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Discussion Starter · #1 ·


The 390 4V has a bore and stroke of 4.05 inches by 3.78 inches. The GT, PI and HP versions have horsepower ratings from 300 to 375 hp at 4,600 to 6,000 rpm. Their torque ratings are 427 pound-feet at 2,800 to 3,400 rpm. Their compression ratios run from 9.6:1 to 10.6:1.

I was wondering about what pistons to go with for my mild build. I was hoping to go with forged, possible 10.5:1 compression, comp 268 cam, edelbrock intake, hooker longtubes, holley 750.

the machine shop is recommending hypereutectic pistons for the build, claiming possible 9-10:1 ratio

parts alone for: arp main bolts and rod bolts, better clevite bearings, keith black pistons .030 over, double roller timing, piston pin bushings... that is all that he named.
the price for him from summit as a dealer was $754.12

does this sound correct? i saw forged speed pros, flat with valve reliefs for $330 shipped. he claims speed pros are not very good.

I have to go in saturday to look everything over and pay for the parts without any labor yet..... I wondered if i should buy everything myself.

what is everyone's opinion?
 

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If I am the guy writing the checks...and all that.
I wonder what his definition of "not very good" means.
I would pick a quality forging (they do cost more) over any hypereutectic.
Check out survivalmotorsports.com for some good info. If you are close to MI maybe he could even do the job for you.
 

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+1. The recommendations are from your machinist are OK. In-fact, unless you expect to race it, plain cast pistons are a viable option as well. Hyper pistons are an upgrade to both cast and forged pistons in the proper applications. This is why nearly all OEM engines now use them (beginning with turbo engines in the 1970's), and why most aftermarket cast replacements are changing to them. There is a lot to know about hypereutectic alloys and HE piston construction, what their pros and cons are, and how to use them. It is a relatively "new" technology advancement that has changed much in the 30+ years that the technology has been applied.

Unless you are better-versed than your machinist on your engine and it's condition, I would suggest sticking with that. If you question his knowledge or expertise, you should find another machinist. Offhand, unless you have special requirements, a standard Master rebuild kit with cast or HE pistons will do you well. But, I'm not there to analyze your situation or know your special conditions.

David
 

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Discussion Starter · #6 ·
I read a little more into them. From the turbo world, and boosted situations, I have always read that forged was better for longevity, but they expand more than a hyper.
I had an SVO buddy that rebuilt his with hypers, stock shape, same compression, but running 18psi, which should be considered safe. he broke a piston and had to go back to forged.

since hypers hold their shape better, supposedly, you can make a more efficient engine. with closer tolerances. That would be awesome to make the Heavy Galaxie get 350hp with decent gas mileage.

I haven't been able to do a parts look up. I have had to stay late at work, and I live over an hour away, so I haven't had much time.

I am a little worried due to 2 close friends' experience with this machinist/builder, but I haven't heard anything else. The biggest complaint was turn around time.

He typically builds engines for dirt track racing.


The reason that I originally wanted forged and to build the engine strong, was in case in the future. I had a plan that I was kicking around to remove the highbeams, and duct that into turbos, and build fiberglass body panels for a '59 galaxie 500 XL lightweight....... it would have to be WAAAAaayyyyy in the future though.
 

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You also have to consider that most likely if you do put a hairdryers on, the motor may have to come apart first. Ring gap would definatly be different from an n/a to a boosted application. na<boosted

In the drag racing world, the most common among boost applications are forged.

Any reason why you couldnt build it yourself?
 

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Discussion Starter · #8 ·
so far, this is just out for machining, and checking againt parts. He told me he can get parts for a little cheaper than me ordering stright through summit.

I'll be building it when the parts are done being machined. I have considered just having him build it since I am so much shorter on time than I used to be.
 

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Here is my opinion

1 - Getting somewhere between 9 and 10:1 is not precise enough, especially with that 268H cam, and 10.5:1 is way too high

To make sure you maximize power and minimize the chance for detonation, shoot for max 9.75:1 static compression and don't go under about 9.25:1

This means measuring everything, he should calculate compression using a planned deck clearance of no more than .010 with a .041 gasket (common gasket for an FE), actually measure the chambers, then calculate the dish needed to get there. Buy a piston based on what you need to meet your goal

In addition, he should degree the cam to make sure it is where he expects, my calcs all were based on a 106 intake centerline for the 268, if you change centerline or change cams, the compression requirements change

2 - If forged pistons were available, I would not choose hypers.

Yes, hypers will work fine in most instances, however, failure of a hyper is an emotional event usually resulting in a lot more damage than an equiv forged, even if the forged piston fails too

Note that I said you dont NEED to go forged, but there is no reason not to, and Speedpros are as good if not better as the hypers. In the old days forged pistons expanded a ton and were heavy, but these arent the TRW/Speedpros of days gone by, they are decent pistons

As far as holding their shape better, that again goes back to the comment above, in the old days, low silicon content of forged pistons required big clearance and they grew when hot. Not any more.

