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318 Magnum, daily driver tuning

Detective D

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As the title says, I have a 318 Magnum in a Dakota, with a 5 speed manual. I have been cleaning it up and have plans on touching up the body. 50k miles means I will have this for a while, so I thought I would pick the brains of other Mopar guys about tuning the engine for a little more juice.
I don't want to:
Get into the bottom end, at all, it has 50k miles.
Not sure I want to do a cam, at least not for a while. Lots of tear down of factory seals and good factory parts, I would rather wait until something needs looked at and go from there. Cam recommendations welcome for the future, just keep in mind stock springs in the heads etc.
Not touching the heads, in so much as taking them off anyway. Stuff under the valve cover I am good with messing around with
Lastly, I don't want the thing to start gulping gas, it's a 4x4 Dakota not a drag race car.

I know from the 2001 Ram I had that the log intake is a restriction, from reading about sprucing that up before I sold it to Brother in law instead. I have seen people gut them out to help but I think eventually I would plan to swap the intake off, people online have always touted the M1 EFI intake. Prefer to keep the factory EFI in place, so I don;t want to go to a carb.
I have more questions about things like manifolds vs shorty headers, rocker arms and what ratio can be used with stock other stuff, that sort of thing. Brands to stay away from or that know their stuff. Again not a race engine, but I hate chinesium junk so something in the middle. I have heard Harland Sharp is good for rocker arms, but never used them, and have no idea of other brands to look at.

Despite my reading into things from years back things change, brands have merged, and I haven't really built one of these motors before. The truck is snappy for sure, but I don't need it to tow so would like to bend the curve more towards HP, and let the SBM do it's thing a bit.
So long time Magnum tuners, what did you do and what works best? I did a search and found the results lacking, so thought this might be a good thread for everyone as a consolidation of knowledge. 318's can make really good power and I feel there is some left on the table in factory trim to tune into it without going overboard.
 
On my 94 1500 w/5.9, I did a cat-back, K&N FIPK, MP PCM, shift kit in the 46RH, Crower roller rockers[ 1.7 ratio] and a 1st gen F&B throttle body[ opened up stocker, 52mm?]. Later on I put some MP magnum heads on, had stainless valves and a little higher rate springs[ they were less money then the oe reman units plus they were new], MP headers and a V10 truck cat. Cat had larger in and out on the pipes and was less money than the V8 ones. I did roller rockers and not cam as doing a cam was more involved, produced the least power gain over the other MP parts and was most expensive. The PCM was nice but you had to run premium fuel. One of the biggest seat in the pants improvements I did was mod the TPS unit. You had to back probe the unit with key on/not running and find the wire showing .5v. Once found, you took the TPS off and removed the steel bushings that the two screws go through. Put it back on, key on/not running and set rotate it slightly till that one wire read .7-.8v. Tighten down the screws and check again. Really woke up the responsiveness on the throttle when driving. If you are keeping the beer barrel manifold, make sure the lower plenum gasket isn't leaking allowing oil to creep in under vacuum. If it is, fix that. Hughes makes a thick aluminum unit that clamps on the gasket better. I just reused the steel stocker but put a light coat of grey engine rtv on the gasket when assembling. Let it sit overnight before running to lessen the chance of pulling the gasket in under high vacuum. Putting in a 180* t-stat is helpful on lessening the head crack issues the mags were known for. And I could still knock down high teens to low 20's on mpg depending how I drove it.
 
My 99 Dakota SLT ext. cab 7' bed Magnum 5.2ltr/318cid 46RE/TF
at 4882#s (I live at elevation no sea level)
(Org. was on 31.5x10.5") it has 60k on it now
at about 19,000 I put bigger tires 32x11.5", way better in the snow
has just over 60k miles now, so far so good...
Love my lil' truck, it's my dogs truck, I just drive for him :poke:

Stage I
almost immediately, then I bought a Hypetech Tuner/reader
& 185* Thermostat (didn't org. notice much)

Stage II
added a AEM gauze 6" x 10" (?) coned filter & new airbox
with a 4" alum. intake, & hat
with a 1/2" (13mm) swirl spacer under the OE TB, it was a kit
That started to wake it up & get a mile or so per gal. better mileage...

