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

[Tomas Gunnarsson]

----- 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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