LJDB 103 Posted December 19, 2017 Ok guys my old trusty xflow turbo started to develop lot of blowby and started to miss under light load. Check comp cylinder 2 and 5 are low. Check leak down and it was coming from the crankcase. Pulled the head off and no major signs of a head gasket failure. Engine hasn't been together all that long so gasket still look newish. Block still in car and the Pistons and bores show no signs of wear. Is there another test I can do before a full pull down to check the Pistons and rings. I've blown a head gasket in my previous high comp na setup and the sypmtoms are the same. Share this post Link to post Share on other sites
dex 2,065 Posted December 19, 2017 Few drops of oil in the cylinders ,, see if compression reading changes 1 Valvebouncer reacted to this Share this post Link to post Share on other sites
deankxf 20,266 Posted December 19, 2017 has it burned an exhaust valve? valve seat recession, sticking valve.. if the head is off. what's the ridge like on top of the bore.. if decent, it might have broken a ring if no ridge and no scores in the bore i'd lean towards cracked head, burned valves, etc.(head issues) unless the cam is wiped and no inlet lift on those cyls. 1 Valvebouncer reacted to this Share this post Link to post Share on other sites
LJDB 103 Posted December 20, 2017 Verdict is in. Cracked Pistons between top and bottom compression rings. 28cc mahle Pistons in the bin. It was fun while it lasted. Just had a clutch turn up for it from xelisty. I've got another bottom end here but the Pistons have the large cut out in the oil ring groove. Better than nothing I suppose. Share this post Link to post Share on other sites
deankxf 20,266 Posted December 20, 2017 are the broken ring lands from pinging(timing or crap fuel) or even a ridge on the bore(doubtful) Share this post Link to post Share on other sites
XPT 673 Posted December 20, 2017 What's your ring end gap? Did you open it up from standard to accommodate boost? Share this post Link to post Share on other sites
LJDB 103 Posted December 20, 2017 Looks to have got hot on the exhaust side. Pinged a couple times when I first got it going. Ring gaps where enlarged. 1 deankxf reacted to this Share this post Link to post Share on other sites
gerg 10,871 Posted December 20, 2017 Strange that it's on 2 & 5, as they're one cylinder in from each end of the motor. Does it look like it's had a lean-out?Sent from my CPH1607 using Tapatalk Share this post Link to post Share on other sites
LJDB 103 Posted December 20, 2017 Data logger looked good although I was fattening it up when coming on boost. I'm using a xf efi inlet and have heard they have distribution issues so maybe that was the cause. Clean side of piston is the inlet sideim a little disappointed as all the other piston I have look like this and I'm not sure how they will go. Share this post Link to post Share on other sites
XPT 673 Posted December 20, 2017 What fuel were you using? What were your afrs? Share this post Link to post Share on other sites
LJDB 103 Posted December 21, 2017 U can see why i was trying to fatten it up when coming on boost. I had taken a heap of timing out of it aswell. This was done by road tuning not on a dyno. Share this post Link to post Share on other sites
XPT 673 Posted December 21, 2017 It's far too lean under boost, I'd be aiming for mid 11s under boost. It comes on around 1600rpm and you're in the 13s somewhere then getting leaner again into 14s 😲. Wow no wonder it pinged Share this post Link to post Share on other sites
LJDB 103 Posted December 21, 2017 This log is from early on when i first got the data logger working. As i said i was in the process of fattening it up when coming on boost. Id say the damage was already done. The base tune was already in the chip and apart from maybe twice there was no audible pinging. I suppose me being impatient and not waiting till i could log a/f to give it a thrashing wouldnt have helped the process. 1 Valvebouncer reacted to this Share this post Link to post Share on other sites
Valvebouncer 2,389 Posted December 21, 2017 At least your honest. It’s a bugger that it happened though. Share this post Link to post Share on other sites
Ando81 2,949 Posted December 21, 2017 That sucks mate but yeah props for admitting your error and not blaming everyone else possible. I can understand you being keen to give it a thrashing, I’d be exactly the same. I hope you have a positive outcome 2 Lord_fahrquhar and Valvebouncer reacted to this Share this post Link to post Share on other sites
LJDB 103 Posted December 21, 2017 Spark plugs showed good colour, no audible pinging and a bump up in fuel pressure for good measure gave me confidence it was ok. I don't have a problem admitting fault. I had planned to use a well used 250 as a guinea pig but went with this one instead. I've done everything to this car from front to back and there have been lots of ups and downs. If it was easy we probably wouldnt bother or I'd put a Barra in. Aleast it was only a set of plugs and didn't go completely boom Share this post Link to post Share on other sites
Lord_fahrquhar 2,580 Posted December 22, 2017 Learn from it and build it up again. love the honesty mate too can be hard to admit a times 2 LJDB and Demmo reacted to this Share this post Link to post Share on other sites
LJDB 103 Posted January 2, 2018 Rnd 2 starting shorty. Just finished putting in a used 86da, .030 22cc ACL duralite pistons, backyard ported open Chamber xe efi head. Comp is around 9.1-9.2 with a different NA cam with more overlap. Hooked up the knock sensor into the front head bolt the same a late efi Xf. Il take it easy with this one till the tune is fat as I want it to last the summer. 3 gerg, XPT and Valvebouncer reacted to this Share this post Link to post Share on other sites