I still have the OE wires, cap & rotor on it still too
I did do E3 plugs, so far so good...
OE plugs looked like almost new still, a lil' dirty on the outside,
very light gray-ish on the porcelain inside, looks good to me...
I will do the wires, cap & rotor sometime later...

Stage III
I bought Harlen Sharp 1.7:1 roller rockers (easy bolt on deal)
(only down side was the idle went up like 150rpm, like 800rpm
can't adj. the OE TB, you can get it down, but have to modify it,
remove a lead plug IIRC, it doesn't really need it, so I left it alone
)

Stage IV
then some Flowmasters 3" Delta flow series 50 , cat back system
(those 2-3 things really woke it up, the filter helps it breath, with the new rockers
& the 10% more lift/more power, free flowing exhaust
)
I did also do new rotors, slotted - drilled & better pads, at like 55k...
I do still run 87 oct. no problems ever,
but in summer I do run 89 oct. usually, just to be safer, Calif/ swill fuel...

I do have some Edelbrock 'bolt-on' Chrome 1.6250" x 2.5" shorty headers
to replace the org. stock manifolds...
I got them with my Summit bucks, I had to use them or lose them,
figured wtf, I never installed... yet
Stage V
May do the headers, after my next project 33x10" General Grabbers AT3
& do new shocks while I'm at it
"Actual 33" tall tires" & may buy new lighter wheels 15x8" too possible
(Ultra 050/51 or American Racing Bajas 15x8" also)
put the org wheels away in the shed

Stage VI
I'll probably do the 3.92:1 gears front & rear too,
it currently has 3.54:1, no problem on flat ground down at sea-level
But;
up in the mountains/altitudes the gearing will help some,
especially with the taller tires
be almost back to what it was with the org. 31x10.5's Good Year Wranglers
that were actually 30.33" diameter & them tires didn't last for ****,
the Toyo Open Country MS 32x11.5", actual diameter is like 31.33"
they have lasted for over 41k miles, great tires, up here on these
windy *** mountain roads... wish they made a 33x10"

With the mods/power adders I did...
I actually have more power (how much I have no idea, 30hp+ ?)
& it gets better milage too, seat of the pants feels way better...
Maybe 19-20mpg flat ground/sea level all highway, on road trips
like I-5 going to Redbluff
(we have no flat ground & all highway up here, no freeways either
for 75+ miles around here
)
Putzing around town & in the hills it's now getting 13mpg-17mpg, 15 average.
All depends on my 'driving aggressions'...
Stock it was getting like 12-13mpg, 'maybe' if I was under 65mph 15-17 open hwy...

enjoy, I hope that helps,
it helped my 1999 Dakota SLT Magnum 5.2ltr 4x4

Budnicks 99 Dakota 4x4 #1.JPG
 
Last edited:
Dayam! 50k miles!? Had a 92 that I ordered with a 3.9 limited slip, automatic and no frills except for cruise control, tilt and AC and being a reg cab and short box, it was fun for the times. It ran a 15.30 on stock tires and was right in the Mustang GT 5.0 territory back then. I didn't take the cat off (I'm known for doing that and running a straight pipe) but took the muffler off and it passed emissions testing the first time I had to take it in. The inspector complimented it saying it sounded good and asked if I had a Flowmaster (flowbastard) on it.....all I said was 'I like the sound too' :D. I've been looking for another one for a good while now. And what has been mentioned already sounds good. In fact, the V8 truck got better mpg than any V6 pos I've ever had and I've had a few. The only V6 Dakota I've had that got better and I mean lots better mpg was an 87 reg cab short box.
 
