Author Topic: L31-r longblock EFI Project  (Read 3937 times)

Offline frankentruck

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L31-r longblock EFI Project
« on: December 31, 2017, 06:11:06 PM »
I posted this elsewhere but I’m not sure if it was in the right spot...

Hello. Let me start by saying I’m not a mechanic. I’ve worked on small engines on motorcycles and air cooled vws. Other than that, just maintenance items on various vehicles. Let me also say, all in, I’m trying to keep this project under $4000 bearing in mind the longblock manifold, electronic ignition, EFI, serpentine setup and fuel tank/pump mods. Been kicking around what do with my truck for quite sometime now. Went back and forth on a Cummins swap, but decided to just buy a 1st gen cummins.

I finally settled on l31r vortec longblock from Chevy with a self learning efi system. I’m mostly focused on reliability and fuel economy. Don’t need a bunch of hp, just usable torque.

As the truck sits, it is a 327 with a t400 behind it. That little revver has to push my heavy 3/4 ton, t400, and Detroit locked 14-bolt & Dana 60 king pin front. It isn’t an ideal pairing. The fuel is supplied by dual saddle tanks, only one of which I use regularly. For now I’m sticking with that transmission until I can figure out something sweet like a 6l80e down the road.

My three questions are:

1. What is the best route on the fuel supply? Who makes the cheapest reliable solution to the efi fuel pump? I’ve seen quite a few inline ones that get okay feedback, but I can’t mount it lower than the k20s stock tanks, it would be to prone to getting damaged by a stick or rock. I don’t mind in tank setups as far as cutting one in (I’ll be using por -15 tank paint inside anyway). Who makes the most affordable in tank setup? I want to get ethanol compatible on pump, tank and lines.

2. Which EFI? I am leaning towards the newest version of the Holley sniper efi @$800-1100 depending on if you get their fuel supply setup. I like the feedback on their customer support. I know the more expensive units have the ability to control electronic trannies, but they are double the money and I can wait. Besides, most say they control 4l60e or 80e, not much about other trannies. By the time I get around to that, maybe stand alone tranny controllers will be cheaper..

3. Probably the most straight forward question. I’d like a link to an affordable flex plate for a one piece rear main 350 to a t400 trans.

My main concern is reliable pressure and something that can handle our horrible e15 fuel. This fuel is what has mudded up my current carbureted setup as the truck sees very occasional use. The amount of moisture our newer fuel out here sucks up is incredible!

Since these EFI systems have been out for a long while now and are getting more popular, I figured I’d rely on the most up to date knowledge from this forum, rather than the 5 year old posts google returns.


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Offline Stewart G Griffin

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Re: L31-r longblock EFI Project
« Reply #1 on: December 31, 2017, 07:20:12 PM »
) i don't know about cheapest, but the aeromotive system seems like the most straightforward/easiest way to go, unless you want to try stock GM:
https://www.youtube.com/watch?v=WzQr_12oHKk

What may end up as the cheapest reliable solution is to use a fuel resevoir system----because it may end up being the quickest/easiest way:
http://www.edelbrock.com/automotive/mc/efi/sump-fuel-kits.shtml
http://fitechefi.com/products/40003/

2) If it's an L31 why not try GM TBI?   Technically it's self-learning. ;)


Offline frankentruck

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Re: L31-r longblock EFI Project
« Reply #2 on: December 31, 2017, 07:28:48 PM »
) i don't know about cheapest, but the aeromotive system seems like the most straightforward/easiest way to go, unless you want to try stock GM:
https://www.youtube.com/watch?v=WzQr_12oHKk

What may end up as the cheapest reliable solution is to use a fuel resevoir system----because it may end up being the quickest/easiest way:
http://www.edelbrock.com/automotive/mc/efi/sump-fuel-kits.shtml
http://fitechefi.com/products/40003/

2) If it's an L31 why not try GM TBI?   Technically it's self-learning. ;)

It’s a vortec roller rocker block for a 1997-1999 3/4ton. I don’t want to deal with a wiring harness. All I have in the engine compartment are fuel and 12 volts.


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Offline frankentruck

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Re: L31-r longblock EFI Project
« Reply #3 on: December 31, 2017, 07:32:03 PM »
) i don't know about cheapest, but the aeromotive system seems like the most straightforward/easiest way to go, unless you want to try stock GM:
https://www.youtube.com/watch?v=WzQr_12oHKk

What may end up as the cheapest reliable solution is to use a fuel resevoir system----because it may end up being the quickest/easiest way:
http://www.edelbrock.com/automotive/mc/efi/sump-fuel-kits.shtml
http://fitechefi.com/products/40003/

2) If it's an L31 why not try GM TBI?   Technically it's self-learning. ;)

As for the fuel reservoir, I’ll be dropping the tank, cutting an access panel and painting in there anyway. Would you still recommend a reservoir? I want everything to be modernized for e15 fuel.


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Offline Stewart G Griffin

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Re: L31-r longblock EFI Project
« Reply #4 on: December 31, 2017, 07:37:02 PM »
TBI is only a few wires, but ok.....

If you're going to cut an access hole in the bed and dropping the tank anyways, then fine, i think that's a good way to do it.  For those who DON'T want to mess with the stock tank, i'm thinking the fuel resevoir would be the fastest/easiest way to get running. 
« Last Edit: December 31, 2017, 07:38:53 PM by Stewart G Griffin »

Offline frankentruck

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Re: L31-r longblock EFI Project
« Reply #5 on: December 31, 2017, 07:57:19 PM »
That aero motive system looks promising


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Offline frankentruck

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Re: L31-r longblock EFI Project
« Reply #6 on: December 31, 2017, 08:04:57 PM »
TBI is only a few wires, but ok.....

