The 4L60, which is the same trans as the 700R4 (well, almost), or the 4L60E, electronically controlled by the PCM?
350 TBI build
- Thread starter Marcus W
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Yup, that's possible.
Not really practical unless you put on a huge amount of miles/kilometers every year. The cost to upgrade is pretty high considering the potential fuel economy benefits, and the likelyhood that the vehicle won't meet emissions regulations once "upgraded".
You'd generally do better financially to assure your vehicle is running as GM intended, the brakes aren't dragging, and the tires are properly inflated, than to change fuel-injection systems.
How about the Fitech go street self learning efi system, it’s $1100 CAD and supports up to 400 horse which is more than enough for me. I saw a post on another site about a guy that did a carb swap and was able to maintain the tbi system to control the transmission and gauges, I’ll try to link it below. Basically he changed out the distributor to an HEI unit and plugged in the tps on his carb, the fitech unit has tps on it so I’d like to assume a guy could make it work but I’m not 100% on those details. Worst case I would put a stand alone controlled for the transmission but I’m unsure of what would then happen to my factory gauges, I would like to keep them. https://www.gmfullsize.com/threads/how-to-ditch-efi-and-still-control-your-4l60e.197014/
I believe the factory TBI distributor will still work without the computer, but it won't have advance. I installed my Sniper and just left the distributor hooked up and it works fine and still contributes advance.
If you have the 4L60 and not the 4L60E, the only thing the computer does is control the torque convertor clutch lockup. You can replace that with a pressure switch in the 3-4 circuit and a vacuum switch on the manifold. In 3rd or 4th gear at part throttle? Lock it up. Mash the gas and you lose vacuum, turning off the clutch. Come to a stop and the transmission drops down out of the 3-4 circuit and the clutch turns off. Easy-peasy.
...But! If I were aiming for less than 400 hp, I'd stick with the TBI if I could.
If you have the 4L60 and not the 4L60E, the only thing the computer does is control the torque convertor clutch lockup. You can replace that with a pressure switch in the 3-4 circuit and a vacuum switch on the manifold. In 3rd or 4th gear at part throttle? Lock it up. Mash the gas and you lose vacuum, turning off the clutch. Come to a stop and the transmission drops down out of the 3-4 circuit and the clutch turns off. Easy-peasy.
...But! If I were aiming for less than 400 hp, I'd stick with the TBI if I could.
I have think I have a 4L60E, the truck is a 1994. I’m still trying to decide on which direction to go with the motor, now I’m looking at crate 350’s that make 333 hp and 389 torque that why I am considering the fitech over the sniper. But you have a point at the lower power level, transmission control and guages etc. It would probably be easier to get the tbi to handle the horse power but I don’t know what parts are needed, vortec fuel pump, fuel pump regulator, ported throttle body and a chip?
Also I’m curious do your factory guages still work? If so how did you accomplish that I was told the tbi computer controls them so I’m not sure if mine would work with a different fuel injection system
The EP381 fuel pump from a 96 Vortec will give you plenty of fuel. You can talk to these guys about a bored 46mm Throttle Body that will give you 650 CFM, plenty for a 350 @ 6000 RPM.
https://www.ebay.com/itm/46mm-PORTE...837306?hash=item3d963196ba:g:mpwAAOSw2xRYWVJj
http://www.rvmorsemachine.com/product.htm
Maybe throw some decent heads on it? These flow a little better than the Vortec heads.
https://www.summitracing.com/parts/sum-162109
And data logging, tuning, data logging, tuning, rinse and repeat until you get it right. A mail order chip may get you close but, no cigar.
FWIU the TBI PCMs don't control gauges. Your speedo is fed off the 2000 PPM (Pulses/Mile) VSS through a DRAC or VSSB, Fuel is directly from your sender/pump, Volts is from the cluster itself, Tach is from the white wire off the ignition coil (this may have to be run to the cluster on later models I think.
IMHO, you're losing a lot of control if you disable the computer controlled distributor. It'll allow you to "tune" SA (Spark Advance) based on RPM as well as MAP more accurately than an HEI on weights and vacuum. Especially with the Knock Sensor so, you can retard a little at WOT high revs to eliminate detonation. Here's an example of reducing SA at higher RPMs due to KCs.
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Most guys don't run much advance anyways. Since I target at least 30* all-in, I don't think I'm giving up much. If you know how to adjust the springs, optimizing your advance curve manually isn't hard.
