TBI Motor Swap from Carbed Motor ??

[Kay86K5]

Ok, I don't know if anyone has seen my build thread, but I have an 86 K5 with a carbed 383. I just purchased (on Wednesday night ) a wrecked 89 K5. The motor/tranny and everything runs really well (I know because I drove the thing home doing 65). I don't know how many miles are on the motor/tranny, but I don't really care. It starts up and runs smooth. So my plan is to literally pull my 383/700r that's currently in my K5 and replace them with the TBI350/700r that's in the wrecked vehicle. Also, I will be pulling the TBI tank/fuel lines and just swapping everything over. Considering I am doing this, I think it will make the swap of wiring harness/computer and everything a bit more simple. One question I have is about VSS. I haven't really looked at it yet, but I have read that the VSS is on the back of the speedo. However, I know the speedo in those 89's were electric (electric connector onto the 241). I don't plan on swapping tcases because I have a 241 with a SYE kit on it in my K5 right now (mech speedo) and I obviously plan on keeping that. I have heard of guys deleting the VSS, but I have heard it is always better to keep it for air/fuel mixtures and other reasons. If anyone can give me some advise on what would be best here, I would appreciate it. Also, if there is anything else I am missing in my thought process of this swap, feel free to chime in. Thanks guys

P.S. I know someone will say, "Why don't you swap TBI onto your 383." I have already gone over this in my head over and over, but it is actually simpler for me to just swap motor and tranny's than it is to mess with retrofitting sensors, reworking harness, and getting a new chip burned. I don't really care about high horsepower, I care about reliability when on steeps and off-camber....

 

[70jimmy]

did a swap from a 93 sub into a 70 jimmy, kept the 350 turbo and 205, now I have switched to the 400 turbo. The vss came with the Howell harness I bought. The techs at Howell put it this way. The engine doesn't need the VSS, The original tranny or transfer case that ran that speedo does.

So the vss plug is just hanging there not hooked to anything and I run the original speedo which is off the 205 T case.

 

[Kay86K5]

So to get this right, you don't have VSS hooked up at all? If that is the case, I might go that route just to make it even simpler, and I'll just keep my original mech speedo on my 241. Have you ever had any problems with the way the TBI runs without VSS? I have heard it really helps out on decelerations.

I love TBI's, they are a tried and true motor. My bro has an 88 Jimmy with a bone stock TBI350 that he has hacked up with rockwells under it. He doesn't even have an O2 sensor hooked up to it and he says his motor runs perfect without it

 

[dyeager535]

'89 should most definitely be cable drive. 1990-1991 are the only two electric speedo years, and 1989 is the one year only mech speedo drive 241.

General consensus is that VSS is not particularly critical on TBI, but it CAN cause issues, particularly on deceleration. Think about it this way...GM didn't use it just because it cost them more money.

Run it.

Personally, I'd go with a 1990-91 VSS/DRAC setup and be done with the speedometer cable myself, but that's because I've done it.

 

[eagle mark]

'89 should most definitely be cable drive. 1990-1991 are the only two electric speedo years, and 1989 is the one year only mech speedo drive 241.

General consensus is that VSS is not particularly critical on TBI, but it CAN cause issues, particularly on deceleration. Think about it this way...GM didn't use it just because it cost them more money.

Run it.

Personally, I'd go with a 1990-91 VSS/DRAC setup and be done with the speedometer cable myself, but that's because I've done it.

VSS is needed for TCC lock up per MPH in chip. Lot of off roaders don't need TCC or use it.

But VSS does help idle quality! Does not need to be accurate, except for TCC, just needs to know if moving or not. Can be quite a difference when crawling.

So your 86 has a 700R4, what did it use for VSS?

I've never got it straight with 4x4 and 2wd from 86 to 91...

 

[Kay86K5]

'89 should most definitely be cable drive. 1990-1991 are the only two electric speedo years, and 1989 is the one year only mech speedo drive 241.

General consensus is that VSS is not particularly critical on TBI, but it CAN cause issues, particularly on deceleration. Think about it this way...GM didn't use it just because it cost them more money.

