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#1
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Dome vs Flat top
I'm going to be buying pistons for my 400 stroker soon and am wondering which piston would be a better choice. The engine will have ported 452 heads with 1.81/2.14 valves and I plan on using a 150-250hp shot of nitrous. So with that being said, what piston would be better for my combo......Flat top or Dome??? and what advantages do each offer? Thanks
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#2
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Depends of what compression ratio you are aiming at. Generally flat top is more efficient, but depending of the heads you use they may not be enough to achieve the CR desired. In your case, if your 452 heads have been typically rebuilt they may be at around 84cc's with nailhead valves high in the chamber. But you must measure them to know first, assuming something is just a guess that can be either right, or usually wrong. You must also know the deck height, how close to the deck your pistons are at TDC, and then you can count your CR.
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#3
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If I could machine my way to the desired CR, I'd use flat-tops due to the OEM head's spark plug location.
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#4
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How about the reverse domes in the open chamber heads?
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#5
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Reverse dome is another thing, it doesn't affect the flame travel like a regular dome.
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#6
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i would go with a flat top
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#7
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Fordged flat tops.
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#8
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pistons
flat tops for your combo.
compression # is important when picking out the cam u will use.
__________________
Sapporo Man |
#9
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small cubes require big dome!
If I could I would use a flat top, but when the engine is of little cubic inches, like my 273, domes are needed to get the compression up. I am currently looking at a 15.2 cc dome to get 11:1 with my current project.
The following attatchment is a photo of a nearly finished domed piston I am machining for my 273. |
#10
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Looks good, cuold still be rounder shape. Those "commando" pistons are not available new as far as I know, where did you find yours?
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#11
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That piston is a 40 year old +.030" Jahns cast piston that I found in a $100 junk yard 273 which I raced from 1996 to last year. The compression distance was short, so even with a large dome, the CR too low. I had to mill the block .050" and the heads near .040" in order to get 11:1 CR. The bore in that block was pretty well used up back in 1996 and when I took it apart last summer, it was worse off.
I happened to have a little stroker crank and a standard bore block, so I decided to mate them with the Jahns pistons. The pistons then stuck out of the block a wee too far and the dome was too high in the chamber, so I zero decked them, deepened the valve notch, and reduced the dome to net 15.2cc. Depending on the head I use, I could have up to 11:1 CR. I did not mean to high-jack this post with my projects. |
#12
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BIG CUBES, LOWER COMPESSION, AND PUMP GAS. A COST EFFECTIVE WAY TO MAKE IT WORK.
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#13
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Nitrous, to put simply, is like a supercharger in a bottle. If you plan to run pump gas, and be streetable, a lower more efficient c:r is desired. ie flat tops or reverse dome, preferrably forged with nitrous.
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