LQ4 pistons for boost?
LQ4 pistons for boost? I've been looking for another LQ4 motor for a turbo build. The first motor I bought came from back east and was said to have a valve tick. When I took it apart it had 4 broken pistons on one side, and 2 on the other. Both heads were shot with cracks between all 8 sets of valves and extensive damage from trying to swallow the broken pieces of pistons. The block was rusted .080 thick on one side from the salt as well so there wasn't anything of value left. My second try I told the seller I would not buy unless the heads were removed. Again the heads were shot and there were 2 broken pistons on one side and 1 on the other. I looked at a third this past weekend and it too had broken pistons. So my question is, do I need to order pistons that are thicker between the crown and the top ring, or do forged pistons hold up better? Instead of going with 6.125 rods, should I use a 6.100 rod and go for a bit of extra material in that same area? Stock ones measure around .175.
Teching In
Joined: Sep 2009
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Hey, Ron, nice to see you back in the saddle after leaving comp d and the diesel world. The 5 junkyard lq4's I have bought were all fine in the heads and pistons areas, and only one had block rust issues. For the application I used it on, I felt it wasn't a problem. I wonder if overheating is an issue with the motors you've looked at. Do you intend to change rods and pistons regardless of what you get for a motor? I would certainly think any of the aftermarket pistons (Wiseco, Ross, Diamond, JE, Mahle), would be fine with boost, as the stock pistons are known to be weak. You can also upgrade to better stock heads quite inexpensively if the used motor needs new heads for any reason. Maybe buy a motor with broken pistons and no block rust for a deal and just plan to build it?? This is what I am currently doing, I found a 05 lq4 with a broken head (collision damage) low mileage motor, 300 dollars. Nice factory black paint on the block. And I am in New York....
I only planned on using the block, but I have yet to hear if the forged pistons are holding up . I'm thinking about backing off on the stroke and using a 4.8L crank and a set of aftermarket rods. One of the piston companies make a 4.010 piston for the 3.268 crank/6.3" rod combo that has a bit more material between the top ring and the top of the piston. That along with a stronger material and the longer rod/short stroke might help them hold up. When I first started looking I thought it would be great to just do an LSX with a 4.125 bore and a 4" stroke so my Z would have bottom end like the old first gen(not really, but at least have 1/3 as much :-) ).
