Requiemk Posted February 22, 2010 Share Posted February 22, 2010 75 psi across all 6 cylinders 100 when oil added I brought head/block a while back acl race rings, bearings etc. Engine appears to have non turbo pistons, not a major just means a bit more compression a bit less boost. Mint bores, fucked rings. Looked to be apart recently by head to block cleanliness aswell as the condition on triple layer steel headgasket. Also signs of water going into my oil on small amount of time i ran it, didn't get it hot. Can excess boost cause all rings to fuck out/any suggestions Quote Link to comment Share on other sites More sharing options...
Hemi Posted February 22, 2010 Share Posted February 22, 2010 k disregaurd my other comment i made about fucked rings . not usually to that extent i dont think. and 75psi??? , man that not right homie . my ca is 185 across all four ... your either doing it wrong or got a leak from the compression tester dood Quote Link to comment Share on other sites More sharing options...
Hemi Posted February 22, 2010 Share Posted February 22, 2010 also movement in the piston ?? hrmm i could move my pistons but very very little . prehaps the block has been bored and you still got standard pistons??? Quote Link to comment Share on other sites More sharing options...
EFI_LC Posted February 22, 2010 Share Posted February 22, 2010 75 psi across all 6 cylinders100 when oil added I brought head/block a while back acl race rings, bearings etc. Engine appears to have non turbo pistons, not a major just means a bit more compression a bit less boost. Mint bores, fucked rings. Looked to be apart recently by head to block cleanliness aswell as the condition on triple layer steel headgasket. Also signs of water going into my oil on small amount of time i ran it, didn't get it hot. Can excess boost cause all rings to fuck out/any suggestions cam can cause this... the good thing is they are even.... are you sure water is leaking as thats more a worry.... Quote Link to comment Share on other sites More sharing options...
Requiemk Posted February 22, 2010 Author Share Posted February 22, 2010 Thats why im stumped eh, had mate around gave me a hand doing it. I got those dud compression results yesterday with my home made compression tester, assumed it wasn't sealing so grabbed another, same result. Have used this one in past and is trusted. Engine would start and fire but wouldn't run longer than 20 seconds or so, wasn't keen on reving past medium throttle, likely another issue altogether but worth noting. you can see the ring just down the side of the piston and notably hear piston moving side to side Quote Link to comment Share on other sites More sharing options...
Hemi Posted February 22, 2010 Share Posted February 22, 2010 Thats why im stumped eh, had mate around gave me a hand doing it.I got those dud compression results yesterday with my home made compression tester, assumed it wasn't sealing so grabbed another, same result. Have used this one in past and is trusted. Engine would start and fire but wouldn't run longer than 20 seconds or so, wasn't keen on reving past medium throttle, likely another issue altogether but worth noting. you can see the ring just down the side of the piston and notably hear piston moving side to side woah that a bit of a gap then :S . Quote Link to comment Share on other sites More sharing options...
Requiemk Posted February 22, 2010 Author Share Posted February 22, 2010 Compression was even so i disregarded timing aswell as being spot on when i pulled off the covers. Water i thought was due to headgasket, radiator pressure tester wouldn't grip onto my radiator cap so couldn't do test without buying a tester to suit. Signs of clouding in new oil and can see water marks slightly up dipstick, only shown after engine been running. Quote Link to comment Share on other sites More sharing options...
Requiemk Posted February 22, 2010 Author Share Posted February 22, 2010 yup^^ average considering the head gasket used cost quite a bit of money or he blew it then jipped be, i think its the latter. Wierd results though..... Quote Link to comment Share on other sites More sharing options...
eke_zetec_RWD Posted February 22, 2010 Share Posted February 22, 2010 checked camshaft timing? if its a fair way out can do this. also some forged pistons like ross racing run a huge piston to bore clearence and a huge ring gap when measured cold. Quote Link to comment Share on other sites More sharing options...
Spencer Posted February 22, 2010 Share Posted February 22, 2010 if you can move pistons you have a piston clearance issue, either its had a bore and standard pistons, r all ring lands are kaput?? with no rings you should have naff all movement, stock pistons aye? fuck I dont know sounds suss Quote Link to comment Share on other sites More sharing options...
Requiemk Posted February 22, 2010 Author Share Posted February 22, 2010 camshaft timing looked spot on. tdc both cam wheels lined up with markings and cams positioned in right place. Pistons appear to be stock, bores looked real tidy, no signs of ring wear and can still see honing marks. Appeared to be most of the play in front to back movement, not side to side as where id think it would be due to thrust Quote Link to comment Share on other sites More sharing options...
