Intake cross over blockage or not ?

[cecil4speed]

I've read a few different opinions on cross over blockage. Has anybody had plug fouling or cold weather driveability problems? I drive my car from May to October if weather permits. October is pretty frosty some mornings. Once the engine warms up to temperature you shouldn't notice any difference blocked or not blocked should you? I do have warm fuel problems the same as everyone else, so thought this may be the answer. 1969 340 engine with thermoquad and oem intake. Do I block or do I not block?

 

[needsaresto]

Blocking it may cause cold weather issues . It will help power but also increase fuel consumtion.

 

[cudavert]

I guess it also depends on how important it is to get that little extra power from a cool intake manifold vs. the driveability issue. I might lean a little bit to the "no" side, unless you don't mind warming 'er up for 5 or so minutes before you drive. Overly cold-blooded cars can get annoying.

 

[C130 Chief]

If you are running the OEM style choke, don't block it. Otherwise the choke will take forever to open and your secondaries will be locked out. If you were running an aluminum intake and an aftermarket carb with an electric choke, then blocking it would make sense.

An OEM style air cleaner with the hot air pipe will help winter driveability way more than the crossover.

 

[cecil4speed]

Thanks for the insight guys. I have decided to let it open. I remember years back when I had drivability problems, I had to remove the intake and clean the crossover holes out because they were craboned up and almost shut. Once they were cleaned out, the hesitation problems went away, so I guess this may do the same thing. I'm leaving them open.

 

[Beatnik]

I have mine open on my RPM intake (non air gap) and it's nice because it warms up fast enough so that not having the choke hooked up works out ok. I just feather it and keep the rev's up for about 30 sec's and she settles down. A good carb will help make up the difference on warm up too. That's what I've found anyway...

On the flipside, it does work as a hotbed under the carb for putting extra heat on your fuel, which is never good from a performance and efficiency standpoint.

One of those pick your poison things I suppose...

 

[dodge freak]

Bump an old thread but I ran intakes both ways up here in cool weather Michigan. Having the exhaust heat passages OPEN are the way to go. At night during WOT the intake will get cold even driving it ALL night. I found at night time and cool weather a heated intake will make MORE power--not less.

True, mid summer during the hot afternoons the intake gets too hot but a carb spacer helps keep the carb cool as the air going through it helps cool it off.

During WOT the air goes so fast through the intake it does not heat up all that much.

I believe many people make a mistake by blocking the exhaust heat for the intake which can lead to foul out spark plugs and a stinky exhaust smell.

If you live in the hot South were temps are 100 degrees everyday then you should block the heat off but for everybody in say like Canada its better overall to have the intake heat.

 

[ramcharger]

I live in Colorado where the days are hot an nights are cool. Summers days here can hit 100+ for weeks and weeks in a row and last summer I was having some bad carb boil over problems. I went ahead and blocked off the heat riser as I don't run a choke anyway. Last winter when I had to drive it, it took a while to warm up but it was tolerable.

I tried the same thing years back on a another vehicle I had that was my daily driver and it was miserable, but this back in humid *** Chicago. Reason being is that carb literally frosted over and blocked the transfer slots in the carb. I'd be warming it up and it would just die. I'd have to let it heat soak for 5 or 10 minutes , then try warming it up again, turn it off again etc.

In my experience, it depends on very much on your local climate. Yeah it can get mighty cold here in the winter but there is no where near the humidity and I think that makes all the difference.

BTW, my carb boil over problems stopped once I blocked off the passage. A good insulating gasket or spacer can do the same thing too. I also agree with C130 about the air pre-heater too for dead-cold winter driveability.