Is this a flaw in my intake?

I know this might sound dumb, but is the hole underneath my intake a flaw or is it supposed to be there. If so for what? Its new never used. The intake is for a 394 OLDS, 3 carb.

 

I was told

that the little holes

in the tops of stromberg tops are for heaters

I dont know ifn ima gona blive dat

but that could be your answer

im a doubter

 

Why it's there, I have no idea but if you bolt it onto the motor you'll have exhaust gas coming out of the hole all the time.

 

Its part of the heat stove for the choke.

 

It's for the "choke stove"
little peice of tubing goes into that, and runs up to you mechanical choke. ( the one taht pulls a tiny bit of vac*** while the choke is open, typically covered with an itty bitty peice of screen. )

Tap it and thread a bolt into it. Buy a carb with a true mechanical choke, or get all "fancy" and get one of those newfangled 'lectric ones.

 

hmmm warm weather folks unfamilular with heat rizers and temp controlled choke setups ...

i hate the cold but its nice about 3weeks ayear here

 

Huh? what?

no you will not!..this part is called an intake manifold...not exhaust manifold..there for no exhaust goes thru it.

anyway the little hole is there for a purpose..as said before that is part of the heat riser and it is a pressure relief hole.
the choke set up should go into a well on the other side.

 

Thanks for the quick answers guys. I thought I bought a reject!!!!!!!!!!!!

 

Odd, most V8s from that era have a flapper door in one manifold with a spring on the end that changes size with heat so it opens the door. When the door is closed it redirects exhaust through p***ages in the head to the center crossover in the intake, to heat the carb. When that spring breaks, you know it, too, because it runs like **** cold with the flapper door open.

To me that would imply some exhaust g***es are flowing through the intake manifold, but what do I know.

 

Not arguing with anyone here...but that is in the heat riser part of the manifold
and yes exhaust g***es do indeed go into that chamber..exhaust g***es are what preheats the bottom side of carbs...the hole indeed would be for a choke stove tube.....If you are not going to use a choke stove..Plug the damn hole!!!!!

 

thank you. that almost killed me. those are the water p***ages right!!

 

I must have mis understood what he ment..but yes it is part of the choke ***embly..and no you will not have an exhaust leak...

 

isnt it part of the vac*** break for the choke?
I apologise if im all wrong, i have no excuse, just been mis informed by some olds owners..

 

Hold on.
The cross p***age containing the hole and connecting the two little ports is an EXHAUST CROSSOVER or HEAT RISER whose job it is to warm the intake for better vaporization.
It may or may not have a place for a choke stove or choke tube, probably not, but anway they would be on the OTHER side. If it does have such provision, there will be either a well to contain a little thermostatic coil or a place for heat tube to carry exhaust heat up to such a device on carb. It will have this stuff only if designed for 1950's carbs, not Strombergs/94's.
Hole shown WILL leak exhaust into engine valley; you will have smoke out the breather and probably formation of sludge and acids in the oil. Hole either should not exist or should be closed by a fastener.
What is the whitish area around hole? Was there something riveted there??
Many OEM manifolds had a tin shield so oil wouldn't be heated by crossover, but I don't think that's what you have with only one hole. Maybe it held a riveted tag or maybe it is a flaw or mistake or someone with some odd mod in mind drilled it...but I think you are going to want to fill it, probably by just tapping it and running in a setscrew with loc***e so it doesn't fall out into engine.

 

I'm not sure if you're being sarcastic or not....so I'll jump in with my $.02

The round holes to the front of the manifold (right side in picture) carry water from both heads; there should be a thermostat housing boss cast into the top side - that would then connect to top radiator hose.

Yes - the smaller center 'square' holes p*** exhaust gases from one cylinder head to the other. On one of the exhaust manifolds would be a temperature sensitive spring connected to a 'flapper' valve (officially called a 'heat riser valve') that would direct exhaust g***es from one head to the other instead of out the manifold, in a seperate p***ageway under the intake p***ages. This would allow the manifold to quickly warm up and facilitate fuel vaporization. As the engine got warm, the valve would open and allow the exhaust to exit through the exhaust pipe. Since it was a spring, if the engine was revved-up, the exhaust would push the flapper open and exit through the exhaust pipe.

Common on all carburated engines that I'm familiar with from the 40's on up.

Yes, the little hole is to feed hot air (exhaust) to the automatic choke spring (not a mechanical choke) wihich was another temperature sensitive coil that closed the choke when cold. As this spring warmed up - the choke opened - hence 'automatic choke'

All of this was common in the old days - the first thing to go when you put duals on a V-8 was the 'flapper valve' to eliminate the restriction. In factory duals, when the engine was warming up you would only see condensation coming out of one tailpipe.

