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Thread: 3.4L DOHC Rebuild -DKOV

  1. #1
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    Jul 2002
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    3.4L DOHC Rebuild -DKOV

    You seem to be the resident 3.4L authority.

    I'm seriously considering purchasing this engine and building it up like my 385hp (at the wheels) normally aspirated 1.8L B18c DOHC VTEC.

    Below is the work I had done and would like to duplicate.

    Engine cleaned, balanced & blueprinted
    Head ported & polished, 3 angle valve job & resurfaced/decked
    Block line honed or sleeved & resurfaced
    Chrome Moly or Forged Higher Compression Pistons
    Chrome Moly or Forged Rods
    Chrome Moly rings
    Tulip shaped titanium valves
    Higher flow injectors & larger fuel pump
    Power Pulley
    Higher Lift Cam
    Bigger Bore Trottle Body
    Cone Air Filter with ceramic downpipe
    Mandrel Bent ceramic manifolds with 2" down pipes
    High flow coverter & muffler

    Is any of this not available or possible with this engine? what other modifications do these engines allow?

    What engine work did you have done?

    What is the best year to go with?

    What are the hp limitations of the individual parts of the stock bottom end (block, rods, pistons & Crank).

    Are the rods, crank & pistons in this engine cast iron? If so are there chrome moly or forged parts available aftermarket

    Attack Roadster, F355 Spyder, F512TR Coupe &amp; Diablo Roadster<br /><br />If only money grew on freaking trees!!!

  2. #2
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    Dec 2001
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    Re: 3.4L DOHC Rebuild -DKOV

    Resident? Yes... Authority? No way

    I am not sure just how much is translated between the GM 3.4L DOHC and your 1.8L B18c DOHC VTEC so I'll due the best I can

    The 3.4L DOHC is factory balanced with forged rods already. There was, for a short time, a forged crank option to replace the stock cast crank after a recall made by GM. There are aftermarket pistons but no other aftermarket bottom end parts that I am aware of. Valve grinds are 3 or 5 angle (I went with three).

    Decking the Head will give you another point to 1.5 in compression if you are after that but if you ultimately have plans for forced induction, I wouldn't go that route unless you intend to replace the factory gaskets with o-rings.
    I'm all for porting and polishing. The intake is paramount... upper and lower. I also ported/polished and enlarged my Throttle Body allowing for more airflow and much faster throttle response time.

    So far, I haven't found any need for increasing the injector size or flow rate, but did add a Stillen fuel pressure riser system to compensate for the revs/airflow and fuel needs. It provides an increase in pressure of up to 25 additional pounds or so.

    Exhaust is important and I went with 2.5 inch, NO cat and very limited mufflers. In fact, you might argue after seeing my car, that I have none at all In my case, I found the stock headers to be more than adequate for airflow and with minor polishing, have proven to be very efficient.

    CAMS... Here is a place to get some serious HP increases but note that there are NO aftermarket cams for the 3.4L DOCH or TDC motors. You'll have to get a CUSTOM cam ground. Be carefull though... Go to much toward ultimate HP, and you loose usable low end torque. It's a balance, trust me! Plus, with the 3.4L DOHC or TDC motor, you have FOUR cams to grind!!! That's some ching! Add to that, 3-angle grinding 24 valves... Sheesh!

    I've been asked which 3.4L DOHC is the best to get many times. Answer is, NONE of them... The motor was built from late 1990 to 1996 or 1997. The 1990/91 and the 1992 motors were known as 3.4L TDC or Twin Dual Cam. THESE motors are, in my opinion, the best to get.

    The late 1990 motor and some of the early 1991 motors that were installed in the Pontiac Grand Prix particularly, had some serious advantages...

    NO speed limiter
    NO MAF sensor
    HIGHER Rev Limiter
    In some VERY rare cases, 275 BASE HORSE POWER
    Plus, as an added bonus, that were mated to a factory Getrag 284 5 speed tranny!!!

    The Coil packs on these motors were located underneath the started against the block. Once installed in a Fiero, they don't get much airflow so it becomes neccessary to relocate them to a different location... In a COOLER place

    What I did is relocate my battery to the front compartment and mounted the coil packs where the battery and tray had been removed. Not only looks good but is VERY functional!

    The 1993 - 1996/97 motos have the coil packs mounted up on top next to the TB so it's easy to spot them. Also, the TB is completely different.
    What work have I done? Alot... Nearly everything I can think of. Let me clarify, work I "had done"... I'm no machinist

    I've mentioned the porting and polishing and enlarging of the TB, upper and lower intakes and headers. Valve job, Head Decking. The exhaust system I talked about. Fuel Pressure Riser...

    I also reduced toating mass by removing the power steering pump/pulley and fabbing an idler. Added a crank shaft Underdrive or Power Pulley. Had the heads done with copper o-rings rather than factory gaskets. New rings and seals were done at the time of install.

