Hello HAMBers, I am currently looking to build a 327, going for around 350-400hp. I will be driving the car around regularly, but will stomp on the gas on occasion and have some fun with it. Long story short, lots of street use. I am, however, stuck on what pistons to go with. Do I want cast or hypereutectic? I have read on the benefits of both, but I am still unsure of which to use for my application. I am going with either Silv-o-lite cast or Keith Black hypereutectic. Thoughts? Also, what would be a good cam to use? I don't wanna over-cam the engine, as I have had problems with unintentional jackrabbit starts with my old engine in the past. Any and all input will be much appreciated. Thanks guys!
Hypereutctic has to do with the silicon content in the aluminum. 375 hp is not a problem with correct compression ratio and camshaft selection. Hyper E doesn't like nitrous from what I think I know. Best street cam overlap will be at 112 degrees for the street and 110 degrees for some of the sound that is less than Comp's Thumper series at 107 degrees. A cam will sound "snotty" with overlap < and lift numbers > that will have a tendency to not be as streetable with a heavy car with an auto trans. Many more variables that what I have started on. Old engines that are worn have a tendency to dislike combustion pressure changes due to a change in cam profile. Do a full rebuild? Might be better money spent.
The Hypereutectic pistons do not like any boost, so if your thinking blower, nitrous or turbos down the road, stick with cast or better yet, put forged pistons in it.
Thanks for the input so far guys! I should note, there will be no NOS boost. Just good ol' fashioned carburetion. Ooops, I meant Cast in the thread ***le, not eutectic, but aren't those the same anyways?
Hypereutectic/eutectic are a CAST piston. They are just of a higher silicon content in the aluminum; the more silicon, the more "brittle"; and, they tend not to break as much as shatter. This occurs with detonation/nitrous-fuel lean out conditions/higher CR's. IF you run everything "right", "all the time", you're fine. Regular cast pistons tend to be more forgiving under the same conditions. But, the car companies started going with the hypereutectic, to save money over forged, and being computer controlled and all, and you know who followed, the piston manufacturers. If you're going to be at all hard on the motor, go forged. If it's mostly a daily driver, go cast. I'm building another 327 also, and have FOUR sets of pistons to decide on using; the forged flat tops, the forged factory style hi-perf piston, a flat top rebuilder set, and a set of flat top Speed Pro Hypers. I won't be using the Hypers for sure, and they are for sale, cheap. Me personally, I'd also stay away from Silvolite/K.B., just due to the upper ring land/heat/ring end clearance problem so many seem to have with them; if you like file fitting rings go ahead and use them. I'm certain not everyone will agree with me on this, but hey................ The other thing, try and find a NOS set of pistons, otherwise you'll be buying "Made in India" pistons. Butch/56sedandelivery.
http://www.jalopyjournal.com/forum/showthread.php?t=655194&highlight=hypereutectic http://www.jalopyjournal.com/forum/showthread.php?t=474343&highlight=eutectic I don't profess to be an expert but found # 153 interesting, entire thread is worth a read
for a daily driven street car with out nitrous or blower the hyperutectic pistons are great. forged are only really necessary when your getting up there in power and have a blower nitrous etc etc alot of the pistons made today for normal rebuilding processes are hyperutectic. cast pistons are usually found in cheap rebuild kits or harder to find pistons for odball motors, alot of the kanter kits are cast pistons. jeff
I ran hypereutectic pistons in one of my stock cars engines years ago. The short block consisted of stock rods and crank with the HP345 hypereutectic pistons. I was racing on an extreme budget, but did opt to have the ***embly balanced. It had camel hump heads and a .485 lift hydraulic circle track cam. I would turn that little motor 7400 rpm every weekend. The motor had well over 1000 laps, both dirt and asphalt, before it let go while leading a race. I believe that motor would still be running today, but I got greedy and put some 1.65 rockers on without checking the valve to piston clearance. I was thinking the valve reliefs were deep enough; expensive lesson learned. My engine was used for something totally different than what youre using yours for, but the hypereutectics are decent pistons and can handle some abuse. That engine ran and won against others that were dynoed in the 450hp range, so I believe mine made over 400hp; never dynoed though, too broke. I think they'll work fine your application.<O</O
All great info guys. I guess the question now would be which piston is better for cold weather start-ups, and stop-and-go traffic: cast, hyper, or forged? This might just be my biggest concern.
I had hyper e's on a 302 with a blower did not last long. from what i remember the upper rings need more attn. but to the point of having a goal and building to it, the blower was an after thought. .02
Hypereutectics (good or bad) were designed exactly for that purpose. They are high in silicon reducing their expansion and thereby allowing tighter machining tolerances. This was EPA driven in the 70's
Here is my advice.... Call S.R.P. Sportsman racing products. They are the best value for the money. Call their tech and ask them. 350 or 400 hp isnt that much to worry about. UNLESS, your plannin on N0S. I am runnin SRP pistons in my Mustang, 15:1 and have beat the hell out of it at the track since 2003. What ever they recomend, is good for me.
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