Piston Notching

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Topless1995GT:
I understand that in the case of the 302 stock pistons, when you convert to a 185 cc head that the pistons need to be notched. Is this the case with the stock 351w pistons or are they capable of larger heads without the pistons being notched, and if so how much larger?

knucklefux:
not enough information to answer that question appropriately.  in short, not necessarily.  all depends on the actual head (wedge, canted valve, etc.) and the cam used...as well as where the top of the piston is in relation to the deck at tdc.  also, cam timing will play a role as well.

i think aboutt the only thing you can so is swap the heads, then check the piston to valve clearance.  others will give you the address for the tech article on this site, i say look for it...cause i'm lazy like that.


as long as you aren't changing cams or cam timing, you should be ok.  you could also call the manufacturer of the heads, they will know more about it.

fidstang:
All heads, block deck height, pistons and gaskets are defferent per vehicle/engine. when ever swapping heads or cams, it is good practice to perform a clearance check. There is no definate answer here, my pistons required elongating the stock reliefs. With my current cam I was only at .016" of clearance on the intake side. There are other options to use other then notching the pistons, like stepping down to 1.9 intake valves or going with the versatile Twisted Wedge heads. I belive that the 302's and 351's used the same heads from the late model engines. That would leave the valve designs the same. What year motor?

Topless1995GT:
It's the stock motor out of my 1995 F-250.

fidstang:
Quote from: Topless1995GT on July 27, 2006, 01:32:29 pm

It's the stock motor out of my 1995 F-250.

If you feel you need the 185's, go with them but, be prepared to "notch" those stock reliefs. Isky sells a tool you install in place of the valve. Works awsome, if you can swap out a set of heads, you can use this tool. :drink

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