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post #1 of 19 (permalink) Old 02-21-2013, 03:46 PM Thread Starter
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Lets see what we can do with this 3.5

Ok well in my new classes this semester im taking engine reconditioning and automatic trans rebuild classes.

in the engine class we may supply our own parts and by the end of two semesters you should have a engine build 100% to spec ready to run, was going to grab an engine for my dads durango seeing as its at 240k miles but they wanted 450$ at the yard for one, while it was only 150$ for my trep. durango's are only in the "premium yard". so we pulled a 3.5 from a 95 and called it gravy.

anyway in the class we literally have everything you could need to machine a engine however you like, the teacher even calls the class "engine machining" not reconditioning. well i would just feel like im missing the potential if i do not "update" this engine as much as i possibly could.

From what ive researched so far the design has been around about 18 years from 93-11, with the end result a 46hp and 44tq increase from its release, with versions 2.7, 3.3, 3.5 and ,4.0

it seems the increases from the 1st gen 3.5 to 2nd gen as many if you likely know is from the heads, with softer springs and wider intake valves, and the differences in the block the pistons are lighter 2nd gen, with heavier rods (i dont know how much that really makes a difference) also i think the pistons have a flat top on 2nd gen and that increases the compression and makes it inteference?, the first semester of the class consists entirely of the heads so ill start with that, widen the valve seats, port, polish intake, throw in the 2nd gen valves/springs, i have the specs from 94, compared to 04, and the valves/guides are exactly the same besides the intake head diameter, intake valve lift is .40 mm more in 2nd gen, i still need a bit more research on that but it seems entirely doable, and that can take up my time while i research the more adventurous idea...

Now someone once told me that the 1st gen could not be modded into a 4.0? i didnt look into it at the time but now i ask why not? i assume its something to do with the oil pan, as i believe the blocks are exact same in 2nd gen except iron not aluminum? many small differences can be handled easily, i noticed the 2nd gen guys having to grind out some on bottom of cylinder for crank clearance, i still need to do much more research on the project but im curious as to why i was told it couldnt be done?
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post #2 of 19 (permalink) Old 02-21-2013, 04:07 PM Thread Starter
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oh and i completely forgot the main thing i was going to ask, anyone have a link to 4.0 engine specs, i cant find anything on the web or the nitro or pacifica forums.
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post #3 of 19 (permalink) Old 02-21-2013, 04:37 PM
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Sounds like just the thing to do!!!

The only thing you may run into is the lack of computer support to make it run right - mechanically it will be potentially flawless - but if you can't feed it, no point. I don't know, but bigger injectors are the first thing I'd find before you go modifying the heads too much.

Perhaps custom injectors (using standard Bosch style injectors) and a custom injector rail (top feed, rather than bottom feed) would be a solution? Of course there is always a megasquirt.

Very exciting to see where you go with it.
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post #4 of 19 (permalink) Old 02-21-2013, 06:16 PM Thread Starter
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yea i need to look more into the fuel delivery, among many others, i was deff planning on new injectors, and need to look into a computer to run it, i saw the guys with 2nd gens had larger then needed injectors with a computer controlling it to better compensate for fuel differences between idle and WOT, i was gunna look into something like that for a 1st gen computer... a better fuel rail would be nice as well, maybe i could look into getting a higher pressure threw the lines for better spray, haven't looked into that yet, hehe so much research to do, im having the hardest time finding the 4.0 rebuild specs

my teacher was telling us how they are putting 20,000 PSI threw diesels to make them quite as a gas engine, irreverent but interesting as hell, esp when you can cut steel with water at that pressure.

Edit: i actually just checked and see that dodgebob ran stock injectors for a while before upgrading, makes sense to be ok as the stock would likely be enough at lower rpms while your still breaking in the engine, but fuel delivery is deff high up on the list.

