Jehannum Posted October 6, 2011 Share Posted October 6, 2011 So, after a bout with a sticky intake valve that kissed a piston in my L24, I resolved to rebuild my E31 head. Back in '08, when I was rebuilding the car after an accident, I had the head checked for flatness, and it was a bit off, so they cut 0.003" off. The shop I took it to this time (to do guides and seats) told me that the height is is 4.227" high, 0.008" below the minimum height of 4.235", and that the previous mill job(s?, at least one of which must have happened sometime before I took ownership) was/were done badly (their fly cutter picked up a repair weld around the water jacket in the back and grooved the head around #6). The only other evidence of previous repair besides height is the #6 intake seat is steel instead of brass (like 1-5). The exhaust seats are all steel. I'm not sure where to go from here. Is the head scrap? Will I have to shim the cam bearings when I get it back? Is 0.011" below minimum height enough that my plugs are going to collide with pistons? Will I forever have to run 8000 octane to prevent detonation (detonation isn't an issue now)? They want to cut it .003" more and push me into some MLS head gasket (I know Tomei does a 1 and 1.2mm head gasket, but the bore is set for L28). Setup: L24 (P30), flat-top pistons, stock rods, stock crank, E31 head (apparently too short ever since I bought the damned thing), SU carbs w/SM needles, and 6-1 MSA header into mandrel bent 2.5" exhaust Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 6, 2011 Share Posted October 6, 2011 E31's aren't a dime a dozen, but they're not hyper-expensive either. If the head is straight and the other issues fixed, I would be inclined to just run some cam tower shims and drive it. If it's going to cost hundreds of dollars to fix it and then you need a valve job etc on top of that, I'd go find another one. I wouldn't to the thick head gasket, as it moves the head out of the quench zone and so it might be more ping prone with the thick headgasket than without. Quote Link to comment Share on other sites More sharing options...
madkaw Posted October 7, 2011 Share Posted October 7, 2011 Nissan sells a head gasket for the 240 that is 1.2 thick- pricey 150$ Quote Link to comment Share on other sites More sharing options...
Jehannum Posted October 7, 2011 Author Share Posted October 7, 2011 E31's aren't a dime a dozen, but they're not hyper-expensive either. If the head is straight and the other issues fixed, I would be inclined to just run some cam tower shims and drive it. If it's going to cost hundreds of dollars to fix it and then you need a valve job etc on top of that, I'd go find another one. I wouldn't to the thick head gasket, as it moves the head out of the quench zone and so it might be more ping prone with the thick headgasket than without. I was going to do the valve job in any event, because it seems every E-31 I can find around here is subject to enough **** built up on the back of the valves, or detonation in #6, or wiped cam lobes that I'm better off just scooping it up and dropping it at the shop. I'm really just curious whether the plugs were in danger of being smacked. Quote Link to comment Share on other sites More sharing options...
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