I am planning the 307 piston change in my 250, last time I had my local shop get them, they were a universal type piston with more valve relief cuts then needed. All the cuts added up to a lot of lost compression. What brand are you running? what part number? Joe

i run trw forged 307 pistons # L2314-F BUT I THINK THERE hard to find now

there 4 valve relief flat tops

You really do not need any valve reliefs in the pistons unless you are going to run a huge cam.
The reason being,the valves do not have much of on angle to them. Like SBC 23 degree standard head.
Never measured the valve angle on our 194-292 heads,I would guess less than 15 degrees?

MBHD

thats just the way they come. if you dont want valve reliefs then you have to get custom made pistond. and there spendy

Thanks guys, I figured they all might have the valve reliefs. I will start checking again. Joe

Joe according to my Sealed Power book there is only a cast version available....#295AP is the flat top 4 valve relief version....the other piston offered has the .270 deep recess which is what you try to avoid....the c/r listed for the .270 deep piston is 7.2 for the v-8 application...fats

flats with the 4 valve reliefs will give you 9-10 to 1 compression. isnt that good enough for a street engine ?

Yes, 9-1 is where I want to be or around there. I think what my shop ordered in were the 7-1 pistons. The counter person wasn't the normal one so they ordered the first thing that said 307. I will go for the cast Sealed power ones and see how that goes. Joe

If you use the 307 pistons in the 250, how does the deck clearance usually come out? Is it close to "zero deck"?

No, it will not be close to zero deck(if block has not been decked before)
You will need to deck/mill the block after you mocked up all your pistons/rods.

MBHD