with grooved heads and what the results were? If the grooves helped in at least one of the three aspects they are supposed to help: reducing detonation, added hp/tq/, added mpg, that would be worth doing in my book as long as nothing else was compromised.

 

I have cut grooves into three sets of LT1 heads. None of the engines belong to me. The one I'm most familiar with is a 383 LT1 in a 65 Vette (ran 9.98 yesterday). It's a bracket car that belongs to a good friend; we race together every week end.

The primary reasons he runs the grooves are because with complete combustion the oil runs cleaner, fuel consumption is down about 20% and the car idles cold like never before with something like 270 degrees duration @ 0.050"

He does not know if the grooves helped HP/torque, he has made too many changes to determine performance benefits of the grooves alone.

He does not know if the grooves helped with detonation, he runs racing fuel.