    All in all, it benches out at 322.xx HP. Not to shabby if you ask me

    I am currently installing a Turbo system onto this motor currently and will have the newer forged pistons installed with new rings/seals. This is a custom self-designed kit that requires a few components to be installed so the car will be down for a while I suspect.

    The turbo will put out 18 lbs of boost although I will never run that. I'll run 7 lbs to begin with and maybe boost to 11 lbs if all goes well. 14 lbs is really pushing it I think. Using a very basic formula, if I did run at 14 lbs, I'd be putting 550 +HP!!! I'll be plenty happy with 450HP though

    That's alot of stuff to talk about and I probably missed something... If you have any other questions, hit me. I'll do the best I can

    DKOV -

  3. #3
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    Join Date
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    Re: 3.4L DOHC Rebuild -DKOV

    The 3.4L DOHC is factory balanced with forged rods already. *There was, for a short time, a forged crank option to replace the stock cast crank after a recall made by GM. *There are aftermarket pistons but no other aftermarket bottom end parts that I am aware of. *Valve grinds are 3 or 5 angle (I went with three).
    Hmmm do you think the forged crank is still in the GM Performance Catalog?

    Oh goodness No rods! *

    What's the compression ratio on the stock pistons

    As for valve grids. I was planning 5 angle intake & 3 angle exhaust.

    Decking the Head will give you another point to 1.5 in compression if you are after that but if you ultimately have plans for forced induction, I wouldn't go that route unless you intend to replace the factory gaskets with o-rings.
    hmmmmmmmm. What about composite gaskets

    I'm all for porting and polishing. *The intake is paramount... upper and lower. *I also ported/polished and enlarged my Throttle Body allowing for more airflow and much faster throttle response time.
    How much did you overbore it? Is your engine the one with the attached trottle body?

    Exhaust is important and I went with 2.5 inch, NO cat and very limited mufflers. In fact, you might argue after seeing my car, that I have none at all *In my case, I found the stock headers to be more than adequate for airflow and with minor polishing, have proven to be very efficient.
    How the hell did you pass the smog tests?

    Arent the stock headers unbalanced?

    Did you have the headers match ported with the head?

    CAMS... *Here is a place to get some serious HP increases but note that there are NO aftermarket cams for the 3.4L DOCH or TDC motors. *You'll have to get a CUSTOM cam ground. *Be carefull though... *Go to much toward ultimate HP, and you loose usable low end torque. It's a balance, trust me! *Plus, with the 3.4L DOHC or TDC motor, you have FOUR cams to grind!!! *That's some ching! *Add to that, 3-angle grinding 24 valves... *Sheesh!
    Oh dam, this is the next biggest hp boost next to porting.

    Did you have this done? What was the cost?

    The 1990/91 and the 1992 motors were known as 3.4L TDC or Twin Dual Cam. *THESE motors are, in my opinion, the best to get.

    The late 1990 motor and some of the early 1991 motors that were installed in the Pontiac Grand Prix particularly, had some serious advantages...

    NO speed limiter
    NO MAF sensor
    HIGHER Rev Limiter
    In some VERY rare cases, 275 BASE HORSE POWER
    Plus, as an added bonus, that were mated to a factory Getrag 284 5 speed tranny!!!
    So i guess your recommending the 1990-91 Pontiac Grand Prix motors

    Is there a particular vin I should look for from those years, to guarantee i get the right motor?

    I've mentioned the porting and polishing and enlarging of the TB, upper and lower intakes and headers. *Valve job, Head Decking. *The exhaust system I talked about. *Fuel Pressure Riser...

    I also reduced toating mass by removing the power steering pump/pulley and fabbing an idler. *Added a crank shaft Underdrive or Power Pulley. *Had the heads done with copper o-rings rather than factory gaskets. *New rings and seals were done at the time of install.

    All in all, it benches out at 322.xx HP. *Not to shabby if you ask me
    Is that 322 at the wheels or flywheel?

    My engine budget is about $10,000-$11,000. Do you think this would cover: the engine & 284 getag costs, swap & rebuild parts & labor?

    Does ACE or Design One do engine rebuilds?

    I have to find someplace familiar with the 3.4L dohc with a dyno, flow bench and the proper stones to resurface alluminum. This hasn't been the easiest combination to locate.

    I am currently installing a Turbo system onto this motor currently and will have the newer forged pistons installed with new rings/seals. *This is a custom self-designed kit that requires a few components to be installed so the car will be down for a while I suspect.

    The turbo will put out 18 lbs of boost although I will never run that. *I'll run 7 lbs to begin with and maybe boost to 11 lbs if all goes well. *14 lbs is really pushing it I think. *Using a very basic formula, if I did run at 14 lbs, I'd be putting 550 +HP!!! *I'll be plenty happy with 450HP though
    Whoa! I'll be happy with around 320hp 330hp.

    Will your setup have external blow off valve & Intercooler?

    Attack Roadster, F355 Spyder, F512TR Coupe &amp; Diablo Roadster<br /><br />If only money grew on freaking trees!!!

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