What do I need to perform a vacuum leak free intake manifold change?

[WH23G3G]

I'm really seriously considering reinstalling my 73 400-4bbl original intake and Thermoquad and do away with the Edelbrock 600 and Weiand intake I had installed. The Thermoquad has been off for a year sitting in the trunk, it was rebuilt about 2 years ago by Carb Xchange. So I'm hoping it still is good. But I want to make sure I do a perfect job on reinstalling the intake. I know it's just a valley pan gasket but when I had the shop put on the Weiand they installed the crossover gaskets which I had forgotten to do when I rebuilt the motor and it was leaking. When I do the intake here at home I don't have access to a grinder to grind the gasket surfaces down. I can take the intake to a shop I know to get the surfaces clean. I'll just use a Fel-Pro valley pan and crossover gaskets. Would the factory originally have had the ones that were blocked or unblocked? Do I need copper spray or anything special for the end gaskets?

[rt green]

usually a felpro valley pan gasket kit will come with the sealer to use and tell you where

[69wannabe]

Just take some emery cloth like 120 grit and clean the gasket surfaces and the heads when you take off the other intake. If you are putting a cast iron intake back on there I would use the gasket (valley pan) with the heat cross overs open and not blocked since it takes cast iron alot longer to heat up than it does aluminum. Intake swap on a big block are cake, and there isn't coolant running everywhere which is also nice!!

[Ghoste]

And the original ones were unblocked, otherwise it defeats the purpose for having the heat crossover in the first place which is to warm the bottom of the plenum for cold weather running and the choke thermostat on manifolds so equipped.

[fy469rtse]

And possibly the best advice I can give is to sit intake on heads without any gaskets and such,
This will let you see if it sits flat on heads, if it does then your chances of not having any vacuum leaks will be better

[b5blue]

   Larry Shepard has a good write up in his book. Have the heads been milled? What head gasket was used? Have any intake surface's been milled? Has the block been decked? Any change from original factory build can change the intake to head gasket clearance. \\_______//   
   You can set the intake on the installed heads and shim the 4 corners to get a reading of that thickness. Then figure and order the right thickness intake gaskets with the valley pan. Sounds like a pain in the butt huh? Had I known all this years ago I'd had done it rather than ream out my six pack's intake mounting bolt holes ( ) years ago.
This is why you'll see intake gasket sets with different thickness available. 
   I recently bought an old CH4B intake for my 440, the intake holes on it are reamed.    I know why...........
 

[WH23G3G]

I doubt my block has been milled. It's a 1976 .040 over block with correct 1973 400-440 heads, 1973 400-4bbl intake with floor jets, non-egr. I speculated that when the previous owner of my 73 Charger replaced the 318 drivetrain that the block may have been a remanufactured block. Because all the externals are correct for 73, the hood is from a 73 400, the rear end, and transmission were too but the transmission has been replaced. I even scored the correct 6321S Thermoquad correct for a 73 400-4bbl. I just want to put everything back the way it would've have come if it was a 73 400-4bbl originally minus the idle stop solenoid because I've got to wire it up first but I do have it. So I was going to just get the stock replacement Fel-Pro valley pan and unblocked crossover gaskets how it was intended. Do I need copper spray or Permatex High Tack to install the crossover gaskets? Do I need to use copper silicone instead of the black silicone that comes with the Fel-pro kit? I'm swapping back to this original intake because when I initially had the car at the shop they thought the carburetor was no good so they made me buy that Edelbrock and new manifold when all along it was just the original manifold gaskets were leaking. I forgot to put any of the crossover gaskets on at all just the pan itself and it was leaking on the sides. So there probably was never anything wrong with the original carb. I had it rebuilt a couple years ago.

[fy469rtse]

The idle stop solenoid just goes to ignition source , I think you can just tap in to starter relay, , ignition source, so when ignition off , solenoid off,
I would still lay intake manifold on with out gaskets to make sure it sits flat, not uncommon for decks to be out of square to each other

[WH23G3G]

I looked and the solenoid goes to the field terminal on the alternator. If I ever decide to put the Edelbrock on will it work on the factory 400 intake? I just want to see if it runs better with the Thermoquad than this little 600 Edelbrock.

