73' Riviera Vacuum Leak

[JamesDole]

Several months ago I re-built my 1700. I bumped it up to a 1800 as it was the same price. Re-man crank, cam, rods, heads, etc...The re-build kit came from Kustom1. I have a vacuum leak at the 1-2 intake manifold. I have tried multiple gaskets, with and without Copper Sealer. I've trimmed back the tin to make sure it wasn't getting in the way. The only thing I haven't tried is doubling up the gaskets. Not even sure if that's an option. I've even tried a different manifold. The manifolds I am using are after market. They came with my Solex carbs from Aircooled.net. I do have the stock manifolds but haven't tried them yet. Any suggestions? Am I missing something?
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66' Euro (Pan off restoration)
Sold 63' Sedan
73' Riviera Camper
Sold 54' Oval (Sedan)

[Tcash]

Make sure the manifold mounting surface is flat. File them flat. or with a piece of 400 sand paper taped to a piece of glass , sand them flat.

[JamesDole]

Tcash, I tried filing the manifold flat. It wasn’t easy as the file would get pieces of aluminum stuck on it and it would then slightly gouge the surface. I then tried sandpaper. Still no luck, still a vacuum leak when I sprayed starting fluid at the base of the manifold. I think tomorrow I will try the stock steel manifold as this is separated in the center and not one piece like the aftermarket aluminum manifold. If that makes sense.
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66' Euro (Pan off restoration)
Sold 63' Sedan
73' Riviera Camper
Sold 54' Oval (Sedan)

[Tcash]

Put a light coat of grease on the mounting surface. Put the manifold on by hand without the gasket. Then pull it off straight up,and inspect grease for thin areas.

[timvw7476]

Some cylinder cover tin can foul the flange area where the manifold meets
the head surface, the vee area between the intake ports.
If you can place a gasket over the studs & see nothing blocking the gasket
area, you should be OK.
Also make sure your studs are actually threaded down deep enough in the
head itself & they are all capable of exerting proper clamping force.

[JamesDole]

Thanx Tim. I did already trim back the tin. After installing the manifold I try and flex the tin around the manifold to be sure it’s not pinched. I will make sure the studs are threaded all the way down. Just running out of ideas. The 3-4 manifold seems to be fine, just the 1-2 that’s giving me grief. Today I’m going to try and double up the gasket and see if that helps. If not, I’m gonna try the stock steel manifold.
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66' Euro (Pan off restoration)
Sold 63' Sedan
73' Riviera Camper
Sold 54' Oval (Sedan)

[JamesDole]

This morning I tried two gaskets stacked. Started the motor, let run for a few minutes then sprayed starting fluid, no vacuum leak. Drove it for about two miles, brought it back, sprayed it again, vacuum leak. I've tried everything that has been suggested. Could there be something wrong with the head I got from Kustom1??? Don't know what else to do except try the stock steel manifolds. I'm at the end of my rope and have been fighting this for over two weeks now.
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66' Euro (Pan off restoration)
Sold 63' Sedan
73' Riviera Camper
Sold 54' Oval (Sedan)

[Tcash]

is one of the studs pulling out?
Torque them to 18 ft/lbs, run it, let it cool retorque and repeat. If one of the stud is pulling it will loose torque.

Suprising two gases did not work! Usually even if they are a little warped two gaskets will work.

The head could be leaking. Dye test it.
https://www.google.com/search?q=dye+test+for+leaks...ent=safari

You could use Plastgage on the mating surface. Torque it down and see where any uneven spots are.
That what I use grease for.

Good luck
Happy Father's Day
Tcash

[JamesDole]

I have now tried the stock steel manifold and there is still a vacuum leak. I can only assume that there is something wrong with this head from Kustom1. I don't know what else to do.

The motor was carefully built with Kustom1's 1800 re-build kit. Every step was meticulously followed using the Bug Me/Jake Raby video. Other then the vacuum leak, everything seems good.
_________________
66' Euro (Pan off restoration)
Sold 63' Sedan
73' Riviera Camper
Sold 54' Oval (Sedan)

[JamesDole]

I've been using the paper gaskets which seems to be the consensus of the type 4 searches.