Run it.

Personally, I'd go with a 1990-91 VSS/DRAC setup and be done with the speedometer cable myself, but that's because I've done it.

Good info, thanks. However, as far as I know the first half of '89 was mech speedo 241's, and the second half of '89 were electric speedo 241's. Don't know if someone knows different, but that is what I have read.

VSS is needed for TCC lock up per MPH in chip. Lot of off roaders don't need TCC or use it.

But VSS does help idle quality! Does not need to be accurate, except for TCC, just needs to know if moving or not. Can be quite a difference when crawling.

So your 86 has a 700R4, what did it use for VSS?

I've never got it straight with 4x4 and 2wd from 86 to 91...

Yes my 86 does have a 700r4, just not sure how anything was used for VSS. But, I am going to be swapping the 700r4 from the '89 into mine (was told is was rebuilt 6000 miles ago, seems to shift really good).

Mine is truly built for offroad, however I do like to drive it on the road every once in a while, so if I can somehow get VSS to work right, I would like to. I guess I will just have to start tearing it down and see how everything plays out. We shall see. All I know is that this is going to be 10 times better than my stupid Carter carb , no matter how much time and effort it takes to do this swap

 

[Kay86K5]

Starting stripping the parts blazer tonight of some of the wrecked sheet metal. Found out it does have a mech speedo 241 . This mean not only do I have a great extra tcase for my existing tcase, but all I should have to do is just swap gauge clusters and we should be all good to go for sensors. I can't wait to get this swap going. I know this is going to take some time to complete, but I am having trouble showing patience with this. I want to get this done so bad.

 

[dyeager535]

You don't need to swap clusters. All the clusters starting in about 1983 (not sure exactly when they went from transducer cruise to VSS cruise control) to 1989 are identical in regards to the VSS setup, other than the fact that perhaps SOME of the early production speedometers did not have the hole tapped for the screw that held the VSS "eye" to the back of the speedometer.

Any truck after about 1982 (again, not sure exactly what year, but I seem to recall my '83 did not have the transducer cruise) used the same optical VSS, through 1989.

Mark, prior to 1987 (or I suppose more accurately prior to EFI, since there were isolated, specific carbed trucks past 1987), the trucks used a vacuum switch on the firewall to control TCC lock/unlock based on engine load.

Be careful with the 700 swaps. I stay away from automatics with a passion, but various years may have been wired differently. There are a few people on the board that probably know. Worst case, drop the pan on both and compare the internal wiring.

 

[Kay86K5]

Good info. Thanks. I will have to double check everything on the donor once i get it all torn apart.
I personally dont like manual trannys for wheeling. I played the three foot tango for years while wheeling, and i will never do it again. For just driving around on the street, sure they are fine, but try wheeling with a 4 speed and a puking q-jet on a side hill and you will find yourself cursing that tranny all day. Thats what i did at least. So dealing with auto trannys and their quarks is totally worth the control offroad to me. Plus, this guy had reciepts of this tranny being rebuilt 6000 miles ago. It seems to shift good, so i'm gonna run it

 

[dyeager535]

Well, the carb is a story all it's own. Isn't that why we go fuel injection?

I don't wheel anywhere near hard, but I can see why people would invest in things like doublers with a manual, to keep the clutch from taking up so much of your time and effort.

I suppose I didn't make it clear before, but another way to put the VSS statement, is that any truck that has/had cruise control, that did NOT have the transducer on the inner fender (it was a mechanical component, speedometer cable went to it from the cluster, then another cable to the trans/t-case) had VSS.

 

[Kay86K5]

Well, the carb is a story all it's own. Isn't that why we go fuel injection?

I don't wheel anywhere near hard, but I can see why people would invest in things like doublers with a manual, to keep the clutch from taking up so much of your time and effort.

True, but I still don't have 3 feet. I just can not give up the control of an automatic to go back to a manual....at least for hard wheeling....and that's the soul purpose of why I built my truck.