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Thread: Paging DKOV! *May I pick your brain? 3.4 DOHC

  1. #1

    Paging DKOV! *May I pick your brain? 3.4 DOHC

    I spent entirely too much time online last night, till the wee hours this morning reading posts on Penocks Forum. You were omin-present in many discussions on engines. The one thing I gathered was that you seem to have done a good bit of research on the subject. So, in order to get it all down for posterity, and in a more coherent forum rather than scattered all over cyberspace, I'd like to combine what I know, with what you know, and benefit from your first hand experience with the 3.4, and or 3.5. I guess a good place to start is here, I know the original 3.4 DOHC was under rated and detuned to mate to the available drivetrain. Do you know what way the engine was detuned? Computer program, ignition timing, cam timing? And next, given your choice of either the 3.4 or 3.5, which would you rather have and why?

    That ought to get the ball rolling. ;D Appreciate any info you could provide about your installation too, like did you use a kit or fabricate from scratch (the direction I am leaning towards).

    Thanks, Alex


  2. #2
    Senior Member
    Join Date
    Dec 2001
    Posts
    1,345

    Re: Paging DKOV!  May I pick your brain? 3.4 DOHC

    Well gee... Where to start

    When I started my research on teh 3.4L TDC, I owned a 1991 Pontiac Grand Prix, production #74 of ??????? I was the 2nd owner of the car. The previous owner ordered it in early 1990 before it was available and had it built to suit and deliverd in early 1991. He was/is a cheif steward at Portland International Raceway and wanted the car for track activities.

    After receiveing the car from the local Pontiac Dealership, Weston Pontiac in Gresham, he had the Cams reground and the timing redone. Retarded the exhaust cams. From what I've found, only about 10 degrees.

    I purched the car from him in late 1993 and drove it until New Year's Eve 1999 when I got hit by a drunk driver who promptly ran after the collision. He T-boned me in the Driver's door and broke the left front wheel before swinging around a 2nd time and slamming the car in the rear driver's wheel and side swiped the entire length of the driver's side before bolting. I got his plates and he was picked up about an hour later. In all, my GTP was totalled and I was shaken, not stirred.

    Out of disaster comes hope!!! I had my 1988 Fiero GT that I was preparing for a 355 transplant (someday) and had always loved the pull of the 3.4L TDC in my GTP which is nearly 2000 lbs heavier. Ripped my head off in that car, why not in the Fiero

    So that was the beginning. I bought the totalled GTP back from salvage for $1000. Pulled the motor, tranny, ECU, axles and everything else I thought I might ever need. Including the GTP badges Then I sold the car BACK to salvage for $500. Not a bad deal I think.

    The motor sat for over a year while I got my life together. New Home, 1st child, you know. Finally, I got started on the swap.

    I wanted to get alot done while I was at it so from 1993 until I started the swap, I spent hours on the phone and Internet researching what mods were available for this motor. Found some leads and uncovered some of the history of the motor and of my motor specifically. Discoverd folks that had access to actualy GM documentation concerning the HP output of the first 100 motors and stats. Amazing stuff.

    I had the timed and custom Cams, so my list began to grow from there. When the motor was out, I put that list into action.

    1-Bored the TB, ported and polished
    2-Hone Strued port and polish upper and lower intake manifolds
    3-Port matched the Exhaust, Custom super high flow exhaust with NO cat (or mufflers really )
    4-Decked the head to improve compression to 10.5-1
    5-3 angle valve grind. 5 was available but at a low end loss
    6-New pistons, rings, seals etc. Forged cranks and rods.
    7-Modded ECU
    8-Fuel Pressure Riser and Regulator
    9-Underdrive and lightweight aluminum pulleys
    10-Custom PS pulley application
    11-High torque starter
    12-Custom Axles
    13-284 Getrag 5-speed tranny (Grand Prix GTP tranny)
    14-Auxillary oil cooler
    15-Auxillary tranny cooler

    When all that was done, the motor went into the Fiero and runs super fast and strong. It's loud as hell and I've been pulled over for doing 65 in a 40 (in 2nd gear no less) and excessive noise. The cop was impressed with the motor and car and let me go

    I'm getting ready to tear it down again and probably will in the next few weeks. I'll be adding copper o-rings instead of head gaskets and reworking the heads/pistons to reduce the compression back to 9.5:1 for a Turbo application. That will be a hyrid T-3/T-4 turbo running only 7 - 11 lbs of boost at first with 28 lbs possible. At a full 28 lbs, I'll be putting out over 550 HP and I don't know if the tranny will handle it.

    That is really the weak spot in all this... the tranny. Even the added strength of the 284 is getting close to stressed out with 300+ HP and I certainly don't think the 282 will handle the 450 HP I'm planning on running.

    So, I'm going to have my tranny rebuilt as well and reinforced if possible.

    I know very little about the 3.5L motors as they did not exhist when I started this project. What I do know is that they are essentially a Northstar with the back two cyls lopped off. The engine management system runs the same. Beyond that, I have no clue.

    Yes, I prefer the 3.4L TDC over the 3.5 because I have always loved it. Because of the power. Because of the sound. Because of the speed.

    I have no speed limiter on my car and the rev limiter is set at 7400. Pulls forever and sounds incredible. Can't beat it.

    I've got a huge step-by-step diary for the motor build up I'll have to find. It was alot of fun and certainly isn't over yet.

    I've rambled, I know. But I hope that's a good start for you. Perhaps I can help get you hooked up with some shops that can do some of these mods for you.

    Let me know what else I can help with!

