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> over-pressurized case
bd1308
post Jul 14 2005, 09:58 AM
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runs great without oil filler cap. runs sucky with oil filler cap on. a bit overfilled (damn valvoline guy)....is this the reason?
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Mueller
post Jul 14 2005, 10:01 AM
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better get out your tool box, a few more weeks and you'll be installing a new engine (IMG:http://www.914world.com/bbs2/html/emoticons/wacko.gif)


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bondo
post Jul 14 2005, 10:02 AM
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I nominate you for a V8 conversion. I bet we could sell tickets to that. (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)
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bd1308
post Jul 14 2005, 10:02 AM
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sigh.....

mike, is the oil being overfilled the reason i'm having my problems or is it blow-by?
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ArtechnikA
post Jul 14 2005, 10:04 AM
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what's "a bit" ? lots of AX guys run a qt overfull. is it more overfull than that?
if you think it's a factor (i don't...) drain it all and add 4 measured qts.

case pressurisation is usually a symptom of something else (bad ring seal, usually) but i can't tell you how the crankcase vent hoses should be vented, and i can't begin to guess what's been done to your engine...
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bondo
post Jul 14 2005, 10:06 AM
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On a more serious note.. I doubt it's overfilling, people do that all the time for racing (so it doesn't get starved on turns). Taking off the cap is probably affecting the FI, through the PCV valve.
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bd1308
post Jul 14 2005, 10:08 AM
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its carbed. i think its rings. how much air is supposed to flow through the PCV? I am getting like 1/5 teh total air out of the PCV.
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ArtechnikA
post Jul 14 2005, 10:10 AM
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QUOTE (bondo @ Jul 14 2005, 12:06 PM)
...Taking off the cap is probably affecting the FI, through the PCV valve.

through the PCV valve, across the room, and onto the bench where all the FI parts sit in a pile...

as you may (not) recall from an earlier episode of our ongoing adventure serial, BD's engine is now running on a single central Holley (or Harley, i forget...) carburetor. last i heard it was running great; now, evidently not so, ("sucky" was used...) but i may have missed an episode or two between then and now...

you gotta keep up on this stuff - it won't be into re-runs until Fall...
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Mueller
post Jul 14 2005, 10:11 AM
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single carb........

do you have a line going from the crankcase to the carb or airfilter?

if so, what is happening is that the oil vapor is being ingested into the combustion chamber, oil vapor displaces air and does not burn...so you have a crappy air/fuel ratio


if the crankcase does not connect to the intake one way or another, you need to get a puke tank and a larger diameter hose to relieve the pressure....seems like an odd thing to be happening, but who knows???
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bondo
post Jul 14 2005, 10:13 AM
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I thought a PCV valve was supposed to be pretty much closed at idle.
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ArtechnikA
post Jul 14 2005, 10:13 AM
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QUOTE (bd1308 @ Jul 14 2005, 12:08 PM)
... how much air is supposed to flow through the PCV?...

there isn't supposed to be *any* air...

practically, there may be a little.

if your blowby is overwhelming the PCV valve -- assuming it is the right valve, and working properly, and plumbed where it's supposed to be -- to the extent that it's affecting proper engine operation - that's too much ...
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bd1308
post Jul 14 2005, 10:15 AM
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rich, IIRC the crankcase pressure has NOTHING to do with the induction system....whether carb'd or FI.

i get no oil smoke out of the exhust, so im wondering why the pressure is so high in the crankcase....

the carb episode is finished. DVD coming out soon.
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Allan
post Jul 14 2005, 10:16 AM
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How do you know what the pressure actually is?
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ArtechnikA
post Jul 14 2005, 10:18 AM
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QUOTE (bd1308 @ Jul 14 2005, 12:15 PM)
rich, IIRC the crankcase pressure has NOTHING to do with the induction system....whether carb'd or FI.

i agree.

so i guess i donno what point you were trying to make.

excessive crankcase pressure will make a boxer motor run bad. it has nothing to do with the induction. it has to do with trying to compress the air between the pistons in the case.
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bd1308
post Jul 14 2005, 10:19 AM
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theroretically what would happen if the oil was overfilled past the "safe for racers" point?
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Mueller
post Jul 14 2005, 10:24 AM
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QUOTE (bd1308 @ Jul 14 2005, 09:19 AM)
theroretically what would happen if the oil was overfilled past the "safe for racers" point?

what do you think will happen....it's called path of least resistance...if the pressure is too much, the air and oil will find a way out of the motor...blown valve cover gaskets, pushrod seals, rear main seal...etc...etc...

normally too much oil equals smoke from oil seeping past the rings or valve guides (that would have to alot of oil), esp. on a flat motor
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bondo
post Jul 14 2005, 10:27 AM
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QUOTE (bd1308 @ Jul 14 2005, 09:19 AM)
theroretically what would happen if the oil was overfilled past the "safe for racers" point?

Oil hits crank, crank whips oil up into foam, foam takes up more space, so level gets even higher, and gets more foamy. Eventually your oil pump ends up picking up oil with imbedded air, which it can't pump too well, and doesn't lubricate to well. Oil pressure drops, and bearings die.
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bondo
post Jul 14 2005, 10:29 AM
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You have a dipstick, right? I've had it as high as about 1/2" above the full mark with no apparent problems. Where are you at?
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bd1308
post Jul 14 2005, 10:31 AM
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less than half inch
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mudfoot76
post Jul 14 2005, 10:34 AM
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QUOTE (bd1308 @ Jul 14 2005, 11:31 AM)
less than half inch

Do you have a working oil pressure gauge?

How are you measuring case pressure?

I routinely run with oil level about 1/2 qt high, esp for HPDE events. High speed corners a'plenty at Putnam Park. I've not had a starvation issue, nor an overpressure issue on the new engine...
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