198 Fireball Intake Manifold help

Hello all,
With some encouragement from some of you all I am taking on rebuilding my 2G carb on my own. First time with a carb rebuild. Fingers crossed. Anyhow....in removing it I am Loki g at what appears to be the original cast iron intake manifold. I do t think anything is wrong with it but wondering if its a good idea to upgrade or replace it while I have the carb off? Thoughts?

In doing a quick search it appears it may be hard to find a replacement or upgrade. Anyone have any experience or knowledge about this?

 

No need to replace the intake unless broken. No need to remove and replace gaskets unless you have an intake leak. If it ain't broke don't fix it.

 

True dat! Do you know...it appears there are two holes that funnel exhaust up and around carb as they are full if soot? Is that to warm the fuel for better performance? Or?
http://www.earlycj5.net/forums/album.php?albumid=827&attachmentid=30540

 

Yes it heats the throttle housing, the cast iron base of the carb assy. When you install the new gasket be sure to use the one that allows the exhaust flow thru. Clean the carbon out the best you can. I put carb cleaner in (after poking a wire through) and use compressed air.

 

Thanks. I am worried about having any of that crud fall into the manifold. That wouldnt be very good.

 

Note that the V-6 intake manifold must be removed from the engine to clean out the heat riser ports.

Most that I've seen were so full of carbon deposit that the heat riser ports both needed to be drilled out.
Carefully clean the ports out with progressively larger drills.

The heat riser ports help with cold weather engine warm up.

 

Would this carbon build up point to a lean or rich mixture condition?

 

Everytime I pulled the intake off of my 198, those passeges were always packed full of carbon.
To be honest, I never could tell much change in how it ran if I cleaned them out or not.
Don't forget, there are some passenges in the heads as well.

 

I'd just tape over the intake holes and go after the carbon in the passages. Letting some debris go down the exhaust passage won't matter; it will be blown out the exhaust. Get what debris you can with the shop vac.

The passage is not meant to be an indicator of mixture. Could be carbon from cold running (short trips or no thermostat), disfunctional carb (too rich all the time), oil in the exhaust, or normal for this engine design. Realize this engine only lasted 2-3 years, so the design could have some issues that weren't worked out. Look to your spark plugs condition for better information about mixture.

 

I'm gonna be the the voice of change here. I cleaned those out in my 225 twice, completely packed both times. Both times I cleaned them out the front 2 bolts in the carb broke from carbon and moisture rotting the bolts. When I rebuilt the motor I blocked the ports completely and used a gasket to cover them, that was back in 2005. No problems and to be honest you really would never know they served a function since they plugged up so fast. I say cover them and forget them, this was a half a$$ed design on GM's part anyway. YMMV

 

I'm sure you don't need them in Alabama... or in California, or any place else with a mild climate. Their purpose is to quickly warm the intake manifold (and carburetor?) so that the fuel mixture does not condense out on the cold intake manifold walls. If you do not have the thermostatic flap in the exhaust pipe that blocks one side and forces exhaust through the intake manifold, they do nothing. If you don't care about cold-start driveability in really cold weather, by all means block them off.

The Jeep/AMC sixes used to have a manifold that was heated by exhaust gas, before 1981. Jeep cared enough about this feature that when they redesigned the 258 manifolds, they added an electric manifold heater to the new aluminum intake manifold.

To the OP, it would be helpful to put your location in your profile or sig.

 

Thanks all! This site is so valuable and really helping me get to know this rig as i am new to Jeeps. Lots of great peeps helping each other without looking for payback...a REAL community. Group Hug!

Yep, on the central coast of California....will add location to profile, thanks for the tip.

 

OK I will agree that the exhaust heat passages can be left plugged at the carb base as you live in a warm climate area.

 

If you think our winter weather is mild in north Alabama in the winter you need to come visit. We still have plenty of days here when the temp is 10°-20° below freezing and when we have those, humidity is still in the 70-80% range. The exhaust warmup on these old motors just work so poorly its just easier to let the engine warm up four 5 minutes and forget it.