Hello, I bought a 1999 Dodge Ram for a shop truck and to make it have a little more grunt..LOL... I was thinking about stroking it to a 408.
Now.... want I want to know is; if I can still use my factory 1999 PCM and induction system with maybe some headers and dual exhaust? Or do I have to go with after market ignition and a different induction system?
The operating rage that I will be using the truck for will be aprox; idle to 4500 RPM. I want the low end torque , I am not looking for high horse power.

It will work great, stay small on the cam even stock works great, very mild port clean up on the heads and the intake, use a set of ford 460 blue fuel injectors and it makes a TQ beast. The one I did we got the compression to 10.2 .040 quench a stock cam and very little else and TQ was awesome.

So, even though I have increased the cubic inch... I won't need a different PCM or intake system? If that is the case.. I am going to put the plan into action this next year.

It is not needed but it would probably be a good idea.


The stock intake manifold is awesome at building low rpm tq, nothing comes close till about 2500 RPM period. Probably be a good idea to get it and the plenum plate ceramic barrier coated as it gets a lot heat from the cam oil and the front coolant passage.

The factory PCM is flexible enough to make it run good if you get stuff close enough.

The beer barrel manifold runner's cross sectional area and length causes it to resonate on a 360 cubic inch V8 at roughly 3800 rpm.

On a 408 it will resonate near 3200 rpm, which boosts maximum torque there, near the hillclimb speed range.

Airflow capacity above 4400 rpm will be restricted compared to a manifold like the MPI.

Above 4000 rpm it will be running out of breath for that manifold, but for a tow rig this really shouldn't matter. If you keep the cam stock or close to stock, the stock PCM will do fine.

Yes. PCM has no idea what cubic inch its' feeding.

I disagree with the popular thinking that an exhaust system needs as little back-pressure as possible: On a 360 Magnum I went from:

a 2.5" single with Flowmaster 40

to a true dual, H-pipe and Ultra-Flo style cans

........and it killed my bottom-end grunt. Big mistake listening to advice given on here.


Nice boost in the 3 to 4000 range, but completely useless to me. Not ideal for a daily driver that spends most of it's time at 1800rpm on the highway or trying to grunt it's 5800 pounds from a stop.

Have some before and after sound clips and pics if you want.

Strange. I wouldn't put anything less than a dual 2.5 setup on these magnum engines now just going by experience of trying different things between all the trucks we had over the years. The system we just put on my black truck has no h pipe and no converters. Just 2 mufflers. I lost no bottom end at all I'd say. But my trucks are 5 speed sticks so maybe I don't notice it. My 99 that was wrecked had the same setup before and an auto trans and I thought it was good for low end grunt also.

I put a Flow master dual pipe system on my SST and it killed the bottom end of it too. The good thing is, it rotted out in a couple years. At that point I went to a local supplier of used commercial food processing equipment and bought 3" ss pipe and a couple 3" elbows.. all for less than 100 bucks. Tig welded it together and used a Borla muffler. That was over 10 years ago and still sounds good today.

oh, torque picked back up.

specs on my stock SST 360:
ported heads,60cc chambers,os mp valves,mp valve springs and Crower 1.7 rockers. Blueprinted HV pump, windage tray, oil pan baffles, double roller timing chain,MP intake,MP ecu, March pulleys,160T-stat,MSD coil and wires, JBA headers, Transgo 2 kit, lots of billet trannny pieces, Kevlar and ceramic bands, Richmond 4.10 gears(blown up)

It's not about backpressure. it's about exhaust velocity. by going bigger, your velocity through the pipes at lower RPM dropped, which reduced the amount of scavenging effect and hurt performance.

While you don't want any backpressure at any RPM, you do need to remember that you can go too big on an exhaust for what you're trying to do. Otherwise, we would all be running 2" primary headers with dual 3.5" pipes.

Same idea that while a 1200 cfm carb will flow more and make more power than a 750 cfm carb, you would be silly to think that a 1200 cfm carb on a stock 360 will have good street manners at 1500 rpm.






on the idea of a 408 with an otherwise stock engine...I wouldn't do it myself. the stock intake isn't enough for a stock 360, let alone 408. The way these motors really start to wake up by simply adding headers, intake, and a larger TB really shows how restrictive the stock parts are. In the dakota's those simple "bolt ons" result in a significant increase in hp and torque, and minimal sacrifice at lower RPM torque, They still fry the tires with ease just off idle.

Increasing the inches without doing any tuning is also not the greatest idea. with that model year, you can use SCT. when the PCM is in closed loop, it will read the O2 sensors and adjust fuel delivery to maintain stoich. However, at open loop like moderate acceleration to WOT, cold engine start etc, the PCM will still be delivering fuel for a 360, not a 408 and you will be lean. you could add bigger injectors which the PCM won't "see" but then you're rolling the dice on the tune being right.

You should try SCT first anyway. on a bone stock engine you can improve off idle torque, throttle response, and total Hp. all for just a few hundred dollar investment.

I know that a street toy is different than a tow rig though, but still, going the expense of a 408 build and planning on using stock intake, tb, heads, etc. just seems silly to me. How many guys with old motor homes built their 440s into 499s to improve towing/hauling ability?

Maybe it's just an unorthodox idea and that's why it seems wrong to me.