If you're going to cut an access hole in the bed and dropping the tank anyways, then fine, i think that's a good way to do it.  For those who DON'T want to mess with the stock tank, i'm thinking the fuel resevoir would be the fastest/easiest way to get running.

TBI as in 95 and earlier? How does that work with the vortec heads? I really don’t like vacuum lines. I like the cleanliness in my engine bay now. Not to mention, based on the year tbi was created, it’s not built for e15 fuels. That wouldn’t be as much of an issue in a daily driver...but seriously, the new Cali gas will destroy an old vehicle during dormant, moist winter months.


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Offline frankentruck

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Re: L31-r longblock EFI Project
« Reply #7 on: December 31, 2017, 08:06:08 PM »
...and just to clarify, no hole in the bed, just in the stock tank.


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Offline frankentruck

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L31-r longblock EFI Project
« Reply #8 on: December 31, 2017, 08:22:00 PM »
Just to clarify, this is an all mechanical, carbureted truck. No computers, sensors or any emissions equipment. I’ve read a bunch of people who’ve tried to bolt their tbi system to a vortec engine with problems. I also like how the sniper efi can control an electronic distributor.

I hate to copy and paste but this post covers some problems with tbi on a vortec engine:

No you just can't unplug the computer and run, this is where you'll find that it runs everything from the speedometer, engine, and transmission.

Which engine exactly? TBI is very sensitive to engine size and camshaft. TBI computes the engine's air flow by measuring the manifold vacuum (what GM prefers to call Manifold Absolute Pressure) and comparing that to the throttle position and RPM. It derives a number from that and looks to a map of fuel and ignition curves to select what it thinks is appropriate. Changes to the size of the engine, it's efficiency like adding headers or Vortec heads, and certainly changes in the cam duration and or lift, and changes in rocker arm ratio have profound effects on MAP and where and how that figures in relation to throttle position, RPM, and gearing. There are trimming adjustments for engine operating temperature, air temperature and density, EGR fraction in the inlet air, and free oxygen present in the exhaust stream, and exhaust system back pressure. It, however, does not have unlimited learning potential as your dealer claims. It will not and cannot adjust to anything you happen to throw at it. The "learn" capability is only intended to adjust the engine for production line variations and age related typical wear for the period specified by government mandate. To do this it uses the O2 sensor in the closed loop operation mode (engine coolant above 176 degrees F). For a given map position that the computer is reading from, it compares the fuel mixture and ignition timing, if it always sees the same deviation over a period of time it will adjust the information content in that data block to correct the mixture back to chemically correct. But it only has about a 10% bandwidth of authority, deviations up or down from the standard that are greater than 10% error are not correctable.

A custom chip is intended to take the information and operating parameters and "fix" the data blocks for a correct mixture and ignition timing such that they fall back into the 10% range that Block Learn can correct if needed. Again a miss bigger than that is beyond what Block Learn can fix.

A couple problems encountered with bigger cams is that the range of change in power greatly increases for smaller changes in sensor output variation. This makes it harder for the computer to discriminate fuel flow and ignition timing for a narrower band of information that scales across a wider operating range. It's simply trying to spread itself over more area from less information. This gets to be a problem as the manifold vacuum at idle starts to get less than the OEM of 16-18 inches at about 600 RPM. More cam or rocker ratio runs the idle up while the vacuum goes down. Add to that heads that flow more air than the Swirl Ports that were originally there and you can see this is headed for problems.

Now TBI should support a 350 hp 350 inch engine, but it's getting out there on its upper limits. Tuning becomes most important, it will be quirky and sensitive.

It will not tolerate any vacuum leaks and getting the Vortec intake tight is always a problem. Test for leaks.

The PCV has to be spot on.

The EGR will need to be functional or a chip blown that knows it isn't there. Loss of EGR leans the mixture, a toasted piston or two will result unless this is compensated for by a new chip.

The IAC needs to be carefully adjusted and if old probably replaced.

The wiring and connectors needs to be in very good condition. Many of the electrical signals are very small so damaged wires and connectors have a great effect on performance.

The Vortec heads have no provision to exhaust heat the intake but that capability is in the intake. This makes the intake too cold compared to engine coolant temps, the computer gets confused by this. Simply drill and tap the feed holes from on top and route the bypass coolant thru there on it's way to the heater core.

Connect the EGR, for a Vortec intake this is sourced from the exhaust manifold or a header pipe with a 1/2 inch tube. Use steel and pick fittings that will work. There's a bunch of ways to pull this off including using factory and Edlebrock parts. But you just as well off to use what you can get at the hardware store.

Use an adjustable fuel pressure regulator to trim fuel delivery thru pressure adjustments.

Time the engine properly. There is a brown and black wire that goes to the distributor, trace this to its connector and separate the connector. Start the engine and set the base timing to zero. Shut it off reconnect the connector. The timing including the base will be established by the computer. Any attempt to set the lead more than 2 degrees screws things up, unless the new chip was specifically changed to accommodate a setting greater than the factory. In that case follow the directions.



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« Last Edit: December 31, 2017, 08:25:47 PM by frankentruck »

Offline frankentruck

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« Last Edit: December 31, 2017, 08:56:51 PM by frankentruck »

Offline frankentruck

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Re: L31-r longblock EFI Project
« Reply #10 on: December 31, 2017, 09:36:18 PM »
Anyone with real world feedback on a standalone efi?


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Offline Stewart G Griffin

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Re: L31-r longblock EFI Project
« Reply #11 on: December 31, 2017, 10:56:17 PM »
i mean there's nothing wrong with the FAST, Fitech, and sniper.  They all seem good.  MY personal preference for a stock engine is the GM TBI is all i'm sayin'.