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Let me preface this with Im not a ford guy. But, I dont have any problems with Icon, or 4032 alloy, as long as your clearances are appropriate for the material. Its leaps and bounds ahead of Hypereutectic aluminum.

That being said; some piston top designs are better than others, and while the calculations may give you an SCR thats correct for your application, you should still be mindful of piston top designs and how they effect performance. I remember a Pontiac replacement piston that was horrendous; but on paper, to the uninitiated, it fit the bill. Someone here with more eperience than I may be able to say if this piston is efficient. If its not a good choice, some stroker kit sellers can reconfigure kits if you contact them directly

ETA: I'd also run a DCR calc as a sanity check if you haven't built a lot of combinations
 

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Discussion Starter · #4 ·
The main part that I'm concerned about is that it has four valve reliefs. I know that it's probably not optimum but don't know if would be a bad thing.

I've worked on engines a lot but haven't ever done a complete build so I'm a novice at this.
 

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I am not a Ford guy myself and have never owned one besides my first car but I can say anything old school is pretty cool to me as long as its Detroit then for me most of the small blocks and big blocks of old are some of the best builds out there. On to the Icon pistons, I used a set in my 377 Dart SHP small chevy build (4.155 bore x 3.48 stroke) and I can say they by far where one of the best set of pistons I have ever had in any of my builds over the years. The machining on the pistons are very good and the block I had was honed with a torque plate and I just recently had it taken out and torn down to the short block and I sold it but everything looked very good.

The pistons have good machining and were spot on across the board and are designed pretty well with some areas made to offer increased strength. I had about 10:1 compression on that build and those pistons along with my Scat rotating assembly balanced real easy and well. Depending on what your going to do with your build if you do anything that is normal performance and nothing serious like big shots of nitrous then they should be more then enough for performance and hold up. As far as the 4 valve reliefs vs the 2 valve relief part goes, I have currently on my new 350 Dart SHP build a set of D.S.S 4032 aluminum forged pistons and they have the 4 valve relief and have never caused me any performance issues in the past as far as using flat top pistons goes.

I think the only difference on the 4 valve ones they can go in either direction on some, as on the 2 valve version they have to be put in the correct way or you will have trouble big time and your valves would hit or be close with anything outside of a low lift cam.

I am no expert on the combustion process on how one design would be different then the other and maybe someone like Bogie or one of the more knowledgeable guys will be able to shed some light on that subject. I have had no problems regardless of what type I used over the years. The one main difference is the 2 valve will give a slight boost in compression vs the 4 valve version. I have used the 4 valve type of either Hyper pistons or the forged variety in about 75 percent of all my builds I have had done over the last 20 plus years and have never done me wrong.
 

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4V version are inherent to factory pistons so they were symmetrical to facilitate the ability to stick them in any hole on the production line. Many of the aftermarkets do the same thing for the same reason and while the reliefs do have some extra clearance for compression ratio calculations and usually way more than needed for valve clearances it's not any where near enough to worry about for 90 percent of the street stuff out there. Extra savvy guys might choose a 2 relief flat top for the little extra but and perhaps more so when class racing or even some engines using offset pins. In your case, based on what you told us already, you have nothing to worry about as the ICON piston is a great budget piston and will certainly give you no troubles with valve clearance and a measure of security with the added strength.
 

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Discussion Starter · #7 ·
Thanks for all the replies. It seems like the consensus is that they're OK. I just didn't want to make an expensive rookie mistake. @AutoGear I will find a DCR calculator and put some numbers in to see what I'll have. I didn't even know that they had DCR calculators so thanks for the tip.
 

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Which SCAT stroker kit and what head’s will you use? You need to scrub tge compression ratio calculations and if you’re looking at aluminum head’s there needs to be consideration for milling the block deck to correct squish/quench.

The referenced piston is for a stock bore, is this correct and why is it if it is correct as most new pistons on stroker motors use an over bore to get a fresh wall and corrected clearances?

Bogie
 

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Discussion Starter · #9 · (Edited)
I was looking at a Scat kit. My heads are AFR 185 with 61cc chambers. If I did it right I calculated an 8.414 dynamic ratio. That's with a .040" gasket and the piston .010" below the deck. Those two measurements are not set in stone. I just did a generic google for that piston and that's what came up. It'll be a 4.030 bore and the pin won't be offset like the one in the link. Would the 8..414 be a little high for pump gas.

Scat 1-94165BE: Ford 302 Series 9000 Cast Street/Strip Rotating Assembly 347ci | JEGS
 

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From a long time engine guy, I say ignore DCR as it doesn’t tell you anything useful.
What people are calling DCR sometimes is the point where the intake valve closes, that’s mechanical and not anything dynamic.
The point in which the intake should close and capture the intake charge to the rising piston is very dependent on the intake tract and rpm, IE speed of the incoming air charge. The air charge has a mass, and that mass has momentum, that momentum can, under the right circumstance, actually fill the cylinder as the piston is still rising.
To further prove my point, not one single custom cam grinder uses DCR anything in the design of the cam. Intake closing point yes, but again, that’s not DCR. This idea is named wrong, and even worse, doesn’t work the way the calculators do the math.
This sorta crap gets spread all over the internet in a matter of weeks or even days.
many times it’s been argued on here before and I’ll stand my ground on the subject.
My opinion is ignore it, it’s not telling you anything useful. I’ll add that the intake closing point is adjustable by the way of advancing or retarding the cam to crank interface and by that I mean if you have to do that to get it too run properly or run it’s best, it’s a crutch to the wrong cam to begin with.
Flame away…Rant over.
 

