I just got my 1993 4.9l F150 fitted with a new exhaust system about 2 months ago. I was looking for the loudest application possible becuase i heard that the 4.9l was a fairly quiet engine to begin with. So i picked the 2chamber Flowmaster with the exit BEFORE the rear wheel. <closer to the cab.>

There is deffinately a power boost here, i can't imgine the performance before my new system. The sound is deffinately there but not what i was looking for. The sound is more like a sporty straight six...like those in BMWs rather than the thump of a big V-6. I was dissapointed with the interior noise as well becuase it sounds SSssooooo RICEY inside...but hey...the power gains just drown them out.

The truck is much more driveable and i can now keep up with my friends on the weekends with there Honda Sports..haha. anyone need a tow?!...hope this helps.

 

They list 10-15 hp increase and 26 to 30 torque increase with the 3" single pipe. However the tech said that I would lose performance in the low RPM range--he figured below 2000 RPM and gain above that. That essentially is what I don't want to happen. Perhaps a 2.5 inch system or maybe I will settle for a Flowmaster 70 series muffler and tailpipe. It appears there is a compromise to be made between the RPM range and the total power, but the engine already is a bit sluggish below 2000 and I prefer not making it any worse; but on the other hand, for trailer towing at 70 mph I am turning about 2500 to 2600 and maybe the sacrifice is worth it if I can boost the power in that area. Anyway, there must be something to this backpressure thing. I will research it some more, starting with my Ford engineer neighbor.

 

RGaz,

I have a '92 and woul like to get that Y pipe that you got for your pickup, U say you got it from Catco, I went to some of the auto stores here and they can't get it. I was wonderin how much it cost without that catalatic converter, just the Y pipe. Thanks.

 

I finally talked with my Ford-engineer neighbor. I told him I have gotten a lot of recommendations for the 3" cat back on the 300 I6, but that some were saying that too big a pipe and I would lose low end torque because of lack of back pressure. He said that backpressure NEVER helps power. While he couldn't say whether the larger pipe would help my truck (not knowing the specifics of that motor), he was sure that it wouldn't hurt. He noted that backpressure does help some people--cheap muffler manufacturers and sellers because the easiest way to quiet an engine (and satisfy the typical muffler customer) is to plug it up.

 

The Catco pipe kit without the Cat is PK-4 and cost me $73 from Checker Auto. Checker is part of Kragen and Schuckers if they are in the area. It is special order and they have to look it up in a book (If you get the guy who only runs the computer and doesn't know how to read the books, get the manager). Just find an autoparts store that carries Catco parts and you'll be good. The cat is $108 more.

Later.
Randy

 

I added a 3" exhaust to my 4.9L, and it seemed to help the truck pull on those long grades at highway speed. The next logical step would be the rear Cat with the 3" input and 2.25" exit.

Does the Catco help significantly?

 

ajstephan: So you have a 3" cat back system on the stock cats and it seems to pull better on the highway. Is your truck the newer EFI or carburator? Is the power any better (or at least not worse) right off idle?

Re your rear cat, I measured mine and it seems the stock is 2.5" coming in and 2.25" exit. Wouldn't you want a 2.5" input and 3" exit on your new rear cat?

I also was told by one of the exhaust companies that the later trucks, at least by mid-90s, has a newer honeycomb cat that is pretty free flowing stock and the only cats that need to be changed are the older pellet type.

Paul

 

Hmmm...I thought I measured my rear Cat at 3" input and 2.25" exit. I'll crawl under and measure again. If it's a 2.5" input, I won't bother replacing it since a 0.25" increase in diameter (from 2.25 to 2.5) is a minor improvement - at best.

I have a injected '95 Ford F150 4x4. I didn't notice a difference in around town driving, but overall I get about 0.5 mph improvement (now 14mph). The upper end has a slight improvement, but not enough to convince me it may not just be my imagination. Could be theres another 10hp there, but nothing dramatic.

