Author Topic: 360 engine smoke valve seal question  (Read 621 times)

Offline matt63

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360 engine smoke valve seal question
« on: July 29, 2008 - 12:57:35 PM »
My 408 stroker has about 500 miles on it now and still smokes when accelerating hard and shifting gears.  It really bugs me.  I'm wondering if the engine could be sucking in oil through the intake guides when the throttle slams shut between shifts.  It runs great otherwise.  I had the engine out a month or so ago and did notice that there seems to be some grey crap built up on the valves just below the guides which struck me as odd.  I didn't pay much attention as to which valves but assume it is the intakes.  I've got Eddy Magnum heads but the springs and seals were replaced with "Dupont premium positive 0.530 valve seals for double springs".  I seem to remember the guy saying that these seals still let in some oil unlike other positive seals.   Perhaps changing them to a teflon positive seal would remedy this.  Any thoughts?  It has been mentioned to me that oil could be sucked past the 1/16 rings under high vacuum but I'm hoping this is not the issue.
Matt in Edmonton

'68 Valiant
'73 Cuda 340 4 speed (408) SOLD




Offline Chryco Psycho

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Re: 360 engine smoke valve seal question
« Reply #1 on: July 29, 2008 - 01:22:28 PM »
check the intake gaskets first & PCV system , do you have a deflecter plate under the covers , guides would be the next place to look

Challenger - You`ll wish You Hadn`t

Offline matt63

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Re: 360 engine smoke valve seal question
« Reply #2 on: July 29, 2008 - 02:06:32 PM »
The intake gaskets have been changed once but I could check them again fairly easily.  There is no baffle in the valve covers although the PCV hose doesn't show any sign of being wet with oil.  Again I could run w/o the PCV briefly to see if this resolves the problem (do the easy stuff first).  If this doesn't resolve things I could then have a look at the guides. 
Matt in Edmonton

'68 Valiant
'73 Cuda 340 4 speed (408) SOLD

Offline matt63

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Re: 360 engine smoke valve seal question
« Reply #3 on: July 30, 2008 - 11:41:07 AM »
I plugged the PCV yesterday and it seemed to resolve the issue.  I'll guess I will have to fix a baffle to the stock Magnum covers (I cut them out)  or spend the $200+ for the Mopar Magnum covers. 
Matt in Edmonton

'68 Valiant
'73 Cuda 340 4 speed (408) SOLD

Offline Chryco Psycho

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Re: 360 engine smoke valve seal question
« Reply #4 on: July 30, 2008 - 11:59:35 AM »
that is an easier fix than pulling the engine apart  :2thumbs:

Challenger - You`ll wish You Hadn`t