What could cause air to puff out of the crankcase, without coolant fouled oil?

enkeivette

enkeivette

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Mar 30, 2008
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Jumped on it yesterday, I spun pretty bad in 2nd, might have bounced off the rev limiter. After I let off, there was light smoke creeping out from under my hood. Pulled over and you can feel air puffing out of the crankcase at idle, a lot of air. There is no coolant in the oil, so I'm confused.

Wouldn't a HG leak allow coolant to fall into the cylinder and contaminate the oil? Could it be a crack in the piston, or maybe a broken ring? I would think even a cracked block would allow coolant to contaminate the oil.

I pulled the SC bonnet off the carb (which shouldn't pressurize the intake at idle with the BOV open anyways) just to be sure it wasn't an intake leak, no luck, still puffs air out of the rocker covers.
 
Yea...like you had nothing better to do this week-end. :banghead:Can't be much else than a holed piston. Even J/E told me not to trust their down-line forged piston (SRP) for my s/c'ed set-up @ 15-16 lbs. boost. (I have J/E blower pistons).
 
I'm kinda thinking that it's a blown out ring and not so much the piston. The pistons are all forged and it's not making that much power to melt a piston.

I've always been suspicious about my rings on the other hand. Last dyno day we had to stop because of excessive crankcase pressure blowing oil everywhere. When the motor was fresh is made 150psi, after break in it made 135-140 psi. Someone suggested that the rings might have been installed upside down.

I'm poor right now so if the pistons are good I'll prob just upgrade the rings, and install them correctly.
 
You have a broken ring and/or a broken piston. If the ring broke bad enough to cause crankcase puffing, it has also trashed the piston ring land and scored the cylinder wall.

You don't even need to do a compression test. Just pull the engine and tear it down. The broken ring/piston will be very evident upon teardown - pre-teardown testing and evaluation is a waste of time - it will only tell you what you already know.

Lars
 
Lars is right.....but I was "poor-boy'ing" it. On a budget, I would find the dead hole and pull the head/oil pan/piston&rod affected, then if the cylinder is not too trashed, ball hone it. Throw a new piston & ring pack in and button her up. OTOH, if it happened to 1 piston, how do the other siblings look?
 
big_G said:
Lars is right.....but I was "poor-boy'ing" it. On a budget, I would find the dead hole and pull the head/oil pan/piston&rod affected, then if the cylinder is not too trashed, ball hone it. Throw a new piston & ring pack in and button her up. OTOH, if it happened to 1 piston, how do the other siblings look?
Click to expand...

Ditto, seen it B-4.......sorry man, that sux the green weenie....

:sick::gurney:
 
I'm not upset at all, it's a project car. I'm supposed to break it, find the weakest link right?

I'm still going to pull the heads off in the car. If the cylinders look ok, I'll change the pistons out with the motor installed.
 
In the long run, it's faster and easier to just pull it, and put it on a stand. As tricky as it was to pull that 454 from that Winnebago, it saved lot's of time in the long run, and was far easier out of the vehicle.
Sometimes more is less.;)
 
big2bird said:
In the long run, it's faster and easier to just pull it, and put it on a stand. As tricky as it was to pull that 454 from that Winnebago, it saved lot's of time in the long run, and was far easier out of the vehicle.
Sometimes more is less.;)
Click to expand...

:bounce: DITTO!!!:clobbered:
 
Pull it.

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Michael.
 
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