I've got a 1600 xflow which pumps smoke out if the oil filler on the rocker box. I'm resigned to a rebore but I want to try one last thing. I've been told by a mechanic to discard the PCV, take a pipe direct from where the PCV used to be to a catch tank and vent the other side of the catch tank to atmosphere. Done all that - makes no difference. Now I've read on this forum to take a pipe from the old PCV outlet to the rocker box and another pipe from the rocker box to the catch tank and vent the other side to atmosphere. So, three questions
1. Where on the rocker box do I put the input pipe?
2. Where on the rocker box do I site the outlet pipe?
3. Do I retain the existing oil filler cap which vents?
Many thanks

I am running a tuned 1700 Xflow. I run a breather straight from the old PCV location to the catch tank. Also run a breather straight from the oil filler cap to the catch tank. I have no smoke issues at all.

Hope this helps.

A properly set up catch tank should vent any crank case compression. So if you are still getting smoke venting out of the oil filler it means two things. Either the crank case vent is blocked or the oil filler cap isn't sealing, or possibly both.

Are you getting anything in the catch tank at all? Also did you check the crank case vent was completely clear and did you use all new hose?

Remove PCV
Run pipe from block to side of rocker
Run pipe from back end of rocker to vented catch tank
Use unvented cap
If it still smokes rings

Running crankcase to rocker reduces the amount of oil in the catch tank on a heavy breathing engine but can increase the amount of water in the oil so regular checks of the oil, look for white froth in the rocker cover, replace oil and filter at first sign of oil contamination

Thanks for all the advice.
The crankcase vent is clear and I'm using new hoses. I'm getting nothing in the catch tank. The oil filler cap appears to seal properly but I've not checked that properly. Something else to try.
Many thanks

use a later cap, which has a hose connection, connect it to a catchtank.

conntact the block breather to the bottom of the catch tank.

under any circumstances, keep the original tin-can crankcase breather, but remove PCV valve

if you mount the catchtank higher than the block-breather connection any absorbed oil will get returned into crankcase

here a good overview, incl. pics

http://www.pistonheads.com/gassing/topic.asp?h=0&t=1534448&r=31856970&hm=192017&mid=192017#31856970


by the way: i never had any uprated x/flow which didnt smoke....even freshly bored engines!!!

[Edited on 3/12/15 by alfas]