piston weight

[piston guy]

Thanks Stan!
It's amazing to see how 14 grams becomes 200 lbs of force at 8,500.

[RDY4WAR]

Piston weight in a street build is not as important as in a race only build. A 4" stroke engine hits over 10,000 fpm by 73 degree ATC @ 8900 rpm. Doesn't everyone try run the lightest piston without sacrificing the integrity of it; I know I do.

This is what I figured. I'm putting together a 393w for a F250 for a towing application. Choice of Keith Black pistons that are 620 grams with 5/64" rings or Mahle pistons that are 477 grams with 1mm rings. On an engine that'll never seek over 5000 rpm, I'm not sure if the few hundred extra for the Mahle pistons will be worth it.

[Mark O'Neal]

Moe used to tell me that 33 ounces at 10,000 rpm is 20 tons.

It amazes me that any of these things stay together.

[statsystems]

Piston weight in a street build is not as important as in a race only build. A 4" stroke engine hits over 10,000 fpm by 73 degree ATC @ 8900 rpm. Doesn't everyone try run the lightest piston without sacrificing the integrity of it; I know I do.

This is what I figured. I'm putting together a 393w for a F250 for a towing application. Choice of Keith Black pistons that are 620 grams with 5/64" rings or Mahle pistons that are 477 grams with 1mm rings. On an engine that'll never seek over 5000 rpm, I'm not sure if the few hundred extra for the Mahle pistons will be worth it.

I wouldn't use any piston with 5/64 rings. For anything.

[engineguyBill]

This is what I figured. I'm putting together a 393w for a F250 for a towing application. Choice of Keith Black pistons that are 620 grams with 5/64" rings or Mahle pistons that are 477 grams with 1mm rings. On an engine that'll never seek over 5000 rpm, I'm not sure if the few hundred extra for the Mahle pistons will be worth it.

The "heavy" KB pistons and thick rings will work just fine for your application. 5/64" compression rings have lost their desirability in the high performance world for obvious reasons, therefore it is almost impossible to find these rings with features such as steel or ductile iron materials, plasma moly or gas nitrided coatings; Napier second rings, etc., etc. But the rings will work well in conjunction with the heavy pistons for a towing application.

[MadBill]

.. Choice of Keith Black pistons that are 620 grams with 5/64" rings or Mahle pistons that are 477 grams with 1mm rings. On an engine that'll never seek over 5000 rpm, I'm not sure if the few hundred extra for the Mahle pistons will be worth it.

If you know/can find the weight of the stock pistons it might influence your decision, e.g. if the KB anvils will require tungsten slugs for balance, the Mahles might be cheaper in the long run.

[RDY4WAR]

.. Choice of Keith Black pistons that are 620 grams with 5/64" rings or Mahle pistons that are 477 grams with 1mm rings. On an engine that'll never seek over 5000 rpm, I'm not sure if the few hundred extra for the Mahle pistons will be worth it.

If you know/can find the weight of the stock pistons it might influence your decision, e.g. if the KB anvils will require tungsten slugs for balance, the Mahles might be cheaper in the long run.

That's a good point I hadn't given much thought. It's a virgin Eagle cast crank 3.85" stroke which is the only part acquired so far. Everything else is up in the air. There's no real budget, just so long as it'll make enough torque to haul the car around, can run on 87, and keep itself together, I'll be happy. That said, if there's anything that can be done to improve upon it as it's going together (thinner rings, less inertia, tighter quench, better valve angles, roller rockers, etc...) that could add up to something noticeable in power and longevity, it may be worth it. Even pulling just an extra 1 mpg out of it (11 mpg vs 10 mpg while towing) would pay for itself in just a few years with how much this thing gets driven. It's got a tired 351w (298k miles) in it now that gets about 8 mpg and struggles.

[rfoll]

It's amazing how much money a 1 mpg improvement can save when you are only getting 10 mpg. At current fuel prices it's over $10 every 300 miles.

[David Redszus]

It's amazing how much money a 1 mpg improvement can save when you are only getting 10 mpg. At current fuel prices it's over $10 every 300 miles.

