I have a rebuilt 455 with cast pistons and zero deck, TA 288-94H cam. I'm getting now a pair of ported edelbrock aluminum heads. would my bottom end be able to handle the added power or will i need to get forged pistons? I sure rather keep the cast pistons I have and hope for the best tell me what you guys think.
What are your horsepower and rpm expectations? I am far from an expert but I would think the cast pistons would be fine unless your gonna be going to 6000 rpm on a regular basis. As for the rest of the bottom end. Rods and crank should be good to 6000 rpm at least. You need to figure your compression and just make sure you run enough octane and the cast pistons will do fine. Hope this helps and I am sure lots of people will chime in here.
Are they new or used, if they are used have they been notched to run with the cam you are using? It sounds like you will be doing more than just cruising around. You might want to spend the extra money just to be safe. Bob H.
I too am not an expert (compared to many of the guys on here), but I'll give you what I do know. It very much depends on your application for one. As already stated, if you're going to rev it high on a regular basis they're probably not the best choice. Also if you're adding any nitrous or anything like that, it would be ill advised to use cast pistons. The biggest thing with cast pistons that you need to watch for is detonation. Make sure your timing is dialed in correctly (among other things like a well degree'd cam) and you're not getting any "pinging" or things of that nature. For street use and the occasional strip trip you should be ok, but if you hear her ping, back off the loud pedal! One thing I dont see you mention is your compression ratio. Have you calculated your static or dynamic with you specific combo yet? If not I recommend it, that is a good piece of info to help understand your overall combo and how things are going to "play nice" with each other. Now for the disclaimer: There are alot of guys out there who are not fans of cast pistons under any circumstances, and you're going to hear that sooner or later. Are there better choices? Sure. But it all depends on your expectations of your build, your planned use once its completed, and of course your budget. There are a lot of good running engines out there with cast pistons, you just have to be a bit more careful with the tuning. Just my opinion though, and we all know what those are like....
the car will see mostly street use with a bit of acceleration every now and then. We don't have tracks here so maybe a couple street races. the bottom end is new, new cast pistons from TA no notches but the cam is mild .504" lift and RPM range is below 6000. I have zero deck and the edelbrocks have 68cc chambers. as for dcr I really don't know how to calculate it. I'm thinking with the heads i might have little over 500HP so what do you think? will it run for a good while at least?
I personally think you'll be ok, but given the fact that you're at zero deck and its easy to do, I would personally check valve-to-piston clearance to be on the safe side. It only takes a few minutes and a small wad of play dough or modeling clay, better to know whats going on inside you engine than not. Here are some very handy calculators that if you know your build fairly well you should be able to get close: http://www.wallaceracing.com/cr_test2.php http://www.wallaceracing.com/dynamic-cr.php As far as power, its always a guessing game short of a dyno session, but that should be a pretty solid street engine. Its not overly different from my build in some regards. Im running a compression ratio in the low 9's (wish it was higher, but thats my fault) with a 288-92h cam (so a little bit bigger cam), edelbrock heads ported by gessler, a port matched sp1 intake and a set of ta headers. It made hp in the 530's and torque in the 570's on a notoriously conservative engine dyno. Your results may vary obviously, but I dont think you'll be disappointed in the power plant. I wouldnt be!
That cam is far from mild! Piston clearance must be checked with zero deck and no notches with over .500 lift, to be safe. Casts (new) should be good to 6000 RPM as long as it doesn't stay there all day. As long as you don't go too far over 500 HP (closer to 600 hp you get, more borderline you get with needing forged), casts should be fine in this regard too. So pistons should be ok as long as you don't abuse it too hard, and check for valve clearance. With zero deck and smaller cc chamber in those heads you may have interference which can bend your valves if you try to fire it up without any checking. I'm not sure how much material Edelbrock puts on their heads compared to stock, whether the chamber is smaller due to closer tolerances with shrouds, or less distance between valves and deck, or what. Highly advised to check piston to valve clearance. Not a pro either, just giving my 2c. Best wishes Gary
Thank you for your input, I'll definitely check valve to piston clearance first. any input on how much I need? or it's good if it's not touching? I sure hope i'm in the same ball park as your engine, 500hp is more than enough for me
Barring valve piston clearance issues on the lift, the only concern about forged and cast at these power levels is detonation. Cast will not tolerate detonation at WOT very long or at all. The aluminum heads help quite a bit in this case at reducing the chance of detonation, but you'll want to be conservative with ignition timing, not run too lean under load and run good gas and be very aware and listen for pinging under load. Cast pistons can support plenty of HP and RPM, but usually the compression requirements to reach good HP goals enters the domain of occassional detonation during the tuning process or if there is a fuel or spark hiccup. Forged pistons are just more forgiving when things are out of wack.
You're quite welcome. There is a minimum number of recommended clearance, but I'm unsure if it varies from build to build or not. I want to say the "old rule of thumb" is around .080" intake and .100" exhaust, but please DO NOT TAKE THIS AS GOSPEL as Im going from (admittedly shoddy) memory here. As far as the minimum clearance, let a few others chime in and see what they say as I am far from the expert in these parts on such matters
I am not sure if the valve placement in Edelbrock heads is exactly the same as stock heads so you must check for interference with the pistons, especially with zero deck height. The critical valve to piston clearance area would be where the flat piston deck meets the radius of the dish and the numbers suggested .080 and .100 should be fine.
What rocker are you using on the edelbrock head. I think your past the limit of the pistons myself and you are taking your chances. Might hold up for cruising around since you won't be at the track who knows. You will know more when you measure valve clearances
I wish Jim could chime in on the matter, I'm sure he has experience with this. I remember reading a post of his saying he uses notches in engines over .500" lift and 240 duration. mine has exactly that much lift and duration. Jim u out there? lol
I have a SP 235 Lunati cam in my 455 496 lift 238-248 duration no Notches but i do not have Edelbrock Heads so there maybe a difference in clearance..BTW If you want a long lasting running 455, My Opinion is keep the RPM's down below 5500 Your stock connecting rods will thank you..
The cast pistons should work fine. Keep the engine from pinging. I would check piston to valve, use a solid lifter. You may get a break here because the Edelbrock heads have the valves in stock location I believe. This will give you a bit more clearance on the intake valve. Compression should be around 10.25:1. Should run great
