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Subic Jeep 01-27-2012 12:10 PM

GM TBI more power needed
Got a GM TBI on a SBC 350 V8 need more power :thumbsup: My Cherokee is heavy over 7000 lbs and on 39.5 inch rubbers.

I was thinking of adding a TBI UNIT: 670 CFM Holley 2-bbl with 80lb/hr Injector


Holley 670 CFM adapted for use with Howell or GM wiring harness and ECM. Uses special Howell calibration PROM. Includes idle speed control by ECM. Suitable for high-RPM small block application and low performance big blocks. With 80 lb./hr. injectors.

This is a investment of 450$ plus the chip 250$ ....

Your comments please!

okjeep 01-27-2012 01:11 PM

Don't do it. Look at the upsized unit from CFM-Tech ( I ran this on my TBI zz4 vortec'd head 350. Gears will be the remaining factor to getting it to move easier.

Billygoat 01-27-2012 01:21 PM

What year is your donor computer?

You can do what needs to be done to be able to tweak and update your programs for not a lot a cash and get more power out of your existing hardware. If you get PE (Power enrichment) to kick on when it should it will help you out a lot. Plus actually dial in your program for the chero instead of the donor.

You can also drop 454 injectors in your TBI - same base unit.

Subic Jeep 01-27-2012 01:30 PM


Originally Posted by okjeep
Don't do it. Look at the upsized unit from CFM-Tech ( I ran this on my TBI zz4 vortec'd head 350. Gears will be the remaining factor to getting it to move easier.

Thanks for the reply!

Gears is not an option at the moment.

Is there something wrong with the Holley unit?

Yes, I have looked at the CFM-Tech products, (my first choice before I found the Holley) Adding all the parts for CMF, its as expensive as the Holly unit. Remember I would have to pay 150$ for the core.

Subic Jeep 01-27-2012 02:05 PM

Sorry far away from my Cherokee, I am at work now, for two months more, before I can pull my computer to see what chip it has. Taught I had a picture but, it does not show the label on the cover of the EMC. grrr

I am not going to have time to learn to tweak my computer, just want to see a explosion in power :lol:

The engine is a 350 years 69-79 basis the casting numbers on the block. Just overhauled it, all bearings renewed pistons and crank shaft are original.

New camshaft COMP Cams Xtreme Energy 4x4 Cam and Lifter Kits
Part Number CL12-239-3
Basic Operating RPM Range 1,300-5,600
Intake Duration at 050 inch Lift 218
Exhaust Duration at 050 inch Lift 226
Duration at 050 inch Lift 218 int./226 exh.
Advertised Intake Duration 262
Advertised Exhaust Duration 270
Advertised Duration 262 int./270 exh.
Intake Valve Lift with Factory Rocker Arm Ratio 0.462 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.480 in.
Valve Lift with Factory Rocker Arm Ratio 0.462 int./0.480 exh.
Lobe Separation (degrees) 111
Grind Number CS X4 262H-11

Rocker Arm Style Roller tip 1:1.5

Product Line RHS Pro Action Small Block Chevrolet Cylinder Heads
Summit Racing Part Number RHS-12002-02
UPC 036584134909

Cylinder Head Style Assembled
Cylinder Head Material Aluminum
Cylinder Head Finish Natural
Combustion Chamber Volume (cc) 72
CNC-Machined Combustion Chamber No
Intake Runner Volume (cc) 180cc
Exhaust Runner Volume (cc) 74cc
CNC-Machined Intake Runner No
CNC-Machined Exhaust Runner No
Intake Port Shape Rectangular
Intake Port Location Standard
Exhaust Port Shape Rectangular
Exhaust Port Location Standard
Spark Plug Style Angle
Intake Valves Included Yes
Intake Valve Diameter (in) 2.020 in.
Exhaust Valves Included Yes
Exhaust Valve Diameter (in) 1.600 in.
Valve Springs Included Yes
Maximum Valve Lift (in) 0.550 in.
Outside Diameter of Outer Spring (in) 1.430 in.

Axle gearing 4.56

Subic Jeep 01-27-2012 02:22 PM

From Pirate

Originally Posted by painter66
Couple things I like about the Powerjection;

One you can get into the computer to tune it. It was just the other day my son and I were looking at it and we discovered the the engine like 13.5 instead of 14.whatever at idle. My son (the Honda guru) said to me that doesn't make sense. I just looked at him and said it sounds better doesn't it it's a big block not a Honda LOL. You can data log with this system look at whats going on and change it in very minute increments. If you have a chip burned your stuck with it. What if you change something on the engine? Hey how about this you change to a completely different engine or you sell your buggy and build another one. Put the Powerjection on and off you go. There is something said for simplicity (It's simple). Why wouldn't you want something that is completely tunable?? Why let someone else guess about the tune for your engine? Yep it will run when you get the computer back or down load thee generic tune, but is it running as good as it could?

here's why. most people cannot/do not/have no idea how to tune "correctly"
you risk not getting the most potential out of your engine, or worse.... hurting it.

