Page 2 of 3 FirstFirst 123 LastLast
Results 16 to 30 of 33

Thread: Setting base timing for performance cam

  1. #16
    Fuel Injected!
    Join Date
    Mar 2013
    Location
    Federal Way, WA
    Age
    53
    Posts
    54
    Never mind. Found what I was looking for. Now to find some injectors.

    What would be the part number for 305 injectors?
    Last edited by srgould41; 04-25-2013 at 10:05 AM.

  2. #17
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    2,019
    Quote Originally Posted by srgould41 View Post
    What would be the part number for 305 injectors?
    5235279

    http://www.gearhead-efi.com/Fuel-Inj...d-part-numbers

    Interesting information on the most recent set of 350 injectors (5235206) I sent out for service.

    dave w
    Attached Images Attached Images
    Last edited by dave w; 04-25-2013 at 09:43 AM.

  3. #18
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    2,019
    Quote Originally Posted by srgould41 View Post
    Now to find some injectors.
    I've got some used 305 injectors. Want to trade your 350 injectors for a set of 305 injectors?

    dave w

  4. #19
    Fuel Injected!
    Join Date
    Mar 2013
    Location
    Federal Way, WA
    Age
    53
    Posts
    54
    Absolutely! I don't know the state of mine. I pulled one out last night to get the numbers off it. They are a little rusty on the bodies.

  5. #20
    EFI GearHead ! EagleMark's Avatar
    Join Date
    Feb 2011
    Location
    North Idaho
    Age
    54
    Posts
    10,477
    Quote Originally Posted by srgould41 View Post
    I am running about 52* total timing and the engine loves it. Like the old saying goes, give the engine what it wants, not what you think it needs.
    You sure? Are you super rich? Something is wrong? 50* is nitro top fuel timing and their spark plugs melt before the end of 1/4 mile but magneto will spark to anything at that point...

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  6. #21
    EFI GearHead ! EagleMark's Avatar
    Join Date
    Feb 2011
    Location
    North Idaho
    Age
    54
    Posts
    10,477
    Quote Originally Posted by dave w View Post
    5235279

    http://www.gearhead-efi.com/Fuel-Inj...d-part-numbers

    Interesting information on the most recent set of 350 injectors (5235206) I sent out for service.

    dave w
    Although his machine does excellent service on TBI injectors, the flow is not all that accurate at TBI pressures. It's not designed for the low pressure.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  7. #22
    Fuel Injected!
    Join Date
    Mar 2013
    Location
    Federal Way, WA
    Age
    53
    Posts
    54
    I have no rich running trouble now. That's for sure. I even added around 2 turns out on the mixture screws. Note that my fuel economy is about the same. So I gained very noticable power for no loss in economy.

    I did all the tuning after weeks of research and discussions on other forums, lots of trial and error, lots of testing and hard pulls, etc.

    Quote Originally Posted by EagleMark View Post
    You sure? Are you super rich? Something is wrong? 50* is nitro top fuel timing and their spark plugs melt before the end of 1/4 mile but magneto will spark to anything at that point...

  8. #23
    Fuel Injected!
    Join Date
    Feb 2013
    Location
    Euless, TX
    Posts
    792
    Quote Originally Posted by dave w View Post
    350 injectors / stock 350 chip on a 305 would be bad! 350 injectors / stock 305 chip on a 305 would be bad! 305 injectors / stock 350 chip / stock 305 chip, would be OK, but not great because of the cam specs.

    dave w
    Having done this swap before, 305 injectors on this 305 would be BAD. Mine ran best on the stock 350 chip and 350 injectors. Had to correct the BPW in the chip and rework the VE table to make it run best. Also had to give it about 10* initial at the distributor.

    I had a Mellings MTC1 204/214 @ .050, .420/.442" lift, 112 LSA, 107 ICL in my 1983 G20s stock 305 with a 92 350 TBI intake, TBI, exhaust manifolds and exhaust system.

    The stock 305 injectors and stock chip are so lean even at 16 psi (the highest I could get the stock pump to output) it was too lean to be driveable.
    Last edited by Fast355; 04-26-2013 at 09:52 AM.

  9. #24
    Fuel Injected!
    Join Date
    Feb 2013
    Location
    Euless, TX
    Posts
    792
    Quote Originally Posted by EagleMark View Post
    You sure? Are you super rich? Something is wrong? 50* is nitro top fuel timing and their spark plugs melt before the end of 1/4 mile but magneto will spark to anything at that point...
    I am going to say his dampner has either slipped or he has the wrong one for his timing cover.

  10. #25
    Fuel Injected!
    Join Date
    Feb 2013
    Location
    Euless, TX
    Posts
    792
    Quote Originally Posted by EagleMark View Post
    Some HEI without vacuum only add 12 degrees through centrifugal advance and depending on weights none at idle. So 20+ is not uncommon on carb with a big cam engine.

    TBI base I always use 0 because it effects injector timing, but in the cal usually 23 for a good idle... it has to drop off idle...
    I always used 6-14* on my setups, especially with a CAM. Makes it easier to start and also brings the fuel delivery in earlier to match the longer duration cams. It also makes the engine run better if the EST should ever go into limp home mode, disabling the ECM controlled advance.

