I can not find a website or article that talks about cast pistons and their use. Everyone says go forged and seems to ignore the cast pistons. At what point is a cast piston not good to use? how much power can a cast piston take? Can a cast piston handle under 6500 rpm blasts in a lighweight 90% street car? Not a race car. No nitrous, super or turbo chargers. Just good old fashioned naturally aspirated power.
Depends on how lucky you are...6500 is kind of at the top end of what I'd expect a cast piston to survive. 5500 would be more reasonable.
how much HP you looking to make with it? With in reason sure a cast piston will survive just fine especially in a street car. But at one point does it become the weak link in the bottom end? When you say "lightweight" are you talking 2000lbs or 3200lbs?
There are many kinds of cast pistons. Are we talking stock replacement cast pistons or specialty race type cast?. Hyper eutectic or plain aluminum? Many different manufacturing differences. Modern pistons are a vast improvement on even 15 year old stuff. The killer of cast pistons is detonation. Rattle em and they get real weak real quick. If you are talking SB Chevy. Cast pistons such as Fed-Mogul. 345's will take 6500 rpm all day for years (budget circle burners love em). As long as there is no detonation. The H345 series (hypereutectic) are even better. Will stand small shots of NOS with a competent user.
You will hate forged pistons for daily use. Get a quality pressure cast piston like a sealed power and dont worry. My 327 has seen years of 6800 RPM shifts with no worrys. as long as your under 10:1 with under 400HP and dont use nitrous its the only way to go, longer life and no noise or long warmups. Spend the money on balanceing IMHO.
Did all the high HP cars of the 60's have forged pistons, less than 400hp and stay under 5500 RPM ? NOPE ! my 435" BB olds has seen 7000 rpm on occasion with cast 10.5 replacement pistons , been in car since 95
this guy is right on, on street forged do not last for real race engines off road yes forged is the real deal I used to run stock chev v8 7500 rpm with stock pistons and rods and yes they will live forever that was using the engines for street stock circle track clearanced out forged pistons in a street car will not last too long if you abuse them and if its cranking HP it will be abused and yes detonation will ruin any pistons way back 12.5 pistons would last a little on street gas, now race fuel is needed for anything above approx 8 to 1 if you have a domed piston race fuel and regular gas can be blended to work very satisfactory and I have even run 11.5 cast pistons on a little nitro and they survived
I ran flat-top cast pistons in a small block Chevy street/strip car for years with no issues. With 10.25 compression, I shifted at 6500 rpm in a 3300 pound car, eventually going as quick as 12.02 at 112 mph in the 1/4 mile on a regular basis. Most street driving was to the track and back, 20 miles each way. The rest was racing down the strip. When it was a bit slower (mid 13's) I ran a 120 HP shot of nitrous once in a while for fun. That got it down to 12.50's at the time. Not that I recommend nitrous with cast pistons, but it can be done if you're conservative. For what you're describing, cast pistons should be fine, and will run quieter on the street due to tighter piston/wall clearances. Forged pistons tend to "knock" a little until fully warmed up, since they need more clearance from thermal expansion.
There is a difference between Forged Race Pistons and Forged Street Pistons. The difference is the race pistons have a centered wrist pin that will make more power but will rattle like a diesel. The street pistons have an offset wrist pin that is a copy of the cast piston dimension and run nice and quiet >>>>.
Cast pistons will stand far more than most people realize. I currently run them in my rail and have built many budget engines in a 40+ year carreer for customers who simply could not afford forged. Thinking back I dont believe we ever had a piston failure from one of them. Many perfomance cars in the 60s were built with cast pistons. 383 440 for instance. You dont hear about either of these engine poping pistons. I have used cast factory pistons for experimental engines. I use them as core to make modified pistons from like the 460 from a 400 mopar (Chrysler Power mag, July 97 $1500 econo Big Block) Pistons were a couple of hundred bucks as opposed to several hundred and since we were experimenting anyway we sacrificed them on the alter of perfomance. We still have them though. We did crack a cylinder wall after a few years racing that motor but not the pistons. We raced that engine four or five years then built a forged version with custom made pistons (Ross) I would always prefer to have forged but I do not hesitate to build perfomance engines with cast if necessay. They are a lot better and stronger than you might think. Course for the bigger better longer higher louder crowd this would seem ludicrous. So be it. Don
Engine Pro 5x, good info on the wrist pin location bit. I didn't know that and wondered why my forged pistons in the BB Buick ran quiet - as compared to what others say about forged pistons in general. Always thought it was due to the 9.0/1 CR. I run 87 octane summer and winter and recently have been running a little more advance, both initial and all-in on the mechanical. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~` Dolmetsch, interesting on the cast piston comments. I ran cast in several engines I put together back in the day. The best one was a 335" Olds Rocket making just under 300 HP according to dragstrip times vs weight of the car etc. Been halfway thinking of using cast in the new engine . . . another BB Buick.
