Cleaning exhaust crossover safe to do with heads on?

[Secret Chimp]

I've rebuilt and retuned my carb and I'm still getting pretty bad mileage out of my car - usually no more than 12. I'm assuming the heat crossover in the intake is clogged since it looks like the intake has never been off of the car.

If the passages from the head are plugged up, is it safe to clean the passages with the heads still on the car? I don't quite understand if the redirection of the exhaust happens inside of the manifold, or the head via a passage the center exhaust ports share to the crossover opening. I don't want to be dropping any carbon chunks down into the center cylinders. Should I be OK by making sure the valves are closed and then vacuuming and blowing out the ports thoroughly when I'm done?

I really don't want to pull the heads off... I'll end up spending hundreds of dollars on other things I find rather than a few bucks on drill bits and Berryman's...

 

[Coronet 500]

I've done it on a Small Block with the correct exhaust valve closed, manifold off with valley taped up and a vacum. It took alot of careful chipping and turned out easier than I first thought.

 

[kursplat]

i've done it a few times with the heads on. i have a shop vac running pointed at the work area while i'm doing it. a second person to hold the vacume while your chipping out the crud helps a lot. don't know how your planning to get it out, but a screwdriver and hammer works fine. just remember, little chunks, don't try to get it all at once

good luck

 

[Cranky]

I've always blocked the heat crossover on all of my junk. It only helps improve wintertime driveability and quicken warmup time....

 

[Secret Chimp]

I've always blocked the heat crossover on all of my junk. It only helps improve wintertime driveability and quicken warmup time....

That's what I'm going for, honestly. It's just an old 318 station wagon. I bought it as a project and fun family car and I'm hoping cleaning the crossover will improve my fuel economy since I've done most everything else tuneup-wise.

 

[Cranky]

The crossover won't do much for mileage except for maybe on the coldest days.....

 

[kursplat]

...and I'm hoping cleaning the crossover will improve my fuel economy since I've done most everything else tuneup-wise.

have you checked the gear ratio?

 

[Secret Chimp]

It's stock, the only non-stock bits are orange box ignition and split duals.