Original Six Pack Intake Installation problem

[thebuergers]

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?

 

[moparleo]

You are correct that the head resurface is the cause of your vacuum leak. I am not a machinist but I am sure that there are a lot of members who can answer your question.

 

[AUSTA]

I had the same problem so i took the manifold to the machinist to be checked & said it was fine.
To check place the gaskets in position & check the manifold should sit slightly high but close enough for the bolts to screw in easily.
I used permatex high tack on both sides of edelbrock gaskets bolted up & let sit for a day to set.
Also do not used the cork on the ends it holds the manifold high and it will not pull down onto the heads a lot of the cork end gaskets available now are quite hard plus the thickness can vary dramatically ,use a good bead of red or black silicone on the ends & drop the manifold directly down don,t slide it.
Done it that way 4 times now with zero leaks

 

[Daves69]

.......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 don't believe the ratio is 1:1.
IMO, Get the full story on the surfacing that has been done before you surface anything. Find a reputable automotive to make any necessary modifications.
If you surface the intake manifold it will change how it fits on future engine builds. It may also affect you when/if you try to sell.
If only the head to block face was surfaced, maybe use a taller head gasket to make up for the .010".

 

[704406]

Daves69 is correct the ratio is something around .6 to 1 I think.
A reputable machine shop will be able to tell you the exact ratio. .010 doesn't seem like enough off the heads to make that much difference. I recall that felpro made a set of thin paper gaskets for each side of the metal pan gasket for the 69 aluminum 6 pack intakes. I used them one time on an cast intake that had a poor casting surface with good success. I'd be very hesitant to machine the intake unless it's absolutely necessary. I have to ask, are you absolutely sure it's the intake causing the leak?

 

[thebuergers]

Thanks to all of you who responded to my request for help. I will seriously consider all of your comments and suggestions and hope I can remedy the situation soon! I'll let you know what happens...

 

[aussiemark]

There is a formula floating around somewhere but from memory you do have to machine more off the manifold then was machined off the heads and the amount machined off the sides will be different from the amount that needs to be machined off the ends (this won't apply to you as the big block manifolds only have sides)

 

[aussiemark]

Why don't you just stick with the aluminium manifold just paint it to suit? it will save you a ton of weight off the front and as the weight is up high it couldn't be in a worst position to effect the handling.

 

[Mick56]

From what I remember, (from 40 years ago, when I built up a 1968 383 Magnum) for every .010 off the head surface, you need to take .0123 off the manifold surface of the head. You should not mill anything off of the manifold, or the manifold will only work with heads that have been milled.

 

[cudabob496]

Six Pack issues and rebuilding

 

[70Hardtop]

Aussie Mark has the right idea - to save a heap of weight up front. That is, if you want to really enjoy driving the car. But if it is a car that is more important for shows to be exactly original, then I suppose you need the original intake. And along with the alum intake, to really improve handling further, put in an alum radiator, use a light mini starter, install aluminium heads and move the battery to the trunk! The difference in handling will be amazing. The Challenger is just so front heavy - my Challenger was up on a hoist once (4 point lift) only had a 318 /904 and with just one arm pushing upwards on the back I could almost tip the whole car off forward. Scary. Then again, it didn't have a fuel tank installed and it only had the tiny 7.25 axle, so those things didn't help weight distribution.

 

[rolling_thunder]

I always use the paper intake manifold gaskets on both sides of the tin gasket... I had one engine a customer brought in with a dead #2 cylinder when it heated up.... chased some problems and then started disassembly... pulled the intake off and walla! no paper gaskets. The intake and heads heated and allowed a vac leak which leaned out the cylinder --- put in paper gaskets and all is right in the world.