I want to thank ALL who posted on this thread.I learned ALOT and i thank you all for it........................YG Almost forgot....One post said he thought the piston pin looked short (maybe due to pic) and i agree .Any thoughts on this i read all the post and didnt see it..........YG
What does the kind of car and intake have to do with pressed or bushed pins ? Some of you guys got to remember this is no all out drag car with a no expense high dollar budget. It was a mild engine in race car terms and also a car I put together to have fun with, not a full tube chassis win at no cost deal. I paid to have an engine built that freaking blew up ! I don't have much money and sure don't have the money to build engines you guys in your hind sight views think I should have built. Believe me I wish I could, because I would still be having fun and not sitting here reading everything I did wrong.
I'm no expert on car pistons, but a company I respect in the motorcycle world published this. <TABLE style="BORDER-COLLAPSE: collapse" border=0 cellSpacing=0 borderColor=#111111 cellPadding=0 width=572 height=210><TBODY><TR><TD height=35 width=600>Hypereutectic Pistons </TD></TR><TR><TD height=160 width=600> There's a lot of talk about Hypereutectic pistons and their applications in performance engines, and we get asked about them a lot. I put this page together to share our view on them. A hypereutectic piston is a cast piston that contains a silicon content above 12%. Silicon levels above 12% do not fully dissolve in the aluminum and thus create hard particles, contributing to increased hardness and wear resistance of the alloy. The harder material offers some opportunity for weight savings versus other cast piston alloys. Similar to the factory cast pistons, a hyper's coefficient of expansion is lower than that of a pure forging, and as a result, they can be fit tighter than a forging. Typical piston to cylinder clearance for a cast piston, whether hyper or not, is .0006 to .0017. By comparison, forgings are typically fit anywhere from .0020 to .0030 in a Harley engine, depending on the application. The combination of a harder material that can be fit tighter is touted as an advantage, because in theory fitting a piston tighter promotes good ring seal, particularly when cold, and to do this with a harder material simultaneously provides good wear resistance and long service life. Furthermore, a cast piston generally costs less to manufacture than a forging, once the molds are paid for. This is why the vast majority of OEM high volume production pistons are cast rather than forged. So why don't we use hyper pistons? Well, despite the aforementioned advantages, there are some characteristics of hyper pistons that we don't think work well in air cooled Harley motors. In particular, the hyper material doesn't shed heat well. This forces certain compromises when used in an air cooled motor and we don't think the compromises are worth it. Because the hyper material holds heat so badly, the rings try to get really hot. The hyper piston makers try to address this by asking tuners to take timing out of the motors, and also moving the ring pack down the piston, farther from the combustion chamber. They also generally specify larger ring gaps to try to avoid ring butting, but unfortunately, ring butting and the subsequent damage is not nearly as rare as it should be when using hypers in a Harley motor. When a ring butts hard, it sticks the piston in the bore. It's not at all unheard of for the piston to literally rip the pin boss out of the bottom of the piston when this happens. The above was assembled by an outstanding mechanic and fellow salt flats racer with a great deal of experience with hypers. This is a guy who's anal about building motors; he checks everything. he's both a fierce competitor and one of the very few people I would personally trust to assemble a motor for me if I were inclined to do such a thing. He told me point blank that he would not be installing any more of them after he saw this. This is the most popular brand of hypers for Harley motors, too. An even wider ring gap may have avoided this, but this negates one of the supposed advantages of a hyper, good ring seal during warm up. The other problem we've seen with hypers is that they're just not tolerant of detonation the way a forging is. The material is hard but also more brittle, and breakage between the bottom of the valve pocket and the top ring groove isn't nearly as rare as it should be, despite the lower ring pack. So for those of us who like to push the envelope, whether normally aspirated or boosted or using nitrous, hypers are not a good choice at all. We're not the only ones who've seen this, either. Even Wikpedia acknowledges poorer resistance to knock with Hypers. Finally, hypers are often more difficult for the do-it-yourselfer to install, because the lowering of the ring pack may put the wrist pin into the oil ring groove, depending on the specific application. The simple method of installing pistons by first preassembling them into the cylinders and then putting the cylinder in place and sliding the wrist pin through won't work on these type of pistons. You must use a ring compressor to slide the cylinder down over the supported piston while the piston is already attached to the rod. Bottom line, at first glance the hyper seems to offer some advantages in the way of quiet operation, longevity, and low cost. But in the real world, in high performance applications, we've found the disadvantages to outweigh the advantages. When I've got a street motor that's built on the verge of being able to use pump gas, and I get caught in slow traffic on a hot day, I'm a whole lot more comfortable knowing I've got forged pistons banging around in my motor. Your mileage may vary of course, and we have no doubt that there are many builders who disagree with us, but this is where we stand. If you're determined to use hypers in your project, we can certainly provide them for you, and we can precisely bore and hone your cylinders for the correct fit. We highly recommend, though, that you get the domes coated with a quality thermal barrier coating. That'll give the pistons a better chance of survival. Also make sure you tune the bike right, as all our data indicates this type of piston leaves less margin for error. </TD></TR></TBODY></TABLE>
Now, I hate to say it, but that broken piston looks a lot like the one that failed for you. Just a little to think about. The Wikipedia reference is correct.
