Things just keep going down hill with this dart. I installed the new street dominator intake on my 440. Did it like ive always done, new valley pan and GOOD sealer, and it wont idle because its leaking along both sides so bad! I mocked the thing up and the bolts went right in and all, but its leaking..I can spray carb cleaner along the sides of it and it will rev a little. Ive sure know my share of people that have put aftermarket intakes on with no issues, so i dont understand this..

Has the intake been milled off?

Some aluminum intakes need the paper gaskets along with the valley pan.

Wonder why? Wont that throw the bolt holes off? Guess i can try. What side of the valley tray do the gaskets go, or do they go on BOTH sides?

both sides & have your machinist check it for flatness but I would get the .015" ones first & mockup/measure & have him mill as needed which'll take care of the fitment & the flatness. Good luck on it.

Both sides? At least the intake side if there lies the problem. The Right Stuff. Schmooie it over the top of the mating surfaces if you have to.

Do you guys noramlly have to mill new aluminum intakes everytime you buy one?

No, unless the heads have been milled. I always use paper gaskets on both sides of the valley pan when using aluminum intakes. I've had several aluminum big block intakes leak so bad that they didn't want to run. The paper gaskets won't throw the holes off by much. I've never had a problem with lining up the bolt holes using them. If the bolt holes line up through the valley pan, they should line up through the paper.

Wonder what the deal is with aluminum leaking so bad without the gaskets? Are they just not machined as well as the chrysler originals or what? If thats the case, its a damn shame for the price you have to pay for them! Ok, do i need to use RTV along with the paper gaskets to be sure the dang thing will seal this time?

Be sure the front and rear corners of the manifold aren't touching the cross bars that hold down the bathtub gasket at the front and rear.

I think that Aluminum moves around so much more with heat cycling than the OEM Iron intakes did. Chrysler did use the paper gaskets in addition to the valley pan when the 440 six packs came out using the Edelbrock sourced manifolds.

Could be that the angles are off slightly due to a set-up error when manufactured, or the end rails on your bathtub are holding the intake up off the heads a slight amount.

I've used .015 paper gaskets glued to both sides of the tub for decades, because I don't want to chance an air/oil leak and have to do the job twice.
Sure, a lot of guys get away with even re-using an old bathtub, but my luck's never been that casual

should I use sealant along with the paper gaskets?

I would. Permatex 99MA "high tack" the thin red spray works good.

May not be necessary, but sure won't hurt. What's the chances that you will want to pull the intake back off in the future? There are a number of good sealers for this job. Which one to use depends on how big a gap needs filled and how difficult it will be to remove the intake in the future.

Right Stuff is probably the best gasket maker I have ever seen. It will fill big gaps and, as the name implies, doesn't even need the paper gaskets. But you may need a crane to pull the intake back off. It is that good. Personally, this is what I use on things that I don't expect to need to come back apart.

High Tack is a good sealant to use on the gaskets. But since it is gasoline resistant, it is a real mess to clean up if you ever need to pull the intake. Have some lacquer thinner or acetone handy for clean-up.

Hylomar A/F is the best sealant if you think that the intake will need to come back off. While it is very good at sealing, it releases the part rather easily. But it is pretty expensive and can be difficult to find. This is what I use on anything that I think may need to come back apart.

And finally grease. Of course grease is not really a sealant, but it softens and helps keep soft paper gaskets and sure makes taking things apart very easy and often allows the re-use of the gasket. For example, I always use grease on my carburetor base gaskets.

John has a good point here. The crossbars are only tapered on one side, it they're installed upside down the taper is now on the bottom and the intake could be held up by the non-tapered side.

I will be sure to check this on this install! I didnt pay any attention to that last time! Thanks for bringing this up! I know you use RTV, the right stuff, etc in the 4 corners, but do you also use it along the whole rail on both ends or just the valley tray alone?

Just use it along the whole rail under the tray, you don't need any on top of the valley tray at the crossbars.

There is no way I would use the "Right Stuff all the way across the bottom of the stock lifter valley pan Especially if you wanted to try and reuse it again later I do use a small dab of adhesive silicone RTV in the corners under the stock valley pan under retaining bars in the corners to seal them up

This is about 5 times in about a week of guys with intake sealing questions.

Many or most aftermarket intake castings need to be ground where they go over the end rails, this is very likely the cause of many non sealing intakes.

I use old/used valley trays with crushed sealing ridges. This adds a bit more clearance for the thin gaskets on both sides of the tray