Villeman Posted September 17, 2018 Share Posted September 17, 2018 (edited) Hey everybody, so we did a full engine restauration on my 76 280z and now I did 700km to break in the engine. It started to run rather rough after 450km and when I checked today, Cylinder Nr. 3 plug was all oily (2 and 4 looking perfect) and i could see an oil film on the cylinder (was up at that point). Also, oil pressure shows rather low (nearly 0 when idling hot and 1/3 on 3000rpm) but that could also be the gauge which is still the original one. So, did I mess up the break in? Engine had to sit quite some time after assembly and we put the rings in ourselves. Whats now the sensible way? (I am 500km away from my shop+tools). Could a head retorque work? I would like to try this before going to a shop for a compression test. Any other good way apart from a leakdown to differentiate headgasket from valve stem (somebody mentioned going to 4000rpm in low gear and have somebody watch for smoke when going off the throttle rapidly)? Also, there is a little leak close to cylinder Nr. 4 on the block but not oil..... Also: no overheating, no excessive oil consumption as far as I can tell that now. Oil is clear, not frothy. Did check for bubling in the radiator or hissing after running it 2 min cold. Pistons were new, as well as rings etc etc. thanks in advance Edited September 17, 2018 by Villeman Quote Link to comment Share on other sites More sharing options...
grannyknot Posted September 17, 2018 Share Posted September 17, 2018 A valve seal may not have been pushed on all the way, or a broken ring. You could retorque but it probably won't help, one way or the other the head has to come off but a compression and leak down test is what you need right now. Quote Link to comment Share on other sites More sharing options...
Villeman Posted September 18, 2018 Author Share Posted September 18, 2018 (edited) Here is the thing. I am positive I could fix the valve seal here and still drive the car (registration going another month before winter break) but definitely not a ring...thats why I dont want to take the head off here, no chance getting it home then (would you say it could be driven 450km in this condition?). Is there any way to visually inspect the valve seals with the cover off? If I get it right I wont gain much from a simple compression test because there already is oil in the cylinder? Any ways I will get a compression kit asap and then see Edited September 18, 2018 by Villeman Quote Link to comment Share on other sites More sharing options...
TimZ Posted September 18, 2018 Share Posted September 18, 2018 3 hours ago, Villeman said: Here is the thing. I am positive I could fix the valve seal here and still drive the car (registration going another month before winter break) but definitely not a ring...thats why I dont want to take the head off here, no chance getting it home then (would you say it could be driven 450km in this condition?). Is there any way to visually inspect the valve seals with the cover off? If I get it right I wont gain much from a simple compression test because there already is oil in the cylinder? Any ways I will get a compression kit asap and then see Have you retorqued the head since the rebuild? I always retorque the head on a new head gasket after a few heat cycles. It is certainly possible for the gasket to "settle" a bit and lose some clamping force. I would do this now if you've got access to proper tools - it's certainly not going to hurt anything. Do the retorque with the engine stone cold (let it sit overnight), use the proper tightening sequence and a proper torque wrench, and back each bolt off 1/8 turn or so before torquing. Just back each bolt off right before its turn to be tightened - don't back them all off at once. Sorry if you already knew all this, but a surprising number of people don't... Quote Link to comment Share on other sites More sharing options...
Villeman Posted September 18, 2018 Author Share Posted September 18, 2018 Thanks TimZ, will definitely do that. Today some friendly 180SSS geeks living 5km away came to the rescue (you cannot imagine how rare datsun people are over here). We checked spark, all good swapped plugs to other cylinders compression tested all cylinders --> no problem here checked valve clearance --> tiny bit off on cylinder 4 did a leak down. --> pressure went away very fast on cylinder 4 and cylinder 3 (sadly I now realise we only checked those two) but no bubbling or hissing anywhere..... did we do something wong? The mechanic said it would most likely be okay since there is no noises anywhere at 6 bar pressure Quote Link to comment Share on other sites More sharing options...
Villeman Posted September 19, 2018 Author Share Posted September 19, 2018 soooo.....I am basically an idiot.... the long version, looks like one injector seized or got blocked. I can still hear it firing with a screwdriver, but less defined, and when I pull the plug nothing changes as opposed to all other cylinders. Can I swap over the plug from cylinder 3? They should all fire at the same time, right? Just to rule out the cable.. Quote Link to comment Share on other sites More sharing options...
TimZ Posted September 19, 2018 Share Posted September 19, 2018 14 minutes ago, Villeman said: soooo.....I am basically an idiot.... the long version, looks like one injector seized or got blocked. I can still hear it firing with a screwdriver, but less defined, and when I pull the plug nothing changes as opposed to all other cylinders. Can I swap over the plug from cylinder 3? They should all fire at the same time, right? Just to rule out the cable.. Yes if it will reach Quote Link to comment Share on other sites More sharing options...
Villeman Posted September 19, 2018 Author Share Posted September 19, 2018 I just multimetered them. Plug/wiring seems good. I guess its either blocked or getting tired. (3 are acutally still the original ones). Anybody has 3 spares? ^^ Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.