Some experienced builders will design a combination, to run at low operating temps, trying to squeeze a little more power. But everything has to work together to make it live.
I built a mild flat-top 350 Chevy for a buddies Corvette back when KB Hyperuetectic pistons first started getting popular. It ran fine for almost a year. Then a piston disintegrated and took out a cylinder wall with it. I haven't used them for another build since and don't intend to. I think they are too brittle and when they break, they really break. For inexpensive, mild engine builds I prefer a good quality regular old cast piston over a Hyperuetectic. I've had standard cast pistons crack a skirt, collapse a skirt, burn the top ring lands or crown, but they usually don't explode. For more serious builds, if it's going to get beat on a lot, they get forged pistons. Besides, forged pistons for SBC's are cheap anyway.
Can we get a specific part number OR brand on the pistons?? The KB hypers are the only ones with a ring gap issue, the Speedpros aren't affected by tight gaps! The post above with the tops pulling off the pistons is accurate! Your builder should have gone over all this before it began. Harry
This is a very interesting read as I build bikes too. However I'm not certain that it would apply to a liquid cooled engine. An "air cooled" engine does have inconsistant heat issues between cylinders. In this case the front cylinder will run much cooler than the rear will and that shows in your big twin photo. The rear cylinder is what let go because it runs much hotter. Thanks for the informative post "Xea". X2 Dooley... X2
Yup, I've had enough of reading everything I should have done ! I said in my first post I didn't understand nor believe detonation did this to my engine. Some great things were pointed out during the discussion pertaining to that and I thank those for that input.
Hey Phil maybe you should have seen Billy at Oddy's about one of those $75,000.00 blower engines maybe then you'd have all the bases covered.
Phil : Your car looks great and I certainly feel your pain ! I listened to the experts when I originally built the 392 and purchased all the rotating assembly from the experts, and what happened ! The motor blew up ! We are just week end warriors who want to re-live the good 'ole days of drag racing in a car which is kool, and your 'J' certainly fits the criteria. This sport is expensive, espically when funds are tight these days. You did what you thought was best and had done what you thought was best. To hell with a response which "may be" negative. Text messages are very misleading sometimes as they are very impersonal. Build that motor again and go do what everyone else wish they could do. Remember, alot of people feel your pain and wish they could be in your shoes with that great ride. How may people actually have a drag car who are giving you this great advise ? See you soon, don't sweat it buddy !
Phil, probably not the response you bargained for, but an overwhelming one never the less. There's a lot of experience that comes with 100,000 (or more) members. Show them a blowed up Chevy and it's like showing a hungry dog a steak. Everybody gets crazy. Opinions are like certain body parts, everybody has 'em. Everybody feels your pain and everybody wants to help. That's a good place to be. Try what I suggested about putting the next one together yourself (put the money saved into better pistons or whatever) and get ready for next spring. You could pull the engine out of the roadster and put it in the Henry J if there is any racing season left. You know that bullet is good. Be thankful that you and your car have generated so much positive interest. Some people come on here and don't get past a couple of "so what" responses to their question. Think of all the love your gettin' ! By the way what is the diff with a Canadian Chevrolet block? If that one lets go you can always blame the Canadians (old South Park reference). Keep us posted, John
The company I work for builds hundreds of motor per year, the vast majority going into racing applications be it circle track or drag racing. Several years ago we stopped using the KB brand of hyper pistons all together after they made a change to their upper ring land. I do seem to remember us experiencing a higher volume of pistons coming apart with the KB brand than we did with the Speed Pro brand. Most of our entry level motors get a Speed Pro, and live fine in hobby and stock car classes turning close to and over 7000 rpms for 25 laps. The extra attention needed for the upper ring on the KB piston is not worth our time to mess with when the Speed Pro brand is usually cheaper, and in most cases stronger due to KB's upper ring lade design, and it seems to me we had problems like you are mentioning here. It is possible it was just a weak piston, and thus being weak, it had even less tolerance for detonation than hypers usually do. If you engine builder is well known for good service, and a reputation for treating his customers fairly, I would say he may be telling the truth. If you do not feel like you are getting the truth, and want a second opinion, do not hesitate to take it to another shop.
