Trevor Fowler

I have built a pair of Dart block gen 4 632 cid engines. I am have problems blowing out the crankseal during break in. I'm using a Dart intake that does not have a pcv valve location. I know the crankcase needs to be evacuated with that much stroke. I am running a complete dry exhaust system ( Hardin Marine cyclone system). I would love to run the good old drag race set up by putting the one way valve in the exhaust and running a hose to a valve cover breatheri. I am Not opposed to an external vacume pump either, but what system is good for a marine set up??? I know there are others out there that have done something I just need some ideas please.

Do you think it would create enough vacuum if I put in a fitting underneath the dominator carb spacer and ran that to a breather in the valve cover?

1MOSES1

worth a shot. The old school big blocks always ran a pcv from the valve cover to the carb/intake.

ICDEDPPL

You`re going to need to get rid of that crankcase pressure and I`m not sure recycling it back into engine is going to do the trick.


I use a canton breather .

MILD THUNDER

Pcv does nothing at wot. Only while under vacuum. If it blew the crank seal, either blowby is excessive, or your breathers are too restrictive.

mcollinstn

Yes and no.
At high vacuum, a PCV plunger pulls all the way towards the intake side, closing off flow (to the metering orifice).
At low vacuum, the plunger moves into the middle position which fully opens the valve to its minimum restriction/ highest flow.
At manifold PRESSURE (backfire) the plunger moves fully towards the valve cover, closing fully to prevent backwards flow.

You may want to look at the ME Wagner PCV

MILD THUNDER

I think the problem is, its a 632ci wet sump. That thing needs to breath. For a wet sump 632ci, that sucker is going to need some good venting at high rpm/wot. All that crankcase psi needs somewhere to go, or as in his case, pushed out a crank seal. A tiny orifice in a pcv isnt going to be able to pass enough of that air thru it. So he can add a couple good sized breathers, or add good sized breathers and a pcv. I doubt the pcv will be very effective as a pollution control/oil cleaner device when ran with big open breathers. Cant see it keeping much vacuum in the crankcase with big open breathers.

The ME wagner valve is a cool piece. Ive been planning to give one a try on my street 540 engine. Really cool how you can adjust it to suit your build.

Craney

Mild Thunder good to see you back.

sutphen 30

what rings are you using?built a few 632's and never had that problem.

blownsvt1

I am the originator of this post I don't know why I used a different logon name. I am using a floating wrist pin with total seal rings, top ring gapped at .23.

I tried something today I went ahead and tapped a half inch fitting into the fuel pump block off plate on the side of the block. I ran a half inch hose up into a catch can. It definitely has a lot of pressure down low in the engine block. It did help with blowing the oil out of the front seal but as soon as I got up into the upper RPMs oil started pushing out the front balancer seal. I did a cylinder leak down test the average is about 3% so there's no issues there. I use harden marine valve covers and I have two of the huge hardened Marine air breathers in each valve cover. You would think that would be completely enough to escape the crankcase pressure but it's like getting trapped in the oil pan crank area.. is it possible that I am creating way too much windage and trapping air down in the pan as the RPMs increase?

zfrilly

Can you put a gauge in and see what the pressure is? seems with the 1/2 hose down low it would be hard to develop pressure. Maybe the leak is caused by something else.