SBC mated to 700r4 with Fitech conversion: Would it be worth the trouble?

[WyattTX]

Eventually, I plan to rebuild a 1985 700r4 and put it behind and SBC 350. I'm aware that this version of the 700r4 is made to function with a q jet carb. But if I did a Fitech fuel injection conversion, could the TV cable still be properly actuated? Is a Fitech really that good? If I wont get much more performance or fuel economy out of it, I'll just rebuild the q jet, and call it a day. Thanks for any input.

[AcampoDave]

"Worth it" with regard to mileage and performace is kind of relative. Let's say you pick up a couple or so MPG's but you only drive the truck 100 miles a month. ...then from a purley economic standpoint the answer would be no. Your return on investment would be very long term. You'd probably do better investing that money in a quality mutual fund. But if you consider the less tangible aspects of making the uprade, like the fun of doing it, the cool factor, and the satisfaction you might get from driving it around... well...only you can decide how much that is worth. I have no experience with Fitech but I have had lots of carburetors and i feel that once you get one dialed in they are just fine for a hobby vehicle.

[DieselSJ]

Originally Posted by WyattTX

Eventually, I plan to rebuild a 1985 700r4 and put it behind and SBC 350. I'm aware that this version of the 700r4 is made to function with a q jet carb. But if I did a Fitech fuel injection conversion, could the TV cable still be properly actuated? Is a Fitech really that good? If I wont get much more performance or fuel economy out of it, I'll just rebuild the q jet, and call it a day. Thanks for any input.

700R4's aren't made to work behind anything specific.

Yes, the TV cable can work with the Fitech throttle body.

Fitech being good - it totally depends on how well you install it and the time you put into tuning it.

Worth it for a 700R4? Depends on how often you drive and how you drive it. Was the overdrive totally worth it in my dually? Yes absolutely. But I also drive it a lot.

[WyattTX]

I think I'll try the OEM style Q jet for now. It's not as convenient as TBI, but it's simple and dependable enough for me to trust it. Thanks for the input.

[LEEVON]

Not sure if the newer Fitech has 700R4 provisions, but I have a 5.3/700R4 with Fitech and had to modify the linkage to mate the TV cable. It's a great drivetrain though.

[Jrainman]

I run a 200 4r witch is operated the same as a 700R4 , I run a fitech on a L31 5.7 so yes you can hook it up ,it took me a bit of research to find out what would work perfectly with this set up , 2 years now with no problems ,but its not cheep, this is the kit I used, alignment and fitment is perfect. got it from either summit or JEGs

[Ziegelsteinfaust]

Do not just rebuild the T700r4 with out considering replacing it's internals with 4L65E parts.

The 4L65E is a good bit upgraded over the T700R4 internal pieces, and it does not change the function of the TV cable. Get a LS 4L65 for your internals.

Do not get a shift kit as Corvette servos work better for most people with out the hard 1-2 hit. If you want more you can always add a shift kit.

Spring for a constant volume valve body. Makes TV cable adjustment alot less important.

I took the lock out torque converter out of my hybrid T700, and am running a standard 2500 rpm stall converter. It removes almost 25 pounds from the rotation of my drivetrain for more snappy performance if you want that.

[WyattTX]

Originally Posted by Ziegelsteinfaust

Do not just rebuild the T700r4 with out considering replacing it's internals with 4L65E parts.

The 4L65E is a good bit upgraded over the T700R4 internal pieces, and it does not change the function of the TV cable. Get a LS 4L65 for your internals.

Do not get a shift kit as Corvette servos work better for most people with out the hard 1-2 hit. If you want more you can always add a shift kit.

Spring for a constant volume valve body. Makes TV cable adjustment alot less important.

I took the lock out torque converter out of my hybrid T700, and am running a standard 2500 rpm stall converter. It removes almost 25 pounds from the rotation of my drivetrain for more snappy performance if you want that.

Did you end up having to use a computer or TCM with your setup? Its my understanding that the old 700r4 is mostly mechanical, with the exception of it's lock up, whereas the newer 4lxx is digitalized, and needs to a have a properly programmed computer. I've never considered mixing and matching pieces, but it's a thought to consider.

