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Engine HP questions

Discussion in 'The Garage' started by ZK5, Dec 19, 2003.

  1. ZK5

    ZK5 1/2 ton status

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    Is it possible to bore and stroke my factory 1987 SBC engine install flat tops and have the heads opened up, install a mild cam AND STILL keep my factory ECM AND pass emissions. /forums/images/graemlins/confused.gif
     
  2. sled_dog

    sled_dog 1 ton status

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    in a word, HELL NO. You can keep the factory ECM but its gonna get reprogrammed big time, and passing emissions is a very little likelihood. My K5 passed emissions with no cats and stock motor that burned quite a bit of oil, built a brand new motor with nothing special but a very mild tow cam, won't pass emissions.
     
  3. ZK5

    ZK5 1/2 ton status

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    Well, I don't think "HELL NO" was the answer I was lookin for /forums/images/graemlins/frown.gif Wonder if I would stand a chance if I had a chip made.
     
  4. sled_dog

    sled_dog 1 ton status

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    yeah I am an idiot so don't mind me. With a cat and air pump setup emissions may not be a horrible dream but I'd say no. Definetally need a chip. I just noticed I said "in a word, hell no"... 2 words...
     
  5. fortcollinsram

    fortcollinsram 1/2 ton status

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    IMO, with the right tuning YES it will be able to pass the smogger...I consider any cam that is capable of working well with the factory TBI ECM as VERY mild...Just for grins, my buddy and I hooked up my truck to the smog machine where he works (he does e-testing at a repair facility in town) just to see what I would blow...Keep in mind that this is a built 454. Bored .030" over, Flat Top pistons, Crane 2030 cam, cranked up fuel press. a bit but still the stock 454 Prom chip. Now it DIDN'T pass, but it was VERY close...I still have the single wire O2 in my full length headers and it is running like poo b/c the O2 NEVER gets hot. I feel that if I spent some time and installed the 4-wire O2 I have sitting here and adjusted the fuel pressure according to the O2 readings, I would have NO problem passeing smog...BUT I have my truck registered in another county as I have no emissions equipment on my truck but I am confident that with some careful tuning, it would pass. Of and it is FAR from the stock 87 350 TBI that once lived under the hood So I feel you well be able to get your to pass after a MILD rebuild EASILY...


    Your OE ECM will work FINE as long as you don't change the over all displacement of the motor by more than something like 5% (I can't remember the exact umber but it is something like 5% or 7%). Your ECM doesn't care if you have dished pistons, FT pistons or a stupid big dome piston that will barely clear the valves.

    The aboslute biggest thing with TBI systems is to keep the duration on the cam LOW...which is actually benefical for a motor you are building for torque. If I were you I would shhot for a cam that has about 204* duration at .050" on the intake side...
    The Stock TBI heads S. U. C. K., suck! I would spend the $$$ and get some Vortec heads or some decent aftermarket heads...You will see GREAT power gains over the stock heads. /forums/images/graemlins/thumb.gif
     
  6. 99firehawk

    99firehawk 1/2 ton status

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    There are many daily driven, smog passing 11 and 10 second cars out there. I find it hard to belive that tbi isnt as tuneable as other modern fuel injection. Just find some one that knows how to tune them and keep the cam on the mild side you should be ok.
     
  7. Thunder

    Thunder 3/4 ton status

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    Shouldn't be too much of a problem if you have the bucks to get the right chip burned for it and some bigger injectors. If you try to run that setup on a stock chip. You wont have to worry about smog. Your engine will blow before you have to get a smog test.
     
  8. fortcollinsram

    fortcollinsram 1/2 ton status

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    [ QUOTE ]
    If you try to run that setup on a stock chip. You wont have to worry about smog. Your engine will blow before you have to get a smog test.

    [/ QUOTE ]
    Why will running the stock PROM chip with FT pistons and a mild cam cause his motor to blow?Sure the motor will need more fuel, but there are fuel pressure regulators on the market for a reason. And tuning a speed-density system like TBI couldn't be easier. All you need is the aforementioned FP regulator, a digital voltmeter and an O2 sensor and some patience. I have seem MANY built motors with TBI that live LONG happy lives. I have seen many guys with roller-cammed 454's with a STOCK TBI ECM put down SERIOUS power and still run a very engine-happy A/F ratio. TBI systems are honesly DUMB and you can change the fuel ratio easily. TBI is nothing more than a smart-carb, IMHO
     
  9. Derf00

    Derf00 1/2 ton status

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  10. fortcollinsram

    fortcollinsram 1/2 ton status

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    Well yeah, an increase in the rated HP of a motor of 65% will def. require some attention in tuning to keep it from running lean at WOT. And the GMPP 330 crate has a pretty bumpy cam for a TBI system with a cam that has 212*/222* I/E at .050". That is pushing the practical limits for the stock ECM IMO. You can make the TBI work on anything, but the key is to make it work WELL and reliably which requires attnetion to detail and proper tuning via the O2 sensor. Otherwise you WILL run the motor WAY lean at WOT and burn holes in your pistons. My 454 at WOT is shiowing .900mV at the O2 with is just a little rich but it is def. getting enough fuel...

    Chris
     
  11. ZK5

    ZK5 1/2 ton status

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    Well heres another plan. I have an 87 Iroc. it's also an 87 305 I'm thinkin bout swappin the complete induction system, computer and wiring harness over to the truck in addition to reworking or replacing the heads.

    Any thoughts?
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    I like that idea. /forums/images/graemlins/smile.gif

    Take everything and swap it over, have to work around some issues, but it would be a nice engine.

    Pretty much what I've done with mine, except I went with Vortec heads. Don't get any ideas though, Vortec heads and TPI don't mix. (cheaply that is) There are a couple of choices in the $5-700 range for a pair of heads that should work awesome for you though.
     
  13. ZK5

    ZK5 1/2 ton status

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    OK, heres what I ended up doin. I decided to do the TPI swap. I sent the block out to have the crank line bored and the bottom end studded and the cylinders bored .060 over it was already .040 over anyway. Then I ported and polished the factory vortec TPI heads and sent them out to have them machined for screw in studs and a valve job and cleaning. Then the entire rotating assembly was then balanced to within an eight of a gram. The cam is very mild with a 254 duration and a 401 lift @ valve. Then I swapped in 1.7 ratio gold race roller rockers from Crane increasing the valve lift to 454. The pistons will be Wiseco forged flat tops w 2 valve reliefs I went forged for the option of adding a supercharger in the future. As far as the wiring for the TPI swap I used the painless kit it's a MAF system not speed density. The electrical is all set and waiting for me to drop the engine in. I also opened up the TPI's plenum and runners and polished them up to. I port matched the intake and sent that out to be coated. along with the Edelbrock TES headers. All thats left to do after the motor comes back is to swap out the TBI fuel pump for the TPI pump and connect it all. I've been told I don't need to have a chip burned it will run fine. But it would help the performance and It's not that expensive anyway.

    any thoughts?
     

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