peewii7 Posted August 4, 2018 Share Posted August 4, 2018 Hi all, I have recently rebuilt my EJ25. After doing so the timing belt snapped (old belt that got oily) I've noticed on cylinder one some damage. Do I need to get the block and/or the cylinder head skimmed / machined or can I just build on top of this. Thanks Quote Link to comment Share on other sites More sharing options...
Tidgy Posted August 4, 2018 Share Posted August 4, 2018 that piston is screwed. looks like you have had some det going on. Was it mapped after it was built? block/head surfaces dont look to great either, were they skimmed before the rebuild? Quote Link to comment Share on other sites More sharing options...
peewii7 Posted August 4, 2018 Author Share Posted August 4, 2018 Previous owner had it mapped (no record of by who) Just a dyno sheet showing 300BHP Block Yes. Head no I pulled it apart as I saw oil in the water and assumed a headgasket was gone Quote Link to comment Share on other sites More sharing options...
Tidgy Posted August 4, 2018 Share Posted August 4, 2018 given the damage i would suggest the whole thing needs stripping down, crank bearings will prob need doing, new pistons, as far as if block is ssalvageable need to see how bad the damage is and see if its still within tollerance Quote Link to comment Share on other sites More sharing options...
peewii7 Posted August 4, 2018 Author Share Posted August 4, 2018 To give some background, I only just built it (first time admittedly) It did 2 hours on idle and a quick trip down the road (3 miles) Just had new crank bearings, crank, rods, pistons, rings, oil pump. If it needs stripping, it needs stripping i'll have to find someone to take the block and heads to get them looked at Quote Link to comment Share on other sites More sharing options...
Mr B Posted August 4, 2018 Share Posted August 4, 2018 Piston looks to be salvageable and if it new more so . You need get that on rollers once built up and fueling/mapping checked as the det is what probably caused HG issue first time round . Block will need good surface clean or skim. Head surface certainly needs a proper smooth finish skim but check cam bearing surfaces as if they are badly scored you best sourcing new heads . Do a fair few of these and if left running with water in oil for long time cam journals and main bearings suffer . Quote Link to comment Share on other sites More sharing options...
Tidgy Posted August 7, 2018 Share Posted August 7, 2018 On 8/4/2018 at 10:01 PM, Mr B said: Piston looks to be salvageable and if it new more so . You need get that on rollers once built up and fueling/mapping checked as the det is what probably caused HG issue first time round . Block will need good surface clean or skim. Head surface certainly needs a proper smooth finish skim but check cam bearing surfaces as if they are badly scored you best sourcing new heads . Do a fair few of these and if left running with water in oil for long time cam journals and main bearings suffer . you'd really reuse pistons with that much damage on them? Quote Link to comment Share on other sites More sharing options...
Mr B Posted August 7, 2018 Share Posted August 7, 2018 ^ If is only crown pitting of a few thou and ringlands and skirt A1 and they brand new and quality then we likely get the set crown dressed and weight matched at the machine shop, from pictures hard to say but it common practice on light pitting and something you review on individual basis . Looks like was a rough build and underlying issue not addressed and must be pretty severe lean/timing condition , valve seating wants be checked and the cam journals as they can be scored real bad on these with poor oil and contaminated oil, don't look like it been skimmed or hot tanked either . Quote Link to comment Share on other sites More sharing options...
Tidgy Posted August 7, 2018 Share Posted August 7, 2018 Gonna need a darn sight more than a few thou to get rid of those, it looks like its nibbled the edge of the piston. Your also going to affect the compression and reduce the strength of the piston by removing material. I would be junking anything like that and putting decent forged new pistons in. yes would cost extra money, but given the cost of a rebuild if they fail, its a small sum given the potential risk. Also advisable do to the bottom end again given the det that bad might well have cause the bearing to be nipped. Quote Link to comment Share on other sites More sharing options...
Mr B Posted August 7, 2018 Share Posted August 7, 2018 Compression will be more effected by head and block facing and HG used, this all can be calculated and compression/ cylinder cc can be set/balanced to desired range and all part of component preparation . Waste of time commenting without seeing them in hand but if not decent/new pistons start with they not worth working with, amount you would remove in that area be minimal concern to piston strength, the edge chip more concern to whether salvageable . head and block surfaces and timing belt being reused gives me idea your extra money kitty won't be that great on this one ... Quote Link to comment Share on other sites More sharing options...
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