[DeTomaso] Venting crankcase to valve cover(was Oilpangasketrecommendation?)

Mon Oct 6 19:43:56 EDT 2008

Did the hole go into the actual valley or into the front cover where  
the timing gear set was slinging oil around.  If into the valley, it  
may have been close enough to a lifter and you got oil from that as  
well.  Don't know, I just know that if I tapped it, I'd aim for  
somewhere high and in the middle.  Though you may be very correct the  
valley could be a real oil storm.

Asa Jay

Quoting Will Kooiman <wkooiman at earthlink.net>:

> Don't vent from the valley.  There's an oil storm in there.
>
> I originally planned on building a hidden vacuum plenum under my Weber
> intake.  I drilled a hole right behind the distributor.  I started making
> the vacuum plenum, but I eventually decided I'd farm it out.
>
> I forgot to plug the holes, though, when I started the engine for the first
> time.  I had a small geyser.  Oil was splashing up through the open vent.
>
> Some FE intakes have a vent near the rear, but they have a wire screen to
> catch the oil.  The vent is pretty tall too.
>
> Most FE intakes have a fill tube near the front that doubles as a vent.  The
> tube has a baffle to help keep oil in the engine.
>
> In my opinion, the best place to vent a 351C is the valve covers.  If it
> blows oil, make it taller.
>
> -----Original Message-----
> From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com] On
> Behalf Of asajay at asajay.com
> Sent: Monday, October 06, 2008 5:52 PM
> To: detomaso at realbig.com
> Subject: Re: [DeTomaso] Venting crankcase to valve cover(was
> Oilpangasketrecommendation?)
>
> I thought the question centered around what would happen -if- you
> vented the valley.  I have to admit it was an interesting thought, one
> which began to make a lot of sense until I started examining all the
> holes between it and the valve covers which to me indicate there is
> plenty of space.
>
> So, if the valve covers start blowing smoke, it probably means there
> is a lot of blow by increasing the block pressure, which in turn
> probably helps suspend oil in the air.  If the valve covers fill with
> oil, there are eight more drainbacks to get it back in the valley.
>
> Maybe the valley would be a better place to vent from, as the vent
> could be placed even farther from any oil source.  But where would you
> tap it?
>
> Asa Jay
>
> Quoting Doug Braun <doug at silicondesigns.com>:
>
>> Thomas,
>>
>> 	I misunderstood and didn't read your posting carefully enough.  I
> thought
>> you were implying that the lifter valley had a means of venting to the
>> atmosphere other than through the valve cover cap holes.  And in my
> attempt
>> to point out that the valve cover holes are the only exit, I made two big
>> blunders.  I forgot to mention the pushrod holes (as Asa Jay pointed out,
> as
>> did you in your posting) and I got it wrong about where the drainback
> holes
>> return to.  I'm sorry, I just created more confusion here.
>>
>> Doug
>>
>> -----Original Message-----
>> From: detomaso-bounces at realbig.com
>> [mailto:detomaso-bounces at realbig.com]On Behalf Of Tomas Gunnarsson
>> Sent: Monday, October 06, 2008 11:18 AM
>> To: DetomasoList
>> Subject: Re: [DeTomaso] Venting crankcase to valve cover (was
>> Oilpangasketrecommendation?)
>>
>>
>>
>> ----- Original Message -----
>> From: "Doug Braun" <doug at silicondesigns.com>
>> To: "Tomas Gunnarsson" <guson at home.se>; "DetomasoList"
>> <detomaso at realbig.com>
>> Sent: Monday, October 06, 2008 6:51 PM
>> Subject: Re: [DeTomaso] Venting crankcase to valve cover (was Oil
>> pangasketrecommendation?)
>>
>>
>>> Thomas,
>>>
>>> Yes there is an issue.  The valve cover openings are the ONLY crankcase
>>> vents to the atmosphere in a 351C (as long as the engine doesn't leak
>> oil).
>>
>>>> I'm with you here.
>>