EFI_LC Posted February 22, 2010 Share Posted February 22, 2010 camshaft timing looked spot on. tdc both cam wheels lined up with markings and cams positioned in right place.Pistons appear to be stock, bores looked real tidy, no signs of ring wear and can still see honing marks. Appeared to be most of the play in front to back movement, not side to side as where id think it would be due to thrust You may need to dial the cam in properly... compression isn't an issue and gaps for pistoms not an issue IMO but the leak is the biggest issue, fix that then check compression, is the gasket on the right way? is it the correct one for that model engine? To give you an idea I run 11:1 compression but only read 125psi on a guage because of my cam and I can see the rings down my bores and run ACL flat tops and filed down rings. The overlap and lobe seperation could be causing the low reading, so now comes the question do you have the specs for the cam as if its a hot cam then it may pay to get it dialed in and I am not sure what a hot cam in a turbo should show as psi. Quote Link to comment Share on other sites More sharing options...
fuel Posted February 22, 2010 Share Posted February 22, 2010 who ran in the engine? Quote Link to comment Share on other sites More sharing options...
Requiemk Posted February 22, 2010 Author Share Posted February 22, 2010 i lost the guys number a while back with my old phone, not local. Already tried to track down but deadened, cant even remember his name to be honest, have had engine for a good year or so. Cams appear standard, no cam gears. There was no mention of difference camshafts from seller. Cams are key wayed onto cambelt pulley and all markings line up so im "assuming" its ok? I haven't played around with cams to much tbh How can you go past the obvious to me of rings/pistons? there is some obvious side to side play with audbile noise being made with wriggle side to side comparing this to other engine with same pistons (standard) and same bore size (measured). Quote Link to comment Share on other sites More sharing options...
mark105 Posted February 22, 2010 Share Posted February 22, 2010 measure your bore diameter if your worried about the play in the pistons, Nissan workshop manual i used to build my RB25 says factory sizing is 86-86.030mm, maximum wear should be 0.2mm so your bore shouldn't be anything over 86.2mm or it should have been bored out and using over size pistons. As for head gaskit as far as i know you can reuse the metal head gaskits (well my old man always has on the avenger) but they always reseal it with some copper head gaskit shit. Could be why your getting water in your oil maybe? How factory is this thing? can PM you link to Nissan workshop manual if you want all factory clearances (or just google the manual) Quote Link to comment Share on other sites More sharing options...
Requiemk Posted February 22, 2010 Author Share Posted February 22, 2010 Its fellow rb compression problem member Bores between both engines are around 85.5 85.6 mark on both engines so that sounds fine. I might look into head gasket reusing but due to possibility of it leaking oil/water ill play it safe a get a new one Quote Link to comment Share on other sites More sharing options...
mark105 Posted February 22, 2010 Share Posted February 22, 2010 haha yeh bloody RB's id say your piston setup is ok, but like phil said who ran the engine in? could be sealing badly. What do your bores look like? (sounds like you got the head off) head gaskit seems like a good place to start due to the water in oil problem. Quote Link to comment Share on other sites More sharing options...
Requiemk Posted February 22, 2010 Author Share Posted February 22, 2010 Guy had engine running in his s13 in new plymouth, was tuned/some work done at dobsons.We cant manage to pin point who it was due to my lack of knowledge but at the end of the day it doesn't fix my compression issue.... Head was definitely torqued down, some blow by was apparent through breathers with cranking so going to take engine apart tomorrow night (head off) and check it over. Quote Link to comment Share on other sites More sharing options...
fuel Posted February 22, 2010 Share Posted February 22, 2010 I suppose even poorly run in, the engine should yield at least 100psi.. a motor I just slapped together with new rings and bearings managed about 100psi evenish before first start up. Quote Link to comment Share on other sites More sharing options...
bubblegoose Posted February 22, 2010 Share Posted February 22, 2010 i tore down an evo engine i was going to tidy up as a spare, brought it as ( rebuilt not long ago but smokes a bit and has low compression readings on all cylinders) thought it was maybe rings and stem seals it wasnt, these are where the pistons are now every ring land on every piston had TWO big ass hairy cracks in it would be worht checking i suppose if your halfway there just drop on out for a squiz at its crack Quote Link to comment Share on other sites More sharing options...
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