400ex motor blow by

[jgfarmsracer]

i have a 99 400 that started blowing oil out of the crank case

breather anybody know anything about it, it is a 416 with a 11:1

comp piston ,sparks full race cam, short valve guides, and a new

oil pump

[Castor-426ex]

did you overfill the engine with oil?

[jgfarmsracer]

no i sure didn't, i even tried it with only 1 qt and it still does it

[Castor-426ex]

how long does it take till it starts to blow by?

sounds like the rings are worn etc. and letting the comp from the motor get into the crankcase

[jgfarmsracer]

just as soon as i start it


it has done this ever since i rebulit it, even durinin the first start up it had a lot more pressure than my stock motor

[Dudefire607]

It's your rings my man. Probably didn't seat correctly. You need to get yourself a glaze breaker and a new set of rings. Sucks, but at least it's cheap. I had the same problem with a 327, oil shootin' out the dip stick tube! Talk about a bummer...

Good Luck,

DF

[swamprider7]

Did you gap your rings properly?

[kineo3]

I have stock 2000 400ex with the same problem. I have it in the shop right now. I have done a compression test and a leak down test and the dealership said there is nothing wrong with this motor. The leak down test came back a little high but well within opereating parameters. I am going to tear it apart and put a set of rings in and hope that does the trick. I have found that this is not very common, you must be lucky like me.

[Leo]

Originally posted by RED121572
Rings? Come on, think about this....

He said oil is blowing out the crankcase vent. The crankcase vent is on the crank and connects to the airbox. Something is amiss with the bottom end. If the rings were bad, oil would be blowing out the tale pipe.


The compression blows by the rings, pressurizing the crankcase, and pushes oil out (if bad enough)..

If it started right after a rebuild I'd be willing to bet that either the jug was bored out of spec, or the rings are on wrong (upside down, all the gaps lined up, oil ring not assembled properly) something of that nature.

Leo

[jgfarmsracer]

thanks guys for the help, i'm goin to get into it tonight, hope it's just the rings

[skemp]

I have an old Ford Festiva I picked up for $100 that has a little blow-by problem. Exhaust comes out the valve cover when I take the cap off, and the oil has the strange scent of gasoline... Who would think on a car with only about 200k on it. ;) It still runs great though!

Anyway, most likely a ring problem, but this situation is strange considering you just did a rebuild. Perhaps the shop that did the bore job didn't hone the cylinder enough, or in the right pattern, or even not at all... :eek: This would cause the rings not to seat or at least not properly. Another possibility (but not as likely) is that you have a valve problem. Unless it is really bad, I wouldn't expect it to leak enough to cause that much pressure, but a bad seal or worn seating surface could do it I suppose. Just pay attention when you tear it down and look for any valvetrain problems.

Good luck man, I don't think it will be anything too costly. :)

[jgfarmsracer]

i pulled the head off last night,valve's are great , their is no ring grove, the oil ring(bottom) might have been stuck a little.Had the jug checked today and it's great and straight . So i'm going to hone it and put new rings in it.

[norcalatver]

what did you finally find out about your blow by? I've had the same problem since my 505 rebuild. It only happens when really screaming the motor at the dunes though. I'm running 250lbs. of compression also.

[jgfarmsracer]

it was the rings