Spread bore intake manifold for vortec heads

[77 K20]

For sale is the manifold that came on my GM HT383 engine. I bought the engine in August of 2014 and have switched to another intake manifold due to cold weather issues. If you don't live in the far north I'm sure it would be fine for you.

GM Intake #12496820. Dual bolt pattern spread bore manifold. Has provisions for EGR. Comes with EGR block off plate, GM 180* thermostat P/N 10202456 and GM thermostat housing # 10108470

http://www.summitracing.com/parts/nal-12496820

Description:
This Vortec manifold was designed for ultimate horsepower and torque to be used with Vortec cylinder head, P/N 12529093, 12558060, 12497186 or 12464298. This aluminum four-barrel manifold will accept Holley or Quadrejet carburetors and is EGR equipped. Use intake manifold gasket P/n 12529094 and eight special manifold bolts P/N 12550027. You can use EGR P/N 17052693.

Manifold height: measured from end rail of block to carburetor mounting flange - rear - 5-1/4", front - 3-3/4"

To hook up EGR with this intake, following parts are required:10220275 EGR pipe, 12552329 fitting, vortec exhaust manifold # 12557828, 12557828DT (tapped for O2 sensor) or ED1476 weld-on fitting kit for use with headers.
To plug EGR pipe hole in intake, use GM 12556596 or a 10AN plug.


$165 + shipping

 

[77 K20]

Forgot something- also included is a spread bore to square bore aluminum adapter.

Edelbrock 2696 adapter:

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[77 K20]

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Also have an open style carb adapter that would go with it. I'm spring cleaning my garage and need to make room.

$100 + shipping.

 

[77 K20]

Sold.

 

[85Jimmy]

Manifold for cold weather

I know its been awhile since you posted this but you mentioned you replaced this manifold due to cold weather issues. What did you end up going with? I'm having cold weather issues with my vortec setup.

Thanks in advance!

 

[77 K20]

I replaced it with an Edelbrock RPM manifold 7116. And eventhough it says RPM it is still good at low RPM also. The design has a heat plenum under the carb/TBI. Says you can run exhaust or coolant thru it. It has ports on both sides of the carb/TBI. I plumbed one side to the front of the intake under the thermostat and the other side to the return on the waterpump.

Sadly the first one I bought and installed had a coolant leak. I finally found that after sitting overnight and you pull the TBI and look down into the manifold there was little tiny puddles of coolant sitting on the waffle pattern. I called Edelbrock who firmly denied that could happen. They didn't believe me at all. Said I could spend my own money to ship it to them so they can test it. IF they found a problem then they would fix or replace it. It would take about a month.... and since it was my daily driver that was not acceptable.

So I bought a second one. This was probably about a year later. Guess what? SAME thing- but not quite as bad. My "fix" was to install a 7 lb radiator cap instead and a tube of alumniseal. No- not the best thing ever.... but it hasn't used a drop since. (note on the "leak": it would only leak after cooling down overnight. If I'd go on a 8 hour drive it didn't use any. Only after heat cycling. After 4 drives it would be down at least 1" on my coolant recovery tank)

Running coolant thru it works- fairly well. At first when I start it up cold it has a mis-fire as fuel is puddling in the plenum. I just drive it slow and easy and in about a mile then there is enough heat it is running better. Another 2 miles down the road and it is running well.

I had thought about plumbing exhaust thru it instead. Afterall- that is what the original smallblock manifolds did. Then you'd get almost instant heat in cold weather. But didn't quite know how to go about plumbing that up.

 

[Camar068]

As I was reading this, I thought this sounds really familiar. Glad you got it to stop leaking.

 

[85Jimmy]

Thanks a bunch! This info helps a lot. Sorry to hear about the issues. I would expect better from edelbrock. Hopefully I don't end up with problems because it looks like this manifold might be my only option. It looks like you had the EGR blocked off on the manifold that you sold. Do you think if I plumbed exhaust to the EGR capable manifold cold westher driveability would be better?

 

[77 K20]

Thanks a bunch! This info helps a lot. Sorry to hear about the issues. I would expect better from edelbrock. Hopefully I don't end up with problems because it looks like this manifold might be my only option. It looks like you had the EGR blocked off on the manifold that you sold. Do you think if I plumbed exhaust to the EGR capable manifold cold westher driveability would be better?

I looked and didn't see any other options for a "heated" manifold.

I thought about trying to use the EGR of the old manifold- but gave up on that idea. One port on it is threaded- so that would be ok. The other side of the passage (under the EGR) isn't threaded. How to connect to that? The GM manifold is very expensive also.

From what I remember you are supposed to plumb exhaust to the port marked with a green circle. Exhaust then runs thru the manifold to the dark blue circle. The EGR valve is then supposed to open to allow exhaust into the port marked with the red circle. Exhaust then comes out inside the manifold in the light blue circle.

Also I found the design of the GM manifold is lacking for cold weather. Under the carb the plenum there is completely smooth. Intake manifolds are usually designed with either a waffle pattern or a washboard pattern there to help atomize fuel. When fuel is suspended in an airstream and then suddenly has to change direction by 90 degrees it can cause fuel to drop out of the air and start to puddle. The colder the metal is the more it will want to stay a puddle. If there are ridges then the fuel will move along and once it gets to the top of the ridge it can break away and join the air stream again. And if the manifold is hot/heated the fuel will want to evaporate and get off the manifold.

Also of interest is my engine has 20-21" of vacuum. When drawing air into a vacuum the temperature will drop even more.

 

[85Jimmy]

Thanks again for the explanation! That all makes sense. My current manifold is a weiand stealth, which always seemed cheap. It doesn't look like it's being made anymore, and the folks that built my engine now use the edelbrock RPM you went with. I did notice mine has the waffle pattern at the bottom of the plenum though. It just has no way to get heat under there. My holley tbi injects fuel right under the throttle plates and so that part under the throttle body doesn't seem to warm up.

 

[77 K20]

Glad I can help- I struggled with my new engine a long time before I figured everything out.
At first I thought the cold weather issue was my carb- as it had the old chimney pipe heat choke piece that is supposed to bolt to the manifold. Tried to convert it into a manual choke. Failed. Bought a new quadrajet with electric choke. Nope. Bought the edelbrock TBI.... (still not quite happy with it)

It's been a long expensive experience.

Oh- and you are right- the area under the tbi just doesn't really want to heat up. I used my IR thermometer quite a few times to take manifold temp measurements.