Greetings,

I am building up a mild 5.2L Magnum for my '73 Duster (hotter cam, roller rockers, etc.)

I plan on running a 600-670cfm 4-bbl (probably Holley) either electric or manual choke and an appropriate intake manifold.

My question is this - I have heard that carbureted Magnum engines have poor cold weather characteristics due to their lack of a heat crossover, and as I live in the Pacific Northwest this could be an issue.

Any thoughts?

Block heater?

Don't see why it would matter if it was carb'd or injected. pump it a few times, crank it and the choke should do just fine.

Might just be a little fall on its face-ish during first few minutes of driving in cooler-cold weather.

Yea, it doesn't have the heat cross over holes in the heads to warm the intake. I live in CT and my neighbor has a 5.9 carbed magnum.

It's kinda a pain to get running in the cooler nights in fall when he is still cruising. It's not driven in the winter, but I know he told me when i was looking at building one that he would definatly put a block heater for daily driving.

Never looked into it much past that.

I have a 408 with magnum heads on it . i drive it all year around . If you set the choke up right and the fast idle you won't have a problem. Even when i drive let here cool down she starts right up.

When it gets down to the 30's around here i do have to let the car warm up for a few mins on the first start but then all is good.

If you use a M-1 Dual plane it has a provision for running coolant through the manifold. Mine works good! And you can run leaner mixture which will net better gas mileage. Not the best for all out performance though.

I run that set up with the water running through the plenum area. Problem is it takes about 8 - 10 minutes in cold weather to warm up the intake and warm up the air/fuel mixture. No choke and an open style air filter.

One interesting thing is my water is warm in about half that time, but it's not bog free until way later.

It's 100% most definately the cold intake. I have a capilary style coolant heater. Since it's plumbed up through that plenum passage. I can make it very warm yet the engine itself is still cold. With that situation, the truck drives totally bog free even though the rest of it is cold.

I've got an '86 318 roller cam short block, cam reground by bullet with their HR259/316 lobe for int & ex, hughes 1110 springs, 2.2L retainers, mag heads, headers, eddie RPM air gap, and eddie 1406 600cfm elect. choke. runs fine year round in michigan, gets a little cranky on cold mornings below 15 degrees or so until it's warm.

I strongly suggest this cam, doesn't need roller rockers. mine's going fine with stock mag lifters, pushrods, and rockers.

I had a 318 with mopar performance strocker crank that made it a 390 with magnum heads and 750 holley double pumper with electric choke,I never had a cold start problem but live in Alabama so weather never really gets bitter cold like up north.

I put 440source stealth heads on my 440. Left the stock cast iron intake on there. So the heads are aluminum but unlike stock heads, they don't have the heated exhaust crossover. I did notice it takes 5 minutes longer for the choke to open now on a cold day than it did before. I run a thermoquad, stock choke without the electric assist part hooked up, just the stock thermostatically operated coil running the choke. I know it takes about 5 minutes longer because I drive the car to work daily and I'm closer to work by the time the choke fully opens and it drops to base idle speed at a stop. Cold driveability is no worse really, just have to drive that extra few minutes before the choke fully opens and I can feel it's warmed up. I bet if I had an aluminum intake on it, the choke would open up faster just because the aluminum will heat up quicker from engine heat than the cast iron. It's usually in the -10 to -15*c range before I pack it away for the winter. Once the intake has warmed up, it's just as fine running as it was before.

I live in an even colder part of the pacific NW (sort of) and I drive mine all winter as long as the roads are dry and I have an M1 single plane on magnum heads. No choke and it runs fine after a couple minutes. Just takes some fine tuning of the carb and timing and a good carter carb

When conditions are right, high humidity and 35 or so degrees, it will form ice on the venturi and choke it out. It will quickly met and then restart. This of course is without heat at the carb base.

Could have more problems with humidity than I do, we have very little here but it never frosts up.

Another thing you might be able to do is fab up a heat stove to feed it some warm air from the exhaust.

I have a 360 magnum with an air gap manifold, headers, electric choke 600 holley...and its low compression and stick. The car will stay running just fine but hesitates a little until its warm. You'll have to leave the choke on longer than you normally would, but it runs good enough to drive right away.