polarisman14 Posted June 5, 2015 Report Share Posted June 5, 2015 (edited) I recently tore into my engine to do a full rebuild on it. I found some interesting stuff in there. A rebuild tag, some flat-top pistons that have nothing, and I mean nothing, on the top besides .75 stamped into them (.030"/.75mm over) and the crank was balanced and cut to .010"/.25mm undersize. What I need is some help identifying the pistons. They are definitely cast but almost the entire outside of them is machined and it has vertical slots machined into it every half-inch or so on the piston skirts. I've been looking for a while and can't find anything that looks even remotely close to them besides the sealed power ones which are coated on the sides and have no marking on the top. I'll post up some pictures later but I am just asking if anyone even has ideas of what they could be. It was running a head gasket that was .060" when I took it out, I take it that is the "compressed" size so it's .025" thicker compressed than stock. I'd like to put a stock gasket back in there and raise the CR the half-point or more that it would as long as it won't cause timing issues or clearance issues with the valves as there are no reliefs in the piston tops. I also need to figure out my new CR once I do that. Thanks in advance, Matt Edited June 5, 2015 by polarisman14 Link to comment Share on other sites More sharing options...
NotStock88 Posted June 5, 2015 Report Share Posted June 5, 2015 Pictures? Link to comment Share on other sites More sharing options...
polarisman14 Posted June 5, 2015 Author Report Share Posted June 5, 2015 (edited) Here we go. Apparently I misspoke and they are horizontal lines not vertical. It is more obvious on the piston on the table. I don't have any pics of the top but it is flat and just says .75 stamped into it dead center, that's it. http://i512.photobucket.com/albums/t324/polarisman14/StarQuest/pistons.jpg Edited June 5, 2015 by polarisman14 Link to comment Share on other sites More sharing options...
StarquestRescue Posted June 6, 2015 Report Share Posted June 6, 2015 .75 is .030 over. We need pictures of the top, And the underside of the top. Even shelf wisco's or ems wisco's have some dish. Truck or custom would be flat. Link to comment Share on other sites More sharing options...
polarisman14 Posted June 6, 2015 Author Report Share Posted June 6, 2015 (edited) These are flat. No dish, just flat. I think I am going back there to work on the car today so I can get some more pictures but let me assure you that there is 0 dish on the top whatsoever. I just can't find any pistons for this car, even for the d50, etc that have the horizontal grooves machined into the skirts like that. Edited June 6, 2015 by polarisman14 Link to comment Share on other sites More sharing options...
tsi_tom Posted June 6, 2015 Report Share Posted June 6, 2015 Weren't you the one with the bad balance shaft bearing? Link to comment Share on other sites More sharing options...
polarisman14 Posted June 7, 2015 Author Report Share Posted June 7, 2015 That'd be me, yes. I did the rod and main bearings with the engine in the car a year or two ago and had some trouble-free miles after that but the leaks I had everywhere were a bit too much so I decided to pull the engine and fix it the right way. While it's out of th car getting seals replaced i'm refreshing all bearings and rings. Since I'm an idiot I need to issue an apology to you guys--I was pretty adamant about them being flat top pistons but apparently my short term memory blows. They are dished just like stock pistons. Good thing I'm not on the witness stand or anything . Link to comment Share on other sites More sharing options...
ucw458 Posted June 7, 2015 Report Share Posted June 7, 2015 I just can't find any pistons for this car, even for the d50, etc that have the horizontal grooves machined into the skirts like that. Almost all pistons have grooves like that on the sides. They all spin on a lathe to produce the round shape. Some companies pistons have finer grooves some coarser. Some polish the sides a bit. Doesn't always show up in pictures but when you see them in person you see the fine grooves. Link to comment Share on other sites More sharing options...
polarisman14 Posted June 7, 2015 Author Report Share Posted June 7, 2015 http://i512.photobucket.com/albums/t324/polarisman14/StarQuest/0606151357.jpg http://i512.photobucket.com/albums/t324/polarisman14/StarQuest/0606151357a.jpg So, now that you have the pictures and the CORRECT information, what do you think these are? Just cast replacements from clevite or someone that are .030 over? Any idea how to measure the compression ratio? Link to comment Share on other sites More sharing options...
freebird Posted June 7, 2015 Report Share Posted June 7, 2015 yes that has a dishand just a oem replacement bored over piston Link to comment Share on other sites More sharing options...
