Anybody who does this stuff for a living think there are benefits to be found from applying dimples to the combustion chamber as shown in this PHR article link ?

The builder also did this to certain areas of the piston tops , too.

Call Keck Machine, Brian has played with this in the past. He will be able to tell you what kind of results there was if any. 712-445-2248

Here's a little bit of info I heard from a local guy many years ago when he was experimenting with it. Think about a valve like a spray nozzle on a hose. The less you squeeze it, the wider the water spray is. At very low lifts the intake charge will be a wide spray. The fuel can have a tendency to come out of suspension and return to liquid form as it travels past the chamber around the intake. The dimples around the intake valve help to agitate the mixture and return the fuel back to a gaseous state by "stirring" the mixture back up. His findings on the dyno was it didn't make any more power but strangely the motor did not need as much timing to make the same power. This was tested on a BBC and was probably back in the late 80's. I think if there was any real benefit from it you would see it much more.

I dimpled my first engine, both the head and the piston back in 1972.

So Im the true Pioneer of it My testing of its results wasnt very scientific though.

I judged the results by the Sound and Shake of the engine. And boy did it sound mean and had plenty of shake. A success for sure!


BUT, I was only 12 years old and the said engine was a 3.5 hp lawn mower engine. The theory then was if I make more room for gas and air to fill then any explosion of that fuel and air would have to be bigger. In reality All I did was lower its Compression.

Ok , Sorry for the story, it is true though.





On the Dimpling shown, I can only speculate on its possible advantages or disadvantages.

One fact I can state is that a dimpled surface will allow air to flow more smoothly over it.

On the head where its dimpled it may slightly improve the intake charge flow.

The dimples on the Pistons , hey if it keeps the pistons cleaner for improved heat reflection, that could be a good thing.

Would any of these two things be enough for any noticeble improvement, I dont know. mike

Wouldnt then make more since to dimple the intake runner on the intake, and the head intake runner? I mean by the time it reaches the face of the piston and chamber how much more does the mixture gotta go?
Interesting read but IMo if it was worth its time and effort it would be conman practice by engine builders, and dimple tools would line the catalogs of Jegs and Summit Racing.

I believe it's done to keep the boundary layer of air next to the chamber wall in motion.Golf balls are dimpled for the same reason.Lots of people will suggest building a "quench" chamber or leaving the intake port "rough" to accomplish the same goal.Got to keep the air and fuel in motion and mixed,large liquid droplets don't burn as well.

There was a builder of BMW engines that used small steps instead of dimples in the intake port and bowl. I believe it was patented. As posted, the idea was to keep the boundry layer agitated and fuel mixed. I believe strategically placed steps also improved port flow. With the fuel better mixed there was less tendancy for detonation also. He did a lot of testing, both flow bench and engine to get it right.

I can say that the engines ran well... fairly high CR, low timing requirement and good power with simple parts.

Are you sure they aren't carbon deposite buildup holders to increase detonation?....

Funny I was just thinking about this the other day after a Myth Busters show (you would have to have seen it). I have always found the dimples very interesting, especially since Jim McFarland was a proponent of it and I have a lot of respect for him.

However the clean piston tops on the 455 really make me wonder. Any engine we have ever had that had much clean area on the pistons did not run worth a crap! As in it was slow.

Bill

Back in the 80's when Ernie and Bill Elliott were the Fastest guys in NASCAR. This was suppose to have been one of their secrets.

i had taken a jewlers dremel..and drilled holes in the valve seat just inside the throat ..
i pressed in small pieces of stainless wire..
to do the same....
we never got it wet flowed...but i still think it would work..

that and even putting stainless mesh over the intake gasket port opening...to keep things emulsified..?
i dont have the fixture to test it thoroughly..
cheapst

I dimpled the plenum floor of my modified 71 stock 340 intake, also dimpled the floor of the runners about 2" in from where it meets the head. did it help any? not sure, did it hurt performance? bet not.

back from the dead.

don't wast your time

Let me add .....

Anyone do any mods to enhance swirl ? ... like maybe a direction-dam in the intake port ...??