rayaapp2 Posted May 4, 2011 Share Posted May 4, 2011 Story: So I just picked up a spare E31 for my L24 build. It was on a complete motor in a complete car that looked like it sat on the coast to long without a bath. So I had the owner pull the valve cover and both manifolds so I could pull the head when I got there. As Im loosening up the last head bolt I notice a valve on #2 is hanging half cocked in the spring. I look over at the owner and say well its got 1 bent valve, but I was able to get all the head bolts loosened without breaking them off in the block. I shove a 1" piece of wood down the font, pull the timing chain off, and take out the head bolts the rest of the way. I was able to get the head loose from the block with very little effort. Once the head is off I can see valve heads in several chambers along with some bugs/spider creatures. After propping the head up for inspection I can see that all 12 valves are bent to some degree and that 3 valves have lost their heads. #2 chamber has some biffing near the spark plug threads. Question: So I dont believe there is anyway to bend all the valves like this unless the cam was 90 degrees out in either direction. I didnt even bother to set the engine up at TDC when I pulled it apart to check the cam, because the cam chain and tensioners looked pretty toast to me(even though I stuck a piece of wood down to prevent the tensioner from falling out). I really dont see how this could have run. Is there anyway that the cam could have been off 90 degrees and the starter could have bent all the valves enough that 3 of them lost the heads? In fact two of those broken valves punched holes in their corresponding pistons. What I am worried about is that the valves were in there and could have seriously damaged the head. Im not a head guy so here is question 2. How do cracks form in these heads? Could large metal chunks make cracks or is it mostly a heat issue? Im aware that the head will need new seats and guides, but I was planning on N42 valves with newer style seats and guides(to get away from additives in fuel and oil for the originals). When I get the sand blaster and wash tank going Ill know more about its current condition, but for now I thought Id give you guys a poke at it. Ill get pics up in a bit. Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted May 4, 2011 Author Share Posted May 4, 2011 Quote Link to comment Share on other sites More sharing options...
johnc Posted May 5, 2011 Share Posted May 5, 2011 Throw it away and find another E31. If someone was able to bend all 12 valves they've certainly done a lot more damaged to that head. Quote Link to comment Share on other sites More sharing options...
Leon Posted May 5, 2011 Share Posted May 5, 2011 Throw it away and find another E31. If someone was able to bend all 12 valves they've certainly done a lot more damaged to that head. I second that. I would not touch that head. Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted May 5, 2011 Author Share Posted May 5, 2011 (edited) it measures 107.89mm too... Ill have to straight edge it and blast first before it goes to the recyclers. It was free after inspection so no big deal. I may have a can of that 'pink' stuff around to check it now that I think of it. EDIT I just came up with a better idea if this head is toast. IF this head is ape raped then its the perfect place to experiment with porting and such. Edited May 5, 2011 by rayaapp2 Quote Link to comment Share on other sites More sharing options...
Mack Posted May 7, 2011 Share Posted May 7, 2011 It may not be "era correct", but I would say just to get yourself a maxima N47. smaller chambers and much more modern than an E31, and it already has the bigger exhaust valve. they can still be had for as little as $50. Quote Link to comment Share on other sites More sharing options...
Tony D Posted May 7, 2011 Share Posted May 7, 2011 DO NO BLAST ANYTHING! Nothing is on the combustion chambers that won't be taken off with proper solvent and some soft scrubbing with a toothbrush or maybe a brass brush. If you blast, you will peen over edges of a crack making it very hard to spot. After the combustion chambers are thoroughly cleaned (last with lacquer thinner) then get some SPOT-CHEK from a kit (they would sell the kits at McMaster Carr for $70 some time ago) First some red dye penetrant, followed by white developer. Any cracks will show up as a red line in the white paint. Follow the directions in the kit, and with a cleaned head with the right solvents you will straightaway spot any cracks. Zyglo is nice, but expensive. Spot-Chek is the second best alternative, and can be used on almost any non-ferrous part (like pistons). Quote Link to comment Share on other sites More sharing options...
johnc Posted May 7, 2011 Share Posted May 7, 2011 The poor man's crack check is Kerosene and chalk. Wipe the surface with Kerosene and them wipe it dry with a cloth dampened with Acetone. Rub or sprinkle chalk over the surface and wait a few minutes. The Kerosene will leach into the chalk and show as a brown line. The line won't be as sharp as with a true crack test product, but you'll know there's a crack there. Quote Link to comment Share on other sites More sharing options...
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