Guest Cronic Posted May 27, 2004 Share Posted May 27, 2004 Are they forged? Quote Link to comment Share on other sites More sharing options...
AgentZ Posted May 27, 2004 Share Posted May 27, 2004 Do you mean stock con rods? Quote Link to comment Share on other sites More sharing options...
wigenOut-S30 Posted May 27, 2004 Share Posted May 27, 2004 Everything I have read was that yeah the stock Con rods were forged. I think when I build my spare ZXT block I will go with race prepped rods stock crank and cryo the pistons. It seems like the pistons are really the only week point in the bottom en of the L28. Quote Link to comment Share on other sites More sharing options...
Guest Cronic Posted May 27, 2004 Share Posted May 27, 2004 Interesting, everything I've read said otherwise... Don't cryo treat the pistons... if you're going to take them out.. seriously, get forged... cryo doesn't really help THAT much... the whole system is debated all over. If you're going to take them out... might as well replace them to be safe. I plan on taking a nice 120 shot and 20 psi with lots of fuel to see how much power those pistons can take stock. I hear about 450 or so they give. Quote Link to comment Share on other sites More sharing options...
Guest ON3GO Posted May 27, 2004 Share Posted May 27, 2004 ill be pushing the limits on the stock pistons.. ill keep everybody updated on when they go. Going for over 400rwhp and maybe nitrous too.. Mike Quote Link to comment Share on other sites More sharing options...
technicalninja Posted May 27, 2004 Share Posted May 27, 2004 Yes, stock rods and the crank are forged. In 20 years of working as an Import car tech I cannot remember last time I found cast rods or crank in any Import-Japanese or European. Air cooled VWs had cast stuff. Quote Link to comment Share on other sites More sharing options...
Tony D Posted May 27, 2004 Share Posted May 27, 2004 Air cooled VW's had forged cranks for sure. $1400 for a forged counterweighted Gene Berg stroker hammered in the original dies from Sweden. The rods were forged to my recollection, too, but it's been 92 since my last rebuild on one, so I may have missed something. I swear they were a forged rod and forged crank. The stock crank wasn't counterweighted, but that's about the only complaint I ever had about VW internals... Well, maybe not the only one... Threw a few VW rods, but NEVER had one break. Always bolt failures (stupid kid reusing bolts). http://www.geneberg.com/vwrods.htm Now DOMESTIC crap, THERE is where you get into cast cranks, etc etc etc... I shudder every time I recall my visit to the Buick V6 Engine plant in 1982/83. Compared to the Nissan Engine assembly plant I toured in 85 it was the difference in Civil War Surgery, and the ER today! Quote Link to comment Share on other sites More sharing options...
technicalninja Posted May 27, 2004 Share Posted May 27, 2004 Every air-cooled VW I've be in to (too many) has had a cast crank and rods althought I do not believe I've ever rebuilt one that was made in Sweden. Done some Volvos and Saabs that were (all of those had forged internals). The cast VW parts held up fine anyways. I was just trying to remember any Imports that had cast internals and air-cooled VW is the only one that sticks out. Did not mean to insult the "BUG People." Lots of American stuff is cast but they can hold up fine also. I am also surprised to find out stock forging dies can be used to forge a "stroker" crank. I would like to see how that works. I was under the impression that the forging dies would be shaped reverse of the final part and used in a press that squeezed/struck bar stock multiple times forming part. Would be neat to find a video clip of a crank or rod being forged to see how it is really done. Back to Nissan- Only issues I've had out of L-series rods is failure of reused rod bolts. I've put together many reusing the rod bolts and had them last fine but I've also seen failures reusing rod bolts so I now REQUIRE new rod bolts on any rebuild. As the upgrade ARP bolts are just slightly more expensive that factory Nissan I use them. Occasionally the ARP bolt heads have interfered with circular cut out in rods and I've had to dress up the rod to clear bolts. Mild deburing/polishing and shot peening of stock rods is all that is needed for a max effort street Z and totally stock stuff is probably good for 400 hp level. For a performance engine I would use a matched set (all 6 rods originally from same engine- this is more for balance than strength) and have the balance checked /adjusted. I would not use any lower end part out of an engine that suffered a major lower end failure- good core stuff is cheap. Stock L-series rods are not a weak link in the engine. Quote Link to comment Share on other sites More sharing options...
Tony D Posted May 27, 2004 Share Posted May 27, 2004 no I will have to disagree! The VW has a forged, non-counterweighted crank. That was the odd thing about them: non counterweighted but forged. The flywheel on the VW is also forged. As are the rods. Some of the British stuff was cast non-counterweighted three mainbearing stuff, but the VW's OEM crank is forged. The aftermarket stuff (especially the cheap strokers available in the late 70's and early 80's were cast. Gene berg approached the holder of the original VW forging dies and had them rework for his raw core cranks. For a LONG time, Gene Berg was the ONLY supplier of forged stroker cranks (not welded and offset ground or cast). Gene had a nice technical paper showing photos from the factory in Sweden where he was getting them made, and how they reworked the OEM forging dies to make forgings with more cross-sectional area for those looong stroke cranks he woudl sell. if you want to see forging in work, if you are even in LA, give me a call, and I can direct you to LA Drop Forging. They do a lot of their work outdoors (unfortunately with air hammers) making aircraft landing gear parts and the like. Very interesting to see "big redhot rectangle" go in and BANG BANG BANG BANG comes out as "dull red round thing". Quote Link to comment Share on other sites More sharing options...
