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this is dayadge country
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Discussion Starter #1
I picked up a kegger at my u-pull yard just because. Well to be more specific because it was sitting on top of a 99 3.9 dakota short block not bolted down to anything. Since all the friggin work was already done I figured wth, this is the easiest I could ever hope to get one. ~$20 later it was mine.

Anyways since I am currently time rich, I figured I'd ask about cutting the runners on this. It doesn't have the divider in the center (don't think my 98 does either) I already have a 5.2 throttle body for it, but haven't installed it since I don't see the point since the 3.9 intake bores need to be opened to even justify the mod.

I'm going to open up the throttle bores on this new intake, but is there any point to cutting the runners? I'm not going to tune the truck, it shifts at 5k since it is an auto. Other mods include 3.92 gears, jba headers, and underdrive pulleys. Will cutting these runners back shift the powerband too high? Should I leave them alone and just worry about removing casting flash, opening the tb holes, and un-shrouding the injectors?

Thanks in advance!
 

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DrPepper
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I may be wrong on this, but....

I don't think you have to change the throttle body openings to install a V8 body. The runner mod is the main change that will really make a difference on the 3.9. There have been a bunch of threads and every one seems to be a bit different, I don't think anyone could screw it up without trying. I cut mine up just a couple inches and it is absolutely the best mod for the buck.

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DrPepper
 

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this is dayadge country
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Discussion Starter #3
Thanks for the reply! From what rpm do you notice more power? The way I have always understood it was the longer the runner on the intake, the powerband will be lower and shifted more towards torque sacrificing high rpm hp. With shorter runners, the powerband will be higher and produce more hp sacrificing low end torque. I've searched around the net a lot, these threads always seem to turn into a debate because nobody has actual numbers and it always seems to be a v8 kegger people are talking about in the first place.

Before I purchased this intake, I lined up both the v6 tb that came off of it and a 5.2 v8 tb from a gc on top of it with the bellypan removed too for more light. The throttle holes in the intake lined up perfectly with the walls of the v6 tb but were too small for the v8 one. I would estimate about 1/8" overhang of material all the way around.

I was kind of thinking about angle cutting the runners to promote more laminar flow from the plenum area, since they pretty much suck off of the bellypan in stock form. I just don't want to completely screw the powerband up since Chrysler claims these engines make peak power at 4400 rpm and my truck shifts at 5k is all.

Does anyone happen to know the stock camshaft specs for my 98 dakota? Looking for duration @ .050", valve lift, and lsa. I looked at this site and I don't know how credible any of it is since their duration and overlap numbers are incorrect for the valve timing events they have listed.
 

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Layin Low
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no idea about the cam specs...

but angle cutting the runners? that's the mod to the runners. literally one side you can only cut a max of 2inches (due to the runner next to it from the other side)

and then you can do whatever you want with either making them flat or giving them the angle.

if you're that worried about the bottom end, since you have the intake and you're prepping it anyway... get a belly pan plate and get some additional 1/8th inch plate aluminum. make a turtle and have that direct airflow to the runners once it enters the manifold.
 

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DrPepper
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OK, here is what I did....

I read up on the TB swap and went for a Hughes modified V6 TB. They say that the flow of the V8 TB is more than you need and a cleaned up V6 does nice. It did improve things a bit. As to the V6 vs. V8 mod, it is still one runner per cylinder, so what happens to an 8 will happen to a 6...?
Next my kegger had oil in it and figured I'd change the bottom cover and do the runner mod. I have a V6 5 speed and it would almost never go over 5000rpm and I never did get the rev limiter shut down the engine. On the highway 90-95 was a huge struggle and passing anything was a joke. I did the kegger mod, put it together, ran the engine a bit in the driveway. Took it out and hit the limiter at just over ~5500 rpm, faster than it ever did. The change was mind boggling. Torque was as good as ever and it just opened up the top end. Off idle on up is still very tractable, no surge points.
Next I added the HS 1.7 roller rockers, but that was a dud. It did almost nothing to help the HP & torque, but they sound cool so I left them in.
Last thing I did was changed the 3:55 rear end and put in 3:90 gears. That also was a good mod. It bumped the rpm a bit and made 5th gear a better street gear.
So, what do I have? 3 runs on the Dyno at Mr.Norms gave me the HP & torque numbers below. Don't forget that is rear wheel HP. I found out I am running rich on the top end, still haven't figured that out. Here is the specs for my 3.9 QC.

