Quench

[FirstEliminator]

   Over a year ago, I bought parts to make a 482 for the 68 Colony Park station wagon. The project has been on hold for quite a bit. Today, while cleaning the shop I had to move the 482 stuff. I decided to look at the pistons. They are a Mahle with a 20cc dish. It seems the only part of this piston that has quench is the ring around the outside edge. Is this a sufficient amount of quench area? I thought maximizing that area to mirror the available quench area on the head would be optimal. I looked at another engine that is on hold, a 545 storked 460 with diamond pistons. It has a deep dish, and the quench area is at the top surface of the piston. I'm sure this Mahle will go in the 482 and work. But, a stock engine just works too. Building this engine I feel the intent should be to optimize things, within reason of cost.  If the benefits of quench are not utilized on this piston design, should I look for a different set of pistons? With so little time and a bunch of projects to do I barely have time to do things once. I'd hate to put this engine together to find it has a detonation issue.

  The 482 Mahle is in the foreground and the 545 Diamond is behind.

[Barry_R]

That full round quench band will work just dandy.  I have run pistons with a full spherical dish and a round quench band in EMC engines with great success.  Perhaps Randy (GT350...) will chime in since he was on the leading edge when those were introduced into NASCAR etc - but that basic idea has also been adopted in a lot of OE stuff after a ton of research.

[WConley]

Not my specialty, but everything I understand says that Barry is spot-on.  You just need the little band around the outside edge.  This squeezes the dead edge charge and shoots it towards the center with a lot of turbulence.

Just what you need to make torque and resist detonation!

[blykins]

They work well.

On really large FE's, that's really the only way to get where you need to be.  Gotta have a very large dish and the spherical dish is very efficient.

[FirstEliminator]

   Oh, good. Thanks for the replies. The Mahle appears to have a better finish than the Diamond in the pic. Like they are tumbled sometime in the manufacturing process. Back in the day I made the mistake of building a 460 with the D2VE heads that have a fully open chamber with no quench area. It liked to knock with low compression. T'was a dud of an engine.

   Thanks and happy 4th!   

[scott foxwell]

The real difference between the two is going to depend mostly on chamber design. With a full open chamber and no quench area at the edge (but still a
quench pad behind the valves, opposite the plug), quench will be limited so the reverse dome may be a better choice. Most FE chambers I've seen have some quench all the way around the chamber except some of the really wide-open 427 chambers, but then, a "reverse dome" would be about useless. The reverse dome is only going to be truly effective if there is a substantial quench pad opposite the plug. Also, a reverse dome design (like the Diamond piston you're showing) with the same volume of dish will have a much deeper dish. This might limit pin location in some combinations. That Mahle looks like it has universal valve pockets...no left or right.

[My427stang]

I agree, run them with a tight quench distance and they will do great.  What is there for quench will move things from both sides of the chamber.

I do like a mirror to the chamber when able, but it can make for an odd piston, and sometimes "un-makeable" if you have a very deep D-cup.

[Pentroof]

I do like a mirror to the chamber when able, but it can make for an odd piston, and sometimes "un-makeable" if you have a very deep D-cup.

I think this is where FElony chimes in about the mirrors in his chamber (likely on the ceiling) when he's working his odd piston with some D-cups that others would consider unmakeable.

FElony, wake up!

[Falcon67]

I do like a mirror to the chamber when able, but it can make for an odd piston, and sometimes "un-makeable" if you have a very deep D-cup.

I think this is where FElony chimes in about the mirrors in his chamber (likely on the ceiling) when he's working his odd piston with some D-cups that others would consider unmakeable.

FElony, wake up!

I suddenly seem to want some pink champagne on ice

[cjshaker]

I suddenly seem to want some pink champagne on ice

And bring on the dancing girls...

[Dan859]

FElony's all tied up, he's a prisoner of his own device.

[gt350hr]

  Thanks Barry!
      Yes I did extensive testing on dish designs 18 years ago. An engine builder at the old Bill Davis Racing asked if I would make him a "cone" shaped dish piston with about -15 cc's . The first ones were a simple taper from"almost the edge" to a low pint in the center. The power did NOT improve but it took 2*s less timing to get the power. On tear down the flame pattern showed the carbon was more centralized so we added a "squish band" to the point where .375 was found to be the minimum. Different volumes led to a "spherical radius dish" being created. Torque and HP increases were the norm and almost always a reduction in timing to get it. It is important to note that those engines were "tiny" chamber , state of the art heads but the gains were still there. We felt that the mixture was "focused" better and possibly less "rock'' took place due to the uniform shape.
    In today's market with aluminum heads made for almost any engine the round dish/squish band design works well. The only heads "I" feel need a mirror image dish are "some" of the original iron heads. The older technology bad chamber shapes are more apt to have detonation issues.
     Randy

[FElony]

FElony's all tied up, he's a prisoner of his own device.

No fair. Youse guys partied without me in a thread I didn't read until now. [sobs] Reminds me of my yout [sobs more].

[cammerfe]

I bet you were watching re-runs of 'The Dead-End Kids'. Do you wear your cap with the bill off to one side?

KS

[FElony]

I bet you were watching re-runs of 'The Dead-End Kids'. Do you wear your cap with the bill off to one side?

KS

I'm not nearly old enough to know "The Dead-End Kids". I had to look that up. However, you are welcome to tell us all about it. If we can stay awake through it.