Quench "flame channels" in piston vs. head quench

[MadBill]

I'm planning to carve up my BBC ZL1 heads when I finish the port work, but I'm wondering what effect the "Matterhorn" piston dome it takes to get 13.5:1 with 117 cc chambers will have on the squish jet...

[automotive breath]

Mike,
I decided on the groove angle after studying ignition images; targeting the ideal location for flame kernel development with out fear of kernel quench.

Bill,
My experiences with large dome pistons and grooves have been very positive. Lately I have been building additional cylinder pressure by reducing camshaft duration. The engines are responding with tremendous amounts of low RPM torque with out loosing top end charge.


Here's a few pictures of current BBC projects.

[MadBill]

Nice shots; will help when I get to carving! (Lacking a mill though, I was thinking of a cut-off blade in a radial arm saw, but only after extensive testing on scrap heads..) As it happens, my squish is a little on the high side at 0.045", which, being on an aluminum block, equates to ~ 0.053" hot for a iron one and thus in the range suggested for the process.

[SWR]

In most 2-valve heads where I have applied grooves I've done so with a small angle grinder.. Thin (1mm/0.04") cutting disks,lots of support to my hands and using both arms to guide it along the lines I've made with a permanent marker....works like a charm every time,and take a lot less time than using a milling machine to do them...

Only thing NOT to do is to try to speed up the cut by applying force to it. BIG no-no. Let it cut at it's own pace... then do the "fine tuning" using a thin file.

[automotive breath]

I have cut the grooves in exactly the same way described by SWR with good results; it’s a lot faster than using a mill. It all depends on what you’re comfortable with. Once the initial slot is cut, final shaping is easy with a small file.

Are you using multi groove layouts on 2V heads, if so what’s it look like?

What are you doing with 4V heads?

[SWR]

Are you using multi groove layouts on 2V heads, if so what’s it look like?

What are you doing with 4V heads?

I'll see if I can get a picture taken of the twin grooves I now test in 2V applictions. I'm doing a head in my "spare" time (yeah right) this christmas.

4V heads depends a lot on the type of heads... some have virtually no squish area. But those who have,I do multi-groove. Basically because the areas to cut the grooves are so narrow in most 4V-heads that I doubt one single groove does much,if anything at all...

[Unkl Ian]

AB, I find it interesting that you changed from Somender's original "point the groove directly at the spark plug" to pointing it next to the spark plug on the exhaust valve side. That's exactly what I did and I surmise probably for the exact same reasons.

Mike

Biasing the grooves towards
the hot side of the chamber,because....... ?


Thanks.
Ian

[Telvm]

SWR, could you please post pictures of your grooved 4V heads? I'm thinking on scarring an Opel C20XE/C20LET head in the future.



Takk.

[mpgmike]

AB, I find it interesting that you changed from Somender's original "point the groove directly at the spark plug" to pointing it next to the spark plug on the exhaust valve side. That's exactly what I did and I surmise probably for the exact same reasons.

Mike

Biasing the grooves towards
the hot side of the chamber,because....... ?


Thanks.
Ian

Most angled plugs favor the exhaust valve side of the chamber, first of all. On the compression stroke when the groove shoots a concentrated jet into the open area of the chamber, that jet shoots right in front of the plug (but not directly at it causing flame out) putting the active air/fuel charge where it is most beneficial. Furthermore, that jet will inhance the inherant swirl of most modern heads.

When the spark plug fires and the flame front expands, it will travel down that groove and ventilate the back corners of the squish pad, then begin to work that swirl action from the back side of the intake valve. The straight-toward-the-plug groove creates a more reciprocating motion, while the slightly angled plug enduces a continuous swirling motion.

I don't think it's an earth-shattering improvement, but an improvement nonetheless.

Mike

[Unkl Ian]

Got it,thanks.

[automotive breath]

Telvm,
I found this on http://forums.turbobricks.com

[Telvm]

Thanks Randy, that seems a sensible groove pattern for 4V heads with small quench pads and pentroof.

I'd also like to have a look at the multi-grooves of our norwegian friend, were that possible.


By the way, I'm currently grooving my 2V head. We exchanged some emails on the subject and the Jaguar V12 May chambers, if you remember. This is a good moment to publically thank you for your help .

[Troy Patterson]

I add my two cents worth to this thread.

The grooves work as explained. What the grooves do during overlap is really irrelevent and seems not to adversely effect engine operation and efficiency. The grooves are not a bandage.

I think what is overlooked is that during the combustion process, although the piston is dropping, the combustion pressure is increasing (pressing the piston down), and thereby still placing the grooves under pressure. By virtue of the irregular surface on the quench pad created by the grooves, and existence of mixture motion inherent during the combustion process, there is an alteration in flame propagation / mixture motion as a result. By the accounts cited, a beneficial alteration.

The grooves make perfect sense. Aside from the nay sayers, is there any credible evidence they don't?

I look forward to applying it to my next engine. Power on!

TMPCarbs.net

[Masher Manufacturing]

Got the Ranger 2.0 / 2.3 engine together and have driven about 50 miles.

I cut two 1/16 wide grooves on the closed side of the chamber and pointed them towards the intake valve. One groove is 1" and the other 3/4 long. The depth is about 3/16" on the chamber side tapering to 0.

I looked a the spark plug wear patterns and it seemed to indicate gas flow was from the intake valve side towards the plug. Most of the plug wear was on the exhaust side of the plug making me think the arc was getting blown in that direction. The grooves should increase that flow.

No attempt to reshape the ends of the cut was made other than slightly breaking the edge. They were cut with a thin grinding wheel as the head was swinging from a chain. ( I didn't want to pull the manifolds or dump the carb )

The other changes to this engine were piston replacement due to cracked skirts, and a ring / rod brg change while I was there. The pistons had a fair amount of carbon on them but I don't know how much this affected compression.

The motor now is much crisper, sort of like when you put in a fresh set of plugs when the old ones had 40,000 miles. It is more tolerant to lugging, you know, the rolling stop sign pull out in 2nd gear. The shake is pretty much gone. Power at top end does not to seem to have changed much, this engine has a 2.3 bottom end with a small valve/port 2.0 head so it has always fallen off at high R. Since it is a truck, high R isn't a often used operation.

So, no real hard data but a definite improvement. Next test will be if the motor can now run on mid grade fuel rather than perm. Will also check fuel mileage.

Another mod I'd like to see is a hole drilled through the chamber rather than a groove. I'd tend to think this would offer more if a jet to stir things up rather than just gasses moving about.

[peerless]

Robert,
I would approach this the way I do BBC heads.

Two grooves in the squish pad both pointing just to the exhaust valve side of the spark plug. Stay 0.060" (1.5mm) away from the gasket surface.

Check the deck thickness before you decide groove depth; 0.040" to 0.060" is deep enough, deeper as it gets to the chamber. Remember theres water down there.

I cut the grooves with a 1/16" ball end mill then widen with a file into the chamber.

http://members.cox.net/dnjunk/bmw%20r1.jpg

Hello AB,

Thank you for the advice. I just picked up my cyl head from the shop so I can work on these grooves this weekend. You recommended 2 cuts, but I am kinda new to this.

Can you recommend a single cut pattern?
I only have a handful of precision files, so it will have to be done old skool This is the main reason I would like to only do the one cut.

Thank You,
Robert