Should I even try the metal gaskets?????????
_________________
66' Euro (Pan off restoration)
Sold 63' Sedan
73' Riviera Camper
Sold 54' Oval (Sedan)

[JamesDole]

As per Tim, I checked that the manifold studs were all the way down. I did notice that one of the studs (lower one) went in by hand a lot further then the rest before it bottomed out. In fact I had to turn it back out because it would have been too short. not sure if this is a problem... Loctite?????
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66' Euro (Pan off restoration)
Sold 63' Sedan
73' Riviera Camper
Sold 54' Oval (Sedan)

[Tcash]

Loctite would be worth a try medium strength blue would do.

Are any of the nuts loose when you go to change the gaskets?

[JamesDole]

Thanx Tcash. I am at a loss on this. I've had the bus for three years and have never driven until a week ago. Built custom cabinets for it, custom fold out bed, re-built the motor, new eight ply tires, all new window/door seals, new seat upholstery, new HD front sway bar, replace battery tray, applied for a lost title. It is now licensed and ready to drive. So many things have kept me from driving this bus. Some how I have to over come this so we can take it on a trip. The bus is in great shape otherwise.
_________________
66' Euro (Pan off restoration)
Sold 63' Sedan
73' Riviera Camper
Sold 54' Oval (Sedan)

[Tram]

An old trick I learned with Mercedes years ago is to soak cardboard gaskets (and carburetor gaskets) in ATF before installing. This makes them extremely supple and pliable and is excellent for stopping vacuum leaks before they happen because the gasket won't shrink from heat cycling.

If that doesn't work use two cardboard gaskets coated with Permatex Aviation sealant on both sides.
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Немає виправдання для війни! Я з Україною.

[JamesDole]

I have now replaced the intake manifold studs. Some were only threaded in about 3/8” into the head. I made my own so as to be able to thread them in deeper. Used blue thread lock. Doubled the gasket along with permetex aviation sealer. Waited until the next day before firing it up. Upon initial start up, no vacuum leak. After driving, not even two miles, tested it, and there is that vacuum leak. The only thing I haven’t replaced is the nuts. They seem kinda soft, as in the mar pretty easily. Where can I get a harder 8mm x 12mm nuts for clearance? Not sure what else to try. I’ve had the bus for three years and this is the first time I have gotten to drive it and it runs like crap on a newly rebuilt motor. Can’t get anything dialed in properly.
_________________
66' Euro (Pan off restoration)
Sold 63' Sedan
73' Riviera Camper
Sold 54' Oval (Sedan)

[SamboSamba22]

The intake studs are nice and tight within the cylinder head? Torquing the manifold down to spec should eliminate the possibilities of a vacuum, leak, what carbs and intakes are you running?
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The Bus Barn Ltd. Co.

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[Wildthings]

Just use some Ultra Silicone, if you let it set well before exposing it to gasoline it will last a long time. No gasket needed, it is best to just leave them out. If you still get a vacuum leak it is a very good bet there is a crack in a casting somewhere. You can also get special gasoline resistant sealers at your FLAPS if you are concern about the durability of the Ultra Silicone.

[JamesDole]

The studs are nice and tight. The carbs are Solex carbs from aircooled.net with CB manifolds. Same manifold as 3-4 but no vacuum leak on that side. I’ve tried three different manifolds with no luck
_________________
66' Euro (Pan off restoration)
Sold 63' Sedan
73' Riviera Camper
Sold 54' Oval (Sedan)

[Tcash]

To pinpoint where the leak is.
Hook up a vacuum gauge and or an analog needle rpm gauge.
With the straw on a can off wd40. Spray strategically and note any vacuum or rpm change.
It may be the head leaking. The only way to test is to remove the head and pressure test or dye test it.
I know it would be a pain in the asp. But u could switch the heads side for side and see if the leak moves.

[Tcash]

8mm small wrench nuts.
https://www.belmetric.com/jis-small-wrench-nuts-c-3_58/?zenid=ielalp0iks72cqmspecpuloak4P