Last edited by Ruggels; 02-21-2013 at 06:22 PM.
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post #5 of 19 (permalink) Old 02-21-2013, 06:42 PM
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Originally Posted by Ruggels View Post
oh and i completely forgot the main thing i was going to ask, anyone have a link to 4.0 engine specs, i cant find anything on the web or the nitro or pacifica forums.
http://en.wikipedia.org/wiki/Chrysler_SOHC_V6_engine
It's at the bottom. At least I think this is what you are looking for.
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post #6 of 19 (permalink) Old 02-21-2013, 10:56 PM
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my teacher was telling us how they are putting 20,000 PSI threw diesels to make them quite as a gas engine, irreverent but interesting as hell, esp when you can cut steel with water at that pressure.
Diesels are getting up in the neighborhood of 30,000 PSI now with up to 7 injections per combustion using common rail fuel systems. If memory serves me right, it takes a little over 30 or 40 thousand PSI to cut steel with water alone but its still pretty darn cool.
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post #7 of 19 (permalink) Old 02-21-2013, 11:33 PM
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Gasket matching the ports will do much for you, Increasing the small I believe 48mm Throttle bodies with a 3.3 s 58s on both side will help air flow. Fart as polishing it will not do much. The biggest area to work with is around the valve to help improve swirl and flow.

The Viper and the 3.5 share the same type of injectors, which are bottom feed. keep that in mind. Also, OBD II First gen PCM will not respond very happily to timing differences or at least in a 3.3 they will not.
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post #8 of 19 (permalink) Old 02-22-2013, 08:17 PM Thread Starter
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http://en.wikipedia.org/wiki/Chrysler_SOHC_V6_engine
It's at the bottom. At least I think this is what you are looking for.
close, im looking for the engine specs like the valve, oil, crank clearances and whatnot generally the FSM has them thats where i got the info for the treps engines, so i could mark off the exact differences for all i know the valves on the 4.0 may be even larger then that of the 2nd gen, i think i may end up having to fork over the cash for one if i cant find it after another week or two, ill make sure to get the PDF version if i do however so i can share it with you guys, maybe i could talk the guys over at the dealership letting me get a peak at both the pacifica 4.0 and nitro 4.0 FSM's, the nitro supposedly puts out 5 more hp and 10 more torque i think...

Quote:
The Viper and the 3.5 share the same type of injectors, which are bottom feed. keep that in mind. Also, OBD II First gen PCM will not respond very happily to timing differences or at least in a 3.3 they will not.
That good to know about the injectors, makes me think as long as the trim is adjusted correctly then they should have enough squirt. however i need to look more into how the ECU controls fuel trim, as from what i was reading about piggybank fuel controllers is you may have the problem of the ECU trying to counteract the piggybank readings to readjust itself. as well anything i read referred to OBD II operations not OBD1

As for the timing, some of the piggybanks i was looking at connected into the cam/crank sensor as well allowing you to adjust timing readings, my trep also runs OBD1, which is the reason the engine i got was a 95, we had to pass up one already out of the car but was OBDII and figured at best case scenario i would have to replace entire wire harness worse case, the OBDI BCM, TCM, does not communicate with the OBDII. but still im not sure how well the ECM will like me changing the timing without tricking it first.
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post #9 of 19 (permalink) Old 02-23-2013, 12:38 AM
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Re: Lets see what we can do with this 3.5

Just so you know, there are very few differences between an OBDI and an OBDII engine... Basically it is the tps and the o2 sensors... So you could have gotten either one of them.
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post #10 of 19 (permalink) Old 02-23-2013, 02:25 AM Thread Starter
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i figured as much, the guy i talked to on the phone at the dealership said something about other things they could have changed between obd 1 and 2 so i just went with what he said, but i dont think it will matter at all really, if anything i could see OBDII as being more restricting on the tuning side, but thats just a wild guess.
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post #11 of 19 (permalink) Old 02-23-2013, 11:14 AM
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Re: Lets see what we can do with this 3.5

