I did a search and couldn't seem to find and info on the subject.

So from day 1, I've had blow-by on my 390, ever since I got it rebuilt. Now, I know alot on the subject but never been able to figure it out.

Whats happening is that oil is spewing out of my valve cover breather caps. I know there should be ventilation hookup with the PSV on the left side plugged into the base of the carb. But I axed this because I didn't like the oil pushing threw into the engine. Part of the problem could be the baffling on my M/T covers, but there is a noticeable amount of pressure even at idle, in which you can see steam coming out of the caps. I'm thinking there could be some coolant in the pan creating this.? The engine is now getting tired after drag racing for so many years, but its always had even a little crank case pressure venting out. Compression originally was hovering around 140, but now running around 100 and less. I'm just wondering how normal this is. Even my brothers 500hp 429 has a little steam out of the caps.

One last comment, I do have a high volume oil pump so that could be causing the leaking caps I guess. Pressure is running as high as 70psi, and as low as 30psi.

Oh, and does anyone have any info on rebuilding the valve rails, and what wear to look for? I seemed to be getting alot of valve train noise.

 

I have the same problem as you. Pressure around 100 and oil blowing out both valve covers. Good thing is my truck will not rust

I have a high pressure oil pump too, a Melling HV57, if I remember the numbers correctly. Puts out about 30-40 psi at idle and can go to 60. Two trains of thought since I want mine to last 30K before I pop in a new one.

1) replace the oil pump

2) Tube the PVC and breather together and link them to an oil separator/breather with a one qt capacity. They sell about $80 at SUmmit and PAW.

Right now I am burning most of it through the carb. I would like to get rid of that since it fouls the plugs after a while.

 

Without pcv smoke comes out, normal. I had to junk pcv for a old carb I wanted to put on. Hard driving also causes it to smoke

 

Guys, if you are really getting as much blow-by as you are describing, your rings are probably very worn. If you have had lots of blow-by from day one, chances are the finish on the bores was not done correctly when the engine was rebuilt. But if you still have 100 lbs compression and the engine runs okay, the question is what to do with it now ? I would get some factory style valve covers that have the proper baffles in them, and then get some nice breathers for the engine. I've seen some nice chrysler style ones that have a big hose barb on them. Next get some hose or tubing or something and feed the blow-by from your breathers into the air cleaner. The breathers will get the oil out and let it drain back into the engine, and the hoses will let the rest of the vapours get recycled. There is also gasoline fumes in the blowby, it is better to suck it back in than just let it blow out into the air. As to your oil pumps, the M57HV pump is not causing you any trouble. You might try switching to 20-50 oil and see what happens. The thicker oil will give you higher pressure ( which won't hurt anything ) and will have a tougher film strength. This might help the engine burn less oil. You might also put a restrictor in the passage feeding the heads, if there is less oil under the valve covers, your stem seals won't have to work so hard. DF

 

Thanks for the reply. I had the heads off it after the drag racing and the walls were still showing the hone marks. I also haven't had any oil being burned out the exhaust so the crankscase is only pressuring up. I'd say at this point I need a rebuild because of the low compression, but it seems funny that there's so much pressure build up right from rebuild.

 

Update:

I brought this back up to see if anyone else is having the same problem. I did a compression test on all cylinders and I'm getting 145-150lbs amazingly. Hearing issues regarding restrictive oil drain back, I'm really thinking my HV pump is pooling the oil in the valve covers. My breathers only have a 3/4" hole plus a baffle and still.