Flat Top Pistons
08-29-2003, 07:43 PM
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Car: 1991 Camaro Z28
Engine: TPI 350
Transmission: 700R-4
Flat Top Pistons
does anybody know what the advantages and disadvantages is in having flat top pistons. Thanks
08-29-2003, 07:50 PM
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Car: Formula
Engine: 5.0L
Transmission: 700R-4
Advantage: helps somewhat unshroud spark plug and some of the in take and exaust valves.
Disadvantage: I may be mistaken but I think they actually lower your compression ratio as compared to dome top pistons.
Disadvantage: I may be mistaken but I think they actually lower your compression ratio as compared to dome top pistons.
08-29-2003, 08:09 PM
#3
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The advantage over a dome piston is Flame travel and less surface area.
A flat top piston, compact combustion chambered motor burns the fuel faster requireing less ignition timing to make good power.
Less likely to spark knock under power.
A domed piston motor with a reletivly large combustion chamber
has more surface area for the same cr and the fuel flame front has to travel farther and work its way around and over the dome at TDC. less efficient and more detonation prone for the same cr and octane gas.
Its hard to get a good compression ratio on a small cubic inch motor with a flat top because the combustion chamber has to be so small that you can't put a very big valve in it.
You can build a 350 Ci motor with over 12.5:1 cr with flat top pistons, small cc heads and deck milling.
You can get over 14:1 on a 400 ci motor with flat tops.
The more the combined combustion space at TDC resembles a ball with the spark in the middle, the better.
A hi domed piston motor wedge headed motors combustion space at TDC resembles a "W" A Hemi resembles a inverted "V"
Building your motor so that the piston comes up right close the the flat part of the cylinder head ( quench area) (.040") at TDC., really helps in the design. Pushes all the fuel towards the plug and flame front, for fast combustion and less timing required.
A flat top piston, compact combustion chambered motor burns the fuel faster requireing less ignition timing to make good power.
Less likely to spark knock under power.
A domed piston motor with a reletivly large combustion chamber
has more surface area for the same cr and the fuel flame front has to travel farther and work its way around and over the dome at TDC. less efficient and more detonation prone for the same cr and octane gas.
Its hard to get a good compression ratio on a small cubic inch motor with a flat top because the combustion chamber has to be so small that you can't put a very big valve in it.
You can build a 350 Ci motor with over 12.5:1 cr with flat top pistons, small cc heads and deck milling.
You can get over 14:1 on a 400 ci motor with flat tops.
The more the combined combustion space at TDC resembles a ball with the spark in the middle, the better.
A hi domed piston motor wedge headed motors combustion space at TDC resembles a "W" A Hemi resembles a inverted "V"
Building your motor so that the piston comes up right close the the flat part of the cylinder head ( quench area) (.040") at TDC., really helps in the design. Pushes all the fuel towards the plug and flame front, for fast combustion and less timing required.
08-30-2003, 12:39 PM
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sorry to be a little off topic but i got some pistons with four valve reliefs but there in a dish. how much will this kill my compression with 67cc world heads. will the high flow heads kinda make up for the lost commpression??
08-30-2003, 05:25 PM
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Originally posted by kidcamarosc
sorry to be a little off topic but i got some pistons with four valve reliefs but there in a dish. how much will this kill my compression with 67cc world heads. will the high flow heads kinda make up for the lost commpression??
sorry to be a little off topic but i got some pistons with four valve reliefs but there in a dish. how much will this kill my compression with 67cc world heads. will the high flow heads kinda make up for the lost commpression??
Need a little more info....
Typical dished pistons have a 11 to 13cc dish volume.
They are typicaly .025" to .045" on the hole at TDC (deck height)
Typical flat top pistons have a 5cc volume. (valve reliefs)
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