Intake manifold blockade?

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Ron Grubb

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Recently got my hands on a 273 4 barrel intake. I am in the process of cleaning I have noticed that 2 of the ports are blocked. See pictures. Question: is this intentional or just need cleaned out?

D6BAB16D-7926-4D81-832D-86029E800989.jpeg


B20399EC-01A5-42F1-8D59-8DA658FF6457.jpeg
 

Syleng1

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Exhaust cross over port. Blocked by carbon from engine burning oil.
The cross over helped with warming up the intake as soon as possible so car had better cold start driveabilty. If you want a hot intake clean it out. If you want a colder intake- block them off with thin pieces of metal or use gaskets with built in block offs.
 

RustyRatRod

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If you lived in a warmer climate, I'd say leave it blocked, but in Indiana, I'd probably clean it out.
 

dano

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The tin peice is held with a twit rivet, you can remove these and aid in cleaning the passage.
 

mod5v

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That tin is a heat shield. The exhaust crossover gets so hot it will cook the oil splashing on that part of the intake. There is no access to the passage from under that plate.
 

toolmanmike

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Here in Iowa I would need help with cold drivability if I was driving my old cars daily throughout the winter. Because I am a summer only driver and I start them up and let them warm up almost to operating temp I don't feel a working heat riser and a cleaned out passage is necessary. I just adds to carb heat and fuel evaporation.
 

Dana67Dart

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Technically the thermostat controlled butterfly in the pass side exhost manifold controlled whether exhost gets routed to the drivers side.

Assuming that is functional as soon as the thermostat spring heats up the butterfly opens and exhost no longer is forced to the drivers side.

I'm sure some amount of hot exhost makes it over though.

IMHO I would clean it out as best you can.

If you thermostat butterfly in your exhost manifold functions correctly you have very little to loose.

I live in Northern Colorado, on the coldest days I have no trouble starting my 273. The thermostat spring has not been attached to my butterfly for ever. The butterfly is free to move so I suspect at low exhost pressures, it is partially closed.

I would not remove the heat shield, you don't want loosened rivets falling into your engine. You could drill and tap for bolts where the rivets were and use some locktite.

Cleaning under the heat shield is a challenge, I have heard oven cleaner works well.
 

Rat Bastid

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Recently got my hands on a 273 4 barrel intake. I am in the process of cleaning I have noticed that 2 of the ports are blocked. See pictures. Question: is this intentional or just need cleaned out?

View attachment 1716038961

View attachment 1716038962


I don’t care what’s in the crossover. It ran like that for most of its life. You can bet on that.

Guys love to stew over cold start/warm up issues but like I just said, that crossover has been blocked most of its life.

What matters is getting the cover off the bottom of the intake. That MUST come off and be cleaned.

Ive seen more junked engines because that wasn‘t removed and cleaned I can’t count them all.

Take a rounded nosed chisel and GENTLY tap on the rivet and it will come right out. If it gets a little bend it won’t matter. Just don’t chisel the head off.

Clean the living **** out of the manifold and that plate.

When you go to put it back together make sure the rivets have some press to them. If the fit in the holes like a hot dog in a hallway, take a punch and make three punch marks about 1/8 inch away from the hole.

When tapping the rivets back in, use a BIT of locktite on them and send them home.

Not taking that plate of is a HUGE mistake.
 

RogerRamRod

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What matters is getting the cover off the bottom of the intake. That MUST come off and be cleaned.

Ive seen more junked engines because that wasn‘t removed and cleaned I can’t count them all.

Not taking that plate of is a HUGE mistake.

Can you elaborate on why this will junk an engine?
I tend to clean anything/everything just on principle if I have it apart, but I'm curious about what is so devastating up under there. Old high mileage motors have lots of baked-on sludged-up stuff in them, no?
Obviously, if one was going to sandblast the intake, you'd want to get the media out from under, etc.
 

mgoblue9798

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Can you elaborate on why this will junk an engine?
I tend to clean anything/everything just on principle if I have it apart, but I'm curious about what is so devastating up under there. Old high mileage motors have lots of baked-on sludged-up stuff in them, no?
Obviously, if one was going to sandblast the intake, you'd want to get the media out from under, etc.
The underside of the intake under the plate will be covered with carbon build up just like the passages in the head. The tin is not sealed against the intake, so with expansion and contraction cycles pieces of carbon can make their way into your new rebuild. Just take the time to clean it out and don't look back.
 

Rat Bastid

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Can you elaborate on why this will junk an engine?
I tend to clean anything/everything just on principle if I have it apart, but I'm curious about what is so devastating up under there. Old high mileage motors have lots of baked-on sludged-up stuff in them, no?
Obviously, if one was going to sandblast the intake, you'd want to get the media out from under, etc.

Post 12 pretty much covers it.

I tell people that don’t think it needs to come off to hot tank the **** out of the intake, and do all the voodoo **** that guys do to make themselves feel better and once you think it’s squeaky clean pull the pan off.

Most people are stunned what still in there. And it will kill an engine so fast you can count the time to full destruction in minutes.

It has to come off. Most reasonable people would NEVER think of putting a dirty, unclean part on a new engine but that’s what happens if you don’t take that cover off.
 

CRUZE 418

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I am with post #11. Count the minutes to destruction? I want in on this one!
 

CRUZE 418

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So? Not saying it shouldn't be cleaned, it should be, but it's not going to destroy the engine in counted minutes either.
 

gdrill

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There really isn’t a discussion here. If you rebuild an engine and don’t bother with that little effort, you are risking a piece of crap falling into your cam at 2000 rpm in the first 20 minutes.

IMO anyway.
 

toolmanmike

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There really isn’t a discussion here. If you rebuild an engine and don’t bother with that little effort, you are risking a piece of crap falling into your cam at 2000 rpm in the first 20 minutes.

IMO anyway.
Exactly. Simple, if the intake comes off (or you purchase one), it get's cleaned before installation.
 

Rat Bastid

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So? Not saying it shouldn't be cleaned, it should be, but it's not going to destroy the engine in counted minutes either.


LOL. I’ve watched it happen. I’ve had to autopsy engines that came back in that didn’t make it to finish cam break in.

Evidently what you think doesn’t match reality.
 
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