Air gap manifolds in cold weather

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scrappydoo

scrappydoo

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Hi,
Can I get some feedback on how the air gap manifolds run when it's cold?

I'm concerned that the air gap will cause the motor to run like a pig until it gets some heat into it.

Thanks.
 
Your concerns are correct, as noted from the been there done that camp.

Ever drive a big block? Just like that.
 
You can just make the choke a little fatter etc, maybe add a small resistor if it is electric. Yep can not have it all they do not do good when ice cold on a street motor, nature of the beast...
 
In cold moist weather you can get throttle plate icing too. These manifolds are best used on summer drivers.
 
I have one on my wife's 68 Mustang.... I"m in Seattle, it is VERY cold blooded for the first 15 minutes or so....
 
I have one on the 360 in my 68 Barracuda and the engine does not like to take throttle until it's warmed up in temperatures below 45 degrees. I have driven the car in 20 degree weather and it can be 4 or 5 miles before the engine does not need to be feathered to take gas. My car is a manual which makes it easier to deal with than an automatic. At 40 and above it takes about a mile or 2 before it's happy.

Even when it's warmed up the choke will some times close down a little and keep the idle up over 1000 rpm after a 10 minutes or so run in 20 degree weather.

Adding choke helps some but not entirely since it's the fuel puddling at the bottom of the plenum that is causing the issue.
 
dgc333 said:
I have one on the 360 in my 68 Barracuda and the engine does not like to take throttle until it's warmed up in temperatures below 45 degrees. I have driven the car in 20 degree weather and it can be 4 or 5 miles before the engine does not need to be feathered to take gas. My car is a manual which makes it easier to deal with than an automatic. At 40 and above it takes about a mile or 2 before it's happy.

Exactly the way my wife's car acts... kind of a pain!
Click to expand...
 
LOL, I guess we've all run the Air-Gap with the same results.

Scrappy, The regular RPM is what you want for more than 1-1/2 season driving. Late spring to early fall. I forgot about the iceing and the choke closeing up if it is that cold out. Danm car is all warmed up after 10 min.'s and I strat driving down the road, 30 seconds later, she's back up to a quick idle. Grrrrr
 
Thanks for the replies.

I going with magnum heads, it doesn't look like there are any manifolds with heat crossover.

The Mopar M1 dual plane looks like it has something for water heat crossover but I can't tell for sure.
Does anyone know?

edit:
I've answered my own question, summit have a 360deg. view of the manifold and you can see that it uses coolant for the manifold heating.
Thanks.
 
scrappydoo said:
Thanks for the replies.

I going with magnum heads, it doesn't look like there are any manifolds with heat crossover.

The Mopar M1 dual plane looks like it has something for water heat crossover but I can't tell for sure.
Does anyone know?

edit:
I've answered my own question, summit have a 360deg. view of the manifold and you can see that it uses coolant for the manifold heating.
Thanks.
Click to expand...

All manifolds (even an Air-gap) have the water coolant passage. That's not for heating the manifold. It's for connecting the water coolant passages on the heads and providing an outlet to the radiator. Magnum heads have no exhaust heat crossover like LA heads so it doesn't matter what manifold you use although a manifold that's not an Air-gap style might be slightly better cause the oil being splashed on the bottom side of the plenum will heat it some.
 
I think it would be a good idea to fab up an electrical/coolant-operated heater for the plenum. No other way to get the intake heated up for cold weather. Except, of course, a hot-air induction system similar to what the factory started doing in the '70s. I haven't tried an Air-Gap manifold myself but my 4-bbl. 318 already needs 3-5 min. warmup before I can shift into gear below 50*.
 
fishy68 said:
All manifolds (even an Air-gap) have the water coolant passage. That's not for heating the manifold. It's for connecting the water coolant passages on the heads and providing an outlet to the radiator. Magnum heads have no exhaust heat crossover like LA heads so it doesn't matter what manifold you use although a manifold that's not an Air-gap style might be slightly better cause the oil being splashed on the bottom side of the plenum will heat it some.
Click to expand...

Hi Fishy,
If you have a look at the picture on the summit page there is an extra coolant passage that runs under the manifold where the carburetor sits for heating.
The one you're talking about is where the thermostat sits, I know every manifold has this.

I had a car that used coolant for heating the manifold but the passages were blocked and it was a total pig in the winter.

Thanks.
 
I never noticed that on the Magnum intake. Interesting.
 
You will foul plugs and gas will get in your oil dont buy it.I had a victor on my 327 with no heat cross over, great intake when she was warm up but suck in early spring and early fall.
 
scrappydoo said:
Hi Fishy,
If you have a look at the picture on the summit page there is an extra coolant passage that runs under the manifold where the carburetor sits for heating.
The one you're talking about is where the thermostat sits, I know every manifold has this.

I had a car that used coolant for heating the manifold but the passages were blocked and it was a total pig in the winter.

Thanks.
Click to expand...

Hum... I can't really see an extra coolant passage running under the plenum unless it's that threaded hole in the side of the plenum. It would need an outlet somewhere. Maybe on the side not pictured. Doesn't say anything about it in the description. That must be a fairly new design if it is designed that way, or I'm behind on the times LOL.
 
fishy68 said:
Hum... I can't really see an extra coolant passage running under the plenum unless it's that threaded hole in the side of the plenum. It would need an outlet somewhere. Maybe on the side not pictured. Doesn't say anything about it in the description. That must be a fairly new design if it is designed that way, or I'm behind on the times LOL.
Click to expand...

Hi Fishy,
If you have a look at the 360deg. image, the manifold will rotate and show the underside of the manifold and you'll see the bulge run from the side of the manifold up to the front.
And the threaded opening on the side where the carb sits would be for the heater hose to connect to.
At least that's what it looks like to me.
 
scrappydoo said:
Hi Fishy,
If you have a look at the 360deg. image, the manifold will rotate and show the underside of the manifold and you'll see the bulge run from the side of the manifold up to the front.
And the threaded opening on the side where the carb sits would be for the heater hose to connect to.
At least that's what it looks like to me.
Click to expand...

Wow I didn't know what the 360 degree thingy was for. Guess I should have tried it before. Cool feature. It does look like it runs coolant under the plenum.
 
Just posting an update on this.
I bought the dual plane M1 from ebay and just received it today.
Here are some pictures showing the water passage that comes through under the thermostat.
Thanks.
IMG_0860.JPG

IMG_0861.JPG
 
Hi fishy,
there is a hose barb that goes on an opening next to the carb (which isn't in the photos) completing the circuit.
 
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