704ci Motor Help
 

Just got a 42' Fountain/ Scism Cat from Randy at fasboats.com and brought it to the Lake of the Ozarks, MO. Boat ran good there is just oil coming from the K&N valve cover breathers on both engines. They are 704ci Dart Blocks with Brodix heads. Anyone have any suggestions on what to do to stop it?

How much thats the question. Blow by is normal within reason. If its no to bad you can run a hose up to the flame arrester. If motors are dry sump pipe breathers back to dry sump tank, then breather from top of dry sump tank out back of boat by tailpipes.

Thank you, It does appear to be quite a bit. It is running down the side of the motors to the transom. It probably looks like way more than it really is but there is quite a bit of oil. Everything else appears clean. Im not sure if they are dry sump or not. I'll have to find out. Im still in the learning phase :) Thanks for the info!

you don't know if dry sump or not. where do you check the oil? there are some things you just hafta know...

:worthless_without_p

Keep the rpm's below 5000, dry sump them or clean up oil.

Sorry dereknkathy, like I said still learning. The oil is checked with a dipstick that goes through the oil pan. Below is the link to when it was listed.



http://boatspotter.com/Page.aspx/dii...ain-Scism.aspx

the simplest solution would be breather baffles, somthing like this http://www.summitracing.com/parts/mr...-jxxoCX6vw_wcB If that does not work then catch can breathers work will but you have to drain them periodicaly http://www.summitracing.com/parts/ct...8_sBoCZ-rw_wcB

you can try putting an extension on the kn getting it higher further away from the valve cover which might help, or you can put puke tanks in . a hose off each valve cover that goes to a tank with a vent ..

WOW !!! Boat looks great. Hope you enjoy.
Sorry for sidetrack to subject in thread.

Most likely needs baffles in the valve covers like professor speed is saying. Cruising at 3500 RPM's for a long time theres a lot of oil slinging around under the covers.

If you used the dip stick to check the oil in the oil pan than the motors are WET SUMP, just for future reference.

704 ci is a lot of displacement. Which means there is a lot of displacement under the pistons as well, with a similar size crankcase to a 502. A well thought out and engineered crankcase evac system will prob be necessary.

might think about a puke tank mounted on transom....they are going to be pushing quite a bit of vapor out...engines new ? blowers ? keep a eye on oil level to make sure don't have a ring sealing issue

Those breathers should not be in the back of the engines. You have to move them forward in the valve covers.

Is there more crankcase pressure in front? Like to know the theory on that.

Thanks guys I really appreciate the help. Its all a learning process to me. The motors are fairly new. Tommy @ Chief Engines in Ft.Lauderdale built them in 2011 they have 20 hours on them. He just went through them three weeks ago and said everything was fine.

I believe he knows a thing or two about engines, especially his, so I would....yup....give him a shout. Definately no backyard schit you have.

or,,go to your local wall mart and buy some sport socks and slide them over the breathers for now,,this will help suck up the oil so its not all over the engine compartment..me personally with that big of cubic inch's i would look into a pait of vacuume pumps and catch cans to evacuate the engines..also i like to see the breathers in the front of the engines because when riding nose up the oil goes to the back of the valve covers...

I'd like to think that if the oil is pooling up to the point of the rockers slinging it around more so in the rear than the front, or spring, there are some serious drain back issues. My Dart heads have some pretty large drain holes for the oil in the front/middle/back part of the head. I cant really see oil level rising much under the valve cover especially when the oil is hot and flowing like water. Idk, I could be wrong. I had breathers on my engines 1 in front on port side, 1 in back on starboard side, merc valve covers.. Both leaved the same small amount of residue. https://www.youtube.com/watch?v=9vcWvp_DIWA

I would switch the valve covers from side to side to get the breathers up front and see what that does. If it doesn't cure the issue or make it more manageable you could drill and tap the heads/ oil pan and run external drains from the heads into the oil pan.

^^^^ thats a good idea. I`m still getting oil out the breathers and I have the tall Teague baffle breathers. I`m sure the spring oilers are not helping any but it drives me nuts .

if your boat is moving 70 mph and it is bouncing around a little bit the oil is being thrown to the rear of the valve cover.if the engine is stationary like on a dyno you do not have the foreward motion throwing the oil to the rear.it does make a difference.

