704ci Motor Help
07-10-2014 | 08:55 AM
#42
Platinum Member
Joined: Jul 2008
Posts: 931
Likes: 0
From: Little River SC
The fact he has 704 in the cat, at this point really doesn't matter. Maybe not the best choice for a boat needing rpms, either way the engine is blowing oil out.
He most likely has a 5.300 stroke , and a 4.600 bore, so he is moving a lot of air. I would try 2 breathers per valve cover as a trial. Stefs sells some step breather tubes that are about 3" tall that have to be welded on the top of valve cover. They also have a breather kit with puke tank # 5120. The larger the hoses are; the lower the velocity of the air flow, the tank also has 2 breathers and baffles that also lower the velocity of the air. Give Stan @ Stef's a call, I know he will be able to help you.
Even with a smaller CID engine this can happen, with the location of the rocker arm squirting oil, into breather air stream or to small of ventilation with higher velocity air flowing picking up the oil mist. You can also have blow-by caused by the pistons rings fluttering due to gas build-up between top and second rings. I have had to change the style of breather, I will use; the cast aluminium style with steps inside, some have a cast in top cover and some have a screw down top that has more ventilation area.
He most likely has a 5.300 stroke , and a 4.600 bore, so he is moving a lot of air. I would try 2 breathers per valve cover as a trial. Stefs sells some step breather tubes that are about 3" tall that have to be welded on the top of valve cover. They also have a breather kit with puke tank # 5120. The larger the hoses are; the lower the velocity of the air flow, the tank also has 2 breathers and baffles that also lower the velocity of the air. Give Stan @ Stef's a call, I know he will be able to help you.
Even with a smaller CID engine this can happen, with the location of the rocker arm squirting oil, into breather air stream or to small of ventilation with higher velocity air flowing picking up the oil mist. You can also have blow-by caused by the pistons rings fluttering due to gas build-up between top and second rings. I have had to change the style of breather, I will use; the cast aluminium style with steps inside, some have a cast in top cover and some have a screw down top that has more ventilation area.
07-10-2014 | 10:23 AM
#44
Platinum Member
Joined: Jul 2008
Posts: 931
Likes: 0
From: Little River SC
That's a loaded question! I would have to have someone explain to me how velocity would change from the front verses the rear. All breathers I have installed mostly have been in front, centered and sometimes staggered front to rear. As I mentioned the location of rocker arm spraying oil into air stream would do the same thing, if the oil is only coming from one breather, I would be guessing that would be the issue. It all depends on header clearance over valve cover, I have had 2 breathers on one side only, like a 41 Apache with half- stagger and the port tail pipe runs right over the stbd valve on the inboard side. Those were 1100 hp with 14-71s little over 8 psi.
Thinking about this; this guy could have a small moisture issue that is making some steam and mixing with oil, that will also cause this condition. He could buy, a blow-by-tester also and check it.
Thinking about this; this guy could have a small moisture issue that is making some steam and mixing with oil, that will also cause this condition. He could buy, a blow-by-tester also and check it.
