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Thread: 94 K3500 454 Vortec

  1. #1
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    94 K3500 454 Vortec

    I wanted to take a moment to post my experience with the Flash II with port mod. I have a 94 K3500 that came from the factory with tbi, 5 speed, and 4.56 gears front and rear. The performance and fuel mileage was underwhelming to say the least. With the help of David from Old School EFI I was able to boost performance and fuel mileage but low speed drivability was still not great. David brought up a conversion and was able to locate an intake and injector package for 96 and up Vortec EFI. I found a set of vortec heads and after having the heads checked I installed the whole Vortec top end with the addition of 36lb injectors and a 255lph pump. The original ecm for this setup was a modified 7427 ecm that worked great with the exception of a random hanging open of all eight injectors flooding the engine and keeping the pump running with the KOEO. This occured when priming the fuel system and if you immediately went to cranking the engine you would have never known this was going on. After speaking about this with David and trying to correct the issue I sent an email to Dynamic EFI. The first thing I noticed was a willingness to help on a system they had nothing to do with which made the decision to buy their product alot easier. I purchased a Flash II with port mod and connectors for the ecm and in a relatively short time and help from Bob at Dynamic EFI and David at Old School EFI I was able to get my dually dialed in and reliable. I was also able to accomplish each goal I had for the truck. The truck is more powerful and low speed drivability is incredible and after putting around 600 miles on the new ecm I recorded a best 16.73 miles per gallon checking this buy fuel usage checked at the pumps and not on just the trip program in the WUD. I have gotten to test this new setup in -5 degree weather up to 70 degree weather and in town traffic as well as the interstate. We live in the mountains and this is my four wheel drive vehicle to get us in and out so reliable was extremely important to me. The tuning help from Bob and David as well as the info in the program and on the sight has been second to none. Having tuned quite a few standalone ecms from AEM, Holley, SDS, Fast, and Ecumasters on my Supra I have had alot of dealing with aftermarket systems so it was nice to see this system do everything as advertised. It is nice when you command a change a see and feel it happen on your wideband and seat of your pants dyno. With OBD1 stuff being harder to find I just wanted to say thank you for an amazing product and some amazing help from two great companies. Sorry about the long post and in case anyone is interested the setup is a Gen 5 short block with the stock tbi flat tappet cam, Vortec heads converted to an adjustable valvetrain, Gen 6 intake and Fast 36lb injectors, tbi distributor and Hedman headers with dual 3 inch exhaust. The cam was left in due to covid wiping out all hydraulic roller cams at the time of this build. Truck weighs 6500lbs empty and is a 5 speed with 4.56 gears and 126,000 miles on the truck and bottom end.

    Sean
    Last edited by X-man; 01-30-2023 at 04:45 AM.

  2. #2
    Super Moderator dave w's Avatar
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    Quote Originally Posted by X-man View Post
    I wanted to take a moment to post my experience with the Flash II with port mod. I have a 94 K3500 that came from the factory with tbi, 5 speed, and 4.56 gears front and rear. The performance and fuel mileage was underwhelming to say the least. With the help of David from Old School EFI I was able to boost performance and fuel mileage but low speed drivability was still not great. David brought up a conversion and was able to locate an intake and injector package for 96 and up Vortec EFI. I found a set of vortec heads and after having the heads checked I installed the whole Vortec top end with the addition of 36lb injectors and a 255lph pump. The original ecm for this setup was a modified 7427 ecm that worked great with the exception of a random hanging open of all eight injectors flooding the engine and keeping the pump running with the KOEO. This occured when priming the fuel system and if you immediately went to cranking the engine you would have never known this was going on. After speaking about this with David and trying to correct the issue I sent an email to Dynamic EFI. The first thing I noticed was a willingness to help on a system they had nothing to do with which made the decision to buy their product alot easier. I purchased a Flash II with port mod and connectors for the ecm and in a relatively short time and help from Bob at Dynamic EFI and David at Old School EFI I was able to get my dually dialed in and reliable. I was also able to accomplish each goal I had for the truck. The truck is more powerful and low speed drivability is incredible and after putting around 600 miles on the new ecm I recorded a best 16.73 miles per gallon checking this buy fuel usage checked at the pumps and not on just the trip program in the WUD. I have gotten to test this new setup in -5 degree weather up to 70 degree weather and in town traffic as well as the interstate. We live in the mountains and this is my four wheel drive vehicle to get us in and out so reliable was extremely important to me. The tuning help from Bob and David as well as the info in the program and on the sight has been second to none. Having tuned quite a few standalone ecms from AEM, Holley, SDS, Fast, and Ecumasters on my Supra I have had alot of dealing with aftermarket systems so it was nice to see this system do everything as advertised. It is nice when you command a change a see and feel it happen on your wideband and seat of your pants dyno. With OBD1 stuff being harder to find I just wanted to say thank you for an amazing product and some amazing help from two great companies. Sorry about the long post and in case anyone is interested the setup is a Gen 5 short block with the stock tbi flat tappet cam, Vortec heads converted to an adjustable valvetrain, Gen 6 intake and Fast 36lb injectors, tbi distributor and Hedman headers with dual 3 inch exhaust. The cam was left in due to covid wiping out all hydraulic roller cams at the time of this build. Truck weighs 6500lbs empty and is a 5 speed with 4.56 gears and 126,000 miles on the truck and bottom end.