On my 94 1500 w/5.9, I did a cat-back, K&N FIPK, MP PCM, shift kit in the 46RH, Crower roller rockers[ 1.7 ratio] and a 1st gen F&B throttle body[ opened up stocker, 52mm?]. Later on I put some MP magnum heads on, had stainless valves and a little higher rate springs[ they were less money then the oe reman units plus they were new], MP headers and a V10 truck cat. Cat had larger in and out on the pipes and was less money than the V8 ones. I did roller rockers and not cam as doing a cam was more involved, produced the least power gain over the other MP parts and was most expensive. The PCM was nice but you had to run premium fuel. One of the biggest seat in the pants improvements I did was mod the TPS unit. You had to back probe the unit with key on/not running and find the wire showing .5v. Once found, you took the TPS off and removed the steel bushings that the two screws go through. Put it back on, key on/not running and set rotate it slightly till that one wire read .7-.8v. Tighten down the screws and check again. Really woke up the responsiveness on the throttle when driving. If you are keeping the beer barrel manifold, make sure the lower plenum gasket isn't leaking allowing oil to creep in under vacuum. If it is, fix that. Hughes makes a thick aluminum unit that clamps on the gasket better. I just reused the steel stocker but put a light coat of grey engine rtv on the gasket when assembling. Let it sit overnight before running to lessen the chance of pulling the gasket in under high vacuum. Putting in a 180* t-stat is helpful on lessening the head crack issues the mags were known for. And I could still knock down high teens to low 20's on mpg depending how I drove it.
I will have to look up the TPS thing, first I have heard of that.
The V10 cat is interesting also! Where I live I don't have inspections to do, so I might look at ditching the cat altogether but I need to see where the O2 sensors are at on it. I did a full Magnaflow on my 2001 Ram, high flow cat, cat back dual. It had a flowmaster set up on it but it wasn't stainless so it rotted shortly after I got the truck, lost a tailpipe lol. It had a CAI on it also when I got it, so I can't speak to improvement but it sounded great and pulled hard.
Pretty sure I will be ditching the kegger at some point. The "hot rod" testing I have read over the years that people did with the Dakota R/T/s and a few other things with the 5.9 Magnum all came to the conclusion that the kegger has a bad time once you climb past 300HP and fights against a lot of other stuff.

I spent a lot of time modifying a 94 Mustang with the old 5.0, not for pure power but to be a county trunk highway cruiser. What I aimed at was super responsiveness, better breathing, driving characteristics.... and the HP sort of came with it as I did that. I think tuning wise the 318 can be worked on from the same perspective and be a really fun engine to drive around with. So an open intake and exhaust along with your TPS method I think is on the right direction for me.
 
My 99 Dakota SLT ext. cab 7' bed Magnum 5.2ltr/318cid 46RE/TF
at 4882#s (I live at elevation no sea level)
(Org. was on 31.5x10.5") it has 60k on it now
at about 19,000 I put bigger tires 32x11.5", way better in the snow
Stage I
almost immediately, then I bought a Hypetech Tuner/reader
& 185* Thermostat (didn't org. notice much)

Stage II
added a AEM gauze 6" x 10" (?) coned filter & new airbox
with a 4" alum. intake, & hat
with a 1/2" (14mm) swirl spacer under the OE TB, it was a kit
That started to wake it up & get a mile or so per gal. better mileage...

I still have the OE wires, cap & rotor on it still too
I did do E3 plugs, so far so good...
OE plugs looked like almost new still, a lil' dirty on the outside,
very light gray-ish on the porcelain inside, looks good to me...
I will do the wires, cap & rotor sometime later...