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Bottom line for me:
Now I can hit 100+ mph without any trouble, passing is much improved. It is STILL A V6...!!! But, it is much more agreeable to drive. 1/4 mile times are consistant mid-18's at ~75 mph. NitroHog was there, I let him beat me...LOL.!!
Hope this helps,
DrPepper
 

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Layin Low
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I read up on the TB swap and went for a Hughes modified V6 TB. They say that the flow of the V8 TB is more than you need and a cleaned up V6 does nice. It did improve things a bit. As to the V6 vs. V8 mod, it is still one runner per cylinder, so what happens to an 8 will happen to a 6...?
Next my kegger had oil in it and figured I'd change the bottom cover and do the runner mod. I have a V6 5 speed and it would almost never go over 5000rpm and I never did get the rev limiter shut down the engine. On the highway 90-95 was a huge struggle and passing anything was a joke. I did the kegger mod, put it together, ran the engine a bit in the driveway. Took it out and hit the limiter at just over ~5500 rpm, faster than it ever did. The change was mind boggling. Torque was as good as ever and it just opened up the top end. Off idle on up is still very tractable, no surge points.
Next I added the HS 1.7 roller rockers, but that was a dud. It did almost nothing to help the HP & torque, but they sound cool so I left them in.
Last thing I did was changed the 3:55 rear end and put in 3:90 gears. That also was a good mod. It bumped the rpm a bit and made 5th gear a better street gear.
So, what do I have? 3 runs on the Dyno at Mr.Norms gave me the HP & torque numbers below. Don't forget that is rear wheel HP. I found out I am running rich on the top end, still haven't figured that out. Here is the specs for my 3.9 QC.

Bottom line for me:
Now I can hit 100+ mph without any trouble, passing is much improved. It is STILL A V6...!!! But, it is much more agreeable to drive. 1/4 mile times are consistant mid-18's at ~75 mph. NitroHog was there, I let him beat me...LOL.!!
Hope this helps,
DrPepper


i read your reply and this stuck out to me... after carefully reading thru... is it safe to assume that you do not have exhaust mods?

point i'm getting at is if you help get the air in, then you gotta be able to get the air out as well. adding some headers might be able to get the air out better.

my 97 V6.... i had a dwight ported V6 TB, PHaB headers, hell of a blown belly pan gasket, 3.23 gears in an auto and i was constant at 18.10's all day.

i have videos... but damnit... the new photobucket is LAME. never dyno'd it though
 

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DrPepper
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1,150 Posts
No mods to the exhaust....

Hi Sho, I agree that it would be good to open things up in the exhaust, but, I hate exhaust work...LOL

As to the headers, the available 3.9 headers seem to have their share of maintenance problems and I'm trying to get my #1 project worked on rather than change header bolts and gaskets. If the muffler ever goes it will probably take the cat with it, :mullet: you know how that goes. :jester:

As to the performance, I have 4 doors, 60+lbs of sound deadner and hitches front and rear. I don't think I removed my spare either, "run what ya' brung", as they say.

As to my ability to pull, the orange Power Wagon is well over 5000lbs + trailer, no problem. Getting that Wagon on the road is my #1.
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DrPepper
 

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Home School Valedictorian
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4,204 Posts
Hi Sho, I agree that it would be good to open things up in the exhaust, but, I hate exhaust work...LOL

As to the headers, the available 3.9 headers seem to have their share of maintenance problems and I'm trying to get my #1 project worked on rather than change header bolts and gaskets. If the muffler ever goes it will probably take the cat with it, :mullet: you know how that goes. :jester:

As to the performance, I have 4 doors, 60+lbs of sound deadner and hitches front and rear. I don't think I removed my spare either, "run what ya' brung", as they say.

As to my ability to pull, the orange Power Wagon is well over 5000lbs + trailer, no problem. Getting that Wagon on the road is my #1.

DrPepper
Any progress on that wagon?
 

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this is dayadge country
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207 Posts
Discussion Starter #9
The power looks pretty decent, thanks for posting that up DrPepper. Where the shaky power and torque lines start seem to coincide with where the truck dips below 12:1 afr. Are you using the stock injectors?

What I meant earlier by angle cutting the runner was just that. I was thinking about cutting back 1" off the inside or so, i don't want to take the entire thing back 1". I think this will promote better flow into the runner by reducing the angle of entry for the incoming air. Who knows though, once i get to cutting i might start looking at things differently.

