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I am having a very difficult time trying to successfully install an original (build date of 12/1969) cast iron Six Pack intake manifold onto my 440 cu in engine. My car is a 1970 Dodge Challenger R/T and it originally was a Six Pack car. However, over the years (I have owned the car since 7/1971), I sold the original six pack setup and used other various intake setups. Quite a few years ago, I had a reputable engine builder rebuild my 440 for me and after getting the engine back from the builder, I installed a complete Six Pack setup again, but this time I utilized an aluminum intake manifold. I was very glad to be utilizing a Six Pack setup again. But now I am at the point of trying to replace the aluminum intake with an original cast iron Six Pack intake manifold as I first stated above. I have uninstalled and reinstalled the cast iron Six Pack intake manifold 3 times now and I can't seem to eliminate a vacuum leak. I went back to the paperwork that I received from the builder who professionally rebuilt my 440 and it shows that he 'resurfaced' the heads .010 of an inch. If I am trying to install an original cast iron Six Pack intake manifold, would it make sense that the head mating surfaces would need to be 'resurfaced' by .010 of an inch also? I just can't figure out what else might be causing my vacuum leak. Any suggestions?
 

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I don't know how much assistance you'll find on a modern focused Challenger forum. We had the heads surfaced about the same on the 70 gto we built. We were told it wasn't enough with decent gaskets to cause any problems with the intake and so far haven't had any. We did have some vacuum issues as well with 1 carb so I can only imagine how much of an issue more than one would be. Those were carb and line problems though and not intake manifold related. Good luck!
 

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Look around some of the Mopar performance dealers(like Mancini racing). They used to have an intake pan gasket set with 4 thin gaskets to help with mismatches like yours.
 

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2011 392 SRT, 2010 R/T Classic, 2019 R/T Plus, 2016 SXT Plus
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You might need to mill the intake to match the heads. .010 doesn't sound like much, but you never know.

Could the cast iron intake have cracks in it?
 

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Have you been able to isolate your leak to any one port or is it along the one entire side? I wouldnt think that milling the head to block surface .010 would have much if any bearing on the intake sealing, the gaskets should make up for that easily enough.
 

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If I recall correctly, on the "B' and "RB" engines, for every .010 milled from the block side of the head, .012 must be milled from the intake surface.
Having said that, the milling of the head if not done absolutely parallel, the intake and head surfaces won't match.
Try placing the manifold on the heads without any gasket and see if you can rock the manifold or if it seats solidly. You may be able to use a feeler gauge to determine if it is correct.
I had a new 74 Dart 360 that came from either the factory or the dealer with the intake glued to the heads with 3M gasket sealer. The thick yellow stuff.
At one time, Mr. Gasket offered some thick compressible intake gaskets to address this issue.
Also, if you are not aware of the modifications to the 3 Holley carbs that the MOPAR and Holley engineers came up with, I can email the information to you. PM me with an email address for it. I did this to my Six Pack back in the day, made a big improvement in drive-ability and mid range power.
 
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