mistah mofro Posted June 3, 2011 Share Posted June 3, 2011 For a stroker build with LD28,L24 rods, and KA24 pistons. Do the pistons have to be forged(since rods/crank are from factory)for an n/a build, can you use stock some type replacement pistons even though they may be cast type? Its obvious the stroker build is expensive so i was just curious to see if anyone has done so with close to oem parts. Quote Link to comment Share on other sites More sharing options...
djz Posted June 3, 2011 Share Posted June 3, 2011 What are you using the motor for? I was using cast pistons in my turbo 3.1 but it was only a road car. Quote Link to comment Share on other sites More sharing options...
Xnke Posted June 3, 2011 Share Posted June 3, 2011 You can put whatever kind of pistons you want in your engine, assuming you can obtain them. Quote Link to comment Share on other sites More sharing options...
mistah mofro Posted June 4, 2011 Author Share Posted June 4, 2011 just street driving and weekend free spirit driving pretty much. I was just wondering if the cast pistons were up to the challenge of everyday driving. Quote Link to comment Share on other sites More sharing options...
steve260z Posted June 4, 2011 Share Posted June 4, 2011 Yes, the cast pistons are fine for your application. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 4, 2011 Share Posted June 4, 2011 Challenge of everyday driving? Quote Link to comment Share on other sites More sharing options...
mistah mofro Posted June 5, 2011 Author Share Posted June 5, 2011 Challenge of everyday driving? Lol, im not so modest when it comes to everday driving but theres good roads coming from work that i'd like to hit up when i go home. Quote Link to comment Share on other sites More sharing options...
PalmettoZ Posted June 5, 2011 Share Posted June 5, 2011 I put those same pistons in my 3.1L build and they are plenty stout. Although you will need to do some machine work to them, since with the combo that you have, they will exceed the block by about 2mm's. You can put the pistons in a lathe and turn that amount off the top. It worked great for me. Pistons were flush with the top of the block at that point. Quote Link to comment Share on other sites More sharing options...
duragg Posted June 5, 2011 Share Posted June 5, 2011 I thought the protruding piston was part of the goal and they solved that with the 2mm head gasket? Not my area of expertise, just spent a month researching all that before ditching the stroker idea. I just bought ITM pistons for my L28 NA rebuild and they seem like decent quality, and cheap. zcarsource.com got them for me next day with a little discount. Quote Link to comment Share on other sites More sharing options...
steve260z Posted June 5, 2011 Share Posted June 5, 2011 I thought the protruding piston was part of the goal and they solved that with the 2mm head gasket? Not my area of expertise, just spent a month researching all that before ditching the stroker idea. I just bought ITM pistons for my L28 NA rebuild and they seem like decent quality, and cheap. zcarsource.com got them for me next day with a little discount. By running the 2mm head gasket you lose the quench between the piston and head. But that assumes your running a quench head. Which head are you using? With a P90, P79 or e31(which is too high compression anyway) you'll want to use a much thinner gasket to take advantage of the quench characteristics of the head. If using an E88 or N42, those are open chamber designs and quench is not an issue. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 5, 2011 Share Posted June 5, 2011 Yes, that is why the 2mm gasket came into being. It really helps keep quench proper when using a 2mm popup. Keeps the piston crowns thick to resist detonation, etc... My "?" was referring to the fact that 99.999% of the cars produced for everyday road driving come with cast pistons. Forged are the oddities, and are usually used for higher rpm usage as they are stronger in tension than cast pistons. When in turbo use, cast pistons are fine for a LOT of relatively higher horsepower applications long term as they are in compression from boost loadings, and since the RPM's don't rise above where normal street engines reside, the tensile loadings don't really increase that much. What you see on turbos is detonation collapse of pistons (cast or forged) you usually don't see wrist pins ripped out of the bottom of the thing like you do with cast pistons on an N/A that runs to 8K! "Boom!" Quote Link to comment Share on other sites More sharing options...
steve260z Posted June 5, 2011 Share Posted June 5, 2011 Yes, that is why the 2mm gasket came into being. It really helps keep quench proper when using a 2mm popup. Keeps the piston crowns thick to resist detonation, etc... My "?" was referring to the fact that 99.999% of the cars produced for everyday road driving come with cast pistons. Forged are the oddities, and are usually used for higher rpm usage as they are stronger in tension than cast pistons. When in turbo use, cast pistons are fine for a LOT of relatively higher horsepower applications long term as they are in compression from boost loadings, and since the RPM's don't rise above where normal street engines reside, the tensile loadings don't really increase that much. What you see on turbos is detonation collapse of pistons (cast or forged) you usually don't see wrist pins ripped out of the bottom of the thing like you do with cast pistons on an N/A that runs to 8K! "Boom!" My error..Tony is correct as usual. Quote Link to comment Share on other sites More sharing options...