Don't let this stop the discussion :thumbsup:

FSJ Guy 01-27-2012 02:52 PM

The only reason to go to different (bigger) injectors is if you are maxing out the duty cycle. According to the interweb, you're supposed to stay below 80-85% duty cycle.

You could bump up your fuel pressure for an inexpensive way to get more fuel to the engine. I'm running the regular (350) throttle body on my 401 and have plenty of power. I'm also running the 454 injectors, however.

Look into getting your own tuning hardware/software. $250 for a mail order tune is ridiculous, IMHO. For less than that, you can get all the hardware/software to do it yourself all day long.

derf 01-27-2012 03:10 PM


Originally Posted by Subic Jeep
Is there something wrong with the Holley unit?

It's just overpriced for what you get. Other than that, nothing really wrong with it.

There's cheaper and better ways to bump up the power. A 454 TB with a little time tuning it will give you more than that Holley can for less money.

Subic Jeep 01-28-2012 11:12 AM

I probably could not find a 454 TBI locally .....:eek: anyhow just need 80lbs injectors. (Post Link???? please)

Increasing the fuel pressure is relatively easy by making the regulator adjustable.

Even a type CMF enlarging the bore is relatively easy ;) with small grinder.

I try to post some pictures but the attachment tool just says too large, even try to re-size still to large.:banghead: My photobucket account is blocked by organization :mad:

Here is a good link:

Subic Jeep 01-28-2012 12:57 PM

One more good link from same source!:thumbsup:

FSJ Guy 01-28-2012 08:23 PM


Originally Posted by Subic Jeep

Overall good info. His tech is wrong on the 4 wire O2 sensor, however. Of the four wires, two are for the heater power and ground, 1 is the sensor wire and the last wire is for sensor ground.

FSJ Guy 01-28-2012 08:49 PM


Originally Posted by Subic Jeep
One more good link from same source!:thumbsup:

This is an excellent writeup!

Interesting bit about the choke stove! Yikes!

Subic Jeep 01-29-2012 09:16 AM

$250 for a mail order tune is ridiculous

Originally Posted by FSJ Guy
$250 for a mail order tune is ridiculous, IMHO.

I agree, but it seems to be the norm.

AFI takes $350 for a tune if I remember correctly.

Cheaper alternative with a lot of options


Custom tune $264


FSJ Guy 01-29-2012 10:02 AM

If you're comfortable with a computer, you can burn your own chips for less money. And you can do it over and over again, without worrying and WAITING for shipping. A better deal IMHO, but you need to be comfortable with your computer. :D

Subic Jeep 02-21-2012 04:25 PM

What is the goal here?
1. Get maximum power that the engine can give, as it is mechanically configured now.
2. Doing it in a relatively short time, in a week.

Dynamic EFI EBL Flash system + TT-1 WB controller. Howell / Holley 670CFM TBI with 80lbs/hr injectors ( $ 430 + 189 + 450 = $ 1069.00)

The Dynamic EFI EBL + Holley system could probably get the max power the engine can produce, total cost for the system $ 2069. (old AFI $1000.) I could probably get a few hundred back for the GM-TBI-ECM and O2 sensor. Still the total cost is around $1800

The Dynamic EFI EBL Flash system is relative user friendly, but is it doable in a week, I doubt it.
Dynamic EFI EBL Flash system has good instructions for their EBL flash system written in a way that so I can understand it.
(TBI Tuning part 1 & 2 on their web page)

Fast EZ-EFI® Self Tuning Fuel Injection System (Base kit) $ 1785.00

As the name says installation is fast. Power gain up to what a GM SB can give (550hp) if you have the right parts in the engine.

Fast EZ-EFI® eliminates the whole learning process of tuning a GM TBI.
Wideband Air/Fuel sensor is Included.

Not so good:
No ignition control. (MSD Ignition #121-5520 = 135$)
Fuel pump not included. (150$)
Price very high!


1. What type of ignition systems are compatible with the EZ-EFI®?

Since the EZ-EFI® is a fuel-only system, what ever you have already or would use on a carbureted setup will work. With that being said, the EZ-EFI® needs a very stable/clean TACH/RPM signal. For the best possible performance and elimination of noise issues, we suggest an aftermarket style ignition box. For example; MSD or Accel or any of the aftermarket CD ignition boxes that provide a good TACH output signal. The EZ-EFI® system does come with a Tach Adaptor to allow you get a TACH signal off of the negative terminal of the ignition coil or the TACH terminal of an HEI distributor. Due to that fact that this inductive signal is very noisy and varies with RPM, plug gap, cylinder pressure and so forth, sometimes the Tach Adaptor cannot maintain a clean enough signal for the EZ-EFI® to perform optimally.

