400 Big Block Intake Manifold Gaskets... or not?

[badvs3vil]

Hello,

I have a 1973 Newport with a 400BB in it. I am changing out the Intake for a new one and I ordered a new gasket set as well. It came with 4 gaskets and 1 valley pan.

Fel-Pro 1214 Fel-Pro Performance Valley Pan Gasket Sets | Summit Racing

The question is, I see there are people to say not to use the paper gaskets and only use the valley pan.

The instructions say to put a gasket on each side of the valley pan. However most videos I see, most Mopar guys do not.

Thoughts?

 

[70NEWYORKER]

Cast iron manifold should not require the paper gaskets. Use Felpro brush tack on mating surfaces by the ports and torque it down. The "Loomnum" manifolds move around a lot more than iron. The paper gaskets were for the early 6Pak manifolds before they switched those to iron construction. If you want/need to run the papers I'd just coat every surface with Brush Tack and torque to spec.

 

[badvs3vil]

Ill be running this Intake and the engine has 452 iron heads.

Weiand 8008WND Weiand Action Plus Intake Manifolds | Summit Racing

 

[413]

I like to use paper gaskets on the intake side with an aluminum intake. If they will fit in there. If heads have been milled then they may not fit.

 

[57fury440]

I've never used the paper gaskets with any style manifold and have never had a problem.

 

[1978 NYB]

I have never used paper gaskets on a big block. Valley pan and a small bead of RTV on the front and rear ridge where the intake mounts.
I have an Edelbrock Performer intake and aluminum heads. No problems at all.

 

[CBODY67]

As the factory provided the paper gaskets for the aluminum 6bbl intake manifold (with cast iron heads) engines, there's a reason they did that. Eventually, the metal in the valley pan gasket will wear itself into the softer aluminum, which can result in an intake vacuum leak. Not unlike using a steel shim head gasket with aluminum heads, eventually a leak will happen. This was back when these engines saw almost daily use, rather than possibly what they now see, by observation.

There was one time I thought I had a vacuum leak with my aluminum intake on my '67 383. I chased that suspected leak all over the place to no avail. I got the FelPro 6bbl gaskets and added them to the existing valley pan (which still looked good). I enhanced the seal by adding some black, hi-heat silicone to the beads on the intake, then scraping it flat with a Mr. Gasket gasket scraper. After a day or so of cure, I put it back together. It did sound better that way. Not by a huge amount, but I knew it was as good as it could be. After the success of that installation, I'll do later ones with the paper gaskets, even with an iron intake manifold.

Just my experiences,
CBODY67

 

[Outsider]

Been putting aluminum manifolds on these big blocks for over 40 years, drove these cars to work daily and raced some; here's my experience.

Put your manifold in place without anything, no valley pan, see how it sits. Try a .005" feeler gauge all around the ports, if its a no-go, then just use the valley pan and Black RTV sealant on both sides of the pan around the ports and to seal the valley.

If more than .005"-.015" use one set of paper gaskets on the manifold side and sealant. If more than .015", I would consider milling to correct the error if you can find a shop that has the skill.

 

[Outsider]

By the way, I see the valley pan kit you bought is the high performance version with the blocked heat riser holes in the middle. Because it's the HP pan, it came with those extra gaskets, where the standard street version pan with the center holes open comes without the extra gaskets and is less expensive to purchase.

Hopefully this will match your usage, ie. summer only driving, or you will have to make the extra effort to warm up you engine during cold weather. Though it is a performance improvement to have the manifold heat blocked and virtually a must do for racing, most people prefer the heated manifold for regular drivability in cold climate areas.

 

[badvs3vil]

By the way, I see the valley pan kit you bought is the high performance version with the blocked heat riser holes in the middle. Because it's the HP pan, it came with those extra gaskets, where the standard street version pan with the center holes open comes without the extra gaskets and is less expensive to purchase.

Hopefully this will match your usage, ie. summer only driving, or you will have to make the extra effort to warm up you engine during cold weather. Though it is a performance improvement to have the manifold heat blocked and virtually a must do for racing, most people prefer the heated manifold for regular drivability in cold climate areas.

Thanks for pointing that out. I don't plan on driving this in the winter. Only spring, summer and fall. Should I be ok? TBH, I wasn't sure what "performance" meant in this case. This is all a learning process for me.

 

[Outsider]

Perhaps a cable push manual choke set up would be useful, particularly if you are also going with a new aftermarket carb.