Engine mods on the 3.9!

[daksport35]

i was just wondering what it would get me if i did some internal engine mods such as porting the pistons, bigger pistons or increasing the compression and milling down the heads. what kind of gains would i see? and what kind of specs are on the stock 98 dakota and what could it be modded to?

[themongrel]

Turbo!!! :biggthump :drive:

[daksport35]

i thought about the vortech supercharger from krc performance but it is $4000 what did the turbo run you and how hard was it to hook up? what about the power gains? also the exhaust manifold how did you do that?

[MoPaR DaK]

Porting the pistons? :jester:

[daksport35]

i would like to know about porting the pistons and increasing the compression maybe milling the heads?

[MoPaR DaK]

Porting pistons is a new one to me. If you get new pistons you can get a higher compression ratio. You could also deck the block some or mill the heads to get compression. If memory serves me correctly you actually have to use some sort of forged piston what ever company you choose and use full floating forged V8 connecting rods. But then an issue of the V8 rod sitting into the V6 crank the dimensions are a hair off and that requires machining too. The V6 rods in your truck right now are forged but the pin is pressed into the piston and can't be used with an aftermarket piston. It seems like a real mess from the few pictures and write ups I've seen. You can make a rockin' V6 without messing with alot of that. It would actually be easier to just swap a V8 at that point.

[themongrel]

i thought about the vortech supercharger from krc performance but it is $4000 what did the turbo run you and how hard was it to hook up? what about the power gains? also the exhaust manifold how did you do that?

I did it myself for about $2500. I did it as a remote setup, so the exhause pipe connected right to it then back to the intake. I figure I am good for 125 or so extra HP

[Ace]

STROKE IT :biggthump

[realdeal7369]

i would port, polish, and deck the heads (.025 off the compression side), port and polish the intake slightly, adda 50mm billet tb., headers or the 1992-1993 exhaust manifolds (extrude honed), get some exhaust work done, high flow cat, decent muffler, 2.5-3" exhaust, msd ignition coil, msd 8.5 super conductor wires, go with a different cam, mp computer (if applicable). doing all this should net you in the 240hp-250hp range. remembering stock is what 185-190? get some taller gears, shift kit in the trans,


porting and polishing should net you a nice gain. you would be suprised as to what you would get if a little time was spent on these heads. esspecially in the areas under the valves. the guide bosses are like brick walls. opening up the intake ports (the parts there the pushrods are at), that wall needs moderate modification. both in width and hight. wish i did mine before i put it all back together. I did the v8 heads though. im still going to deck the heads a good .020 off. three angle valve job, and have the machinist finish polishing the heads. i think im going to take off some more material on the intake ports before im satisfied with them.

[realdeal7369]

STROKE IT :biggthump

i researched this, crank is buku coin man....

[MoPaR DaK]

(.025 off the compression side)
I've never understood why people say "off the compression side." Weather you're decking the block or the heads, either way there is less volume in the chamber and compression will be raised. Just food for thought.

[daksport35]

ok..i know a little bit about this stuff but what exactly do you do when you port and polish and how would i get that done? same for decking the block?

[MoPaR DaK]

ok..i know a little bit about this stuff but what exactly do you do when you port and polish and how would i get that done? same for decking the block?
Porting is opening up what ever you're working on more to make it flow better, polishing is pretty much the fine work done after porting, decking the block is where you actually remove metal from the deck (top of the block) and it does two things. If the block is a little warped then decking it down may make it perfectly flat again and it will also raise the compression ratio a little.

[KREWZER]

VegasOutkast is doing some work on his engine, actually a lot of work http://www.dakota-durango.com/forum/showthread.php?t=6187 . I dont know if this link will work since i dont really know what im doing. Just thought this would help.

[realdeal7369]

I've never understood why people say "off the compression side." Weather you're decking the block or the heads, either way there is less volume in the chamber and compression will be raised. Just food for thought.

just trying to clarify where, thats all. thanks though.

[realdeal7369]

ok..i know a little bit about this stuff but what exactly do you do when you port and polish and how would i get that done? same for decking the block?

get a set of carbbide bits, and an electric dremel. get the short 2-3" bits and the longer ones too.

areas to take into consideration. valve guide bosses, intake/exhaust ports, combustion chamber unshrouding (done at the macjine shop), 3 or 5 angle valve job. also taking any sharp edges off anything that may look like it may impead airflow. may take you some time. a good solid day or two will get most of this done. but i suggest you take your time, go slow. make the guide bosses resemble tear drops. youll have to take a shitload of material off to get to this. also need to get a polishing kit, like jegs or summit and probably a few other places has to offer.

i bought a dremel type tool off ebay real cheap. look up the carbide bits too.
or try these http://www.ruffstuff.com/pages/carbide.html

[daksport35]

i somewhat took the hourglass shape out of my v-8 throttle body and it took forever! what kind of gains should i look for with the port and polish?

[realdeal7369]

see if you can get the august edition of mopar muscle magazine. someone else on brought this to my attention, so i grabed it up, and got into doing mine.

if you did your tb with a dremel for the bore hole...man, you did it the hard way. shoulda got the rounded flap disk for a drill. woulda took a little bit, bit it would come out nice though. that what i did to both of my 3.9 intakes. incidentally, im selling one of them. dont need two. pm me and make me an offer....

anyways, if i misread your post, i apologize in advance.

flow rates jumped up when you smooth out the valve guide bosses, short side turns on both the intake and exhaust ports, and a few other key areas. also getting the combustion chamber widened to prevent valve shrouding is a plus. but in my opinion, i would go no wider than what your bore diameter is, maybe even just a tick under that. say if its 3.94 bore (.030 overbore than stock), id have them open up the combustion chamber to 3.935 or so. seeing as how from what the guys on mopar mucle mag measured the heads for the 318 they were working on, they measured 3.905. (3.91 bore is stock). they also did a serdi valve job on the heads. dont know what this is exaclty, but im sure someone on here can fill in the blanks.

cant wait, couple more weeks, and i should have enough coin to take my heads and get them finished up...woohoo :banana2: :biggthump