Holes/Notches/Slots in Intake Manifold 500/472

[mummyjohn]

The good news: after many months of nighttime tinkering, this 500ci beast roars again!

The less-good news: there is a small amount of very light smoke puffing from these holes (pictured), and I have no idea where these holes go (though if I were a betting man, I'd say into the crankcase/rocker arm area).



They line up PERFECTLY with notches cut into both the intake manifold, and the big valley pan intake gasket, making me think they were for alignment.  I don't remember there being anything in there before the motor was disassembled, and the guys at the machine shop that baked the heads and did the valve job - who, by the way, have been flawless, upfront, helpful, and above all committed to doing quality work before making a sale or being fast - said nothing about these holes nor returned me any hardware that should go in there.

So, what do I do with these holes? And is the light smoke indicative of some other issue, or is that normal? (I'm talking very light, visible to my 20/15 eyes only at the calmness of idle)

In the same vein, how hot should this motor run?  My cheap-o gauge shows a steady 210F at idle, 200~205 when cruising, though this is with the heater on; I worry about what would happen if I were to run the air con.

[TJ Hopland]

Those should be alignment pins.  I seem to recall that in addition to locating the intake they also help with the gasket.   Is there a gasket in there?  Hard to tell with the photo and the paint.   If there isn't a gasket that may explain why you are getting some crankcase gasses out there.

Temps sound normal.  These are big engines that make a lot of heat and seem pretty happy around 200*. 

[mummyjohn]

Ya there is a gasket, it also has notches the same width as the manifold and lines up perfectly with the holes & manifold.

So just get a pin the right size and pound it in there?  Sealer necessary?

[The Tassie Devil(le)]

The dowel pins should be there as they hold the gasket pan in place whilst also aligning the manifold.

They just press in, and the only reason they might have been removed is to machine the surface.

If everything is in alignment, I would simply be reinserting replacement pins.  They should be a friction fit in the heads, and a slip fit into the manifold slot.

Bruce.

[mummyjohn]

Well if I had 'em, we'd not be having this conversation...so I'm assuming just measure the hole and getting something that's a slight interference fit is a better choice than using some type of hardening goop to fill the hole instead?

[Bob Hoffmann CLC#96]

Why not contact one of the Cad big block guys, MTS or whatever they're called now. They have to have some from a core block.

[TJ Hopland]

Being in the head I would think those are blind holes so them not having anything in them should not cause anything to leak.   And just being slots on the intake side also should not cause a leak so why are you seeing a leak? 

Can anyone verify that those are blind holes?   

["Cadillac Kid" Greg Surfas 15364]

Actually the OP is correct.  The dowel is in a hole that exits in the first intake push rod cavity.  It is hard to see on a stock head, but mine have the push rod channels opened up for greater cam lift and you can just see the shadow of the hole in the picture.
Opening into the push rod channel means it is open to the crankcase vapors and is a source of vacuum leak and vapor migration.
Greg Surfas

[TJ Hopland]

There we go, a definitive answer.   I would try putting pins in before just trying to fill them with something.  If a proper fitting pin doesn't fit at this stage then maybe I would go for the largest fitting screw held in with RTV.  My theory there is that the screw head would keep them from being sucked in if the engine if they got loose or went under serious vacuum for some reason.   I'm thinking a fine thread machine screw sort of a thing, not a wood or drywall sort.     

[Scot Minesinger]

The pins on the front engine cover are 5/16" standard steel dowel stock.  Go to HD and buy a 1/4" and 5/16" steel dowel stock, probably 5/16" will work.  Don't hammer it in too far.

[mummyjohn]

Yep, I got confirmation from the Cad Co guys that 1/4" dowels are what go in there.

The rear/left one is easy to get in, the forward/right proved a challenge, and eventually I relented and got the air con compressor out of the way - there's no way the pin was gonna go in otherwise.  Sometimes a little more work can ultimately make something easier.

[cadillacmike68]

Now I need to check my engine to make sure the dowels are in place.

Pink???

["Cadillac Kid" Greg Surfas 15364]

You should be able to see them at the two notches along the outer edges of the intake.

Greg Surfas