 

ajstephan: Interesting! You proved that the 3" at least won't hurt. I also have a '95, but get about 15 mpg (17 freeway at 70mph). Remember in this or another thread where Eddie said he got a real seat of the pants power boost off his 3" cat back, but then later we found out that was off dual headers with 3" collectors. Eddie's truck at least proves that if backpressure were needed, a whole lot less than we have would be enough. I think if you go to a larger outlet cat for your second cat it might help. I would be curious what happens if you disconnect the new cat back system and run it open at the back of the second cat to see if you feel more/less power. That would give us more data (and you maybe a ticket:-(). I have been trying to figure a way to test before and after power. When towing my trailer, an improvement should be fairly noticable, but around town... perhaps I should take two freeway bridges about 0.2 mile apart and go 50 in 4th, stomping it at the first bridge and see what the speed is as I go under the second bridge--or something like that.

 

I just replaced the two cats and the second one is definitely 3" to 2.25". I put in a 3" to 3" cat and muffler and I lost no low-end torque. As a matter of fact I think it went up since the cats were so clogged. The system I have now goes like this:

2.25" y-pipe connects to a single 2.5"
the 2.5" is adapted to 3" to the cat.
the 3" cat goes to the 3" muffler (F350 stock)
and the 3" muffler outlet goes to the stock exit location.

Results: Better power across the band, pulls all the way to 4500rpm (used to weaken at 3000rpm), easier starts, better idle, way better throttle response.

IMHO-3" after the cat is the way to go if you are going single exahust.

Randy
88 f150 4X4 302 5 speed 3" custom cat and exhaust.

 

Better power from 3000-4500rpm from an exhaust upgrade? I think I'll be ordering that Catco Cat today!!! I bog down at ~3000rpm as well, but I have a 4.9L, but anything would help. Plus, I get 14mpg highway or in town. I'd at least like to boost my highway milage.

 

RGAZ: The 88-92 must be better than my 95. My second cat is 2.5" inlet and 2.25" outlet estimated from outside diameter. I don't have a Y-pipe as the first cat has two inlets. The head pipes from the manifold to the first cats are about 1.75" OD and in several places are flattened to 1.5" OD. I think the 3" may not help me (possibly a 2.5" cat back would) unless I open up the head pipes. Is the F350 muffler for a larger engine? I wonder if the 300 I6 got a bigger exhaust size when placed in the F350. Your engine used to poop out at about 3000? Mine runs best from about 1800/2000 all the way up to the high 3000's. I get a power surge around the 1800/2000 area.

 

>RGAZ: The 88-92 must be better
>than my 95. My
>second cat is 2.5" inlet
>and 2.25" outlet estimated from
>outside diameter.

That sucks. Must of changed over during the model change.

> I don't
>have a Y-pipe as the
>first cat has two inlets.

88 had that too, but the replacement pipe I got does not have a front cat. Just a Y pipe.


> The head pipes from
>the manifold to the first
>cats are about 1.75" OD
>and in several places are
>flattened to 1.5" OD.

My 88 was like that too (with the flattening).

>I think the 3" may
>not help me (possibly a
>2.5" cat back would) unless
>I open up the head
>pipes.

Good idea.

> Is the F350
>muffler for a larger engine?

Yep. designed for 460.


> I wonder if the
>300 I6 got a bigger
>exhaust size when placed in
>the F350. Your engine
>used to poop out at
>about 3000?

Yep. I got the 302 and it isn't as torquey as the 300. It really needs to breathe or it's a dog.

> Mine runs
>best from about 1800/2000 all
>the way up to the
>high 3000's. I get
>a power surge around the
>1800/2000 area.
>

Now she does that and still pulls hard with the new exhaust.


Randy

 

I put a 3" flowmaster 40 series on my '89 7.5L F350. Major, major difference. Even the stock 460 muffler is junk...
Doug Thorley full lengh headers are next...

 

My '95 F150 4x4 with a 4.9L has 2-2" pipes going into the first Cat, and a 3" outlet. Cat #2 has a 3" inlet(rather banged up though) and a 2.25" outlet, which is welded to my new 3" exhaust.

Not sure why your '95 would have only a 2.5" outlet, nor why your pipes comming from the exhaust manifold is only 1.75".

On the plus side though, your getting better milage than I am!