Thread: crankcase pressure.....

Tweet

Based on a 14:1 compression 496, used for racing and occasional cruising, what is the best way to get rid of crank case pressure? I really don't want to go with a vacuum pump....only because I have no experience in using one. I don't think the breathers with tubes to the headers work that well with mufflers. Please give me some opinions / ideas. Thanks.

You can plumb it into the intake and possibly put the whisle behind the muffler

I never heard of that one.....it makes sense that it would do the job. Have you done it before? Thanks.

yes--the original vents from Moroso had three check valve/anti backfirevalve--- one for the whisle by the collector and one in a hose to the intake(kind of like a PCV) My prostock prostock had two instrument up by the tach--oil pressure and vacume--always looked at all three readings as I crossed the line--could tell by rpm how fst and hp , if not up where it should be vacume/oil pres were clues

well if you use a vac pan with valves in the collectors with a full EX with muffler it wil not work . it will not work .it will not work .did i tell you it will not work . that how many times i tried to use it on the street . had it on a 3inch ex 462 12.5 cr tried it on my 548 14.8 cr street engine with a 4inch EX. and tried it on my 468 with 2.1/2. when you let off you get some back presure close the valves in the collectors and the engine will vent it self by shooting the dip stick out of the tube and blowing oil all over or blowing oil out of the rear main seal the rear main deal just happen last week when i built a 427 for a guy look at him told him over 4 times not to use the race setup with his EX , well it blu oil all over . what jerry could work long as it can vent if you get off the gass the crank case can vent .that vac only work when you have a good flow . you can make up a mainfold with to breather s in it then on each end weld weld 3/4 nips going down to the collectors then it would work . on all my big stuff i just use push in valve covers breather and let it vent

So....really, I'm better off getting rid of the evac tubes that I have going from the valve cover breathers, to the collectors, and just running good breathers in the valve covers? The valve cover breathers will let it vent enough to keep from blowing the rear main?

Originally Posted by lodilobo

So....really, I'm better off getting rid of the evac tubes that I have going from the valve cover breathers, to the collectors, and just running good breathers in the valve covers? The valve cover breathers will let it vent enough to keep from blowing the rear main?

yep i .it could be made to work jerry may know of a way .the manifold deal you may have seen on road racing engines i was goning to try this .i did make up some thing like this for a air boat i built a 526 for but with out the evac hookups that could work . you have to make sure the ex pressure at any rpm is not going to not let the evac valves from working is seamed to happen every time i try to use it on the street. so i just use push in breathers .the rear main seal deal was that the block could not vent the crank case so in that case it is going to and did past the rear main seal it did not pop it out but it did push some oil past it not gallons but a good drip .on that block the rear main seal was the weak link .but most of the time it will blow the dip stick out

I'm going to give it a shot. Thanks for thr info.

Originally Posted by lodilobo

I'm going to give it a shot. Thanks for thr info.

going to what a shot stock evac pan set up not rework it will not work with EX give it a try if you want

Based on Jerry's post....route evac hoses from the intake to the exhaust.... AFTER the mufflers. In fact, before I do that, I will try running no evac tubes.......just good breathers in the valve covers. I get the distinct point that evac hoses from the valve covers to the headers, when running mufflers will make the crank case pressure worse.

I have an L88 I drive occasionally on the street. I've always run my piston to cylinder wall clearance a little loose (.007-.008) because I spin it hard. I run the moroso breathers with the 5/8 outlet in the valve covers. I have the hoses run across the intake and just leave them open under the car. I never run the engine hard until it warms up and hoses don't make a mess or cause a drip. I tried the hoses to the exhaust setup one time and kept pushing the front and rear seals out of the intake manifold.