The only restriction to tuning would be in the computer.
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post #12 of 19 (permalink) Old 02-25-2013, 10:04 PM Thread Starter
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well got to work on em a bit today, got everything taken apart ready to be cleaned, i was also able to get the 2008 4.0 dodge nitro engine specs from the school resources, it would seem that the 4.0 has a few differences but seems Chrysler followed suit of what they did from 1st to 2nd gen....

even lighter pistons then the 2nd gen trep, (which is even lighter then 1st gen), for a difference of 515g in 1st gen trep to 375g in the nitro, thats around 140g per piston, heavier connecting rods from 626g in first gen to 693g (total weight), resulting in + 73g, so becides the deeper cranks the rotating assembly is a full 767g thats almost two pounds off your crank!

while from 1st to 2nd gen trep they increased the intake valve head diameter by about 1.5mm, and softer springs (some say the main cause of the gains from the 1st to 2nd gen is from these two things) and while in the 4.0 the valves stay the same size they actually have .85mm more lift for intake, and around .5 for exhaust valve over 1st gen, and about .5 more both intake and exhaust compaired to 2nd gen, as well for the 2gen it uses softer intake and exhaust springs then the 1st, while the 4.0 keeps the softer intake, the exhaust are more similar to 1st gen rather then 2nd in terms of tension.

so more research on interchangeable springs, valves, etc... i cant figure about where the extra lift in the valves comes from, i think it may be both the cam and exhaust valve together.... the 4.0 exhaust valve overall length is .5mm longer then in 3.5s that explains the lift their, but the intake is the same, as well all cam specs are the same but it does not give me the size of the lopes on the cam (i think thats what they are called)

im going to make a thread with all the 4.0 specs later tonight, the info i have is just printed out so just engine build specs no full section on engine from FSM... yet

edit:
Quote:
The only restriction to tuning would be in the computer.
yea i was meaning on the computer side of things i would think a OBD1 ECM would have less strict programming then a OBDII, and more comparing with the 2nd gen guys rather then the two engines i was looking at but like i said its just a wild guess guess with no merit behind it

Last edited by Ruggels; 02-25-2013 at 10:11 PM.
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post #13 of 19 (permalink) Old 02-26-2013, 03:10 PM
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So, you're building the engine - I assume you're going to drop it into your '94?
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post #14 of 19 (permalink) Old 02-26-2013, 04:13 PM Thread Starter
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yessir, i plan to essentially do as much upgrades on the engine as my budget will allow, i wont have to much worry about machining as the school has everything i could need there. so i can focus my money on parts. ill either sell the old engine or see if i can find a body to throw it in and sell that.

im trying to get the modifications i want to do in a priority order, i dont want to throw in the deeper crank and leave the valves the same, i could see it restricting the engine with the larger differences between 1st and 4.0, im finishing up my research on the mechanical aspects now i need to look into parts costs and interchangeability.
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post #15 of 19 (permalink) Old 03-04-2013, 10:05 PM Thread Starter
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so went in and more cleaning, cleaned the valves, noticed one of the heads was rebuilt before, the valve guide covers were in 3 diff colors, and could see they were milled before, started to pop out the valve guides and noticed that the chamber is different on each of the heads! seems someone threw on the wrong head for a repair, the doner car only had 87k miles on it.

one head obviously gives a higher comp ratio then the other,



anyone know what year the higher comp ratio head came out? i checked all the intake valves and they all seemed to be the same size, i know 2nd gen runs larger intake valves so is this from a first gen i believe, and the doner car is a 95 concord

Edit: so a bit of research has lead me to find the head in the top pic is from a a 93/94 and the lower head is from 95/96/97, and further research has lead to me find that the 2nd gen and 4.0 heads use the design in the lower pic, so a 93/94 head will give a higher compression, that coupled with 4.0 internals will make these heads the most efficient and powerful. available.

Last edited by Ruggels; 03-05-2013 at 02:13 PM.
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