what do you guys think of this? Part II

[Unkl Ian]

A-B-A would require two sets of heads,
with a baseline test of both heads unmodified,
to prove both heads make the same power unmodified.

Then modify one set,test,then test the unmodifed
set again.

Now we see why some of the F1 teams built single cylinder
dyno test motors.

[automotive breath]

…Someone needs to test this ABA before it becomes proven….

Many different tests with on various combinations and operating conditions will be required to provide the proof that is needed. The owners of the grooved cylinder heads that I modified are satisfied because they are enjoying something they have never seen before. It’s not just about raw power, improving volumetric efficiency and combination is the best way to accomplish that. This modification improves the quality combustion to a point that it changes the characteristics of the engine. Some of the changes will require analysis other than dyno tests.

[DavidNJ]

There are some dyno sheets published. However, they all seem to include an increase in compression which would account for any increase in power and efficiency. The question would be: do the grooves reduce detonation enabling more power.

There doesn't seem to be a clear set of rules in sizing and positioning the grooves. This thread started with a different way of orienting them. The geometry of the grooves and other engine assembly specs (quench height, combustion chamber volume, piston volume, etc.) may have a significant affect on their effectiveness.

Mr. Breath, have any of your engines added the grooves without changing compression and had a change in the ignition timing that either a) produced peak power/torque or b) occurred at the onset of detonation?

[automotive breath]

Mr. Breath, have any of your engines added the grooves without changing compression and had a change in the ignition timing that either a) produced peak power/torque or b) occurred at the onset of detonation?

Please call me AB, I run my engines on the edge of detonation controlling detonation with the tune-up. This way I can monitor the effects a specific modification has on detonation and ignition timing needs. When a modification increases turbulent intensity the result is reduced ignition advance and lower octane requirements.

[DavidNJ]

So, AB, do you have specific examples where adding the grooves without changing compression had a specific affect on ignition timing and/or detonation?

[Unkl Ian]

Fresh valve job,increased compression,lines in the chambers,
lines on the backs of the intake valve heads,and inside the intake ports.

"Kinda" hard to say exactly where the improvement came from.

The following certainly isn't a hipo engine application, but relevant just the same:
http://www.herningg.com/projects/groovyheads.html

Now I want to see how long the valves last with
those nice stress risers cut into the backs of the heads.

[automotive breath]

So, AB, do you have specific examples where adding the grooves without changing compression had a specific affect on ignition timing and/or detonation?

I was able to eliminate a detonation problem in a high compression 66 Mustang with grooves and a wider piston to head clearance. The compression was lowered so it might no be a valid example. The power increase was very impressive.

[automotive breath]

Fresh valve job,increased compression,lines in the chambers,
lines on the backs of the intake valve heads,and inside the intake ports.

"Kinda" hard to say exactly where the improvement came from.

Now I want to see how long the valves last with
those nice stress risers cut into the backs of the heads.

Garret grooved his 350 SBC much like the one I did for my Suburban. He added the other modifications you mention; so like you said you can't tell what did what. The disappointing part is he hasn't found the expected reduction in fuel consumption yet.

I feel the same about those valves!

[DavidNJ]

So, AB, do you have specific examples where adding the grooves without changing compression had a specific affect on ignition timing and/or detonation?

I was able to eliminate a detonation problem in a high compression 66 Mustang with grooves and a wider piston to head clearance. The compression was lowered so it might no be a valid example. The power increase was very impressive.

That is probably the point. Without a test just of the grooves, there is no really proof they work. Did increasing the quench height reduce the compression ratio?

[automotive breath]

…. Without a test just of the grooves, there is no really proof they work. Did increasing the quench height reduce the compression ratio?

I wasn’t trying to prove anything, I was fixing a problem. The reduced compression was from the increased squish clearance and the groove holds about 1cc of volume. I didn’t want to lower the compression; the owner wouldn’t agree to mill the heads.
This ended up being the engine that responded best to the grooves that’s why I used the example. Low RPM power increase was phenomenal, to a certain extent from the elimination of detonation.

[DavidNJ]

But how much was from the increased quench and how much from the grooves. Did you drop compresson 1/2 point? Was it that or the grooves?

It may have been the grooves? Why did you also lower the compression ratio?

[automotive breath]

...It may have been the grooves? Why did you also lower the compression ratio?

I wanted to keep the compression constant to avoid the potential power loss from lower compression. I order to do that we would have had to measure the volume of the increased squish clearance and the volume of the groove and reduce the combustion chamber volume by that amount, or increase the size of the dome. The owner wasn’t interested in doing either. I thought we would lose power because of the lower compression, but we actually realized a substantial increase in power, like I said “to a certain extent from the elimination of detonation”

[DavidNJ]

The discussion of compression vs. ignition timing is interesting...I've heard people post credible (?) experience on both sides. However, it seems that the test of the grooves would be adding them to a cylinder head that was pulling ignition to compensate for compression. Skimming the head to maintain the same quench and compression would be nice. However, if it was only 1-2ccs, maybe the change in ignition timing would be so large that it would be obvious.

[automotive breath]

The work that I'm doing on the 355 in my 68 Camaro is relevant to what interest you, the combination is boring and I don't talk about it much. I'll fill you in as it develops further.

Last night at the races, the class I was running in had about 32 cars, six had grooved cylinder heads. Jr. lost oil pressure in his Nova in the first round; that left five. When we were down to 8 cars, all 5 of the cars with grooved heads were still in. I can assure you every one of the owners including myself were pleased.

I was late in the 1/4s and lost to Wag in his 65 Vette.




Later last night Fabian took the win in his 67 Camaro with a hole shot to the quicker Vette in a heads up grudge match. He's running the two groove layout I posted earler.

[JamieWebb]

I build small engines into karting racing engines, typically in the 200cc engine range.

I have also played with it. I do not have conclusive evidence one way or the other on the heads I have slotted. I have tried single slots, multiple slots, and varying widths and depths. Our problem is, in our main series we focus on we are mandated to use a carb that is always borderline too rich and have to use pump gas. Even when the plugs are indicating the combustion chamber is operating the way it should be, when you pull the head there is always dark brown/light black discoloration of everything.... no matter if it's slotted or not.

Our motors typically run 8.9-9.3 CR and around .050" on the squish.

But like I said, on our 20hp motors (after buildup) I have not seen conclusive evidence from the dyno that it helps or hurts. But every advancement we make in the carb, ports, and valve seat area shows up VERY clearly on the dyno and on the track.