Piston experts needed

[Crazy440]

It's time for me to get some edgumacat'n on piston and the differant types.
Ok, Please describe why you would choose one type over another:
1. Flat top (why the indents?)
2. Domed
3. Dish

And I've put on a pic of a piston from John Forces FC.  It appears to be a flat top with part of it missing.  LOL.  What purpose would there be to having that part of the piston shaved.
Thanks
Crazy

[Dodge69_440]

good question, I have found myself asking the same thing many times, anyone want to fill us in?

[Challenger340]

The JF Piston looks from a BA HEMI headed Engine ?

I'm guessing for flamefront propagation on the A fuel deal because of how fat they run 'em ?  I dunno !

Those guys can "punch up" the turbulence with the screw, and don't need the dome so much as the T/Alcohol guys, who've seen limits on their Blower Boost/overdrives over the years.

I dunno why though, Nitromethane is damn near explosive Detonation Velocity once it ignites in that atmosphere from my understanding. The oxygen release is not only a catalyst, but self-oxidizing ?
Way beyong me, but I'll go with the missing HEMI dome on the JF Piston as a flamefront thing, and do the Compression with the Blower.

Just my guess,  Anybody ?

[Challenger340]

First Piston;  Regular type flat-top, symetrical valve reliefs, Pistons probably built with centered Pin(no offset). Pin offset is usually for quiet, and to prevent wear. Can be installed either bank if "front" or "notch present. Cheaper to produce/cast/machine.
That, or,
It's a 4 valve head type Piston ?

Second Piston; Dome type configuration for Rat motor(BB Cheb), used to punch up the turbulence in the chamber, and increase compression ratio of the engine.

Third Piston; low Compression "ashtray" type dish head. Actually a very good design on some Blower applications, even though totally devoid of any quench characteristics, albeit, must be a "forged" type construction for the Blower deals.

Just my thoughts, Anybody ?

[Chryco Psycho]

it is Far better to use a flat top piston for flame travel over a Dome piston , often this requires using a Smaller combustion chamber to get the desired compression ratio though
dish pistons are generally used in strokers where the compression ratio needs to be lowered due to increased comprssion with extra stroke otherwise I never use a dish piston
domed pistons will increase compression but impede flame travel so it is a less desirable way to increase compression over using a smaller heads , this is my Main complain with Eddy RPM heads , the combustion chamber istoo large to offset the heat loss to alum requiring the use of a domed piston to maximize compression & I have experienced interferance with the valve placement in Eddy heads using stock domed pistons   

[Crazy440]

This is a reply that I got on another board, about the John Force Top Feul piston.

"Blown fuel motors are in the 6.5 -7.0 compression range so it takes a flat top piston with the large Hemi chamber to get that kind of compression. What appears to be a missing part is actually the intake valve relief. Hope that helps."

Thanks for all the info.
Crazy

[firefighter3931]

it is Far better to use a flat top piston for flame travel over a Dome piston , often this requires using a Smaller combustion chamber to get the desired compression ratio though
dish pistons are generally used in strokers where the compression ratio needs to be lowered due to increased comprssion with extra stroke otherwise I never use a dish piston
domed pistons will increase compression but impede flame travel so it is a less desirable way to increase compression over using a smaller heads , this is my Main complain with Eddy RPM heads , the combustion chamber is too large to offset the heat loss to alum requiring the use of a domed piston to maximize compression & I have experienced interferance with the valve placement in Eddy heads using stock domed pistons   

I'll agree with most of what has been said here. The flattop at zero deck is the hot tickeet for a pump gas street engine. With a 440ci pump gas build....the e-heads 84cc chamber is perfect when you zero deck the block. Resulting compression is 10.5:1 with perfect .040 quench when using the composite felpro gasket. If you wanted more compression, you could mill the heads for a smaller chamber or go to an indy head with the 75cc chamber. The problem with the Indy heads is that if you're looking to build a pump gas motor with a zero deck, the chambers are too small and the resulting compression is too high (Pump Gas). The domed piston comment i agree with....poor flame travel and a bandaid to increase compression on a cylinder head that has too big of a chamber to begin with. The comment about the e-heads causing interference with the domes due to valve relief location would also apply to Indy heads....this is using a factory replacement "dome" style piston....whch is really built for a factory open chamber head....not a closed chamber aluminum head. Apples and oranges, inmo.

The dish piston as mentioned above is only to reduce compression. They do have their place in a stroker build and a custom dish will dial your compression where you want it to be. A good quality (dished) stroker piston will be flat on the quench side of the head and open underneath the valves. The piston pictured above is poor all around with low compression numbers and no quench due to the design.


Ron