As far as holding their shape, thats the problem with Hypers...when they fail, although this is an exaggeration to make a point, "glass holds its shape better than wood" but what happens when you try to bend it? A hyper fails by shattering, a forged piston tends to just roll up.

3 - The edelbrock intake is a good choice if choosing an RPM, the stock Performer is a turd and the Victor is too radical for the cam.

4 - The 750 carb is on the large side of OK, anything from 600-750 will work.

5 - Be sure to recurve the distributor, stock FE distributors have too much advance and it comes in too slow. In street driving you'll think you picked up 2 more cylinders with a good recurve

6 - If you can afford any performance head work, now is the time to do it. Port match the heads, clean up the bowls around the valve guide area, and have a performance valve job done. There are cost effective undercut stainless valves out there, search Alex's Parts on Google. It could be a 50 hp difference, even with a mild motor, with no downside on torque.

As far as who buys the parts, doesn't really matter, but he makes a little profit on the parts, you get a little better deal on the build. You buy the parts, he will probably make it up elsewhere.

The real benefit of him buying is that he will be forced to stand behind his work, if you buy it, its almost certain anything that is wrong is your fault
 

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This isn't the thread for it, but I'd really like to know where folks are getting their failure mode analysis for cast, HE, forged billet and conformal forged pistons. Based on real-world info, data and statistics from piston designers, manufacturers and both production and performance builders - the info in this thread is either rumor or assumption. I'll leave it at that.
:frown:
David
 

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Based on real-world info, data and statistics from piston designers, manufacturers and both production and performance builders - the info in this thread is either rumor or assumption.
Everybody knows that 75.2% of all statistics are made up, anyway!
 

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LOL.. yeah, the ones on the internet are anyway. Well, gotta go, I'm meeting this French model I met on the internet. Bonjour!
;)
David

EGGGGZACTLY, its on the internet, has to be true.... ;)
 

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This isn't the thread for it, but I'd really like to know where folks are getting their failure mode analysis for cast, HE, forged billet and conformal forged pistons. Based on real-world info, data and statistics from piston designers, manufacturers and both production and performance builders - the info in this thread is either rumor or assumption. I'll leave it at that.
:frown:
David
In addition, I'd love to see your data, because I am just not hearing the same in my circles

I dont usually quote other builders, but if I quote myself, you won't believe me :rolleyes:

Barry R, who posts here, worked for Speedpro and of course because pretty famous for FE stuff posted this on the FE forum

332-428 Ford FE Engine Forum: hypers

Here is another from him, although admittedly this was a discussion about not enough ring gap, so arguably you could toss this one out, but it paints the same picture

332-428 Ford FE Engine Forum: Its simple - Risk versus Reward

Here is one from a more "reputable forum"

Hypereutectic vs forged • Speed Talk

This one of course doesn't directly support my position as it says hypers are decent, but remember a hyper piston IS a cast piston.

Back to Basics: Preventing Piston Problems: Engine Builder

From the above document....Cast pistons are much more brittle than forged pistons. A ductile forging can often survive a close encounter with a valve without shattering, which is why forged pistons are a good choice for high performance engines.


I am still looking to see if I can find a "credible" test, as in lab based, but seeing a few failed hypers without external help over the years and no forged failures (again without other things bouncing around) I don't see why someone would recommend an equally priced alternative forged piston

Although I do have to say admittedly, a 268H cammed motor can run stock cheapo cast pistons and get by, but hyper vs forged is a cost/benefit issue more than anything else. In a possible misapplication of your logic, I would buy the absolute cheapest piston available regardless of material.

Bottom line, if 2 pistons are similar weight and high silicon, one is cast and one is forged, the forged will be more forgiving. Just like any other cast vs forged part in any earthly made machine
 

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as the engine builder for classic roadsters (cobras) thru the 90s i built a pile of motors from 289s to 427s... we used hyper on everything that wasnt raced or supercharged... hypers fit better and grow less because of the insulating glass ( up to 18% on keith blacks) hit them with a valve and they shatter like a glass plate but do the same to a forged motor and it will wreck something else instead like the block.. we also raced them in the wissota bmod windsors without issue (faster than forged because they reflect heat) at 500 hp we went forged to get lighter is all......
 

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I don't know him or the product, but it seems like a lot of cash for them to set it to a generic non-performance 2500 curve. Be aware, you may catch a rash from Ford guys for having a GM ignition on your car. I don't care, but some do. A lot. BTW - why do you want to change from what you have?

David
 

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