[b5blue]

I doubt my block has been milled. It's a 1976 .040 over block with correct 1973 400-440 heads, 1973 400-4bbl intake with floor jets, non-egr. I speculated that when the previous owner of my 73 Charger replaced the 318 drivetrain that the block may have been a remanufactured block. Because all the externals are correct for 73, the hood is from a 73 400, the rear end, and transmission were too but the transmission has been replaced. I even scored the correct 6321S Thermoquad correct for a 73 400-4bbl. I just want to put everything back the way it would've have come if it was a 73 400-4bbl originally minus the idle stop solenoid because I've got to wire it up first but I do have it. So I was going to just get the stock replacement Fel-Pro valley pan and unblocked crossover gaskets how it was intended. Do I need copper spray or Permatex High Tack to install the crossover gaskets? Do I need to use copper silicone instead of the black silicone that comes with the Fel-pro kit? I'm swapping back to this original intake because when I initially had the car at the shop they thought the carburetor was no good so they made me buy that Edelbrock and new manifold when all along it was just the original manifold gaskets were leaking. I forgot to put any of the crossover gaskets on at all just the pan itself and it was leaking on the sides. So there probably was never anything wrong with the original carb. I had it rebuilt a couple years ago.

So in this case you do not know what exactly was done to the block/heads. You DO know before it leaked somehow. Do the gap check to know what paper gaskets to use. 

[Ghoste]

X2!  Because originally there were no paper gaskets in there and the valley pan functioned as such.  The only time you need the paper ones is if the block or heads have been worked on, otherwise adding the paper will end up actually creating a leak instead of curing it.

[WH23G3G]

Yeah I know the heads weren't milled and I doubt the block was. So to do the gasket gap check I just put the bare manifold down without the valley pan first? Should I be measuring the gap or will I just be able to tell if it will need the crossover gaskets? I got my original intake's gasket surfaces cleaned off today by a shop because I don't have a gasket remover wheel to use with my air compressor. This thing is definitely heavy. It's going to be akward trying to get it in easy. What about the Edelbrock 2186 aluminum intake? Is that ok to use in place of this? It looks as if my Thermoquad will still mount to it. It says it's spread bore or square bore and it has the open choke well like my original. A lot lighter too. Only thing I don't like is it has EGR and no readily available egr block off plate. Could I just add a new egr valve to it and put a vacuum cap over the hose fitting? Did the Mopar performance replacement 383-400 intake have the open choke well? I can't even seem to find them for sale anymore.

[Dino]

You do not need to dry fit the intake manifold as you can tell if the surface is uneven and if gaskets are needed.  As mentioned on a stock engine you probably don't want to use them.  I used a thin bead of Permatex ultra copper on both sides of the valley pan and under the rails to ensure a leak proof install.  Worked like a charm.  If that Edelbrock intake is the Performer then the TQ will fit, that's what I'm running.

[WH23G3G]

Ok I'm at the last step of giving this Edelbrock one more try before putting original intake and carb back on. So I have the 1400 Edelbrock 600CFM with the carb bowl vent tube. I think the only Edelbrock with it. Because I actually want all the hoses hooked up on my Charger. I've got the heated air cleaner, OSAC valve, vapor canister, and idle bypass valve. I hooked up the OSAC hoses just like the factory had it with the OSAC hose to carb going to the timed port on the Edelbrock. I've got the hose coming from the air cleaner snorkels going to the manifold vacuum port on the carb. I think that would be the proper setup for those hoses. But I'm wondering about the vapor canister hoses. Obviously the one on the canister that says carb bowl goes on the canister vapor vent connection on this carb. I've also got one on my vapor canister that says "purge" and I hooked it to the back of the Edelbrock using a 1/4" fitting which in the Edelbrock instructions says it's for the brake booster. So a rundown there is 5 vacuum ports on this Edelbrock 1400. I've got the OSAC system hose on the timed vacuum port fitting because in the 73 Dodge service manual it says this vacuum advance creates no vacuum at idle, which in the Edelbrock instructions says that's where it should go. the pcv port obviously goes to my pcv valve hose, the 3/16" manifold vacuum port I've got going to my dual snorkel air cleaner vacuum pods, the vapor vent on the top going to my vapor canister that says "carb bowl", and on the back my vapor canister hose labeled "purge" going to the 1/4" fitting that is labeled power brake port in the Edelbrock instructions. Does that sound like it should all work the way it was intended?