    Sean
    Thank you for sharing your experience / review about Dynamic EFI and me (Old School EFi)

    The Excel spreadsheet I developed for Dynamic EFI was helpful.

    Lower AFR Averages.jpg

    Upper AFR Averages.jpg

  3. #3
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    Was the flooding problem tied to anything?

  4. #4
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    Quote Originally Posted by ras"86 View Post
    Was the flooding problem tied to anything?
    Best I can figure is something in the 7427 ecm was not happy being converted to run the multiport setup. I bought an extra set of injectors and a brand new distributor to see if that made any difference and it didn't. I checked and rechecked my wiring and I also had another 7427 ecm converted with another memcal and it still did it. Once the Dynamic EFI ecm was installed it has not happened since and I made a point to prime it everytime on start up to make sure. Again you don't have to prime it but that is a habit I got into with my 97 S10 because of a bad check in the fuel pump letting the rails empty leading to prolonged cranking. I actually was curious if maybe the distributor was landing on a tooth in the pickup wheel causing it to trigger something. I would get out and physically unplug the injector adapter and start it to run all the fuel out of it, then plug it back in and it would be fine.
    Last edited by X-man; 01-30-2023 at 08:36 PM.

  5. #5
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    Quote Originally Posted by X-man View Post
    Best I can figure is something in the 7427 ecm was not happy being converted to run the multiport setup. I bought an extra set of injectors and a brand new distributor to see if that made any difference and it didn't. I checked and rechecked my wiring and I also had another 7427 ecm converted with another memcal and it still did it. Once the Dynamic EFI ecm was installed it has not happened since and I made a point to prime it everytime on start up to make sure. Again you don't have to prime it but that is a habit I got into with my 97 S10 because of a bad check in the fuel pump letting the rails empty leading to prolonged cranking. I actually was curious if maybe the distributor was landing on a tooth in the pickup wheel causing it to trigger something. I would get out and physically unplug the injector adapter and start it to run all the fuel out of it, then plug it back in and it would be fine.
    What conversion was used for mpfi? I'm considering doing one to my 94 suburban, going with a 98 L31 and 6395.

  6. #6
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    Not sure which part of the conversion you are asking about but the mechanical was an L29 top end with Fast 36lb injectors and an L19 distributor. Fuel lines were custom. The ecm started as the original 7427 ecm and was swapped out for a Dynamic EFI EBL Flash II with port mod.

  7. #7
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    Just trying to understand if it was something in the changes posted by 93V8s10 MPFI.zip. Posted here. Thanks.

  8. #8
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    Quote Originally Posted by ras"86 View Post
    Just trying to understand if it was something in the changes posted by 93V8s10 MPFI.zip. Posted here. Thanks.
    The best person to speak with on that would be David at Old School EFI. He is a wealth of knowledge on that kind of info. I know when I started this process he sent me an email on the process I would be more than happy to forward them to you if you want to email me. Supraman500hp@gmail.com

  9. #9
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    I may do that, Thanks.

  10. #10
    Super Moderator dave w's Avatar
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    I've been successful with several MPFI conversions. I'm dumbfounded what was causing the flooding. The origins of the MPFI conversion were from HP Tuners.

  11. #11
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    I'm going to change to a l31 and wanted to go mpfi and trying to get every thing ready. Still considering a 0411 but have concerns about the 4l60e.

  12. #12
    Super Moderator dave w's Avatar
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    The 16197427 MPFI conversion is a good option for the L31. It the budget is available, an 0411 / L31 is a better option.

  13. #13
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    I have the 6395, would like the 0411but I'm concerned about the 94 4l60 with 0411. Time to check my local supplier, junkyard.

  14. #14
    Super Moderator dave w's Avatar
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    Quote Originally Posted by ras"86 View Post
    I have the 6395, would like the 0411but I'm concerned about the 94 4l60 with 0411. Time to check my local supplier, junkyard.
    6395 can also be modified for MPFI. To the best of my knowledge, the 0411 only works with 1996 and newer 4L60E's.

    0411 requires wire harne$$ work.

  15. #15
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    That's what I thought, ill probably modify my 6395 or a 7427 and keep it simple for now . What changes were made to the 4l60?

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