Gasoline is cheaper than milk and much cheaper than beer.

[piston guy]

RDY4WAR,

The toughest thing to do as a "racer" is not "overbuild" it. If it's only going to 5,000 max there is no need for a 6,000 rpm cam , manifold or heads. I recently built a 521 Ford stroker for my F350 box truck race car hauler. Two goals in mind TORQUE and still pass emissions ( CA required). The original plan was a mild hyd roller, aftermarket aluminum intake and heads. Went with a "tiny" hyd roller , 9.2 compression , Production iron big valve ( PI) heads and big port iron ( SCJ) intake. The results were 515hp @4,800 BUT 628 ft lbs of torque @3050 rpm. The low end torque would have suffered with the "hotter" parts and made power beyond where the engine runs. Emissions would have been a challenge but now pass with flying colors. In fact they are less than the tired original 460!
Properly done , I could see a 392 with 400 hp ( easy) and 500 tq on 87 octane that would work with the stock torque convertor and get better mileage.

[RDY4WAR]

RDY4WAR,

The toughest thing to do as a "racer" is not "overbuild" it. If it's only going to 5,000 max there is no need for a 6,000 rpm cam , manifold or heads. I recently built a 521 Ford stroker for my F350 box truck race car hauler. Two goals in mind TORQUE and still pass emissions ( CA required). The original plan was a mild hyd roller, aftermarket aluminum intake and heads. Went with a "tiny" hyd roller , 9.2 compression , Production iron big valve ( PI) heads and big port iron ( SCJ) intake. The results were 515hp @4,800 BUT 628 ft lbs of torque @3050 rpm. The low end torque would have suffered with the "hotter" parts and made power beyond where the engine runs. Emissions would have been a challenge but now pass with flying colors. In fact they are less than the tired original 460!
Properly done , I could see a 392 with 400 hp ( easy) and 500 tq on 87 octane that would work with the stock torque convertor and get better mileage.

The top end is somewhat figured out. I was just gonna reuse the 351w heads and just clean them up. With a -22cc piston, it should be about 9.1 compression with a .039 gasket and zero deck. The cam I haven't thought too much about yet but thinking something that'll be easy on the valvetrain like a Comp High Energy 268H or similar. I plan to reuse the Weiand stealth intake and Holley 600 that's on it now. I might switch to a FiTech throttle body EFI if there's any mpg advantage. It won't make squat for power above 3500 rpm but it also doesn't really need to. My thoughts with the pistons is longevity and efficiency based.

I have considered the big block route. I have a '78 460 block sitting around that just needs to be cleaned up. I'm hesitant to build it for the reason you mentioned... "overkill." I fear the bigger cubes and heavier engine would just hurt mileage while not giving much towing advantage. If I'm entirely wrong about that, please let me know. The thought did just cross my mind that I might could run a taller gear with the big block to let it cruise 400-500 rpm lower and still have sufficient towing power.

[piston guy]

Don't underestimate the factory iron 4V intake. I WILL make more torque than the stealth. I had the same situation to deal with. The problem you would see with the 460 is the extra weight hurting the mileage a bit. In my case the engines are the same weight ( virtually).

[rfoll]

I recently made the change from a 402 BBC to a 400 SBC in my C20. No comparison at all. The big block made way more power than the tired 350 with 172 valve 882 heads that came in the truck, but the 400 SBC makes more torque in the lower rpms where a truck lives. The bonus was an additional 2 mpg, and removing 150 lb. from the nose of the truck.

[amcenthusiast]

Newton's three laws is where one might start to learn the scientific explanation.

Those laws of Physics have not changed since.

The heavier pistons will require heavier counterbalancing.

The increased inertia will require more fuel to match the former acceleration rate of the lighter components.

Basically the goal is the opposite from the proposed question.

[rustbucket79]

Bin the factory Windor heads for E Street heads (1.9" intake valve models) and you will be much closer to your goals. The dished pistons you mentioned with a little decking, shooting for 9.5:1 and a mild cam in a 392 will give you a bunch of torque where it counts, close to 350 hp, and great fuel economy too.