View Full Version : Question: PCV for the new motor?

03-30-2010, 02:54 PM
Okay, so I've got a 1275 now in the Tunebug. It's got the little canister on the timing cover, and the port on the intake.

I know that on the stock setup these two are connected with some sort of PCV valve. So what's the wisdom on what I should do?

And does it need to be done before the first engine light-off?

03-30-2010, 05:08 PM
On my 1500, I have just a hose from the v/c to the air cleaner. Very little blow by since my rebuild and no oil. Apples to oranges, but that's what's up with mine.

03-30-2010, 06:04 PM
Drew, It needs to be done or you will likely push oil out the rear seal. On a 1275 a Flying Saucer PCV Valve needs to be in there. There needs to be a measured amount of vacumn from the intake manifold. Likely until rings seat you will get some major blowby, increasing crankcase pressure, and pushing out oil someplace. There was another thread on here in the last day about PCV Valve that Frank responded to as well as I with our experiences trying to run without one. I'd hate to see your nice paint get oiled up on the first start of Hap's new motor. MAybe Hap can chime in here cause I'm guessing he's already started it to run it in..

03-30-2010, 06:05 PM
Well Drew I had a rebuilt 1275 last year and hooked up a new PCV value and the engine leaked at the rear seal like the Mississippi River in spring. Toasted the PCV and ran hose from the timming cover to a home made catch tank and it stopped leaking.



03-30-2010, 06:43 PM
I donít know if this helps but I/'ve running like this for quite a while doesnít seem to bother and no oil being blown out anywhere. the vent can is stuck on the front chest cover. It has a 1098? maybe 1275 rubber seal timing cover and the river gate tranny kit with the oil seal. A annoying quarter drip when its shut down other than that no oil escaping.It's the only crank vent on the car. Little coolant splash down the back of the filler neck and on to the edge of the tank from topping up its not oil.
I know you have the 1275 but I would think that you could aleast fire it up with out the PVC with atmosphere vent.Heck my 948 just had a draft tube when it was new!

03-30-2010, 09:25 PM
A annoying quarter drip when its shut down

Forgive me for asking, but what's a quarter drip?

Is that like half a hole? :jester:

03-31-2010, 06:54 AM
I drove my 1275 for a year with the PCV intake port plugged & the timing cover vent open to atmosphere - the PCV valve was faulty & I would smoke out a city block when stopping hard or climbing hills if it was hooked up, a year later I caved in and bought a new "pancake" type & all has been well since.
The 1275 had at least 2 different PCV arrangements, the early "pancake style" & then a different type that actually T-eed & went to 2 separate ports on the intake from what I recall.
So in short,in my opinion (and that don't mean much) for the initial fire up, plug the intake port & leave the cannister open to atmosphere, but eventually figure out what style your motor is supposed to have (pancake or later style), source the bits & get er' hooked up !

Hap Waldrop
03-31-2010, 07:16 AM
My vote would be for running a hose from the timing canister to open air or to a catch tank with breather, crankcase pressure is just that pressure, it does not need a vaccum to be pulled, we don't use vaccum on the race cars just alot of enlarged vents to a catch tank with breather. On my MGB, they have upward tube coming from the front lifter cover I just have one of those small slip on valve cover K&N type filter, works like a champ. think of this way MG/AH didn't employ a PVC system until the US goverment forced them to, it was never their choice to do so, and not a choice you are mandated to follow.

03-31-2010, 08:09 AM
quick question for hap..should you feel any crankcase pressure from that small can on the timing cover? i've never had it off but it looks like just a catch can. was a 1275 vented thru the timing cover as well as the valve cover?

03-31-2010, 09:13 AM
Thanks all for the tips. I'll use a hose to open air for now, and will look into some sort of catch tank in the future.

I assume that I should cap the opening in the intake manifold where the PCV would normally connect.