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My response in Bold.


I was looking at a Scat kit. My heads are AFR 85 with 61cc chambers. I presume you meant the 185 cc intake head.


If I did it right I calculated an 8.414 dynamic ratio. That's with a .040" gasket and the piston .010" below the deck. A hair wide at .050 but these head’s have a really good chamber and aluminum moves heat pretty fast so this should be safe from detonation. Here’s where life gets edgy as best power is just short of the detonation limit. But with all the dynamics involved that point is always fluid so, and especially with a carburetor, we’re forced to seek a one size fits all solution.

Those two measurements are not set in stone. I just did a generic google for that piston and that's what came up. It'll be a 4.030 bore and the pin won't be offset like the one in the link. Would the 8..414 be a little high for pump gas. Need to know your static ratio as well. Similar to my statement above the operating compression ratio and actual compression pressure is a fluid situation with many affectors, with DCR we’re picking a point we know presents a good average that is workable for all these dynamic conditions. You can see this in action where with a variable timing cam gear is adjusted to advance or restart the cam. Advancing the cam closes the intake earlier where retarding it closes the intake later. This is changing a lot of things but from the stand point of what the DCR calculation is doing to where the intake closes in crank degrees is a huge swinger and that changes the torque and power peaks and curve shapes by considerable amounts with just a few degrees of change in the intake centerline position.

Scat 1-94165BE: Ford 302 Series 9000 Cast Street/Strip Rotating Assembly 347ci | JEGS

The 4032 alloy piston buys a lot of space for surviving detonation and its high silicon content allows it to run clearances more like a hypereutectic cast piston which stabilizes the ring contact with the bore thus improving compression and operating pressure preservation above the piston ie lowers blow by. The SCAT 9000 casting is a very strong piece.
Sounds like your on a good path with this.

Bogie
 

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Discussion Starter · #13 · (Edited)
That was a typo on the 85 and they are AFR 185 heads. The static CPR would be 9.591. The two cams that I'm looking at and the figures that I gave are for the smallest cam. I'm hoping I can run this with a C4 and 3:25 gears but if I put an overdrive in later on I'd change the gears. This will be in a 66 Mustang Fastback that weighs about 3,000 lbs. I'm looking for a fun driver and not a serious race machine.

Xtreme Energy Computer Controlled 216/224 Hydraulic Roller Cam for Ford 5.0L (compcams.com)

Xtreme Energy Computer Controlled 224/232 Hydraulic Roller Cam for Ford 5.0L (compcams.com)

The kit in the earlier link is for the Scat 1-94165. There is a Scat kit that would be a little more expensive with Icon 16.5cc volume pistons. Scat 1-94180BE. I haven't figured out for sure which pistons this one has yet but I'm thinking it would be an upgrade from the FHR piston. Would it be extra insurance to use this kit to keep detonation at bay?

Rotating Assembly Product Search - SCAT Crankshafts

I tend to overthink things but I don't want to make an expensive mistake and would rather err on the side of less performance than to have something harder to get along with. We have 93 octane gas in my area but that could change at any time.

I appreciate all of the input and I do like all of the old Detroit cars too.

Here are the parts that I already have.

5.0 roller block
C4 automatic transmission
AFR 185 61cc heads
3:25, 3:50 and some gears that IIRC are 3:6? something.
Roller lifters
1.6 Roller Rockers
Edelbrock RPM intake
600cfm and 750 cfm carbs. I might need something in between but I figure the 600 would work for right now.
 

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The only issue with 2618 is you want to warm the engine up before leaning on it.

The 2618 does more thermal expansion than 4032 so a bit more clearance is usually provided especially in competition engines that are run hot. For a street driver the 2618 can be tightened up and just running peacefully till the temp gauge is in the normal range is all that’s needed. However, if these pistons are set up tight don’t add nitrous or other forms of boost and don’t go racing otherwise they can be set up for a daily driver. A good machinist should be able to give you good advice regarding this.

Bogie
 

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Discussion Starter · #16 ·
The only issue with 2618 is you want to warm the engine up before leaning on it.

The 2618 does more thermal expansion than 4032 so a bit more clearance is usually provided especially in competition engines that are run hot. For a street driver the 2618 can be tightened up and just running peacefully till the temp gauge is in the normal range is all that’s needed. However, if these pistons are set up tight don’t add nitrous or other forms of boost and don’t go racing otherwise they can be set up for a daily driver. A good machinist should be able to give you good advice regarding this.

Bogie
Which do you think would be the best or safest way to go? The 16.5 dish or the 11cc dish.
 

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Discussion Starter · #19 ·
Is this a compression ratio question or are you considering two different material pistons with different crown volumes?

Bogie
I was wanting to know which dish would be best for my application because of the compression ratio that they would make. The 11cc dish piston static CR would be about 9.59 and the 16cc dish piston static CR would be about 9.057. This is figuring with a head gasket of .040" and the piston below the deck .010" and these can be changed if needed. So would the static compression ratio of 9.59 be the best for my application or would the 9.057 be the best? No boost and maybe a trip or two to the tack just to see what it will do.
 
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