What causes excessive Blow By
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=19353
Printed Date: September-28-2024 at 2:17pm
Topic: What causes excessive Blow By
Posted By: Riley
Subject: What causes excessive Blow By
Date Posted: September-07-2010 at 11:12am
| Our Mustang engine runs good. We've put about 20 hours on it. It has never been rebuilt or had a valve job to my knowledge. It doesn't use oil or smoke. When running along at speed it gives off a Blow By smell that gets stronger the faster you go. At idle it doesn't give off any fumes. It has a vacuum tube running from the engine to the base of the carb and the oil cap is vented. What causes an engine to do this? |
Replies:
Posted By: GottaSki
Date Posted: September-07-2010 at 12:06pm
|
heh, the engine is not broken in yet.
If you don't witness vapor from the oil cap, then it could be as simple as a small oil leak from a valve cover gasket, onto the exhaust manifold. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: 63 Skier
Date Posted: September-07-2010 at 2:33pm
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Any chance it's exhaust smell, not oil? You could have a small leak from the exhaust manifold gasket or hose and it might give you that smell. I'm not sure why, at speed, you smell anything with the breeze going by! I have that exhaust smell following me at just below planing speed but it goes away with a few more mph. ------------- '63 American Skier - '98 Sport Nautique |
Posted By: Riley
Date Posted: September-07-2010 at 3:01pm
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I'll try checking for an exhaust leak and tighten down the valve cover. I never thought of that. It smarts your eyes and burns your throat afetr a while. ------------- |
Posted By: GottaSki
Date Posted: September-07-2010 at 3:13pm
I believe the when the ventalation is inadequate, the cockpit with windshield creates a low pressure area that pulls air from the bilge up and dumps it by your feet and swirls around. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
63 Skier wrote:Posted By: 63 Skier
Date Posted: September-07-2010 at 3:13pm
|
My ventilation setup (or lack of) is interesting. There is no bow vent, no stern vents, nothing. The floorboards have a gap around the edge. The former owner said the idea is the engine pulls air from the motorbox, the make-up air flows all around the bilge keeping fumes from collecting. It seems to work, I've never smelled anything from the engine. That's why I'm surprised you could smell this so strongly with the boat moving fast, you'd think there would be enough air flow.
Because of this, and no blower, I open the box for a few minutes before 1st startup, good idea anyway to look over everything. ------------- '63 American Skier - '98 Sport Nautique |