FlaTop Pistons

[Anonymous]

I have my engine at the engine builder and gave him my copy of Dave's book. He wants to use Ford 2.3 flat top pistons which he estimates will give me 10to1 comp ratio. I seem to rememeber the book recomending dish pistons. Questions:
Dish or flat top?
Is 93 octane ok for 10 to 1?
Is overheating a concern?

Thanks Craig

 

[MustangSix]

IMO, while there are a lot of considerations (cam, level of preparation, ignition, etc,) 10:1 is too much for iron heads with a slow-burn, simple wedge chamber on 93 octane fuel, esp if you are not running some sort of electronic engine management system, water injection, or some other form of knock control.

A more reasonable static CR woulb be around 9.5:1 or even as low as 9:1. That would allow for variations in fuel quality, air temps, etc.

 

[Anonymous]

Thanks for the reply. As of now I have pretty much followed the book; 260 cam, 3 1V carbs on an Offy, larger valves port match&polished, mild p&p exhaust, port divider, headers, Petronix, 3 row radiator, flex fan. My builder thinks these improvements will allow 10 to 1. This car will strictally be used as a cruiser or occasonal driver so fuel cost is not important. should I still have concerns?

 

[CZLN6]

Howdy Back Buzstang:

If you follow the Falcon Performance Handbook you will note that 10:1 is pushing it. Especially if you have an auto trans, are below 1,500 ft elevation, drive in summer heat, have a high gear ratio, in a heavy car.

Clearly, you will be happier with 9.5:1 or less. And I would encourage you to log on to our website and run the specs on your engine to figure your CR more precisely before you decide. The CR calculator makes it easy.

The question of dished as opposed to flat-top piston is clear. All else being equal, in a wedge combustion chamber engine, dished pistons make more power. They also help in controlling knock.

My reccommend to you is to use small dish pistons and deck the block to zero deck height, and use a NAPA Victor head gasket at .045" thick. Assuming a .030" overbore, with a small chamber (early) head ccing at 46 your CR will be 9.5:1. With a late model large chamber head cced to 54 you'll have 9:1. Either will be right for your combo and no worry about pre-ingition if tuned properly. Decking to zero will improve your engines quench and improve combustion.

Adios, David