Taking the sharp edges off piston crowns

What do I use to smooth the edge of the dish and valve relief to prevent hot spotting and detonation when spraying?

how much are you spraying ? that edge of that piston looks mighty thin .........

Sand Rolls work fine.

dfree383 wrote:Sand Rolls work fine.

Just don't get too aggressive

bruno wrote:how much are you spraying ? that edge of that piston looks mighty thin .........

I've got a Zex perimeter plate thats 100-300hp. I'll start at 100 or 150 until I get used to it. Plan is to go the whole 300 eventually. You don't like the look of the piston obviously, will it be a problem at those levels?

I'm not sure how he can see how thick the piston is by a top shot???? Xray Computer Monitor?

dfree383 wrote:I'm not sure how he can see how thick the piston is by a top shot???? Xray Computer Monitor?

look at that corner Dave , it looks thin at the top looking down , were the valve relief is

that looks deep to, how deep is that creator?

Its a 39cc dish. Heads are 72cc chambered P51's. Had to go that big of a dish to get CR down. Ended up at 10.7:1 if I remember correctly. Will be running on premium pump gas, mixing in some race fuel when spraying.

bruno wrote:how much are you spraying ? that edge of that piston looks mighty thin .........

bruno wrote:

dfree383 wrote:I'm not sure how he can see how thick the piston is by a top shot???? Xray Computer Monitor?

look at that corner Dave , it looks thin at the top looking down , were the valve relief is

So am I going to have problems spraying 300 on that piston in your opinion Bruno?

The edge does look thin from the top, but also how far the top ring down is plays a part in this ??

I would lightly sand roll the edges and I glass bead the top of my pistons as well.. Thanks, SJ

The top edge of the first ring gap is just over 9mm from the top of the piston. (0.36" or so)

Beast wrote:

bruno wrote:how much are you spraying ? that edge of that piston looks mighty thin .........

bruno wrote:

dfree383 wrote:I'm not sure how he can see how thick the piston is by a top shot???? Xray Computer Monitor?

look at that corner Dave , it looks thin at the top looking down , were the valve relief is

So am I going to have problems spraying 300 on that piston in your opinion Bruno?

sir im no way shape or form a piston guru, , let alone a nitrous one ,but were i circled is were i think you could have some issues------- but i would start out small and read the plugs on every pass till i know its was a clean tune .....one word " PATIENCE" also give Steve Johnson a call @ Induction -Solutions and can help you out with your tune to take some of the guess work out of it

Beast wrote:Its a 39cc dish. Heads are 72cc chambered P51's. Had to go that big of a dish to get CR down. Ended up at 10.7:1 if I remember correctly. Will be running on premium pump gas, mixing in some race fuel when spraying.

lol. gess its the pic....that 39cc dish looks like its 1/2" deep. why I asked.

Bruno is correct i would be very careful with those pistons, your are just not putting them in the ideal environment, just take your time with your jetting and always ck your plugs

The intake valve relief has to be where it's gotta be. The only to make that area thicker is to have more o.d. , i.e. bigger bore.
Diamond piston @ 4.560" bore........SCJ/P51 relief.

bruno wrote:

dfree383 wrote:I'm not sure how he can see how thick the piston is by a top shot???? Xray Computer Monitor?

look at that corner Dave , it looks thin at the top looking down , were the valve relief is

The only problem would be Ring Placement close to the Ditch in those IMO, The Edge at the relief on the top shouldn't be an issue, its not knife thin.

That's a nice looking piston. As to the "smoothing of edges", start with a very fine sanding roll and only knock off the edge. Two other steps I like is media blasting the dome/dish (please mask from above the ring lands down) after using 1000 grit paper to "touch the piston up". There's no need to get carried away, be gentle! I'm not for sure, but I think the intake charge will take care of the intake valve area as long as your tune-up is good.

Just my $0.02,
Dave.

Induction-Solutions wrote:The edge does look thin from the top, but also how far the top ring down is plays a part in this ??

I would lightly sand roll the edges and I glass bead the top of my pistons as well.. Thanks, SJ

LivermoreDave wrote:That's a nice looking piston. As to the "smoothing of edges", start with a very fine sanding roll and only knock off the edge. Two other steps I like is media blasting the dome/dish (please mask from above the ring lands down) after using 1000 grit paper to "touch the piston up". There's no need to get carried away, be gentle! I'm not for sure, but I think the intake charge will take care of the intake valve area as long as your tune-up is good.

Just my $0.02,
Dave.

What does media blasting/glass beading the crown do to help?

Is it a nitrous specific thing?

Blasting the surface with or w/o spray will eliminate the sharp edges and compact the surface.

Lem Evans wrote:Blasting the surface with or w/o spray will eliminate the sharp edges and compact the surface.

Making them less detonation prone