The big cube motors have more blow by. I think you should move the breathers to the front (maybe as simple as swapping them). I would look into the pcv system to.

Wannabe

Is it that the oil fills up so high that the rocker arm on the 7 and 8 exhaust valves are is slinging it ? Or the spring itself ?

I had to mount mine in the rear this year because the tall teague breathers wouldn't clear my stellings if they were in front. Hope I'm not gonna have an issue

call tommy

Definitely call tommy. He's been building offshore engines a long time.

Hey guys, I found best with my blown 600+" motor is the tall baffles like Teague and the magic trick get some fuel cell foam. Pull the cap off the baffle and fit some fuel cell foam in the top and put cover back on!!:bunnydance: This has 99.999999999% fixed all my oil issues out the breathers. Before I did the foam after every time out i was back there wiping up damn oil.That and make sure you don't have oil coming out the oil dip stick. It would be a good idea to get a long spark plug boot over the dip stick to seal that up. Good luck!!

Skydog http://www.amazon.com/Racing-20217-F...fuel+cell+foam

Would evac tubes work? I have a 23 T-bucket with the evac tubes welded into the header. They are connected a hose to where the breathers would be on the valve covers and that stopped my oil issue at the valve cover gaskets. I don't see why this wouldn't work on a marine application. Just make sure they are properly baffled and keep checking your oil level.

http://i115.photobucket.com/albums/n...pse0489640.jpg

My question would be why did they put those low RPM monsters in a cat? I could see a big heavy Apache, but I would think that is a terrible application for a 704ci. Shows how dumb I am.

That's a HUGE cat man.

Why do they have more blow by?

My 632 has short el cheapo K&N breathers and not a drop of oil comes out. Previous 598 not a drop with same breathers. 598 6100rpm 632 6500rpm.

1. tons of stroke whipping air and oil around in crankcase
2. Unless the block is super ultra tall deck the piston pins are prob way up in the pistons with short skirts to clear that mongo stroke which causes the piston to rock in bore easier and compromises ring seal
3. as mentioned, the volume of crankcase is no kore than stock vs pumping action of pistons with a long ass stroke. I have a 2 cyl OMC air cooled engine in something that has tiny crankcase but large bore pistons and stroke, if you open the oil fill while its running it pumps air out of crankcase like a air compressor and whips oil around ferosiously

I would also tend to believe there is some ring seal issue, did the original builder "freshen" motors or test run them and say they are good to go? I would think about a leakdown test if we are talking alot of blow by. Everyone crys about them not working but I have had excellent results with my blown 540 using zero gap rings, less than 5% leakdown after dynoing and until it hits 80-120 hard hours very little blow by, I do also run tall breathers on front of valve covers, Smitty

I understand what you are saying and it makes sense. But I've been around these types of motors and have seen the opposite. I had an 865 in front of me running with the valve cover off and didnt have oil all over me. Granted it wasn't wide open spinning 9000 rpm but I noticed no signs of excess windage. Honestly, what I've noticed with these types of motors is that it seems like they have less windage. I mean the crank and rods practically hit the block. Oil gets scraped off the crank and rods by the block. I had a 496 that puked way more oil than the 598 or 632 I've had. Same valve covers and breathers on all 3 motors. And the 496 spun 1000 less rpm...

Are they blown? Are they dry sump? I feel when you get to 600+" dry sump is in order and even more so with boost.

No I'm poor. Can't afford cool stuff like a blower or dry sump. No, actually I was gonna go with a dry sump but engine builder talked me out of it said it was a waist of money on a motor like that.

A pair of 704cid's will have more Blow By Me's.

On a serious note,

I think blow by is being confused with windage and drainage. These are not the same.

It's like people calling water intrusion, water reversion. These are not the same.

Yeah I know what he was laying down. The point I was trying to get across is no matter how big the motor is it should not have so much windage that it pushes oil out the breathers. If the breathers are baffled and oil is being pushed out there is probably an internal problem. As Arcticfriends said I think a leakdown may be in order.

BB - I only quoted you so I could add the 'Blow By Me's" As in Blow Right By Me . LOL