|
Title: Steps in combustion chambers..yes or no?? Post by: Brandon Sinclair on December 01, 2009, 22:50:38 pm I have noticed that a lot of the heads today have seating steps around the perimeter of the combustion chambers. I own heads with the step and others without.
What are the reason for the steps other then adding more cc's to the combustion chamber, and what are you experiences running heads with or without steps (which do you prefer and why?) Thanks Title: Re: Steps in combustion chambers..yes or no?? Post by: 181 on December 04, 2009, 16:37:53 pm I believe that it was a factory way to decrease compression ratio on in example 043 castings. When ordering my Stage 2s from Steve Tims, I had the step removed completely so it doesnīt screw my deck height and then I had my chambers reshaped for correct volume.
On larger bores it canīt be used as a "shim" because inner diameter of the step is smaller then outside diameter of the piston (I donīt know if this can apply to stock 85.5 bore). Deck height is a distance between top of the piston and quench areas in the head chamber. Title: Re: Steps in combustion chambers..yes or no?? Post by: Bruce on December 04, 2009, 17:02:12 pm Deck height is a distance between top of the piston and quench areas in the head chamber. Deck height is the distance between top of the piston and the top of the cylinder.Title: Re: Steps in combustion chambers..yes or no?? Post by: 181 on December 04, 2009, 17:51:11 pm I agree, if there is no step in the head.
Title: Re: Steps in combustion chambers..yes or no?? Post by: Brandon Sinclair on December 04, 2009, 17:56:25 pm How many cc's are in your head without the step?
Title: Re: Steps in combustion chambers..yes or no?? Post by: Bruce on December 04, 2009, 22:00:05 pm I agree, if there is no step in the head. The head has nothing to do with deck height.If there's a step in the head, it's part of the chamber volume. Title: Re: Steps in combustion chambers..yes or no?? Post by: Brandon Sinclair on December 04, 2009, 22:09:18 pm Maybe I posed my question wrong.
What is more beneficial, no steps in the chamber with all the cc's coming from hand porting and unshrouding of the valves or the step and the normal port work by the valves or does it not matter much? Title: Re: Steps in combustion chambers..yes or no?? Post by: Jim Ratto on December 04, 2009, 22:15:58 pm I think the step is doing the same thing (to CR) as a copper head gasket. Doesn't do anything as far as squish area (except raise it away from piston face). I would rather have a head w/o step, a machined (to remove chamfer) cylinder top and a reshaped chamber that ehances "squish."
For what it's worth, Jerry would "step" new heads on his mill, just as a quick way to gain a few CC and lower CR. Title: Re: Steps in combustion chambers..yes or no?? Post by: 181 on December 06, 2009, 21:51:48 pm on topic: http://lowbugget.com/0_deck.html
Title: Re: Steps in combustion chambers..yes or no?? Post by: 181 on December 07, 2009, 23:42:42 pm http://www.rbracing-rsr.com/squishcalc1.html
This is one excellent article which explains better what i couldnīt explain earlier. many people set up their deck height to 0.04-0-05 but when they install head with step included, their quench is down the drain. |