I think I still have my electronic distributer, not entirely sure I might have given it away…

FSJ Guy 02-21-2012 07:00 PM

See JeepsAndGuns' thread about swapping over to the 16197427 PCM. I was intimidated at first, but it's very easy to do if you're already comfortable with programming the 12277747 ECM.

Swapping to the EBL system will get you a P4 class ECM which is similar (but not the same) to the 16197427 PCM. You can buy these PCM's on ebay, but you'd have to find a seller that would ship to you.

Either way, swapping computers will not in itself get you more power. Swapping to larger injectors will help in that department. The advantage of a P4 class computer is that you have a faster data output from the computer. The '7747 ECM outputs at 160 baud. The '7427 PCM outputs at over 8,000 baud. Instead of an update every 1.5 seconds or so, you get virtually instantaneous output. It makes tuning MUCH easier, IMHO.

I would recommend trying the larger injectors first. A wideband will be very useful with WOT tuning. For regular driving, it is not required for a good tune.

I think you could get a very good tune with the EBL ECM within a few days. It'll just cost you in gas money! :D

Woodchomper 02-21-2012 09:20 PM

Injector Flow
I just did some quick calculations on injector flow and if I am correct the 5.7 injector (61.2 lb) at a fuel pressure of 22.2 PSI will flow at the same rate as the 80 lb BB injector at 13 PSI.

So another option to consider would be to run EBL and a VRFPR (vacuum referenced fuel pressure regulator) with a fuel pressure setting of 22 PSI. You could try this setup before buying a new TBI unit. The nice thing about running a VRFPR setup is that at idle the fuel pressure is lower (say 13 PSI) which lets you have a longer pulse width (longer on time) for a smoother idle. If my understanding is correct, with the 80 lb injector the pulse width at idle is small and the fuel spray has bigger droplets.

The EBL easily supports VRFPR and comes with some excel support files to help when setting everything up.

As far as buying a wideband sensor goes, this is a good idea no matter which route you go. I would never trust something that tunes itself. In this case the wideband sensor would give you a window into the tuning that you may (EBL, Megasquirt, Homebrew) or may not (Off the Shelf - Self Tuning) control.

Subic Jeep 02-25-2012 10:38 AM

Will these work?
Aeromotive 13301 - Aeromotive Universal Bypass Regulator

Same from Summit

Fuel Pressure Regulator, TFX™, 3-60 psi, Black Anodized, Carburetor, MFI, Gasoline, Alcohol, Each $129.95


These TFX™ universal bypass fuel pressure regulators from Trick Flow® are ideal for bypass applications where more fuel flow and superior pressure control are required. Fuel pressure can be adjusted from 3-20 psi, making them perfect for carburetors, or you can install their included high pressure spring and adjust the fuel pressure from 20-60 psi for your EFI fuel system. The regulators also feature a boost reference port that will raise fuel pressure on a 1:1 ratio.

• GM 7.4L V8 TBI injectors $215.99


Subic Jeep 02-25-2012 10:47 AM

Turbo City e-bay
GM TBI 87-95 vacuum referenced fuel pressure regulator

US $95.00

The horsepower is limited on the GM TBI engines by injector size and fuel pressure. This regulator assembly allows the use of higher than stock fuel pressures on the standard injector. Standard fuel pressure is 9-13 psi, our unit includes a 17 psi spring (use of a non stock fuel pump required). The fuel delivery is modulated by intake manifold vacuum to help the engine run cleaner at low speed and at idle. Every 2.5 in of vacuum applied to the regulator lowers the fuel pressure by 1 psi. With a base pressure of 17 psi and 14 in of manifold vacuum at idle, the resulting fuel pressure will be 11.4 psi. Under WOT the fuel pressure will go to 17 psi. Custom chip programming may be required to function properly. This regulator is a “must” for installing a 502 or 498 big block in your 87-93 GM truck. Comes complete with required diaphragm, high pressure spring, spring shims and vacuum fittings.

Recommended fuel pump 635-212 intank replacement 40gph

FSJ Guy 02-25-2012 11:58 AM


Originally Posted by Subic Jeep
GM TBI 87-95 vacuum referenced fuel pressure regulator

US $95.00

That would be the VRFPR that you would use. The larger injectors also look correct. Hopefully the $215 price was for BOTH injectors.

I would try the injectors first. I have the larger 80 lb/hr injectors and do not have issues at idle.

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