I have seen the teepee come up before, but I'm not really sold on doing it. I just got my v8 tb back so I'll probably start working on this manifold soon. I read around a bunch online yesterday and came up with a formulas for tuning a runner length for a desired rpm, but I am unsure about a couple things. So I want to look that stuff over again.

The whole reason I started this thread here and didn't piggyback off of a v8 thread was that I wanted to hear opinions and feedback from the v6 crowd. I figure the v6 crowd would notice it more if these mods were causing problems... and well my trucks a v6.

DrPepper, the improvement in my truck from headers alone was crazy. It pulls much stronger from 3k all the way up. Drilling out three broken bolts that had broken off on their own beforehand sucked though. Putting the headers in is a breeze aside from that.
 

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Layin Low
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1,313 Posts
The power looks pretty decent, thanks for posting that up DrPepper. Where the shaky power and torque lines start seem to coincide with where the truck dips below 12:1 afr. Are you using the stock injectors?

What I meant earlier by angle cutting the runner was just that. I was thinking about cutting back 1" off the inside or so, i don't want to take the entire thing back 1". I think this will promote better flow into the runner by reducing the angle of entry for the incoming air. Who knows though, once i get to cutting i might start looking at things differently.

I have seen the teepee come up before, but I'm not really sold on doing it. I just got my v8 tb back so I'll probably start working on this manifold soon. I read around a bunch online yesterday and came up with a formulas for tuning a runner length for a desired rpm, but I am unsure about a couple things. So I want to look that stuff over again.

The whole reason I started this thread here and didn't piggyback off of a v8 thread was that I wanted to hear opinions and feedback from the v6 crowd. I figure the v6 crowd would notice it more if these mods were causing problems... and well my trucks a v6.

DrPepper, the improvement in my truck from headers alone was crazy. It pulls much stronger from 3k all the way up. Drilling out three broken bolts that had broken off on their own beforehand sucked though. Putting the headers in is a breeze aside from that.
how did you do that?

i do have 2 V8's (one on stand), a 4 banger, and a newly acquired 3.9. (had a 97 3.9 a few years ago)

but i know of at least 1 bolt that is broken on the exhaust manifold... i was gonna pull the heads and have any that need it, drilled out locally and then it would allow me to put in better head gaskets haha
 

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Layin Low
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Hi Sho, I agree that it would be good to open things up in the exhaust, but, I hate exhaust work...LOL

As to the headers, the available 3.9 headers seem to have their share of maintenance problems and I'm trying to get my #1 project worked on rather than change header bolts and gaskets. If the muffler ever goes it will probably take the cat with it, :mullet: you know how that goes. :jester:

As to the performance, I have 4 doors, 60+lbs of sound deadner and hitches front and rear. I don't think I removed my spare either, "run what ya' brung", as they say.

As to my ability to pull, the orange Power Wagon is well over 5000lbs + trailer, no problem. Getting that Wagon on the road is my #1.


DrPepper
Exhaust work sucks so damn much... i'm doing true duals off of midlengths on my 5.9 QC... such a pain...

the 3.9 headers do have issues... but it depends on the source as well. ebay PHaB headers aren't gonna have the same quality as, lets say, Gibson.

are you just restoring the wagon? any pics of the build so far? seems pretty awesome
 

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DrPepper
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1,150 Posts
Good point on the injectors....

I installed 4 hole matched Ford injectors, but they are supposed to be a match for the capacity of the stock Mopar 1 holers.

As to the angle cutting of the runner, I don't think it will hurt a thing. My theory (how's that go about everybody has one..?) I think the runners are to close to the bottom cover and the intakes are restricted. Simply opening up the area so air can enter the runner with less restriction would be a help. When you get it apart put a straight edge across the bottom and see how restricted the runners are. I used a pneumatic die grinder and bought a burr made for use on alumuinum so it didn't "load up" with cuttings. $18 at a tool supply and it was worth is. Cutting was perfect and never had to clean it.

