Got a 1986 F250 with a 351W. Long ago I put a chrome air cleaner on my 1970 Skylark and I remember it ran poorly in the cold/wet...for winter, if one were to put on a more open air filter, would it run poorly ? Is a stock unit better for winter and a custom one more for summer?

Also wondering about the K&N if it's worth doing-better mpg?

 

My truck runs great with my open element air cleaner, regardless of the season.

 

A carb needs a constant air inlet temp in order to deliver a consistent air/fuel ratio. If your engine is properly tuned for warm air and you feed it cold air you will have a lean air/fuel ratio, causing the engine to run poorly. That's why the stock air cleaner has a temp sensor and a vacuum-operated door that opens to hot air off the exhaust manifold when needed. Regardless of the brand, an open filter does away with the temp control, and the only way to get the engine to run properly with the cold air it will see in the winter is to enrichen the mix. Then, when summer comes you'll be burning extra gas for no reason - unless you re-jet the carb.

 

I see...time to haul out the vac diagrams and put all those hoses back!

 

I'm planning on running a stock-ish air cleaner. It'll be a 351 HO cleaner with two snorkels instead of one. Only the passenger side snorkel will have heated air to it, but it will supply warm air to the carb even in the middle of winter.

As for K&N, I'm a fan of their filters for anything but EFI. The reason I won't use them for EFI is that the oil from the filter will eventually foul the mass air sensor. Yes, you can clean them fairly easily, but it isn't worth it.

 

I tried an open element on my 351W and it didn't like it in winter. Went back to stock setup and all good. I have a hose on the filter housing that goes just above the exhaust mainfold, but I am missing the piece that goes onto the exhaust manifold. Probably should fab one up before winter sets in again.

 

I removed the sheet metal stove from the 351M in Dad's truck as I pulled the engine, thinking I would reinstall it during the reformation. However, it is in very poor shape so I plan to fab up a replacement in stainless.

 

I run an open element filter on my 351W. It runs just fine in the freezing cold or boiling hot heat. It's only iced up once for a little bit the entire time I've had it.

 

That says your carb is running rich in the summer.

 

But I adjusted it for 50-70 degree weather lol. I've driven it a lot in the hot heat and when I pulled the plugs they all had a great color to them.

 

If you want an open element in summer (and HOT underhood air) just flip the lid over.
It will be open all around.

 

Anyone remember the Olds W30 with its dual cold-air inlets to the air cleaner? Wonder why they did that instead of going with an open element filter like has now become the "cool" way to dress up your engine?

 

The only reason why I have an open element filter is because when I bought the truck it had no air filter assembly at all.