Going through oil [Archive]

07-15-2005, 12:43 PM

First let me say that I plan on having a leak down test done in a few weeks to try and figure this out, my freinds shop is just too buisy right now to do it. In the mean time im gonna continue to use the boat as I have been. I just wanted to ask the ? and see what experiance others have had with this sorta thing.
Im running a BBC in my boat, this is the 6th season on this motor and it has approx. 150 hrs. I have allways babied it and as pathetic as it sounds never held it wot for more than 10 seconds. It has allways gone through oil and my oil has allways gotten dark very quickly (withing an hour or so of run time). Its run rich in the past (espesially the first two seasons) but not in the last few, yet my oil continues to turn dark in a short time. Ive tried smelling it but cant really smell that its burnt or that im running rich. This motor has also allways had alot of crankcase pressure, even with a pcv it still vents a little out the dip stick tube at times, not sure why. Im thinking the rings may have never seated properly? It runs and has allways run great, never let me down. I had the heads gone through before last season so im pretty sure my problem isnt there. Also, for what its worth the motor was setup with tight clearances a standard mellings oil pump and 10 quart pan. My oil temp is between 160 and 185 and im running Mobile 1 15/50. In the past ive run Kendal GT and Valvoline VR1 20/50, just switched to the synthetic this season and notice an increase of oil usage but better oil pressure. Depending on the results of the leak down test im thinking of just getting it honed and a new set of rings after this season, and mabye new bearings? What do you guys think? Any thoughts or suggestions would be appritiated.

SmokinLowriderSS

07-15-2005, 03:37 PM

Any smoke indications at all, smoke on letoff? What kind of valve seals you have? I'd be wondering why your rings may not have seated good. What type of rings did you use? Do you have a set of compression readings? Even w/o a leakdown, that tells you something. Run a comp test, then run again after shooting a squirt of oil in the cylinders (1 at a time) to help seal rings. Well sealed rings will show No change.
If you re-ring, yes I'd replace the lower end bearings just because they are cheap and you are there. My rebuild/upgrade last winter found SHOT factory A400 bearings after I have to estimate 300 hours but also NO cyl wear. I'm happy with Clevite 77's.
BTW, I've run mine WFO for MILES at a time, even on 150HP Nitrous for up to a mile teaching a Baja about speed.
Here was my last engine break-in schedule.
20 min for cam, 2,000 to 2500, no idle --- done. (new cam & valvetrain)
1 hour, no extended idle, run no higher than 3,500, no WFO. - done
1 hour, no higher than 4,500, no long WFO but short blasts OK. -done
1 hour no higher than 5,500. I'm topped off at 4,700 off N20. done
Installed remaining valve springs (only put outers in to break cam in) at 7 hours, then Nitrous OK. done
Have about 12 hours on her, runs hard, tuning carb issues but minior ones. No oil usage, no starting issues, givin' her he!! now. :2purples:

revndave

07-15-2005, 03:45 PM

My motor went through some oil at RWYB.Did a leak down #5 and #7 were at 50%. :frown: Took motor apart found 2 bent rods,2 bent pins,1 broken valve spring,2 bad valves and both head gaskets were blown.Rings and bearings were in great shape.Motor was running bitchin at the time.Just had burnt alot of oil that day.My oil temp runs about 150 to 210.Good luck with your deal.

SmokinLowriderSS

07-15-2005, 04:03 PM

Dayum RevnDave!!!!!!!!!!! Well, at least she didn't let go in an expensive way. :D

revndave

07-15-2005, 04:20 PM

Dayum RevnDave!!!!!!!!!!! Well, at least she didn't let go in an expensive way. :D
Thats funny. :D My engine builder called up and told me all that.He ended call with its not that bad. :D Could be worse.Could of let go at 7,000rpm. :jawdrop:

SmokinLowriderSS

07-15-2005, 05:10 PM

Yea, bent rods & wristpins are only a stroke of luck from broken ones. Got any idea what did it? I'm suspecting some water injestion.

revndave

07-15-2005, 05:43 PM

Yea, bent rods & wristpins are only a stroke of luck from broken ones. Got any idea what did it? I'm suspecting some water injestion.
Dont know what did it.Engine builder said water or fuel.Could of been that way when I bought boat also.Oh well.Get a new bullet done a go have some fun.Sh*t happens when you have big power engines.

szokejohn2

07-15-2005, 06:07 PM

here is the problem! you have a worn oil ring(s) or bad combustion rings.The reson that your engine is using oil is the oil rings that are desgned to lubricate the cylinder walls ,are pulling the oil in and the compression rings are letting the oil into the compression area.That would account for high pressure in the crankcase/block.The only solution is to rebuild the motor or keep adding oil the engine.
My 460 ford had a simular problem,I adjusted the timing too far advanced wich inturn crack all the piston tops .the engine which had never before used oil,now burned 3 quarts an outing.

desertbird

07-21-2005, 01:06 PM