Responses all well and good. Probably the builder has never had this experience (esploding KB pistons). Might have had good experiences with KBs. Maybe the builder should have checked with the HAMB first? Builder making good. All is well in the world. I tend to be on the builders side. ALL humans make mistakes. He was probably told by HIS wholesaler that the pistons were the best thing since sliced bread. If he called KB do you think KB would tell him not to run their pistons? The ignition breakup concerns me more now. Borrow a known good points distributer and run that . Whats in the roadster? If HEI, put it on a distributer machine. Couldn't hurt. John
I just want to say that there were some great advise and angles on this thread and I appreciate it. One of my pet peves is the hind sight thing, everyone knows the answers after the fact. I can ask someone what they think the problem might be if the car is not running right and they have no idea. Sure as shit as soon as you find the problem and relay it back to them of course they knew exactly what the problem was, can't stand it ! That being said, the new engine will have forged pistons and make sure it has good rod bolts. I'm also probably going to go with a MSD 8570 distributor as I save up the coin for it. I hope it stays together and one way or another you guys will know. One Finger John the distributor in the roadster is a points style with a Crane Xri ignition module in it. It was set up on a machine with the points still in it, then later switched to the module for the rev limiter benefits. The last race is tomorrow and I have no plan to swap engines, I have a back problem and the amount of work is just to much. I've got 6 months to get this car ready again and it might just take all of it.
I wish all goes well for this incarnation of your engine. Sounds like you have moved on to a stronger combination. Keep us posted.
I'm running the exact same distributor combo and I haven't had any trouble as of yet. I was at the track the other night shifting at 6000 rpm. Sorry to see your engine scatter, I hope you get it back together for next season. Good luck!
...The illiteracy was always there just waiting for the right moment to shine. One of the good things about English being such an advanced language (still evolving) is it's developed to the level where you can craft a statement in English that has only one proper interpretation. Other older languages rely more on which words are used, inflection and such and how the person is using it in the personal encounter. But they don't evolve as well because it isn't deemed appropriate to change anything... where as English has a solid underlying blueprint to build on that is open to slang and allows a lot of word substitution without changing the meaning. In English it means everything where the words are placed and how the words are puntuated and not so much how the person using them feels about what he's saying... unless we get into swearing lol. that's a colorful art and all about the heart lol
Im with unkl ian how does detonation pull a wrist pin out of a piston? I would bet that the pistons were cast kb hypereutechtics. If so you may want to look at a forged piston on the next engine. The keith blacks wont take high rpm for very long. Sorry for your loss
Since this was brought back around, I will give an update not an english lesson, not even old english the cologne lesson. The engine builder ended up sorting through the old pieces and inspecting/measuring to make sure those that were good were actually good. He machined the new block which consisted of boring,align honing,decking and clearencing plus massaging oil passages in the valley. He only charged me 400.00 for that, through in a set of forged rods and assembled the new engine, also included blending the heads where they got banged up. The rest of the parts, forged pistons,ARP bolts, intake/exhaust vlaves,oil pump, bearings,soft plugs etc. were sold to me at cost. This engine was run on his engine stand before leaving and other than a vaccume leak at the carb gasket and short fuel supply it ran great up to 5700 rpms. At that point best to fix the fuel and vaccume issues so I brought it home. The important part is I felt he did me right and I hope this one lasts much longer.
Glad you are happy with the outcome with the builder and he worked with you. Hope you have better luck with this one.
That's the piston setup I had on a race motor in my old Vette. The motor gave me problems after 3000 miles. The JE pistons are good, but the skirts are very short & use full floating pins, and they require aftermarket only 6" rods. Probably ok with Carrillo or Manley rods, but not the cheaper Chinese H beams. FWIW, it might be better to stay away from these 383 stroker kits. For what I had in mine, I could have built a nice 427 big block. Since then, I am a big believer in factory parts, and US made [expensive] parts. No offshore stuff. If you are limited to a small block only, you may want to consider building a 355. After my 383 problem, I built a '70 LT-1 spec 355 motor with ALL gm parts> forged 350 crank, press-fit rods, TRW forged 10 to 1 pistons. I did step up to better heads - Dart 200 Pro 1. This motor has held together now for 11 years and 50,000 miles. The popular 383 is overrated in my book. I can understand your sadness. I have been there before.
Swade41, I know exactly what you mean. I go through the same from time to time. There are days when we take the digger to the track only to be told that we are doing EVERYTHING wrong! One says the nozzles are too big - the next says the nozzles are too small! Even down to using the wrong aluminum polish on the body! Most of the time it's comical other times it gets mighty old. The bottom line is that YOU are out there doing it! I'd rather make the mistakes and learn than to sit back and just keep dreaming. Lots of experts at the track and here on the net - some actually are others just think they are - just focus on the fun - the good ones have a way of bubbling to the top! Sorry to see the carnage - glad to see you bounced back and got it together. More impressed that your engine guy made a real effort to get you going again!! Looking forward to see you tearing it up again!!!! Edit: Opps! That may not have sounded right - by tearing it up - I mean the strip!!!!!!!
Glad it all worked out for you Philip. In a few months we'll be back out there and I'm going to need a new arch rival. LOL I may have a surprise for you.
Hopefully I can get it to Thompson this year and run with you guys, well not run against you cause you'd whip my ass, but you know what I mean. Jeez Art, I race one day and you are building a better engine ? I just asked Leroy this morning if he thought you'd step the motor up or not...lol
Leroy who? Haven't heard from him in a week. He's finally putting a motor in his truck...after four years!
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