So the 300 needs to breath better eh???

I am really want to swap out the intake, & the exhaust - so that it will breath -
What is a good pipe diameter to use for the exhaust?
How about a muffler(s) i like a nice mellow tone that is fairly quite - but if you step on it / it opens up w/ authority (wink/wink)

Open to ideas here...

 

Yea..stock they're kinda all choked up..but they're a monster wanting to he released! I'm in the middle of the swap right now..and as far as some minor fabrication for a heat plate and throttle stuff....its cake. As for The exhaust..not sure exactly..but from what I've read is go somewhere between 2" to 2.5" to yield the best results. Mufflers...hmm..well..also from what I've been reading..a lot of guys go with a glass pack or bullet type exhaust such as cherry bomb or thrush. Nothing radical..just enough to make it purr then growl.

 

That's pretty much it. 300 cubic inches is quite a bit, so 120hp is pretty lacking for its size. It mainly suffers from the ability to get air in and out.

For a single pipe, 2.25" or 2.5" seems to do the trick nicely. A bit of the aftermarket stuff is 2.5" so that's what I've gone with and am happy with it.

No real advantage to going with duals (unless you like the look) since all it is is more expensive and offers no bonuses. But, if you do, don't go much over 2".


Check out the sticky at the top of the forum. There's lots of videos with different types of mufflers for the 300. Listening to them individually will give you a much better idea than any advice anyone can give you.

 

X2 with AB

 

68 cabby & abandoned bronco...

Cabby, so you are doing a 300 now? If so can you give me a complete run down of all that you are doing so i can use it as a guide??

A/B - the headers i looked at (headman) have two outlets
A previous owner put duals on the truck but they are poorly done......

Another item to clear up...

 

Well..a/b has guided me a whole lot..and I'm still in the midst of the build if thats what ya wanna call it. All I did was find the intake from eBay or even Craigslist may have and intake. I got the intake..found a set of dual efi manifolds. Then essentially mach up the heating plate for the bottom of the intake using a set of gaskets from a parts store. No special gaskets are needed just the regular 300 exhaust/intake gasket. Find a good carburetor..I'm still doin that. After that find a way to plug the egr hole on the exhaust manifold. These steps are just steps..not necessarily in order. This is what I'm doin now. But its simple really. Well..my 300 is out. Of the truck cuz its a swap I'm doin from a previous engine.

 

Ok - let me get this right - you are using Electronic Fuel injection heads?? Why??

Why not use the stock head & do a 3 angle valve job - port & polish - mate the head, the header & intake to the head / & polish the interior intake runners & the header inlets????

What is the gain using dual??? EFI heads??
Please explain....

 

Noooooo haha no efi swap or conversion..I'm swapping the stuffy log exhaust to the efi manifold. The heads are pretty much the same. The efi set up is actually 2 sets of 3 that bolt up where the log exhaust did. Each one has its own collector so essentially you can run dual exhaust and it makes it breath soooo much better. As a/b has told me..the bonus jump from stock to efi manifolds is enormous and the jump from efi manifolds to headers us minimal. Many guys like to go the efi manifold route cuz for 1 ..its cheaper. 2. You won't have to worry about gaskets blowing through and such...3. If there's problems with your starter..as headers like to eat them cuz of heat..its easier than having to take off a header..the efis are easier to work around..and 4..y would you wanna pay over double for headers than may half for a setup specifically made for the engine? Its just preference really. The advantage to efi exhaust is better breathability over stock. Not sure about heads or anything..although when you have the intake and exhaust off..it would he the prime time for installing a cam or like you said..porting and polishing or working on the head. I'm not sure if ill go that far just yet..but many guys live by that just adding the better intake and better exhaust with a bigger carb make this engine come alive.

 

Well said, 68cabby, you've definitely been paying attention.


Gbodnar, a great alternative to using headers is to use the EFI exhaust manifolds that were on the EFI equipped trucks. They're a direct bolt on and are a huge step up from stock.

Stock:



EFI exhaust:







If you're going for an all out performance engine, headers are the way to go, but for a great boost over stock, you simply can't beat the EFI manifolds. Even with the stock 1bbl, you will notice a HUGE gain.

And yes, even without all the extras, a straight up stock engine with an exhaust upgrade and an intake/carb upgrade (no internal changes) will be plenty for a lot of people. I know it was for me.

 

You're only saying that because a lobe wiped on your Comp Cam.

But yeah, an Offy intake with new exhaust and a little ignition work wakes up a 300 real good.

 

Lol, well... Those things happen.


But even so!

 

Just to throw out there, the chevy inline six 250 and 292 stamped rocker arms will replace the factory rocker arms with a 1.75 ratio vs the ford 1.6 ratio getting a little more lift from your cam.. I've heard they are a direct replacement, but I went ahead and got my machinist to put bigger studs in mine so that I could run the aftermarket full roller 1.75 rocker arms

 

Ok so EFI exhaust manifolds is the budget free breathing way to go - what years are direct bolt ons??? I have a 1985 300 - about how much do the EFI manifolds run???

Any conservitive ideas for replacement carbs / i would think a 600 or a 650 would be to big - i always liked webers - any direction here???

 

Any years will bolt. 600 is the max u wanna run..but they work wonderful

 

Maybe so - but mama sometimes has a leadfoot, so does my daughter - i think a husband/father limiter is a better way to go.....

I have no idea the gearing in it all tho if'n I was to hazzard a guess - I would guess a 4:11 - since the short time I had it on the freeway, it seamed top out fairly quickly like my buddy's truck use to & he had 4:11 gears in it.

The truck once drivable will be mainly driven on the freeway where average speed is 70mph to 80mph
What would be a decent gearing?

When I rebuild the front end, I would like to replace all the stock rubber bushings w/ polyureathane - which will handle 100% better, and I will be 6' under before them puppies will need to be replaced. I did it on my '87 XJ8 (350) & it made a world of difference - so that is a definete upgrade!

Anyway - waiting for a chance to finish tittle transfering - before i start the work - so until then I ask questions & learn....