I concur, I have ran many a cast piston motor way up on the rpm scale. Its all in the tune as well, I sprayed a few different sbc motors with 100 shot and a crapload of rpm's and have never ever tossed one. I had one I installed a turbo on and ran 8# .....and I flog the living shit out of my motors, worst thing is that you blow it up.....never have....its all in the tune.
Another trick from way back that the old-timer racers used to do is take the original cast off-set pistons and install them backwards as to offset the wrist pin even more. This made more power but the pistons sounded like they were trying to fly out of the engine at any moment. This required a tight straight bore but was short term and cheap h-p method >>>>.
Look at the high end street bike stuff. There are cast pistons running 10,000+ RPM all day. Hypereutectic cast aluminum is really good stuff.
A forged is what you want for racing , nitrous , turbo or huffer ! They will also be noisy until they get warmed up ! They also cost twice as much as a good set of cast ! Not a good choice for a street only engine . For a good engine that you run on the street and have fun sometimes on the track , cast are fine but upgrade from stock ! hyper cast are a good one that will take a good bit of HP . There are many good pistons on the market and you do get what you paid for . Cheap is shit ! So choose wisely for the application that you will be using them on . I don't think you ever gave us an idea on what you are building , what it will be used for or what do you want out of the engine ! This would be a HUGE help in the choice of pistons you will need ! RetroJim
Ok Lippy Her's MORE of LESS !! These particular forged noisy ass centered wrist pin pistons fit a 292 6-Banger !! >>>>.<center> <br /><br /> <br /><br /> </center>
I've been running forged pistons in every thing I own or have owned. 500cid cadillac, 350 chevy, harley panhead, harley evo and never had a problem with noise or early wear. I put 110000 miles on a harley with forged pistons and never had a problem. There is a difference between forged pistons for the street and for racing. Racing pistons are softer to be able to take harder hits from nitro or blower use, but they will not last on the street and yes they are noisy. Street forgings have more silicon and are hyperutectic forgings and will last longer than a cast piston under any circumstances and will run just as quiet if installed with correct clearances. Unless you are building a stock type engine (350hp/SBC or less), I would always use forged pistons. I know that modern production engines run cast pistons and make way more power than that but you need to remember that these engines also have sophisticated engine management systems, knock sensors a.s.o. There was a long thread about this subject on the HAMB some time ago, do a search, there was a lot of good info on that. I would rather spend some extra bucks and have peace of mind (and have the ability to later on upgrade the engine for more power) than to have to worry. Just my 2 cents
Forged are better, but in the 60s I had a 301 in my 57 Vette with solid skirt Jahns cast pistons with .010 clearance that won 48 straight features at Hialeah Speedway in a late model modified then with a cam change went 3 more years on the street before I put a new 327/365 in it. Never did blow it up and it ran 7000 RPMs all the time street racing. A little noisey at idle, pistons sounded like they were swapping holes. I wouldnt worry a bit about using cast pistons.
