In the process of building a 416 small block stroker. Putting aluminum heads on and a Howard's cam in. This will be a street rod/car show car. Would like to see at least 500HP in the end. That's roughly 1.2HP per cube. Question is,...would it make much difference with a flat top or dish piston at the same compression ration. I need to have the block decked. Pistons would be way down in as it sits now. With all being equal, is a flat or dish piston better. Any approx. numbers between the two pistons or is this splitting hairs? Thanks.

Depends on the chamber of the cylinder head.

Gus

Either a 62 or 65 cc chamber. I can mill the deck, go 63 or 65cc chamber, (not much difference) and a thicker or thinner head gasket. If I can get the same compression of 10.5:1 with either piston, does one make more power?

I thought everyone wanted a flat top.

That's what I thought but before going that route, I wanted to make my best choice but can't find the actual difference. If a few horse no big deal, if 20-30 or more, then I will go with flat tops. Wanted to buy a rotating assembley from cnc motorsports but they do not have my comp. ratio so was wondering if it went with the next best piston choice in a flat top then deck, and gasket accordingly.

I did a 470 low deck with Diamond pistons. They did a small dish that mirrored the chamber shape of my Edelbrock heads(instead of a dish across the whole top of the piston) to put my comp ratio at 10.2:1. If I did a flattop I would have had to go to a bigger chamber head....not really sure which would be better but I'm very happy with the combo I chose. Runs great on just about any fuel I put in it.

I believe number one after CR, you want squish, no matter how you get it, is better than none.
,040" being the normal goal?

I am assuming .040".

If you are trying to make power then you want the piston to be close to zero deck, not down in the whole. You should be able someone who makes a zero deck piston for a 416.

Play with an online compression ratio calculator if you have not already to see the CR difference between flat tops and dished. My memory is dished is more for the 9:1 or so range, and flat tops with two valve or four reliefs will get you to around 10:1 or a little over depending on gasket thickness. I would not zero deck a block. Better to leave a small amount on top that way the block has some material for future machine work next time it gets rebuilt.

I just built a 418 SB with eddy heads. A flat top with squish would have been too much compression for the street so we had to have it dished in the valve area to bring it down to 10.3 to be street safe with pump gas. I can’t remember how many cc the dish had off the top of my head.

There is a line of thought that says having a dished piston (cup dish) makes the fuel air mixture more compact and easier to light off and burn. One that mirrors the combustion chamber being optimal.

However, that generally requires custom pistons and a close relationship of you wallet with the piston maker.

Personally, it is my opinion that level of retentiveness is high grade turd polishing for anything other than a nationally competitive race setup.

But then again, I tool around in a flathead powered 51 Plymouth, so ymmv.

While all this might be true . There is no way similar combo's ,only difference is a dish or flat top, going to be a 20-30 hp difference. Put me down for the flat top.

If your cylinder head has a quench pad, use it. 0.037 to 0.039 is supposedly optimal piston to quench pad clearance.

Some of the info gathered over the years points to a dished piston allows a centralized combustion and less power loss to the outside cylinder wall. Makes sense.

A dish piston is almost always a compromise weather it is a mirror of the chamber or not. A flat top is almost always best. I ran a 410 stroker SB with flat tops and iron magnum heads, unshrouded the 2.02 valves to the bore wall to open up the chamber a tiny bit .030 quench, rounded off the sharp edges on the piston to about 1/4 inch radius, and it ran crazy good no detonation on 91 octane and still got good MPG. 220@.050 .575 lift hydro roller.

Mostly a Ford guy, but the tech info applies to most engines.

https://youtu.be/URyZ8h_U310?si=y1nGoBIxIb56NstP

Think about buying a set of custom made reverse dome pistons so you can get the quench needed to make power with the lower compression ration that will be safe for todays and future pump gas

Can't get it answered any better than that. I have seen this guys other vids and is spot on. David Vazard said basically the same thing once I looked into it today. Thank you very much for this video!!!!

I didn't finish the whole video yet, but my biggest takeaway that I haven't heard before is the need and maximum benefit from having quench on opposite sides, that effectively attacks each other, and those are my words.