    DKOV -

  3. #3

    Re: Paging DKOV! *May I pick your brain? 3.4 DOHC

    Thanks for the reply. I spent all last night, till about 5 AM reading posts on GMForums.com. Great Fiero section, and great secion on 60 v6's. I linked a lot of items but now I need to organize it because my favorite places is getting unruley. There is an interesting link to someone who did a custom manifold for a newer style engine. I'll post it when I dig it out.

    Cam phasing was mentioned, but no one seems to be absolutely sure as what to use, so they just post their results which makes it not very scientific, usually with other simultaneous mods.

    Have you dynoed your car yet? Or G-teched it?

    I was all ready to do a 3.4 bottom end and call it a day for now. I was looking at turbocharging later (BTW they have an awesom thread going on there on turbocharging. Tons of links to the stuff we would all need) I have talked to Turbonetics on recommendations for the pushrod 3.4, now I will have to speak with them in reference to a Twin cam setup... see if it matters or not. After reading your posts, I got really interested in your engine... earlier I was leaning towards a newer style, for the simple reason that later versions tend to, but not always, have useful refinements. The North Star is so wide most people can barely get it in there, and usually have to cut the deck lid torsion bars. I assume that this problem exists for the V6 version and that it is due to the wider 90 degree.

    There is something to be said for the older motors, pre-OBDII, and for those interested, it seems relatively simple to use the computer from a Grand Prix Turbo. You can flash the eeprom, but the best part about it is it is set for Turbo use already. (this applies to the pushrod 3.4, 3.1, 2.8 people) That particular ECM was used in a variety of cars, so all one has to do is come up with the TGP chip, or a copy of the program in order to burn a new chip. There was a long discussion too on programing. (I wonder if this is the custom ECM Design One uses for the Stage Two setup... for all that extra money $800. How much do you want to bet?) As far as we are concerned, with the DOHC or TDC, we will have to be more creative but I'll bet that the programing from the 3.4 pushrod could be a good baseline. I like the Idea of a better flowing head (four valves) and a turbo.

    There is a GM Publication on the aurora for racing. They did, after all, have those in the 700-800 HP range in indy cars. I think I'll buy it because I am sure a lot of the info will translate over. The aurora and Northstar are virtually the same, and the LX5 as you mentioned is two cylinders shorter, but the same in principle. I am sure cam info if there is any well be realvent to your style of motor as well.

    It's a pain to phase cams in a normal car, but who wants to do it in a Fiero every time they make a dyno run!? Not me. Thats why I was looking to see if you had any specifics on the grinds you have and HP ratings. I'll Talk to Crane and CompCams and see if they have anything or any ideas. They already have a grind for a 3.4-2.8 Turbo.

    For what it's worth, I use to program on the fly with the Accel DFI system in my 87 GTA. I built a custom 355 for that car and I had it doing 145+ (before we ran outta road) with 5 people in it, and still got 28 MPG Cruising at 70MPH. Programming in that realm I can handle, but some of the stuff on the GM forum was way over my head, it might take me a while to catch up with some of it. One good point though, apparently, if one has the right equipment, and it dosn't cost much, you can save programs and simply reprogram eeproms and pop them in and try them. On the fly would be better, but it is a lot cheaper than a Haltech or other type. And if the program is trash, just flash the prom and burn it with a new program!! Pretty cool stuff.

    My target here is 300 HP Naturally aspirated. I think it is attainable with your engine or the new LX5. And that is applying regular ol hot rodder techniques. If they had 270 HP for real, then I think with porting and polishing and a few other changes that 300 is a real good baseline. Add a turbo and the extra is gravey.

    One more note on related drive train stuff. The Cadillac CTS is a manual car (although it has RWD). 220 HP short star... but there are rumours of a more sporty version in 04 with higher output. GMpowertrain dosnt have much info on the new motors yet (the ones coming) but they did have some specs on the new style getrags, and the setup in the Grand prix G-force is the same thing we have in the Fiero. The CTS may make a good computer setup to run with a stick for those leaning to the new style motors. The G-force has the 3800 Supercharged motor, 280 HP 280 Ft/lbs torque, with a new gizmo called tackshift, similar to the Ferrari Paddle shifters on the 355, located on the steering wheel! Now isnt that cool... just what we need for the 355 kits to give them that extra authenticity.

    Ok, that oughtta get things rollin... Your turn Mr. DKOV. I want all the gorey details, and hell, if you don't have hardcore numbers talk to me about my new GTech pro. If I have to I will send it to you to run us a good baseline before you rip apart your beast. Very accurate toy, and cheaper than a dyno, although not much cheaper than a dyno run.

    Thanks, Alex

  4. #4
    Junior Member
    Join Date
    Mar 2002
    Posts
    5

    Re: Paging DKOV! *May I pick your brain? 3.4 DOHC

    I got to drive DKOV's Fiero again today. BIG GRIN.
    This car has 300+ available. If you can get close to this engines performance you will be pleased.

    I don't know why nobody else believes how fast and how much TORQUE this motor has.

    Experience is what you get when you don't get what you want!!

  5. #5

    Re: Paging DKOV! *May I pick your brain? 3.4 DOHC

    Well, if he lived closer I'd get him to take me for a drive! ;D

    I've been researching the 3.5 (short star). The theory goes like this, the Aurora was used in Indy racing... GM has a manual out for building aurora race engines (I ordered it), and the Northstar is based on the Aurora, IE so is the 3.5, just minus two cylinders.... and if this is true, the Aurora racing manual I hope will have cam timing and other mods for more ponies... maybe it can apply to the 3.4 as well. I am leaning towards a 3.4 based on his performance figures, but I will wait till I have the info on the Aurora to see if there is any advantage to going with the newer 3.5. One disadvantage is size, it is wider. :-[

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