StarquestRescue Posted June 7, 2015 Report Share Posted June 7, 2015 Surely just a stock compression cast replacement. There were numerous brands. None stood out from the rest. Link to comment Share on other sites More sharing options...
polarisman14 Posted June 7, 2015 Author Report Share Posted June 7, 2015 Nice, good to know. I kinda started the thread when I thought there may have been some kind of special aftermarket pistons in there but it's good to know what I am working with. Now to see if I can get past the 350whp mark with them. Link to comment Share on other sites More sharing options...
freebird Posted June 7, 2015 Report Share Posted June 7, 2015 yea, their not forged or hyperutectic......i'm pretty sure....just a cast aluminum piston for .030.I also have the same piston here for another block. If you have high goals of HP why not use a wiesco? Link to comment Share on other sites More sharing options...
polarisman14 Posted June 7, 2015 Author Report Share Posted June 7, 2015 Because 350 isn't high. More than a few people are runing at or above that level on stock internals. My long term goal is to put some wiseco 7.8;1 pistons in there to improve the spool a bit and step up to bigger injectors and meth injection to get over the 400 mark with a longer powerband due to quicker spool. I just don't have 2500 bucks laying around. Link to comment Share on other sites More sharing options...
polarisman14 Posted June 8, 2015 Author Report Share Posted June 8, 2015 And just for reference I got my parts in the mail today--Enginetech coated main and rod bearings and piston rings. Not sure what they measure yet as I haven't put them in the cylinder bores but I will be doing that Thursday. I don't think they are file to fit but if they are on the tight side I'll be opening them up a few thousandths to the .018"-.020" range to make room for bigger boost (20+psi as I am already running 22 and plan on going higher) and higher cyl pressures. Thanks for all your help guys even with sending you on a wild goose chase to help. Link to comment Share on other sites More sharing options...
StarquestRescue Posted June 9, 2015 Report Share Posted June 9, 2015 Forged is $525 . Now is the time. http://www.enginemachineservice.com/ems/parts/conquest/pistons.php Link to comment Share on other sites More sharing options...
polarisman14 Posted June 9, 2015 Author Report Share Posted June 9, 2015 (edited) I know, I know. If I had the spare money laying around I would do it but if I am going to do that I'm gonna do it all at once and do the pistons, bigger fuel pump, injectors, methanol injection, and a retune to the tune of ~$2000 (ID1000s are expensive!!!). With a 10 month old it was hard enough scraping up a couple hundred bucks just to do the refresh but I want the car to be reliable so I can take the wifey and my little girl out for ice cream . Thursday I will be pulling the valves one at a time and inspecting them--if the valve guides are worn or show excessive play I'll order some of those as well but with the installation being a little more time consuming I'd rather not. At a minimum the valve stem seals are being replaced and I will quickly lap the valves to valve seats with lapping compound. Not looking to take a lot of material off, just cleaning off the mating surfaces to ensure a good seal and compression and putting it back together. Then I'll be honing it out just enough to restore a cross hatch in the cylinder walls and putting it all back together! Edited June 9, 2015 by polarisman14 Link to comment Share on other sites More sharing options...
