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Crankcase ventilation System

Discussion in '"Stock" Alpine' started by mamoose124, Nov 4, 2019.

  1. mamoose124

    mamoose124 Diamond Level Sponsor

    My 1592cc engine had no crankcase ventilation valve and the tappet chamber was simply vented directly into the environment via a rubber hose draped over the bell housing at the back of the engine. I’m installing a 1725cc engine but since I don’t have a ventilation valve, I’m wondering where I should vent the tappet chamber outlet; does it make sense to simply connect it to the oil filler tube? Any suggestions will be appreciated.
  2. Jimjordan2

    Jimjordan2 Gold Level Sponsor

    On my Series V 1725 that would route to the intake manifold.
  3. mamoose124

    mamoose124 Diamond Level Sponsor

    That is correct jimjordan2 but, if I'm not mistaken, it inters the intake manifold via a crankcase ventilation valve, right? Since I don't have one and don't really want to purchase one unless I must, I'm wondering if it is OK to simply rout it to the oil filler tube.

    PETER CLAYTON Donation Time

    If you do vent to the oil filler,I would advise fitting an in line flame trap,you do not want to risk any chance of igniting the crankcase oil vapour.
  5. Tim R

    Tim R Silver Level Sponsor

    On one of our 1725s we vent both Tappet chest cover and rocker cover to atmosphere through open tubes. This works well with no problems.

    Tim R
  6. hartmandm

    hartmandm Moderator Platinum Level Sponsor

    Mike Y

    What intake manifold and carb / carbs are you going to use with the 1725?

    Mike H
  7. mamoose124

    mamoose124 Diamond Level Sponsor

    I have a weber car and manifold.
  8. mamoose124

    mamoose124 Diamond Level Sponsor

    Well, I could vent both the Tappet chest cover and the rocker cover to the atmosphere but I'm trying not to polute any more than necessary.
  9. mamoose124

    mamoose124 Diamond Level Sponsor

    I do have a flame trap I was planning to use if I vent the tappet cover to the oil filter. Just wanted to know if this was an OK way to manage venting the crank case.
  10. husky drvr

    husky drvr Gold Level Sponsor


    Tappet cover to oil filler? That's not venting the engine, just sealing it up. I suspect you wont like the results short or long term.
  11. Tim R

    Tim R Silver Level Sponsor

    The risk on joining tappet vent to rocker cover vent is that you pressurise the engine. I read a report of a guy with a Triumph who had his dip stick blow out when he did something similar. I am not sure if that would happen on an Alpine engine but Rootes vented it for a reason.
    If you are using the club manifold with your Weber it is important not to use the PCD in the threaded hole on inlet No 4 (its ill make then engine run too weak on No 4 and cause you problems, just fit a blazing plug).
    Any increase in pollution is small compared to what comes out of the exhaust already, it is just a practical way of running the engine. Also don't forget on later 1725s they did away with the tappet chest vent completely and just vented the rocker cover to the carb.

    Tim R
  12. husky drvr

    husky drvr Gold Level Sponsor

  13. 65beam

    65beam Bronze Level Sponsor

    This photo shows one of the new 1725 short blocks set up with the side cover with the vent tube from a series 2. The car has the oil filler cap and valve cover from the series 2 installed 110_0590.JPG
  14. mikephillips

    mikephillips Donation Time

    Probably won't blow out the dipstick, but you can get oil being blown out of the dipstick tube if the engine gets pressure since it enters at the bottom of the oil pan. Found this out 40 years ago with a worn engine, it could blow out a quart in 20 miles.

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