A correction to the post above mine - Oldsmobile intakes (same as Buick, Pontiac, Caddilac to name a few - Chevy was the first V-8 I encountered back than that did cover the valley with the mainifold, don't know about Ford and Mopar of that era) did not cover the engine valley - there was a seperate pressed (stamped) cover to seal off the engine valley so that hole could be accessed for a 'choke stove'.

 

White area around hole does not make sense...I'd bet a nickel that previous owner had that hole covered by a bit of tape with selling price on it, placed there to conceal hole!

 

Thats a damn good bet.Bruce!!!!I'll second that

 

it won't flow into the intake because this is a "divorced" type intake, like a modern motor- the intake floor is seperated from the lifter valley by a valley plate. it's a great place to lose a 7/16th socket.

The hole is on the bottom, 'cause that's how Olds did it back then. I know it doesn't make a whole helluva lot of sense unless you can see the top of the intake, too. Once you make it to a "machinable" surface on the top, You're already into the transition for the carb. there was room under the intake for the port (which, does indeed have exhaust running through it, a design every g.m. product featured to this day) to heat the bottom of the intake- not just for cold weather, but for better fuel atomization. most decent aftermarket intakes ( well, ones designed to make power) has these filled. I have never seen a set of performance heads that have a provision for an exhaust crossover.

Point being?

put a bolt in it. You live in California.

 

Here are some more pics. Its an Offenhauser. It looks like they grinded the surrounding area, thats the blemish you see in the pics.

 

Huh!
it has a port in the top, too?

then for sure put a bolt in the bottom one.

and while You're at it, You might as well drill a hole between 2 and 3 and tap it for a vac*** port. ( if you plan on power brakes.) remember the center carb controls vac*** advance, and if You are running an Automatic, Trans vac*** as well. Yes, You could pull it brom the back of the third carb base, but the distributor and wirse like to live there instead.

Boldly forward, My Son! Go fast! Scare children!

 

Stick a piece of wire in it to see if it is open to the inside of the cross over. Most of the choke stoves **** air through a tube in an exhaust manifold or the carb heating crossover. The exhaust gases don't get inside that tube and into the choke. Fresh air is ****ed through the tube and that warm air warms the choke. If it is a tube that goes all the way through the intake and comes out on top, then there probably is nothing to worry about.



The tube coming off of the choke thermostat on the rear carb goes to a tube in the crossover that goes all the way through the intake and comes out the bottom similar to yours. If you stick a wire in it and it comes out on top, you probably are ok.

If it is actually a hole in the crossover, I'd drill it and tap it for a machine screw or you will have an exhaust leak as others have said.

 

So, Lux, the tube from coil on carb goes through hole in top, through exhaust p***age, and out...so valley is its pickup area?? I'm used to the later one with a loop for tube to divorced choke...
Anyhow, is a stromberg type setup with no choke coil, so must be plugged to keep exhaust out of vallley (and out top) since there won't be a tube for manual choke carbs...

 

Had something similiar with a Pontiac manifold. It CAME with new gaskets that blocked the heat p***age port on the heads.

 

So does this hole come on all new Offy intakes? Or is it a flaw? The reason I ask is because I just sold it and I don't want to screw the guy over. I sold it as NEW and didn't notice the hole when I bought it.

 

Its not a flaw. It was cast in there on purpose. A tube runs through there to help feed the choke system (typically Rochester/Holley but others too) warm air to open the choke as the motor warms up.

-Bigchief.

 

Thanks for the education - I had no idea!! sorry.

 

It was posted about having " a hole in the bottom" and "a hole in the top", in the exhaust runner;

I just looked at an old school Olds intake at the Tweeters swap in M*** last weekend. The lower hole was threaded, and a fitting with a copper pipe was installed to run the auto choke on a rochester center carb. That pipe ran from under the manifold, up to the choke.

 

Do your new manafold gaskets have block off plates for the exhaust cross over? I lot of them will have nock out plates or optional block off plates that come with the gaskets. I'd plug it anywaysI guess unless you want to draw from it for a choke stove spring. But I guess I'd just run a choke cable for the center carb & say the hell with all that stuff & plug the dang hole.


the top "hole" just looks like a threaded boss to me probably for mounting a throttle linkage stand, spring etc? No?

bet it don't go all the way through.

 

Yep. The stock stuff is usually alot more graceful. I actually prefer the type that has the coil down in a "stove" on the crossover (mid sixties g.m.) Just a simple Bi-metal strip. no muss, no fuss.

 

The old late 50's-60's Caddy manifolds with AFB carbs have a single tube going into the manifold. Fresh air is picked up underneath the manifold in the valley area. Consequently, the Caddy AFB has no ****** on the p***enger side of the air horn. In contrast, most Pontiacs of the same era (earlier models were like the Caddy) have two tubes and the Pontiac AFB has the ****** that picks up filtered air. The Offy manifolds equipped with the hole have a tube pressed through it that mimics the Caddy design. No need to plug the hole if not using it.