polarisman14 Posted June 10, 2015 Author Report Share Posted June 10, 2015 So, what gaps am I shooting for on the rings? I read that the upper limit of the top ring is .017 or .018 somewhere on here but that for running higher boost levels, more is OK and actually encouraged to give room for higher rates of thermal expansion and cylinder pressures. I was planning on running .020. If rings are not specified as file-to-fit, but are tighter than your desired end gap, can you still file them down to open the gap up? Do the middle and lower ring need to be opened up as well, or left alone and just the top ring altered? For reference, I am running the FIP MPI manifold and TEP cam, stock 7:1 pistons .030" over and anywhere from 20-25psi, approx. 325whp or more. Not sure what I am running for plug gap right now but if it's anything more than .025" I will be tightening up to that spec as well. Thanks guys. Link to comment Share on other sites More sharing options...
polarisman14 Posted June 12, 2015 Author Report Share Posted June 12, 2015 Sweet. New cast pistons on order, somehow 2 of the 4 pistons had cracked ring lands but neither of them actually separated totally from the piston, so the compression and leakdown numbers were good and no scoring on the piston walls. I consider myself lucky but $130 lighter. Link to comment Share on other sites More sharing options...
StarquestRescue Posted June 12, 2015 Report Share Posted June 12, 2015 Sweet. New cast pistons on order, somehow 2 of the 4 pistons had cracked ring lands but neither of them actually separated totally from the piston, so the compression and leakdown numbers were good and no scoring on the piston walls. I consider myself lucky but $130 lighter.No surprise there. Cancel the order and put the 130 towards forged. That other stuff you do not need right now. 1 Link to comment Share on other sites More sharing options...
ucw458 Posted June 12, 2015 Report Share Posted June 12, 2015 Yeah, so easy to put forged pistons in now and the other stuff later. Link to comment Share on other sites More sharing options...
Dad Posted June 12, 2015 Report Share Posted June 12, 2015 Too much boost/ detonation killed your ring lands Link to comment Share on other sites More sharing options...
polarisman14 Posted June 13, 2015 Author Report Share Posted June 13, 2015 (edited) If that's the case then how is it that some of the members here are running 400whp on stock internals? I literally do not have the money to do that right now. I have $50 left in my project car account after the pistons and I still have to buy a couple other small maintenance items to get this all back together. I'll just run a more conservative tune and lower boost levels while I save for forged pistons. It only takes a couple hours to pull the oil pan and head and plop new pistons in the car eventually. At a minimum I would have to do forged pistons AND a retune (can't run the same tune on 7.8:1 compression as 7:1) which is about 500 bucks more than I can afford versus putting this back in there and cutting the boost down to 15psi and running it, so that's what I will do. Edited June 13, 2015 by polarisman14 Link to comment Share on other sites More sharing options...
StarquestRescue Posted June 13, 2015 Report Share Posted June 13, 2015 "If that's the case then how is it that some of the members here are running 400whp on stock internals" A lot of these cars seldom leave the driveway. Some of them are running on cracked pistons. Most go for it on the dyno. Steet hp tends to be less. You will likely be ok with the aftermarket replacements for a couple of years. Record base line compression and leak down tests after break-in. And retest every so often. Link to comment Share on other sites More sharing options...
polarisman14 Posted June 13, 2015 Author Report Share Posted June 13, 2015 Yeah I am planning on doing the forged internals in the next couple years but you know how it is--few people have just one hobby and I am one of those for sure. Building a wooden boat from scratch and working on my snowmobile sucks up a lot of my other spare cash. The main goal of this build was to just refresh everything and make the car more reliable. I'm one of the guilty ones with these cars that swung for the fences first time out and put go fast bits on there instead of maintenance items. Now I am going through and doing it the right way and doing everything maintenance related along with cleaning up the wiring. When this process is done THIS time it'll be something reliable and more powerful than stock but not over the top just yet. Once I save up some more coin I'll go for it with the 7.8:1 wisecos and a better fuel pump and injectors. Everything else is already ready for bigger power somewhere north of 400whp. I didn't mean to come off as dismissive of your suggestions, I just need this to be reliable so my daily driver can come off the road for a while for maintenance. Link to comment Share on other sites More sharing options...
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