PalmettoZ Posted June 5, 2011 Share Posted June 5, 2011 I think that normally the goal would be to have the pistons at TDC flush with the block, not protruding out of it. The 2mm gasket is a solution to that problem. When I bought my 90mm diameter gasket it was just 1mm thick, and over priced at whatever it was that I paid for it (225.00 or so?) from Motorsport auto. The 2mm thick one is just 2 of those riveted together. My cylinder pressure was 200 psi at that point, not sure what that equates to in terms of compression ratio. My pistons were ITM as well, and I think they are good quality for the money. Having built a 3.1 I have to say that for a 6 cylinder its a great motor, but it's not cheap and a PITA to get all the (used) parts together to build one. Unless you want to spend big bucks and order all new stuff off the internet from Kamarei. It's a motor for the Datsun purist who wants to retain the straight 6. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 5, 2011 Share Posted June 5, 2011 Steve is correct, I didn't correct him---many people put the 2mm gasket on to 'drop compression' and they absolutely kill any quench. It really is a terrible idea. I have had this discussion with someone before. Really the last thing you want is a big thick head gasket. Ideally it would be bore-specific so you didn't have a compression loss in a 91mm bore gasket surrounding an 89, 88, or even 87mm bore! That ring around the top of a flat-top zero deck height piston is not a good thing, and really isn't in a pop-up either...but it's the compromise you must make. If you think the 3.1 is expensive...you should have seen the cost on the 3.5 kits back in the 80's... Quote Link to comment Share on other sites More sharing options...
mistah mofro Posted June 10, 2011 Author Share Posted June 10, 2011 So to get the pistons flush with the deck, should i get pistons with a 2mm shorter pin height? Also if im using an e88 will i still need a 2mm headgasket? Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 11, 2011 Share Posted June 11, 2011 Argh... Deck height is irrelevant if you have a gasket thickness that is compatible with the amount of positive deck height. I thought I just explained that---it's what the 2mm gaskets were designed to accomplish... You are more than welcome to spend $600 for a set of pistons which are correct pin height to be able to use a standard gasket. Or you can spend 1/3 that price, and just put the 2mm head gasket on and be done with standard-availability popularly sourced pistons. See the logic of the design criteria? "Clever those Japanese!" Quote Link to comment Share on other sites More sharing options...
tyler031734 Posted June 12, 2011 Share Posted June 12, 2011 Argh... Deck height is irrelevant if you have a gasket thickness that is compatible with the amount of positive deck height. Hey Tony, I thought a thicker head gasket would result in a bigger "weak link" in the chain? Also isn't there an issue with the top piston ring coming up to high in the bore? Ive never had a KA piston in hand but isn't 2mm pretty close to the top ring? Thanks for the knowledge. Quote Link to comment Share on other sites More sharing options...
mistah mofro Posted June 12, 2011 Author Share Posted June 12, 2011 I just wanted to know if the 2mm pin height different would have the pistons flush with the deck. Quote Link to comment Share on other sites More sharing options...
PalmettoZ Posted June 12, 2011 Share Posted June 12, 2011 Yes, custom pistons will get you the lower pin height which will give you flush pistons with the top of the block. JE can make you a set. But like Tony says, they are expensive and the 2mm gasket is the other cheaper option. That being said, I think that those larger 91mm head gaskets are getting harder to find now. Tyler031734, your right, its not good to get the top ring that close to the top of the block. As a compromise I would recommend filing the top ring with a little more clearance for additional expansion due to heat. Or coat the top of the pistons with a ceramic coating to help keep the heat off of the piston. I know that this is a common problem for the stroker 5.0 Ford motors due to the really high pin height. Keith Black pistons recommends the additional clearance on the top ring of the pistons they sell for this combo. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 14, 2011 Share Posted June 14, 2011 What kind of rpms are you guys thinking of turning that stretching a rod to put the top ring over the top of the deck? If you're 0.040" in the bore, hell even 0.020" from the ring coming out, you are more than far enough down the bore... Only way to tell is assemble it and turn it over. Quote Link to comment Share on other sites More sharing options...
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