As to the headers, it probably does help a lot, I just don't have time to fuss with it now. :huh:

9t9: As to the project '57 TW-PW (sorry about the high jack) it's slow going. I've been trying to remove a rear brake drum for over 6 months and it still hasn't let go. It's a drum on a tapered axle shaft, so it isn't anything like the Dakota's....! Made my own puller so it would fit and will keep working on it with heat and penetrating oil/wax/ GOK? until it lets go. Engine and trans are in and functional, just no brakes. Woo-Hoo!!! Thanks for asking
http://s182.photobucket.com/albums/x32/DrPepper_V6/57 Dodge Town Wagon Power Wagon/
DrPepper
 

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this is dayadge country
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Discussion Starter #13
how did you do that?

i do have 2 V8's (one on stand), a 4 banger, and a newly acquired 3.9. (had a 97 3.9 a few years ago)

but i know of at least 1 bolt that is broken on the exhaust manifold... i was gonna pull the heads and have any that need it, drilled out locally and then it would allow me to put in better head gaskets haha
i had to use pneumatic drill, pull the air cleaner stuff out and part of the inner fender. the front 2 bolts around cylinder 2 and 4 were snapped, and one by cylinder 5. i tried drilling small and using broken bolt extractors and a torch, but i couldn't get enough heat on it to break them free. the cylinder heads just absorbed it all no matter how long i held the torch on them. I ended up having to drill them out entirely and tap the holes to 3/8" nc.
 

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this is dayadge country
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Discussion Starter #14
I have been working on the intake a fair bit. the runners are cut, i want to try to get in deeper to take the big round cast in things off the walls of the runners. I need to open up the throttle holes still too. Things are easy with that carbide cutter I bought for aluminum! I'm glad that was suggested, doesn't plug up at all and cuts like butter! Cost me $30 though. I'll take some pictures when it's all done.

Does anyone happen to have some good pictures of their injector holes as they were stock? It kind of looks like someone has worked on the ones on this intake I have.
 

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DrPepper
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1,150 Posts
Correct tools do make life easier....

As to the injector holes, on the outside there shouldn't be much you can do since the injector has to sit at the correct height to engage the fuel rail. On the inside of the runner I opened things up a bit but more of a cleaning than a reshape of the area. You can see it in the 1st pix. Push an injector into the hole (if you have one) and see where it sits. The spray goes right down at the valve head.

DP
 

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this is dayadge country
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Discussion Starter #16
but angle cutting the runners? that's the mod to the runners. literally one side you can only cut a max of 2inches (due to the runner next to it from the other side)
I just wanted to post this picture to better answer what I was talking about:



This is NOT how I cut mine. That just looks wrong, imho.

My decent camera is dead and the charger is still in Canada, but I got my junk one working and it doesn't like taking pictures of shiny metal even on macro. Sometimes it surprises me though. So keep your fingers crossed that I can get some decent pics for you guys with the potato I'm using. You've been warned though! lol!
 

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DrPepper
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1,150 Posts
It's not to far off from mine....

Here is a fuzzy pix of mine from a different angle....

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Seems to have a lot more trying to smooth stuff than I did. Hay, it's a 3.9, whatta ya want.... :jester:
DrP
 

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this is dayadge country
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Discussion Starter #18
It's a 3.9, I need all I can get!:jester:

The potato didn't work out, but the wife was nice enough to lend me her camera so the pictures don't look like you're 10 beers deep! It still has aluminum shavings on it you can see in the pics, I'm not done yet.



a view from the other end:



Also, I took some measurements of the throttle body hole situation. Just reading off of a pocket scale, the 5.2 tb opening at the bottom is 2". The holes in this manifold are 1-7/8". Here's a picture of what I'm talking about:



I have a hard time believing all these guys who say "I put on a v8 tb and got more power :drive:"

And here's what a couple of the injector openings look like:



don't ask me why that^ bloody picture keeps getting turned sideways... and the other side is a little different:



So I'm going to fix those up, and open the throttle holes next. I still want to do more smoothing. Bought a nice circle template today so I'll lay that out soon.
 

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DrPepper
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1,150 Posts
It's the internet, do you really believe everything on it...???

I will be interested in how it turns out. I didn't go as far as you did but it probably won't make any difference. Your's will not have a restriction at the inlet, that is for sure.
Another thing I started to do and didn't get to....Insulate the belly pan. All this mumbo jumbo about cold air intakes ...and they run the intake air right across an aluminum plate with 200+F oil splashing on the bottom. There are several articles about "air gap manifolds", or manifolds with the underside of the runners elevated above a plate that covers the valley. The thought I had was to sandwich a 1/4" cork pad between the aluminum cover and steel OEM cover. It would take studs and nuts to tighten it all up. Then seal the area around the cork with high temp RTV. That would drop the temp of the aluminum bottom cover considerably and the intake air would be cooler. All theory. IMHO
DrPepper
 
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