[Stormin08]

i just used this...
https://www.summitracing.com/parts/f...iABEgK-qPD_BwE

and this...
https://www.summitracing.com/parts/prf-60109/

89 swapped to Fi-Tech easy street 600hp,
not the greatest pic, but you can see how the linkage lays out. the supplied bracket did need a bushing which i got from holley...( AND I HAVE 6 MORE SETS FOR A GOOD HOME IF NEEDED)

[tdangle]

I don't know about the Fitech but an OD trans is really nice if you have 3.73 or lower gears. Even if you don't drive that much it is so much nicer not cruising at 3000 rpm on the highway. My mileage went up, but I'll probably never recoup the cost since I don't drive 10,000 a year. We have all gotten spoiled with modern cars being quiet and cruising a high speeds with the engine just loafing.

[WyattTX]

Stormin08, that's a great looking engine bay. Thanks for the pic of the mounts, now I have an idea what I'm dealing with. I'll definitely try to opt for an overdrive transmission. I'm still exploring options for fuel delivery. I'm thinking more and more about adapting an early '70s q jet with the electronic q jet's linkage. I think an older style q jet would offer some more adjustment possibilities, than the later style electric one. I don't know if I want to take the plunge and convert to TBI just yet. I do enjoy the noise of a q jet, even if it costs some gas to hear it sing.

[Ziegelsteinfaust]

Originally Posted by WyattTX

Did you end up having to use a computer or TCM with your setup? Its my understanding that the old 700r4 is mostly mechanical, with the exception of it's lock up, whereas the newer 4lxx is digitalized, and needs to a have a properly programmed computer. I've never considered mixing and matching pieces, but it's a thought to consider.

No the T700r4, and 4L60 are mechanical. The 4L60 is a bit up graded, but uses a electric speedo. Although function is mechanical in nature. For both the lock up converter is electric, and they sell a kit to use it.

You do not need the lock up converter. You get the converter you want, and a kit to plug something in the valve body. I didn't rebuild my trans so I am not sure exactly what wasdone here. Just make sure your rear gear/tire combo allows fluid lock up at the speed you intend to drive or you are better off down shifting.

So with my trans has a 2500 rpm stall, my rear gear, and tire height I will be at 2500 rpm at 75.

I didn't go with a the lock up converter for performance reasons, and the Camaro it's going into. Fuel economy is not much of a concern. Anything around 15 mpg hwy will be perfectly fine.

The 4L65E is purely computer controlled, and is the best one if your after a all around performer. By that I mean street manners, tow haul mode, and lock up functionibility.

[Ziegelsteinfaust]

Not to confuse you more. So I added this as a separate post.

But converters are filled with fuzzy logic when you buy off the shelf.

Car weight, axle weight, rim/tire weight, tire height, tire compound, engine hp/tq, and cubic inches all effect the converter stall.

A 500hp/300tq 8000rpm 302 is not going to stall a converter as hard as a 350hp/500tq 454 which will have a hard time hitting 6000rpm.

My converter is rated at 2500 rpm for a 450hp big block in a 3500 pound car. Well my engine is a 475 hp maybe or hopefully 500hp 383 LT1 reverse cooled engine. Also my car will weigh about 3000 pounds when done or 3200 with my fat but in the driver seat. Hopefully less, but I am guessing right now.

So my engine due to its high tech, and performance build. Should roughly be the same at flash stall as the nominal big block the designers used.

But my reduced vehicle weight will reduce effective stall the converter will do.

So let's say in my Camaro my 2500rpm stall is really a effective 2400epm stall.

Now pull my engine trans combo out, and drop her into a crew cab dually. With a BBW 14 bolt full floater rear, and extra 2500 pound weight. That same nominal 2500 rpm stall may now be 3300 rpm effective stall. Atleast in terms of flash stall, but it will act like a hybrid stall in reality. Since it is trying to "lock up" but vehicle weight, and Dynamics hold it back.

So when you buy one. Consult your favorite company to discuss what changes may happen, as they have many many options.

[WyattTX]

Thanks Ziegel, that makes things make a little more understandable. I'll likely end up using 3:73 rear gear. It looks like I can reuse the OEM wiring for the lockup. I haven't decided on torque converter yet, but I'll probably figure that out in due time.

[jhrusk]

I have a 700r4 with a b&m shift kit also use the b&m lock up module. Both have worked great so far. I run 30" tall tires and 3.73 gears. Cruises out great. Now the fitech on the other hand is a big No it's not worth it. I learned that the hard way. Ended up using it for a wheel chock and getting a sniper. So far so good. Also don't discount a good carb set up.

[Stormin08]

^^^^ kind of agree with this...

the purchaser of my ride is having tuning issues, as i did...truck will probably make its way back and get a swap.

[WyattTX]

I think I'll just get a properly rebuilt Q jet. They work well enough. My current Q Jet runs a little rich. I might try to work it out, but I'm no Q jet expert.