Stage III
I bought Harlen Sharp 1.7:1 roller rockers (easy bolt on deal)
(only down side was the idle went up like 150rpm, like 800rpm
can't adj. the OE TB, you can get it down, but have to modify it,
remove a lead plug IIRC, it doesn't really need it, so I left it alone
)

Stage IV
then some Flowmasters 3" Delta flow series 50 , cat back system
(those 2-3 things really woke it up, the filter helps it breath, with the new rockers
& the 10% more lift/more power, free flowing exhaust
)
I did also do new rotors, slotted - drilled & better pads, at like 55k...
I do still run 87 oct. no problems ever,
but in summer I do run 89 oct. usually, just to be safer, Calif/ swill fuel...

I do have some Edelbrock 'bolt-on' Chrome 1.6250" x 2.5" shorty headers
to replace the org. stock manifolds...
I got them with my Summit bucks, I had to use them or lose them,
figured wtf, I never installed... yet
Stage V
May do the headers, after my next project 33x10" General Grabbers AT3
& do new shocks while I'm at it
"Actual 33" tall tires" & may buy new lighter wheels 15x8" too possible
(Ultra 050/51 or American Racing Bajas 15x8" also)
put the org wheels away in the shed

Stage VI
I'll probably do the 3.92:1 gears front & rear too,
it currently has 3.54:1, no problem on flat ground down at sea-level
But;
up in the mountains/altitudes the gearing will help some,
especially with the taller tires
be almost back to what it was with the org. 31x10.5's Good Year Wranglers
that were actually 30.33" diameter & them tires didn't last for ****,
the Toyo Open Country MS 32x11.5", actual diameter is like 31.33"
they have lasted for over 41k miles, great tires, up here on these
windy *** mountain roads... wish they made a 33x10"

With the mods/power adders I did...
I actually have more power (how much I have no idea, 30hp+ ?)
& it gets better milage too, seat of the pants feels way better...
Maybe 19-20mpg flat ground/sea level all highway, on road trips
like I-5 going to Redbluff
(we have no flat ground & all highway up here, no freeways either
for 75+ miles around here
)
Putzing around town & in the hills it's now getting 13mpg-17mpg, 15 average.
All depends on my 'driving aggressions'...
Stock it was getting like 12-13mpg, 'maybe' if I was under 65mph 15-17 open hwy...

enjoy, I hope that helps,
it helped my 1999 Dakota SLT Magnum 5.2ltr 4x4

View attachment 1490190
That does help, I think what you did is pretty close to what I am after also.
Do you know what the rockers item number is? I looked them up on summit and they have a couple versions all saying for Chrysler, same ratio(1.7) but then some are 400 bucks and some are 550.
ckessel mentioned Crower, Summit has those too but the price has gone up! So right now I am looking more at the HS rockers.
My Ram had factory 33's(Off Road Edition) and Chrysler opted for 4.10 for it, so I think you will deffinately want to change the gears if you go up another size tire!
The never used Wrangler original full size spare is under my truck yet, I will need to get that out and look it over. 31.5x10.5's, the spare and all around, but truck has Perelli Scorpios on it. I don't even know if they make those anymore. Date code is 2008 though, and they have some cracks! They have like 90% tread yet, and I only take it around local so I will probably run them anyway and keep an eye on them. If I recall right, they were some pricey shoes back then as truck tires go so I would think the quality should be good.
 
For the 94-02 Ram trucks, the V8 & V10 cats are mirror images of each other other than pipe diameter and 96 on using 2 O2 sensors. One of the plusses from my time working parts at the dealer.
 
That does help, I think what you did is pretty close to what I am after also.
Do you know what the rockers item number is? I looked them up on summit and they have a couple versions all saying for Chrysler, same ratio(1.7) but then some are 400 bucks and some are 550.
ckessel mentioned Crower, Summit has those too but the price has gone up! So right now I am looking more at the HS rockers.
My Ram had factory 33's(Off Road Edition) and Chrysler opted for 4.10 for it, so I think you will deffinately want to change the gears if you go up another size tire!
The never used Wrangler original full size spare is under my truck yet, I will need to get that out and look it over. 31.5x10.5's, the spare and all around, but truck has Perelli Scorpios on it. I don't even know if they make those anymore. Date code is 2008 though, and they have some cracks! They have like 90% tread yet, and I only take it around local so I will probably run them anyway and keep an eye on them. If I recall right, they were some pricey shoes back then as truck tires go so I would think the quality should be good.
part # on the rockers from HS 1.7:1 ratio at Summit Racing S70037
it says they're $432.99
I bought mine many moons ago now

