19concept88

I have a 1988 300 block that has been bored 40 over and has a mild cam. The stock heads are ported and polished along with roller rockers and lifters. The intake is a dart high rise with a holley 850 double pumper. I am blowing oil out of my rear main seal over 3,000 RPM's. My oil pressure gauge at idle is fine but when I get on it it builds up to 70-80 and stays there until I drop down below 3,000. I pulled the motor and replaced it and the very first time I put it back in the water it did the same thing again. I have no idea what is causing this. I am tired of having an oily bilge. If anyone has any ideas or has had this problem I need some help. Thanks for reading and appreciate any information out there anyone can give me. Thanks

BigDaddyM

I'm not really sure, but I know there's people here who would be able to help.... only thing that comes to mind is some sort of blockage, but I'm confused as to why it would blow out the rear main seal, and not blow something else out first....

Chris Sunkin

Which direction are you installing the seal? I've seen them in backwards before. Are you rotating the seal so the ends are staggered from the cap? How is your crankcase ventilation? Any modifications to any of the block's ventways? What valve covers? What oil pan? Possibly over-filling? Any exotic windage tray/scraper system? Standard cam drive?

19concept88

I have newer style valve covers from a 502 that are not baffled. We had to cut the baffles off for them to fit correctly. I have routed ventialtion two ways. 1) I routed both lines to back of carburetor and 2) I currently have breather valves not PCV to flame arrestor. The rear main was put in correctly I know what you talking about when they are incorrectly installed. I think it is a crankcase ventilation problem. I have also been told that there is a valve in the oil pump that could be stuck as well. Any other ideas would be appreciated. Thanks for chatting about this

Chris Sunkin

I don't know that there's any way around baffles. You can try a puke tank but it'll eventually fill up with extended running. I don't know what you have going on with the routing to the carb but unless you have a 3/4" hose from both valve covers running to the flame arrrestor, you don't have enough. Without baffles, it's going to fill your arrestors with oil anyway.

19concept88

There is a T fitting that comes off the back of the carb that helps with crankcase pressure. We changed the routing from the carb to the flame arrestor. I think I will try the 3/4 hose and see what that does. I think I only have 1/4 hose coming from breather valves.

Chris Sunkin

My guess is the fitting you are talking about is the vacuum tap for auto accesories

Without baffling, you'll get the full force out of the tubes. You need something in between, like a catch tank. It will expel oil until you have no more or it chokes out the engines, so be careful.

Comanche3Six

80 psi seems excessive. I would think 60 psi.