I have a '98 4.6L with the M5OD. I'm looking for some more low end power. I don't need a ton, but my truck sometimes seems a little anemic.

First, I know that I need to get rid of the Flowmaster and probably will end up with a Magnaflow. I have the Flowmaster Force II kit installed (comes with a 50 series muffler). Would I be able to just buy a Magnaflow muffler and plug it into the spot where the Flowmaster is now? The pipes are 2.5" mandrel bent.

I also have a AEM Brute Force intake that is not currently installed on the truck. I will probably just do the Gott's mod and call it a day there.

What else could I do to increase power? I had a Gryphon tuner but got rid of it. I wasn't convinced that it really added that much power. Most of the perceived improvements seem to come from improved shifts, which I get no benefit from, obviously.

I'm looking for relatively simple mods (no superchargers or anything) that are going to give a noticeable performance improvement.

 

Simple... a throttle body spacer! (just kidding)

Not sure if replacing that muffler will make much of a difference (plenty will probably argue both ways) especially for the cost, but if you're looking for every additional HP you can get, go for it. You might be able to make a simple swap; it depends if the 2 mufflers have the same length and connections. A tuner should give you a bit more power but it's not going to give you a lot. With a non-supercharged gas engine, I think in order to gain appreciable power improvements you need to add a combination of mods to really notice a difference.

I would go with the Gotts mod on the air intake. Unless you get a custom tune, I don't think the aftermarket air intakes are worth the money.

If your truck seems a bit 'anemic' I would consider replacing the plugs (or at least checking them; I noticed an improvement when I replaced the plugs with NGK's) and getting a motor induction cleaning (Motorvac) or take apart and clean up the intake. Run a bottle of fuel system cleaner (Chevron Techron, BG44K or Amsoil P.i.) thru the tank or if you're really adventurous remove and clean the injectors (maybe overkill). You could add electronic fans (not so simple)...

 

when i said simple i really should have said "not outrageously expensive" like a supercharger. i'm an auto mechanic so doing the mods myself won't be too big a deal. my truck is always kept up on maintenance items, but plugs/wires is definitely something that needs to be done. i have the parts, just haven't had a chance to get them put in yet.

i understand that a combination of parts will be needed to notice an improvement. i guess what i'm really asking is what i should be looking at with a budget of around $800-900 that will get me the most gains.

 

You could go power improved. All you need basicly is a set of PI heads and a PI intake manifold. You'll pickup maybe 30 hp, not a lot but its noticable.

 

and just to clarify (i know it's been beaten to death around here) what years/models are those from? so i know what to look for when pricing them out.

 

http://www.mre-books.com/sa82/sa82_5.html Check this out.

 

the truck runs perfectly. it's not that it doesn't run right. it's been widely discussed around here that flowmaster is more geared toward that flowmaster sound and not so much performance. to be honest, i'm not even sure that i really like the sound of the flowmaster. i think it's a bit too obnoxious and doesn't have that nice tone that a lot of people are getting. i really only went with that since that's pretty much what everyone else around town does.

 

so any 4.6 or 5.4 99+ head is going to be PI and work with my engine? and i will also need the intake obviously since that article states the intake port was redesigned. so it's just a straight head swap and that's it? no tuning or anything needed?

 

You must have a PI intake manifold to match the PI heads. No mixing PI and non PI heads and intake. Some people get a tune some don't, Just remember that your compression will increase to around 10:1 so detonation without a tune is possible. Not a difficult swap in my opinion.

 

yeah that's what i meant when i said intake...the intake manifold should have specified. the throttle body i have will mount to the new intake? doesn't sound like it's too involved. if i run 89 or 93 octane without a tune, that should prevent any detonation shouldn't it?

 

I knew what you meant just making it as clear as possible. Use the throttle body from your current engine. Make sure the new intake has the blend valve in the lower intake and you will also ned the hole in the driverside cyl head for the CHT sensor. Higher octane will help if you experience detonation. So far I haven't had issues with mine but I don't tow anything. Use your current coil packs that way you can also use your current wire harness and PCM. You may want to consider installing new exhaust manifolds or headers while you have the heads off and install them before you put the heads on the block just temporarly move the trucks exhaust system rearward two inches so you have enough room. Pull the fan and fan shroud off and you will have plenty of room to crawl up into the compartment to work. Make sure you readup on the valve/chain timing and before you remove any timing chain tensioners, rotate the crank so the keyway is at 12:00 and LEAVE IT THERE until the tensoners are reinstalled with the new cyl heads. You don't want to bend any valves and you will if you start turning the crank with the heads installed and the chains removed. Good luck.

 

is this swap something that can be done in a day? honestly never done heads on one of these trucks before. my truck is my daily driver and it can't be down for more than a day.

 

It took me close to 20 hrs to do it myself and I have torn down and built hundreds of these engines. Some guys will be faster some slower all depends on what problems you run into as well. Just one messed up bolt or nut can add an hour or more to the job. If you can only work on it during evenings or so then give yourself a week to do the job.

 

Yeah I looked it up at work today and book rate is 18 hours to replace both heads. Definitely not something to be done in a day. Maybe if I get an entire weekend off work somehow (yeah right lol) I can get a couple guys to come over and wrench away. Until then I'll have to figure something else out performance-wise.

 

The PI swap would be the best "cheap" mod you could do to your truck, IMHO.

Also, I had a noticable increase when I switched to e-fans and UDP's.

And yes, ditch the Flowmaster for a Magnaflow, Gibson, etc. (something with straight-through flow).

Besides headers, a custom tune is next on my list of mods. The pre '04 trucks aren't as "de-tuned" from the factory as the newer ones.