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why and what to do about crankcase pressure

3K views 11 replies 10 participants last post by  Outlaw 
#1 ·
Finally got a day off to take the boat out for 1st time since installing the new tunnelram setup. After a small bit of tweeking, woooooohooooo!! damn what a difference. Did a bit of tearing it up and decided to stop for a bit in a vacant cove and give everything a quick once over and SHIT oil all over the place.
Well after wiping things down and some closer inspection we discovered it was blowing back out dipstick and breathers at a very messy rate of speed.
I have read that this is pretty normal when running tunnerams (not sure why) but what the heck is the best cure?
460 Ford - basically stock - mild cam.
Any help would sure be appreciated. Weather is finally to damn nice here to be cleaning - time to be terrorizing Thanks :)devil
 
#3 · (Edited)
It isnt just worn out engines, or engines with a bad valve that can do it.

Fresh engines and efficient roller cams generate a lot of crankcase pressure.

(Providing everythings actually right.)

I had to switch to dual breather speedway style valve covers for my 500hp 406.

If you dont relieve that pressure you will start pushing out gaskets and thats bad....


Uncle Dave
 

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#4 ·
I am new to jetboating but I'm not new to high performance engines. On a few motors I've built I have had to run a crankcase evac system to relive psi. It is essintualy a hose in each valve cover that runs to your headers to pull the psi. out. I'm not sure if this would work on a jet or not due to the water system. A kit could be had from just about any mail order catalouge for around 50$.
 
#9 · (Edited)
i often wonder about those flame arrestors with the dual ports i kinda have the same issue with mine
 

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#11 · (Edited)
Well here is what I am trying 1st --- There are now 3 breathers on the valve covers. 2 of them now have the "baffle style" groments in them, the other has an open groment as it will still be the oil fill as well. I compared all 3 breathers and put the one with the tightest bend in the flap inside the opening hoping maybe it would help.
I am thinking that after realizing the the baffle style groments exsisted and now it isn't a nice unimpeded straight shot off the rockers that things will be all better. Oh ya - also have a rubber carb vent cover that will fit snugly over the dip stick tube if it still wants to fling oil.
Here where I live in Idaho, if the word "performance" is anywhere even closely involved with a part you can flat forget about finding in stock here so this was about the only route I had the option of and still making the lake this weekend.
Will let you know how it goes
 
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