440 exhaust cross over to block off or not - that is my question

[SGTPaul]

Hi, while getting parts together to rebuild my 68 440 HP I'm trying to decide if I should block off the exhaust crossover or not. My car is a 68 Charter RT 440 HP 4spd 3:54 Dana. Will be going all factory from front to rear. Living in the Detroit area and will plan on driving the car April +/- to October +/- time frame. I've done some research on this and still on the fence which way to go. Car when done will be for cursing enjoyment, car shows, a little traveling, and perhaps a trip or two down the 1/4 mile. I understand the cross over helps drivability a lot in the colder months. It heats the intake to heat the incoming fuel-air mixture which helps a lot in cold weather, and it heats the choke as well in the intake to heat the choke coil on the intake. I guess my concern is that is the cross over is closed off how does that affect a stock choke? I presume it will eventually heat up the intake and the choke will open. Yes? Will it just run rough until the choke opens? Any hep is appreciated.

 

[R413]

My advice, don't do it. I've done it and was not worth it. stumble and bog until you are driving 20-30 minutes. The choke won't come off on time, will be late and run rich. That's not good for the new engine, so you try to back off the choke then cold starts and drivability are not good. Dark plugs and smelly oil. And this happens when in the mid 50's.

The heat in the intake atomizes the fuel in the manifold. Without it the atomized fuel drops out of the fuel air mix and forms droplets, that's not what you engine runs on.

Have you ever has a small block mopar with the common carbon plugged heat crossover and they run like garbage? Then you clean it out and it purrs again?

Do you use ethanol free fuel? It is much better, doesn't boil out when you let is sit hot. Doesn't evaporate out as fast when parked for a week.

Look here for MI stations
Pure-gas.org - ethanol-free gasoline in the U.S. and Canada

 

[furious70]

If you're going all OEM carb manifold and choke you shouldn't block it.
If you're hot rodding, you can block it

 

[Daves69]

IMO, it'll likely blacken things out the exhaust as well.
Then too, if you must, consider electric heated choke or at least set up a manual choke......
oh................
....and don't forget to adjust it.

 

[Don Frelier]

Stock divorced choke don't block it.
Electric choke then yes block it.
Personally I prefer the latter

 

[oldbee]

https://www.pure-gas.org/

^^^^^ What he said. My heat riser spring is broken, so I just wired it open. Factory choke opens just fine in driving season.

 

[zyzzyx]

I put an Edelbrock carburetor on my engine with an electric choke. The intake is an Indy dual plane that has room
underneath for air circulation. I blocked off my crossover with two small pieces of 0.015 Stainless Steel shim stock.
Before I did that I crammed some aluminum foil down in the head to keep the heat away from the intake gasket.
You need a choke until the car gets up to temp otherwise it won't be happy!

 

[Runcharger]

I wouldn't bother blocking it. Miniscule benefit IMO.

 

[SGTPaul]

Thanks all. Sounds unanimous to keep it open. Will do!