Intake block off plate

[theogre5150]

I have an offy intake for my 240 (thanks danno ) and I am purchasing some headers. There is a spot on the bottom of the intake that matches up with the factory exhaust log. What do I need to do to cover this up? Do I just need to cut some metal and seal it up?

[cdherman]

The bottom of the offy does not communicate in any way with the intake itself. You are in Alabama and the time of the year where the carb needs heat is seldom if ever.

So just leave it open. No harm.

Its us folks that drive in near freezing, humid weather that need carb heat. For us, there are pictures of block off plates that allow warm water from the heater hose to circulate through the base of the intake, providing heat to the base of the carb.

[j41385]

If You just mean a block off plate, to prevent vacuum leaks, it doesn't need it. It's not a leak.
What it is...is a chamber that heats a spot under the carb to help keep the fuel atomised in cold weather. I have an offy C and header, it runs like Crap in the winter without heat. And Let me tell you its not Freezing here like you would think in the winter. Usually 40's and rain. If you want a way to keep heat and add flow, Look into the HD 300 Log manifold, that thing flows like the Mississippi and heats the intake.

If you don't want a log, I am going to discourage you buying a Hedman header, they dont fit in bumpsides, despite being listed as 1965-96 F100-f350 2wd trucks. What will work better is if you get the dual exhaust manifolds for the 1987-96 efi 300 and bolt them on. But with those you still don't have heat.

[theogre5150]

I just don't want to restrict any flow. I still have my stock exhaust log but I have been told that I need to get away from that.

[69rangerman]

I'd advise against blocking it off.

When I went 4 barrel on the 302 I read about the "cooler fuel charge=more power" stuff and blocked off the heat riser to the manifold.

For 3 weeks I had very hard cold starting, 30 minute warm up time, and major hesitations until the engine was 100% up to operating temp. Spark plugs turned black and fouled constantly from the cold/wet/un-vaporized fuel.

After I removed the block off and re-installed the manifold with the riser opened all of that mess vanished and it starts every time no matter the weather, 10 minutes to operating temp, clean plugs, more power.

I live in Florida and, at least on the 302 blocking off the riser was a no-no.

Good luck!

[willowbilly3]

You might also adapt an electric EFE grid from some other car.

[Jake11]

They do it like that, heat the intake so the carb won't ice up. If the humidity and temp are right, the carb
will start making ice inside. It chokes the carb so the air can't get in. On a rainey day with 45deg. temp or so
it can happen. So they run heat to it to stop that. Just keep that in mind. If it starts slowing down on the highway
you will have to pull over and let the ice melt out. Then it will run fine for another 15 to 20 miles.
Get some of that silver tubing they make to run hot air off the exhaust manifold and rig it to the air cleaner
and you should be ok. In the summer you can take it off. Jake

[theogre5150]

I ended up buying a set of stock headers from an '87 off ebay. I hope to have all of it put back together by the end of this week. Thanks for all of the help and suggestions on this.