[TR] TR4 road draft tube plug

John & Pat Donnelly pdonnel1 at san.rr.com
Mon Sep 7 14:52:48 MDT 2015

Well, I bought the vented cap when I bought the valve cover from TSI. It has a hole on the top, but who knows how much it's really venting.  I have roller rockers installed so I need the extra room.


No, the draft hole is still plugged.


A mechanic once told me that is you take the valve cover cap off when running, then put a shop rag over it you should only see a little deflection. When I did it to my car it went up 3-4 inches. That was my big clue that I needed more venting.


All PVC valves are different and each handles different volumes. Some have springs that only actuate with a pressure differential. I don’t know about the GP PVC valve but you might look around for another. They're cheap.



From: Triumphs [mailto:triumphs-bounces at autox.team.net] On Behalf Of Geo Hahn
Sent: Monday, September 07, 2015 11:53 AM
To: Brad Kahler
Cc: Triumphs
Subject: Re: [TR] TR4 road draft tube plug


On Mon, Sep 7, 2015 at 10:08 AM, Brad Kahler <bkahler1 at gmail.com> wrote:


...Also, is your valve cover cap vented (i.e. TR4A style) or non-vented?



Those terms (or something) confuse me.


My late TR4 does not have a vented cap - it seals tight.  I presume that TR4As are similar.  Early TR4s and all TR3s had a cap that vents to the atmosphere.


If you are fighting blow-by (and I think you are) it would seem that a vented cap might help -- and since your engine apparently has a road draft tube fitted as original then I believe a vented cap would have also been on it.



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