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408 rediculiously simple question

351 Mustang

408 rediculiously simple question

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Old 11-29-2007, 06:34 PM
  #1  
psuhillbilly150
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Default 408 rediculiously simple question

Ok this seems extreamly stupid of a question to ask but i am gonna throw it out there incase anyone has some slick tricks up their sleeves.

Built my 408 used gray RVT silicone to seal the gap between the intake manifold and the block. LEAKS LIKE HELL. The silicone had set for 3+days untill the motor was run. All serfaces were cleaned with gum cutter 2+2 the nastiest solvent I know of. What else is there to do. Is there a cork gasket that can seal that? I am running a 1986 block with a victor jr intake with vitor jr port matchedheads.

HELP
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Old 11-29-2007, 07:17 PM
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r.barn
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Default RE: 408 rediculiously simple question

I would just try again with Black RTV.
Might have just been some bad luck on the leak.
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Old 11-29-2007, 07:20 PM
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Mustangkiler
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Default RE: 408 rediculiously simple question

ultra black or ultra blue, only way to go.
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Old 11-29-2007, 08:20 PM
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Indy
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Default RE: 408 rediculiously simple question

Don't use the cork stuff! It'll just pop out. I had the same problem, but I use the Blue RTV. I found that I did not have enough PCV (positive crankcase ventilation)! I had 2 breathers on my valve covers and just plugged the PCV port on the carb (you know, just like the showy looking engines in the mags). I pulled the intake back off and re-sealed the lifter valley-intake gap with the RTV. Reconnected the PCV hose to from the carb (could be intake) port to a valve cover with a new PCV valve...and it never happened again.

Now you might already be running the "regular" PCV system and still have this problem. So, you might not have enough vaccum to evacuate the built up pressure in the crankcase, lifter valley etc... you could need an auxillary vaccum pump to evacuate that pressure. IMO.

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Old 11-30-2007, 02:38 AM
  #5  
Ford1158
 
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Default RE: 408 rediculiously simple question

Look for the semi-squishy rubber gasket that wraps around both sides of the bottom (like an upside down U) and has waffle texture on top and bottom contact areas that hold RTV and squeeze as needed. I don't know which engines or gasket makers have that but my '91 5.8 and '85 5.0HO did. Dealer might be able to help locate it. Used ultra black RTV.
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Old 12-03-2007, 03:55 PM
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86_Notch
 
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Default RE: 408 rediculiously simple question

try with rtv black, put a really thick bead along the block surface and in the corners where the heads meet, and let it set up for a few mins before bolting the intake on. i've made the mistake of putting the intake on too soon and had leaks, hope this helps
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Old 12-03-2007, 04:35 PM
  #7  
aode08
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Default RE: 408 rediculiously simple question

You cant rtv that area with great results, you will need the cork pieces, although I prefer the felpro blue rubber, then rtv the corners considerably



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Old 12-03-2007, 04:53 PM
  #8  
aode08
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Default RE: 408 rediculiously simple question

also on your carb gasket to manifold, give him a smear of rtv on both sides all around and let dry overnight before install.


Your gonna have one sick engine
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