yeah the gear change will happen
just be a while

I have my org. GoodYear 31.5" spare under the truck still too
never took it down :BangHead:

when I do the tires I'll do 5, probably 5 wheels too
& have the spare in the tire rotation schedule, like I should do
($2500 later)

I thought about going to the 4.10 also...
listed as a 4.11:1 by USA Standard rear $362.99
& 4.10:1 by Richmond $575.99
or their Richmond ExCel line $369.99 rear & front dana-35 $208.99 (4.10:1)
& Motive Gear 4.10:1 $567.99

or SVL driveline 3.90:1 $265.99
or Motive gear 3.92:1 $467.99
or Dorman 3.92:1 $322.95

all over the map on prices & that's not even the fronts
I can do just a gear change in my 9.25" & not change anything else
(except maybe bearings & seal) if I do the optional 3.92:1
I have to check the carrier specs to see if I could go to the 4.10:1
I know some say 9.25" in carrier is good for 3.54:1 gear ratio & up,
I'm not sure if that's the Dana-35 too, I have sure grip/track lock front & rear
(Dana-35 itty bitty ring gear 8 bolt 7.563" ring gears/1.376" pinions)
& still have no issues
 
Last edited:
part # on the rockers from HS 1.7:1 ratio at Summit Racing S70037
it says they're $432.99
I bought mine many moons ago now

yeah the gear change will happen
just be a while

I have my org. GY 31.5 spare under the truck still too
never took it down :BangHead:

when I do the tires I'll do 5, probably 5 wheels too
& have the spare in the tire rotation schedule, like I should do
($2500 later)

I thought about going to the 4.10 also...
listed as a 4.11:1 by USA Standard rear $362.99
& 4.10:1 by Richmond $575.99
or their Richmond ExCel line $369.99 rear & front dana-35 $208.99 (4.10:1)
& Motive Gear 4.10:1 $567.99

or SVL driveline 3.90:1 $265.99
or Motive gear 3.92:1 $467.99
or Dorman 3.92:1 $322.95

all over the map on prices & that's not even the fronts
I can do just a gear change in my 9.25" & not change anything else
(except maybe bearings & seal) if I do the optional 3.92:1
I have to check the carrier specs to see if I could go to the 4.10:1
& still have no issues
Thanks for the part number!

As for gears, for something like this it might pay to hawk on the CL and facebook market for a while and see if some show up. These axles have been around for years and years and the offroad guys love to keep going bigger and better and upping their gears as they go, so stuff does pop up. It is how I got my 3.55 set for that Mustang back in the day for $50.
 
For the 94-02 Ram trucks, the V8 & V10 cats are mirror images of each other other than pipe diameter and 96 on using 2 O2 sensors. One of the plusses from my time working parts at the dealer.
I will definately keep this in mind. I haven't dug into pipes yet as the factory stuff underneath looks like it is 2 years old due to the miles on the truck. Pipes are a bit down the list as other things haven't aged well regardless of miles, like the stereo speakers.
A few things I do not expect to find second hand, but I generally watch online marketplaces for things. There is a set of headers for $150 bucks right now within driving distance that look nice I might go check out, that sort of thing. The cats is interesting, people do part outs on second gens around here because the body fails to rust(salt kills all in WI) so one more thing to keep an eye open for.
 
When I worked at that dealer, V8 cats were going up a c-note every month. Weird but no big as all the ones we sold were warranty repairs in the shop. Mopar screwing themselves. And the V10 was less money. Go figure.
 
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