  11. #26
    Fuel Injected!
    Join Date
    Mar 2013
    Location
    Federal Way, WA
    Age
    53
    Posts
    54
    My damper has not slipped. I used a piston stop to degree it. The timing marks line up correctly.

  12. #27
    Fuel Injected!
    Join Date
    Mar 2013
    Location
    Federal Way, WA
    Age
    53
    Posts
    54
    My cam has the exact same specs as yours. It's even out of the same year and vehicle ;)

    David, any thoughts on his comment about the injectors and timing?

    My Holly Blue pump is modded for 18 PSI, but I have not modded the TBI regulator.

    Quote Originally Posted by Fast355 View Post
    Having done this swap before, 305 injectors on this 305 would be BAD. Mine ran best on the stock 350 chip and 350 injectors. Had to correct the BPW in the chip and rework the VE table to make it run best. Also had to give it about 10* initial at the distributor.

    I had a Mellings MTC1 204/214 @ .050, .420/.442" lift, 112 LSA, 107 ICL in my 1983 G20s stock 305 with a 92 350 TBI intake, TBI, exhaust manifolds and exhaust system.

    The stock 305 injectors and stock chip are so lean even at 16 psi (the highest I could get the stock pump to output) it was too lean to be driveable.

  13. #28
    Fuel Injected!
    Join Date
    Mar 2013
    Location
    Federal Way, WA
    Age
    53
    Posts
    54
    It personally makes sense to me being a carb guy. Yes, I'm old ;)

    I have proven that my engine likes the spark advance to by high.

    Quote Originally Posted by Fast355 View Post
    I always used 6-14* on my setups, especially with a CAM. Makes it easier to start and also brings the fuel delivery in earlier to match the longer duration cams. It also makes the engine run better if the EST should ever go into limp home mode, disabling the ECM controlled advance.

  14. #29
    Super Moderator dave w's Avatar
    Join Date
    Feb 2011
    Posts
    2,019
    Quote Originally Posted by srgould41 View Post
    My cam has the exact same specs as yours. It's even out of the same year and vehicle ;)

    David, any thoughts on his comment about the injectors and timing?

    My Holly Blue pump is modded for 18 PSI, but I have not modded the TBI regulator.
    "Had to correct the BPW in the chip and rework the VE table to make it run best."

    That's the key to tuning! There are slight tuning differences (VE ~ BPW) between engines, even when the engines are identical.

    I posted a Base Pulse Width (BPW) calculator here: http://www.gearhead-efi.com/Fuel-Inj...BPW-Calculator

    The BPW calculator is usually accurate within +/- 2 BPW for the 1227747 for a mild performace cam, and usually dead on calculation with a stock cam.

    The only accurate way to tune is with data logs and wide band O2. Anything else is an estimate of what the engine needs. The BPW calculator would support my suggestion that a 305 engine with 305 injectors programmed with the stock BPW would be a good estimate to start with. The BPW calculator would support my suggestion that a 305 with 350 injectors programmed with the stock BPW would be rich.

    Without seeing what the actual corrections are for a specific engine, I would expect the BPW calculator to be "Close Enough" as a starting point for most mild cam upgrades. I've tuned engines that required small fuel pressure adjustments, and small BPW adjustments, after using the BPW calculator, but I had data to show how much change was needed.

    dave w

  15. #30
    Fuel Injected!
    Join Date
    Mar 2013
    Location
    Federal Way, WA
    Age
    53
    Posts
    54
    After thinking it over and over again, I agree that starting with a 305 chip and injectors is the way to start. What I end up doing later on will depend on just how it runs with the first chip. It's not a race car so I don't need every pony I can eek from it, but it does need to run well, especially at lower RPM's.


    Quote Originally Posted by dave w View Post
    "Had to correct the BPW in the chip and rework the VE table to make it run best."

    That's the key to tuning! There are slight tuning differences (VE ~ BPW) between engines, even when the engines are identical.

    I posted a Base Pulse Width (BPW) calculator here: http://www.gearhead-efi.com/Fuel-Inj...BPW-Calculator

    The BPW calculator is usually accurate within +/- 2 BPW for the 1227747 for a mild performace cam, and usually dead on calculation with a stock cam.

    The only accurate way to tune is with data logs and wide band O2. Anything else is an estimate of what the engine needs. The BPW calculator would support my suggestion that a 305 engine with 305 injectors programmed with the stock BPW would be a good estimate to start with. The BPW calculator would support my suggestion that a 305 with 350 injectors programmed with the stock BPW would be rich.

    Without seeing what the actual corrections are for a specific engine, I would expect the BPW calculator to be "Close Enough" as a starting point for most mild cam upgrades. I've tuned engines that required small fuel pressure adjustments, and small BPW adjustments, after using the BPW calculator, but I had data to show how much change was needed.

    dave w

Similar Threads

  1. Replies: 21
    Last Post: 04-24-2013, 04:37 PM
  2. Setting up my TBI
    By 1great40 in forum GM EFI Systems
    Replies: 23
    Last Post: 04-18-2013, 06:46 PM
  3. Setting up WB in the ADX editor.
    By POZE in forum TunerPro Tuning Talk
    Replies: 101
    Last Post: 02-06-2013, 04:50 PM
  4. Base timing for TBI-HEI with .060 spark plugs
    By helo in forum GM EFI Systems
    Replies: 5
    Last Post: 02-05-2013, 10:58 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •