402 BBC oil leak when driving but not at idle??

I have a project and last week I drove it around for the first time any distance.
It sprung a pretty good oil leak somewhere. It's a 72 chevy 402. The strange part is, it doesn't seem to be leaking at idle.
I had it running for a while this weekend and it didn't leak while I was under it.
When I drove it around the flywheel was covered in oil and flung it all over, I bought a new 1 piece oil pan gasket for it, but I was wondering if anyone here has had a similar leak.
I have to check if it has a PCV valve, I honestly haven't paid attention to see if it does. I know one valve cover does have a breather. Would not having a PCV valve make this kind of difference?
Since the only thing I figure is the higher rpm's are causing the leak??
It does have good oil pressure.
It's not leaking out of the oil filter
It doesn't look like it's out the sending unit either but it's difficult to tell.
any help is appreciated.

 

How much oil pressure does it have while the RPM's are up?

 

i'm not sure on a big block but on the small blocks there are threaded plugs around the cam area on the back of the block if there is no sealant on the plug threads it will leak something to think about

 

i can't remember if the bbc has this are not, i changed the fuel pump on a sbc and there is a bolt hole that is in front of the fuel pump push rod, so i take the short bolt out and use a longer bolt to hold the rod up so i can get the new pump in. forgot to put the short bolt back in after i took the long one out. no leak at ildel and at lower rpm's but if i
stood on it oil would go everywhere, because of the fan and belts it took me alittle bit to find it. i hope yours is a easy fix, good luck.

 

Sounds like potentially a rear main seal, but before you get too concerned about that check for a PCV valve and make sure the crankcase is properly vented. If it isn't, you can build up enough pressure to push oil out where you normally wouldn't. Dipstick tube, oil fill cap, v/c gaskets, oil pan gasket, rear main seal, ...Well, you get the picture.

 

Without a PCV valve in good working order, it will leak out of the rear seal.

Note that the flow rate for pcv valves are not all the same.

A lazy fix is to add a second pcv valve, I have done this before to control a rear seal leak on a 468.

 

It's in the back of the block, the front is dry, I'll have to check on the pressure, I don't remember the numbers. I'll also take a look at the pcv, I hope that is it.

 

i just reread your post so x what i had said i misunderstood what you wrote. when you said pvc i took it it was on top or front of engine. man i hate lunch time reading.