m4xwellmurd3r Posted March 3, 2008 Share Posted March 3, 2008 well I'm glad to hear 15-20psi is safe on a stock engine. I plan on putting headstuds and good rings on my turbo build, but i'm only going to run 12ish psi Quote Link to comment Share on other sites More sharing options...
blueovalz Posted March 3, 2008 Share Posted March 3, 2008 I realize this doesn’t matter as the short lock needs to be torn down and rebuilt regardless, I just want point out what that scuffing really is, it is not your wrist pin. Thank you. The photo evidence was not matching the early explanation, but this explanation seems to have hit the mark. Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted March 3, 2008 Share Posted March 3, 2008 well I'm glad to hear 15-20psi is safe on a stock engine. I plan on putting headstuds and good rings on my turbo build, but i'm only going to run 12ish psi Remember that Big-Phil comletely blew up his old engine with one detonation instance at 20PSI. In engineering we have what is caled a "safety factor". It is the amount of stress that a part was designed to safely undergo without failure divided by the amount of stress that causes failure. When you up the boost you are reducing your safety factor closer and closer to the number one.(bad) With less of safety factor available even the least amount of detonation can can sen you under the number one and give you a basket case of a motor. "Safely" I would use no more than 14-16 PSI on a stock, unopened, 75k-150k mile motor with a stock-ish turbo WITH an intercooler...depending on your mods. Big-Phil's nice "stock" motor is FRESH with new rings and bearings, etc... so he can have a little more freedom with "fun" things like more boost etc... Just my 2 cents... Quote Link to comment Share on other sites More sharing options...
Tony D Posted March 4, 2008 Share Posted March 4, 2008 Yes, with cooler (read sober) heads prevailing, BRAAP is correct, the pattern is different than what was in ours. It does look like a broken ring land. Looking at it again, it looks too far 'to one side' to be the piston pin anyway. BRAAP is right, the 'double score' is what we had. Not a polishing like you have. But then again....going on my second Big Gulp of Captian Morgan & Diet Coke may have had some bearing on my exuberance that evening... Come to think of it, I still have some DC in the Big Gulp out in the truck, I better go get it before the ice waters it down too much and get a-mixing. JeffP sunk the rings and lands on Five of Six cylinders at 8.39 psi of boost. Boost really is irrelevant, you run lean and detonate, things will break, some sooner than later. As for what caused the interference to walk.... I'm thinking something like 60+ miles running at 8500rpm+ in 1.5 and 5 mile bursts... It was up to 8400 by the end of the first mile at Bonneville, and then gained 500 rpm each mile subsequently... That might have had something to do with the small ends 'moving around a bit' and loosing grip on the pins and letting them walk to the walls. Quote Link to comment Share on other sites More sharing options...
jeffer949 Posted March 4, 2008 Author Share Posted March 4, 2008 well i took the motor out this afternoon and took that piston out here is what i found so who has an extra turbo piston laying around they wanna mail me??? Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted March 4, 2008 Share Posted March 4, 2008 I've got 4 ok turbo dished pistons out of an engine I recently bought from the classifieds but they were on a car with a 20G turbo with blocked wastegate which is probably what caused #5 to break a ring land. That said, I might not trust the rod bolts on the assembly if I do mail one. I'll try to remember to bring them in tomorrow. Quote Link to comment Share on other sites More sharing options...
cholag Posted March 4, 2008 Share Posted March 4, 2008 this is the build that i will be doing on my 83 280zxt motor. 1.I had the head re-built they put new spring and valve seals and they ground the valves. 2.I got the cam and rocker arms ground with delta cam BTW they did a great job and did it for $105 and thats with shipping 3.Maybe forged pistons depending on what you guys think of my build or new stock pistons, rings, and pins 4.Balanced crank 5.New bearings 6.ARP head studs, main bearing studs, and rod bolts 7.24x12x3 intercooler 8.Holset hy35 turbo 9.Blow off valve 10.The 440cc supra injectors because thats what everyone uses 11.60mm throttle body 12.1mm felpro head gasket 13.mega squirt computer I already have the head completed and the inter cooler is in the basement. But with this build I want to run 15-20psi of boost so I am wondering will i be safe on NEW stock internals or should i go big with forged. Quote Link to comment Share on other sites More sharing options...
jeffer949 Posted March 5, 2008 Author Share Posted March 5, 2008 thanks but i got a whole set of pistons on the way and a new set of perfect cicle rings on the way and a gasket kit. so i should have every thing by friday Quote Link to comment Share on other sites More sharing options...
m4xwellmurd3r Posted March 14, 2008 Share Posted March 14, 2008 Remember that Big-Phil comletely blew up his old engine with one detonation instance at 20PSI. In engineering we have what is caled a "safety factor". It is the amount of stress that a part was designed to safely undergo without failure divided by the amount of stress that causes failure. When you up the boost you are reducing your safety factor closer and closer to the number one.(bad) With less of safety factor available even the least amount of detonation can can sen you under the number one and give you a basket case of a motor. "Safely" I would use no more than 14-16 PSI on a stock, unopened, 75k-150k mile motor with a stock-ish turbo WITH an intercooler...depending on your mods. Big-Phil's nice "stock" motor is FRESH with new rings and bearings, etc... so he can have a little more freedom with "fun" things like more boost etc... Just my 2 cents... Yeah, I know what you mean. My engine will be a fresh engine, totally overhauled. And i'm going to be anal about tuning. I'm really anal about certian things, and perfect tunes is one of those things. I will also run an intercooler on mine. Basically I want the engine to be overbuilt for what I'm doing to it, to help increase that safety factor a bit, as well as make sure it's tuned the best it can be. The highest I'd ever go would be 15psi, I don't want huge power, but I do like acceleration haha. Thanks for the tips though. It won't be a while till I turbo it. I plan on sucking every ounce of power out of the stock engine by tuning it, and adding a few parts, but keeping the long block bone stock. Quote Link to comment Share on other sites More sharing options...
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