It's a given that forged are more expensive than cast, OK. Now, in the cost of a complete project ($3,000 upward of $50,000 depending on the build) what percentage is $200-$300 more for forged pistons? In reality not enough to bust the budget. Has anyone ever observed the torture a forged piston wil take? I've seen drag engines drop a valve, wedge the head between the piston and head, beat the head into the top of the piston and still not discintigrate. You can then take that piston and beat it to death with a hammer on an anvil and you still only have one piece of misshappen aluminum The same thing happening to a cast piston will shatter the piston into a dozen or more pieces, allowing the rod to take out the cylinder wall (maybe the whole side of the block), break the cam in a couple of pieces and probably do the same to at least 1 or 2 adajacent cylinders. If cast piston engine comes apart at 6-7,000 rpm you don't have to disassemble anything. You just go down the track with a broom and sweep up the debris, unbolt the carb and distributer and deposit the rest in the nearest trash container. As far as the added noise, I challenge you to detect anything objectionable when high performance exhaust system is employed (you guys with air conditioning , highend stereo systems, heated seats, and power steering need not respond, real hot rods are not so equipped). after 5 miles (at the most) the extra clearance needed for the forging will be taken up by heat expansion and no longer an issue. The valve lash of a .030/.030 Duntov cam will drown out the noise of forged piston slap. Frank
"Another trick from way back that the old-timer racers used to do is take the original cast off-set pistons and install them backwards as to offset the wrist pin even more. This made more power but the pistons sounded like they were trying to fly out of the engine at any moment. This required a tight straight bore but was short term and cheap h-p method >>>>. " Actually I have done this in many motors since the mid 60s. You will be hard put to hear anything and if you do it will only be when really cold. The power difference isnt huge but it is perceptable. As to reliablilty doesnt make a rats tail dfference. I have had reverse hung piston engine run 100,000+ (383 Mopar) if noise was a factor in reliabilty diesels would go about 100 miles in comparison. Since the loud noise doesnt bother diesel owners why should a very slight, maybe you might hear it when cold bother us? A forged race piston with its non offset pin makes more noise and a lot more whan cold. Some foreign makes do not use an offset pin. Seems to be particularily an Nor Amer design. I read once where Smokey Y once stated that he even gets his custom made forged pistons made with backwarsds or reverse offest because of the extra power offered. Back when i was young we had no money for fancy stuff so we did all this stuff because we could afford it. Because if course it cost nothing. It was the normal way we did things and we did not suffer early failures . I dont recall ever hearing a slap either even though we were warned. I think it is right up there with the story that plastic timing chain gears were quieter than steel or iron ones. Could be but if it is not distinctly perceptable to the naked human ear then i choose power over quiet everytime. In my book on BB mopar we recommend reverse hanging the pistons. Why ? Because when we do we go faster and there appears to be no actual real life downside. Don
Reverse-offset piston pins have been tested. Actually, positive, centered, and negative pin offsets were tested on the same engine, in controlled ambient conditions, with a highly calibrated dyno. In a NASCAR engine shop. I know this firthand, because I designed the pistons. No HP advantage was obtained from either offset. In that series, if there was any advantage, even 2 hp in a 800+hp engine, they would be using it. Positive offset is purely a noise reduction feature. As someone else above has said, if we had a better idea of the application in which you will be using these pistons, we could make a better recommendation. engine type? CI? horsepower desired? weight of the car? Al or iron heads? FI or carbed? Detonation will kill pistons. Period. Cast, forged or even steel pistons (altho it takes over 3bar of boost to do so). Better to tune a little on the fat side, than burn down a motor.
Until now, I have always gone to the vendor that sold the cheapest piston and bought them. Been trough a lot of motors, never busted a piston. Never asked, but I'm guessing most have been cast. When I upgrade the 292 with valve-work and cam I'll no doubt use forged. Forged are noisy? Give me a break. Running clearances/dimensions are the same, forged are stronger than cast.
Every Mustang GT from 1985 through 1992 used forged pistons from the factory so any argument that they are noisy or not going to live on the street is hooey in my opinion. That said, I have a thing for FE's and I like the 352. It's super cheap to buy because everyone thinks they are a waste. Build a 390 or a 438 is what I see or hear all they time. Phooey! I would like to put a nicely dressed 352FE with a comp cams 292 cam, lightly worked OE heads, a 2x4 intake with two small carbs (like 2 little 480 cfm 1.08 Autolites) in a t-bucket. Back it with a built wide ratio, shift kitted C4 (because they are small) and a 3.25ish geared 9" or Explorer 8.8". When I say light weight I mean under 2000 lbs. I'd likely make a drag strip pass once and a while unless they said I needed a roll bar and then I'd not make anymore passes. I'm talking near daily use in the summer months and spirited street rips. Probably not even see 6000rpm. Probably make less than 400 hp.
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