Tony D Posted May 27, 2004 Share Posted May 27, 2004 to clear this up: the Swedish company bought the dies from VW when they stopped forging cranks in-house in the mid 70's when the water cooled line started pushing them out of the original plant. The volume of Air Cooled stuff paled with the Rabbit coming on line, so like any other thing in the Automotive business they outsourced, and the company was in Sweden. When Gene decided the cross-area of a welded crank was the reason for the cranks braking, he approached VW and they directed him to the owner of the dies. From them, he worked for a sole-soure supplier arrangement, and made a run of cranks. True to his word, Gene held the prices to under $1000 for a loooong time, and when he went back and checked the cost of another run in the mid 90's (just before he died as I recall) he sent out a letter informing his customers that due to the cost of a new production run, the current supply of forged cranks would be it, and that he reserved the right to only sell cranks to people buying a full set of parts from him (or who were getting a replacement part). So this is how a Swedish Company started supplying VW cranks to VW. Quote Link to comment Share on other sites More sharing options...
Guest Cronic Posted May 27, 2004 Share Posted May 27, 2004 Yes, stock rods and the crank are forged. In 20 years of working as an Import car tech I cannot remember last time I found cast rods or crank in any Import-Japanese or European. Air cooled VWs had cast stuff. Honda. I rest my case. Quote Link to comment Share on other sites More sharing options...
wigenOut-S30 Posted May 27, 2004 Share Posted May 27, 2004 Interesting' date=' everything I've read said otherwise...Don't cryo treat the pistons... if you're going to take them out.. seriously, get forged... cryo doesn't really help THAT much... the whole system is debated all over. If you're going to take them out... might as well replace them to be safe. I plan on taking a nice 120 shot and 20 psi with lots of fuel to see how much power those pistons can take stock. I hear about 450 or so they give.[/quote'] What I have read on cryoing is that it is mostly used by motorcross guys. They cryo like everything in there trannies as well as there motors. I know it would not be quite as strong as forged but it would be a good bit stronger then stock. the process can be done locally to me for around 80-100 bucks.. That is WAY WAY cheaper then 7-850 bucks for forged pistons. I dont plan on having more then 300-350 to the ground. I do plan on doing alot more research on it before I build my spare L28T block up. Quote Link to comment Share on other sites More sharing options...
Mack Posted May 27, 2004 Share Posted May 27, 2004 according to the "How To Hotrod and Race your Datsun Nissan" book, the stockers are forged and if you shotpeen and polish them, they are supposedly good for up to 600RWHP in road race form, not just drag racing. I would not worry about the rods, now the pistons..... as far as cryogenically treating pistons, it helps a LOT in the face of detonation and lean conditions and anything to do with rapid heat expansion. when a piston expands due to heat, it does not expand uniformly around its circumference, some spots expand faster than others, and when that one bit that expands faster, it snags the bore wall. there was one place that took 2, 2 stroke bike motors, one got a cryo treated stock piston, one got a stock piston. they ran them at some RPM's while constantly leaning out the mixture. the non treated one overheated and seized up, the treated one eventually stopped because the mixture got too lean to run. they took it apart, teh barrel wasn't even scored. food for thought.... Mack Quote Link to comment Share on other sites More sharing options...
wigenOut-S30 Posted May 27, 2004 Share Posted May 27, 2004 Hey mack.. Thats the kind of stuff I have been reading about cryoing as well. I still will do alot more research before I decide what to do. Quote Link to comment Share on other sites More sharing options...
Guest Cronic Posted May 27, 2004 Share Posted May 27, 2004 Well all the tests I have heard about cryo treating have been inconclusive... besides... Z pistons have weak ring lands, and I don't think cryo will help that... it's not about expansion in our case... it's about thin ring lands.... but if it helps you out. Right on. I just would personally spend the extra money to be safe. Then again, I plan on making over 500 to the wheels. Quote Link to comment Share on other sites More sharing options...
Mack Posted May 28, 2004 Share Posted May 28, 2004 Cryogenics here is a decent webpage, but of course they have a service to sell so wthey will make it look as good as they can, but some of it makes sense. My machinist in fargo said he had some stuff cryotreated (races at the dragstrip and circle track on the weekends) and he sent in a bic disposable razor just for fun.... he got 4 shaves out of it, he normally gets one. thats real world experience! lol!! but seriously... I have heard that brake rotors last 3 to 4 times as long once they are cryo treated. it looks like there is science to it and its not just "snake oil" It might even hlp with the ringlands. it re-crystalizes the metals crystalline structure... who knows. I may have a set of stock pistons done and see what it does. Mack Quote Link to comment Share on other sites More sharing options...
Guest Cronic Posted May 28, 2004 Share Posted May 28, 2004 Now Im no expert on it. Most of what I've read is hearsay from other people. But I was under the impression by cryotreating parts, it actaully decreases the space between the molecules, hardening the item. The only downside I can imagine to this would be A. It's still not a forged piston. B. I belive it makes said item more "brittle" and prone to cracking and such. But I can't be quoted on this, cause Im no physics major. Quote Link to comment Share on other sites More sharing options...
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