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Flat Top pistons
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Author:  Beanie [ Mon Nov 11, 2013 11:33 am ]
Post subject:  Flat Top pistons
Hi all

Just getting set to build a new motor and im at the stage of choosing pistons ... now apart from the different Brands avaliable i have the choice between dished and Flat top ... Motor will be 1275 and .020'' or .040'' over bore ...

The story that i had always heard was that the A series head doesnt work with flat top pistons ... something like it doesnt create the correct swirl and squish in the cylinder ... has anyone heard this too or heard any different




Thanks in advance

Beanie
Author:  drmini in aust [ Mon Nov 11, 2013 2:26 pm ]
Post subject:  Re: Flat Top pistons
Many folks (me included) used to run Mahle forged tops in 1275s, I found the only problem was getting the C/R down below 11.0:1 so I could run 98 premium unleaded on the street.
With a stock 1275 head and flat tops C/R was around 12.0:1? (I think).
I ran 2x BK450 gaskets for a while then I opened the standard chambers up a bit instead.

As for squish a flat top should be same or more squish as a dished one? The squish comes from the head shape.

Squish??? Here's my other head, currently in use on the 1360, there is bugger all squish, however this just needs more ignition advance to compensate.

Image
IMGP2253 by k_green1310, on Flickr
Author:  Beanie [ Mon Nov 11, 2013 3:45 pm ]
Post subject:  Re: Flat Top pistons
Thanks Kev motor will be running Avgas or E85 so really want the compression up around 13.5-14:1

running a VP5SP cam so it makes peak power at 8200.... not going to be much under 3500rpm but should be fun ..
Author:  drmini in aust [ Mon Nov 11, 2013 6:25 pm ]
Post subject:  Re: Flat Top pistons
I reckon flat tops then. :P
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