>>> Vent-wise, the lifter valley lies between the crankcase and the valve
>> covers
>>> so oil from the heads drains into the lifter valley and then to the
>>> crankcase.
>>
>>>> I have looked at pics I've taken and ones found in the Tom Monroe
> rebuild
>> handbook. To me it seems like the head drains don't exit into the lifter
>> valley. The oil drainback holes are actually outboard of the outermost
>> headbolts.
>>
>>  Crankcase venting gasses and head oil drain back are both
>>> fighting for passage (in opposite directions) through the heads' two
> each,
>>> 3/8" diameter or so, drain passages.
>>
>>>> I see this differently. Oil primarily runs down the drains. Crankcase
>> gases can pass up those drains too unless they're filled with oil. Should
>> they be filled with oil, gasses can pass up into the lifter valley past
> the
>> camshaft through the four 1/2" or so holes above the camshaft. I
> understand
>> that there's also a certain amount of oil flow from the lifters going down
>> these holes at the same time. From the lifter valley there are eight
> pushrod
>> holes (~1/2") to each valve cover that are only partially filled with
>> pushrods.
>>
>>   Any blowby that the lowly PCV can't
>>> handle gets shoved into the air cleaner assuming the stock type emissions
>>> hose is present between the oil filler cap and the air cleaner.
>>
>>>> This is the way it's supposed to be as far as I can tell. The hose
>> connected to the intake could never handle much gas flow.
>>
>> Tomas
>>
>>
>>> -----Original Message-----
>>> From: detomaso-bounces at realbig.com
>>> [mailto:detomaso-bounces at realbig.com]On Behalf Of Tomas Gunnarsson
>>> Sent: Friday, October 03, 2008 12:02 PM
>>> To: DetomasoList
>>> Subject: [DeTomaso] Venting crankcase to valve cover (was Oil pan
>>> gasketrecommendation?)
>>>
>>>
>>> Is there really an issue with venting the lower part of the engine to the
>>> valve covers? I'd have thought that even with the head drains completely
>>> filled with oil returning to the crankcase there'd be enough combined
>>> passage area through the lifter area floor and pushrod holes to vent
>>> whatever blowby there is.
>>>
>>> Tomas
>>>
>>> ----- Original Message -----
>>> From: "Barry Seib" <oldwheel at mts.net>
>>> To: "Drew, Mike" <MikeLDrew at aol.com>; "DetomasoList"
>> <detomaso at realbig.com>
>>> Sent: Wednesday, October 01, 2008 11:01 PM
>>> Subject: [DeTomaso] Oil pan gasket recommendation?
>>>
>>>> Mike
>>>> I think Larry may be right on with his suggestion. If there is no leak
>>>> except at high RPM, that's a very strong indication that no matter where
>>> the
>>>> leak is, excess crankcase pressure is likely causing it. I suspect the
>>>> factory PCV system is totally inadequate for sutained very high revs.
> You
>>>> might try the same run with extra NASCAR or circle track type breathers
>> to
>>>> see if the problem is solved.The other issue is making sure that the
>>>> crankcase can breathe to the valve covers (if that's where the extra
>>>> breathers are). If the heads and drainbacks are all flooded with oil so
>>> that
>>>> can't take place, you will have to remedy it first - or put a breather
>>>> directly to the crankcase by some other route to stop the leak. MD must
>>> have
>>>> dealt with this issue a long time ago.
>>>>
>>>> Dawg? What say you?
>>>>
>>>> Barry
>>>>
>>>> [DeTomaso] Oil pan gasket recommendation?
>>>> Larry - Ohio Time Corp larry at ohiotimecorp.com
>>>> Wed Oct 1 12:54:55 CDT 2008
>>>>
>>>>
>>>>
>>>> Hi Mike,
>>>>
>>>> You may want to check you venting / PCV system. At high RPM the blow-by
>> is
>>>> at its highest. I have seen crank cases pressurized and blow oil out a
>>>> normally good seal. If your heads are full of oil the venting system may
>>> not
>>>> be working to well.
>>>>
>>>> Larry (no, tarter sause) - Cleveland
>>
>>
>>
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