boomguy Posted July 19, 2018 Share Posted July 19, 2018 Hi Guys. Quick question about my original matching number block that I am about to rebuild for my 1970 240z. The machine shop that I have taken it to says there is some corrosion on the top of the block and in one of the water passages. They are wanting to deck it until the surface is smooth but they dont know how much they will have to remove. Is it possible to weld these corrosion areas to fill them in prior to surface planing? I am worried that decking too much will open up a bees nest of pistons sitting too high and having to shim the cam towers to take up the slack in the timing chain. Thanks for any replies Chris Quote Link to comment Share on other sites More sharing options...
Neverdone Posted July 19, 2018 Share Posted July 19, 2018 You can weld in corrosion holes on an engine. Make sure whoever is doing it knows exactly what they're doing though. Considering however that you have a Z that isn't in mint condition, and the value will change by a negligible amount, it might be cheaper and easier to just get a new L24 that isn't pitted out. Quote Link to comment Share on other sites More sharing options...
madkaw Posted July 19, 2018 Share Posted July 19, 2018 Measure deck height on your pistons . I believe the L24 engine the deck height is closer to zero. You have more room to shave then in a L28 block. This is based on what I found on my engine when I rebuilt it. Now these weren’t stick pistons , but pin height should have been the same. How much is shaved off the head? My engine is a 71 with e-88 Head . Block is shaved close to .010 and piston was only out .005 ,and head is shaved .050 with bigger valves . No metal contact yet with a 490/290 cam Quote Link to comment Share on other sites More sharing options...
boomguy Posted July 19, 2018 Author Share Posted July 19, 2018 (edited) 1 hour ago, Neverdone said: Considering however that you have a Z that isn't in mint condition, and the value will change by a negligible amount, it might be cheaper and easier to just get a new L24 that isn't pitted out. I know my girl isn't"mint" but she still has her original paint and rust is almost non existent and having carted her original motor home from California about 26 years ago I think the two should be reunited at some point. Although her L28 that is in her now is alot of fun I am finding that a more stock configuration would suit me now. I'll include a photo of her at a recent carbs and coffee. As for the block its good to know that I could have those spots welded prior to planing. There is alot of info on L28 piston heights in relation to the deck but not much when referring to an L24 with the higher quench e31 head. The pistons that where in it weren't stock and were shy about .010 from the deck. I have read that ITM pistons pin height are a bit lower than stock which may mean shaving the piston height I guess. Edited July 19, 2018 by boomguy Quote Link to comment Share on other sites More sharing options...
madkaw Posted July 19, 2018 Share Posted July 19, 2018 So you should be able to shave the block quite a bit. Just make sure you bolt the timing cover to the block so you shave both. Quote Link to comment Share on other sites More sharing options...
boomguy Posted July 19, 2018 Author Share Posted July 19, 2018 40 minutes ago, madkaw said: Just make sure you bolt the timing cover to the block so you shave both. Thats a great tip Madkaw... Thank you for that. Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 19, 2018 Share Posted July 19, 2018 (edited) 2 hours ago, boomguy said: The machine shop that I have taken it to says there is some corrosion on the top of the block and in one of the water passages. They are wanting to deck it until the surface is smooth but they dont know how much they will have to remove. They should be able to estimate the depth with some simple measurements. If it's just some pitting next to a water passage you could probably seal it with JB Weld. Don't conflate coolant pressure with cylinder pressure. Pictures would be neat. Might get some better advice. Edit - not that advice so far isn't good. Just more of it. Edited July 19, 2018 by NewZed Quote Link to comment Share on other sites More sharing options...
boomguy Posted July 20, 2018 Author Share Posted July 20, 2018 Just talked to the machines and he estimates 12-15 thou to clean up the areas. He doesn't advise to weld the block areas that are corroded since it would create bubbles in the steel and the block could crack at those points. I guess a thicker head gasket would help in this situation? Quote Link to comment Share on other sites More sharing options...
HuD 91gt Posted July 20, 2018 Share Posted July 20, 2018 Wide array of metal gaskets in all sorts of thicknesses. If and when the blocked is decked, Make sure to include the timing cover. Quote Link to comment Share on other sites More sharing options...
madkaw Posted July 20, 2018 Share Posted July 20, 2018 Stock HG should be fine Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 20, 2018 Share Posted July 20, 2018 12 hours ago, boomguy said: Just talked to the machines and he estimates 12-15 thou to clean up the areas. He doesn't advise to weld the block areas that are corroded since it would create bubbles in the steel and the block could crack at those points. I guess a thicker head gasket would help in this situation? Add any head skimming to the program. Are these guys building the engine for you or just doing machine work? A good shop should be able to lay out everything that they think they need to do, before they even start. Piecemeal from the internet doesn't seem very quick. Quote Link to comment Share on other sites More sharing options...
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