OK Gents, coming from the land of BB Chevs, where cooler air to carb on a modified engine is better for HP and Mileage I'm puzzled, I have an 85- 300, going to rip all the smog crap off and re do, I have a stock non feedback 1bbl Fo Mo Co carb, exhaust manifolds from an 88 FI motor and Y pipe, currently looking for a Dura Spark 2 to convert, that being said, as I read here about warming plates and such under the carb I'm thoroughly perplexed as to why these inline 6's need to have heated fuel to run properly, can someone please explain why and or the theory behind this, I've learned a wealth of info on 6 from reading here and would like to thank you all for sharing your time and knowledge, Beav

 

I can't think of many production engines in the last fifty years that did not run hot water or exhaust gases or both under or through the intake manifold to warm it up. I remember a 318 Mopar that was quite slow to warm up on what passes for a cold day in Seattle until, acting on a tip from the owner of the machine shop in White Center, I pulled the manifold and tediously drilled and dug all the impacted carbon out of the exhaust passage that runs through all those manifolds. And this 318, like nearly all engines, ALSO had a cuff over one exhaust manifold so it could draw more quickly heated air into the snorkel (shuts off when underhood temps get to about 70F). Most engines ALSO will draw "free air" from outside the underhood area when they have warmed up; more power and fuel efficiency, as you say. Ideally you'd want warm fuel and cool air.

You certainly can get too hot; my '66 Econoline 240 had real problems with vapor-lock on hotter days, a problem with engines where the intake manifold sits atop the exhaust manifold. It's a balancing act, with a moving balancing point.

With these engines, in a temperate climate like Seattle, you can do without a water-heated intake manifold. The exhaust manifold will soon get the intake hot. But for quicker warm-up, and to save engine wear (from the cylinders being stripped of oil by liquid gasoline), having an aircleaner with a snorkel door that draws in hot air (below 70F) is the way to go, plus you get cold air intake when the engine is ready for it. You have to fabricate this for older cars like my old '66, and the '68 bread truck I'm fixing up. The old oil-bath air cleaners were less effective than paper filters (or K&Ns!!), and if you get a fancier carb, the old air cleaner won't fit anyway. (I'm glad I can weld).

 

Heat in the manifold provides a stable environment for the carb/AFR to work in...carbs tend to like that. The cool, heavy air of the coastal areas is a plus but I think driveability and mpg might suffer without the heated manifold...even in Seattle...but probably not in Florida. JMO

 

Harte, the intake manifold on my old 240, which was bolted to the top of the exhaust manifold, getting exhaust heat directed to it during warm-up, and getting loads of radiated heat the rest of the time, got too hot to touch in the summertime. That is too hot for an intake manifold, IMOH, and it certainly led to vapor lock, a common problem in the old vans.

When I get the rest of my new/old bread truck set up, and get to the engine, a 300, I'll replace the crude old exhaust manifold with home-made headers, and the intake with a modified Clifford single 4bbl manifold. I already have welded a water jacket to the bottom of that intake manifold, but I think it would work fine without it. The heat coming off the exhaust headers, even though they won't contact the intake, may very well heat the intake about as soon as it takes the coolant to heat up and start to flow.

Clifford used to, maybe still does, sell a kit for taking heat from a set of headers and piping it to the bottom of the intake manifold. Again, I don't see the need, as long as you have the air cleaner snorkel door to draw heated air into the carb during warm-up. I think that snorkel door with either heated air or outside air intake is one of the great inventions; simple, effective, all positives and no negatives, and any good do-it-yourselfer can put one on an old car that never had it.

But I'd agree with you if it were any other engine that didn't have the intake immediately above the exhaust; likewise JMO, but I do have the experience of the old Econoline with its exceedingly hot intake manifold.

 

Thanks for the reply guys, the reason I'm asking is I was contemplating taking the EGR off when I remove the rest of the SMOG CRAP on this thing, no need for the heated gases if the exhaust manifolds will do the trick!

 

Is an '88 past the smog check roll-up date? If not, you might need the emissions equipment to pass if required for your address.

My '83 came, of course, with the stock log manifolds and with a hot air intake system. I have a 360* open air cleaner and was anxious at first about carb icing without it. But with my carb mounted directly to the manifold, which is heated, I have yet to have a problem. If/when I do I'll fab up a heat stove and piping to get some hot air in the thing. I can see where an "E" brick might have some heating problems probably from poor air flow more than anything.

 

We don't have a big problem with photochemical smog in Seattle, and they don't test for nitrogen oxides, therefore you can pass without the EGR system (which itself actually slightly worsens some of the emissions they do test for!).

I have made my peace with what we all used to call "the smog crap," i.e., emissions control systems. When you have to fix them, and learn how they work, you appreciate them a little more. But I still don't like EGR; any racer who has tried to avoid charge dilution just doesn't like to see it done on purpose.

However, often you can't just disconnect and blank off the EGR system. When exhaust is leaked purposely into the intake charge, the charge is harder to light and burns more slowly. Therefore, EGR engines commonly have the distributor curve advanced to light the fire sooner. So if you disconnect the EGR, and stop diluting the intake charge, you now have excessive ignition advance. When I plugged the EGR on my old 318 it pinged like mad going up hills; I temporarily solved that by disconnecting the vacuum advancer. But doing that, or backing down the static timing, kills fuel economy. The answer was and is to build a distributor with the advance curve (the weights and springs) from an older, pre-EGR engine.

What's an "e-brick," Harte?

 

Mines an 85, 25 years old and therefor does not have to be smoged anymore, if it did, id register it to my property in Jefferson county, no smog checks there, period! I plan on advancing the dizzy where needed, and will keep the stock air cleaner, snorkel etc,