Can hypereutectic pistons be milled?

S_Mazza

Registered User
Hi. This is a theoretical question. I have seen forged piston makers advertise the fact that they can create a custom dish of any shape you want. Also, I know that pistons are sometimes cut down to achieve the correct height relative to the block deck / combustion chamber. My question is, can hypereutectic pistons be cut in this way, or is it only forged pistons? Thanks.
 
Hi. This is a theoretical question. I have seen forged piston makers advertise the fact that they can create a custom dish of any shape you want. Also, I know that pistons are sometimes cut down to achieve the correct height relative to the block deck / combustion chamber. My question is, can hypereutectic pistons be cut in this way, or is it only forged pistons? Thanks.

The only thing to be concerned about is that taking crown material off will expose the rings to more heat. Our rings are set much lower down on the piston than a typical NA motor. If we could run Hellfire rings or something like that it wouldn't be a problem but all rings in the stock sizes are moly filled which require some protection...
 
Ok, that makes sense. I know of at least one Mustang person that has attempted it with a set of forged pistons. The goal, as you probably deduced, is to produce a true chamber-matching quench-producing piston. It seems like detonation is a real problem with these SC motors, and I think that getting proper quench with proper CR could be a real breakthrough.

Of course, someone has probably gone through this long before me. Just wondering.
 
Ok, that makes sense. I know of at least one Mustang person that has attempted it with a set of forged pistons. The goal, as you probably deduced, is to produce a true chamber-matching quench-producing piston. It seems like detonation is a real problem with these SC motors, and I think that getting proper quench with proper CR could be a real breakthrough.

Of course, someone has probably gone through this long before me. Just wondering.

You will not be able to remove enough material to reshape the quench pad.
 
Is detonation that bad with these motors?

Thinking how much spark advance we can run etc makes me think that it ain't so bad. I keep reading how the mustang lads with the 5.0 target around 20 degrees advance with 7 psi of boost, and here we are close to 30 with double that boost....

Frit
 
Well, you know me, Frit. I'm just trying to get away with my high IAT's. ;) Seriously, though, I am looking to upgrade my IC. The piston question is separate, but related somewhat. I am not ready to have Dave build me a motor yet anyway. :)
 
Note that the machine shop may not be real happy to be machining those pistons if you do it. They will be much tougher to machine than a standard forged piston.
 
Is detonation that bad with these motors?

Thinking how much spark advance we can run etc makes me think that it ain't so bad. I keep reading how the mustang lads with the 5.0 target around 20 degrees advance with 7 psi of boost, and here we are close to 30 with double that boost....

Frit

interesting.
 
That's interesting. Well, I am not saying these engines are bad for detonating relative to other engines, but that detonation seems to be the limit on certain approaches to making power. Making a chamber with quench would make for a faster-burning chamber. As I understand it, that would allow the engine to make power with less timing advance and also reduce the potential for detonation.
 
I am not sure if just decreasing the quench area is enough. I believe it needs to be well controlled and engineered.

Folks have tried bumping up the compression ratio thus making the quench area smaller, but all they ended up with was more detonation, not less and had to take boost out of it or run much higher octane fuel.
 
Yes and no. Getting rid of the space between the piston and the pad will get rid of some of the detonation. I believe Slysc had the post about the Chebby boys who had the slashes cut into the quench pad in the heads. This is to assist with the combustion gasses exiting the pad so it can not rattle. It is hard to explain for me but there is a link over on LS1Tech.com that tells how one of the guys has close to 500 HP from 348" on AFR heads. He also claimed he was getting better than 25mpg. However, if you have a closed chamber, it can be hard to get the fuel/air in and OUT (being equally if not more important), but what do I know.

Chris
 
Yes and no. Getting rid of the space between the piston and the pad will get rid of some of the detonation. I believe Slysc had the post about the Chebby boys who had the slashes cut into the quench pad in the heads. This is to assist with the combustion gasses exiting the pad so it can not rattle. It is hard to explain for me but there is a link over on LS1Tech.com that tells how one of the guys has close to 500 HP from 348" on AFR heads. He also claimed he was getting better than 25mpg. However, if you have a closed chamber, it can be hard to get the fuel/air in and OUT (being equally if not more important), but what do I know.

Chris

I don't understand, can you clarify? Are you saying quench style heads are worse for detonation then open style heads?
 
There is a happy medium between the two. If you have too much space between the piston and the pad, it will rattle (with too much compression of course). However, you do not want too much height of the piston or it will smack the head. Now rememeber that you have to have a lower compression if you are going to force it. And with that of course comes higher octane. To keep from having to run it too high, you will have to be sure to have the compression low enough to keep it within your personal limits but as much compression as you can have at a safe level.

Chris
 
There is a happy medium between the two. If you have too much space between the piston and the pad, it will rattle (with too much compression of course). However, you do not want too much height of the piston or it will smack the head. Now rememeber that you have to have a lower compression if you are going to force it. And with that of course comes higher octane. To keep from having to run it too high, you will have to be sure to have the compression low enough to keep it within your personal limits but as much compression as you can have at a safe level.

Chris

What about cam choice? Specifically overlap? Wouldn't that have a larger impact on detonation over the compression ratio alone?
 
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