Carb to TBI

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

usar17

Full Access Member
Joined
May 3, 2012
Posts
596
Reaction score
17
Location
PA
First Name
Shawn
Truck Year
1985/87
Truck Model
K20 Silverado
Engine Size
TBI350/700r4/NP208
Also I don't know a thing about early ECMs. Are they custom to the truck they are in or plug and play? I was afraid the ECM in the C20 (I dont know what tranny is in it yet) wouldn't work in my K10. I dont know what PROMs are haha. I'm a novice with only a basic mechanical understanding :)
 

Jims86

Full Access Member
Joined
Aug 3, 2010
Posts
5,492
Reaction score
135
Location
Patterson,Ca
First Name
Jim
Truck Year
1986
Truck Model
K10 Suburban Silverado
Engine Size
5.7 TBI
*Bringing this back alive :)

My 85 K10 has been dead in the drive way since november now. Rings are....gone probably lol and i don't have a garage or anywhere indoors to work on her.

My original plan was to pull a 350 out of a 1987 C20. Claimed to have been rebuilt with under 10k miles on it. Swap the intake for a an edelbrock 3706 and keep my qjet and vac lines. Easy, $150-$200 for intake, no electronics still.

Further thought of reliability and MPGs has made me think of keeping the engine as is, TBI.

Question:
Besides the actual engine swap, what else would need done?

Sensors? ECM? All new Wiring Harness (I already assume this)? Dash Cluster?

Worth it or not? I'm trying to keep this low budget.

If your 85 had cruise control, and you still have the VSS in the cluster, you are good to go.
First thing, Check PA's engine change laws...I dont know if you need to have it inspected and certified after the swap.
Do not tell them it was put of a 3/4 ton....they wont be able to tell otherwise.
I recommend an inline fuel pump back near the tank. I think I have a pic of my fuel pump somewhere, I will look for it.
Get some aluminum 3/8 fuel line for the return line, and have a 3/8 nipple welded into your fuel filler pipe to attach it to. The return line on the 85 is not big enough, and I think may have a restrictor in the sender. Even better if you can get the 87 tank, then you can just swap it in, but still run the 3/8 return line to the tank.
worth it? In my opinion, yes. easier starts, no choke to mess with, which is important in your neck of the woods.
If you are good with wiring, the harness is super easy to modify, but if not, the Howell harness is the way to go, and they can also provide the proper ECM if you need it. Those 2 items will be the most expensive parts, assuming you have all the hardware from the 87.
On the flip side, Like I told Imann, you can stay carbed, and get that manifold that I mentioned, with no other issues to work out, and still get excellent results.
If you do stay carbed, I would highly recommend staying with the thermostatic air cleaner setup, and make certain that the choke operates smoth, and is adjusted properly. I recommend an 1100 RPM cold idle. The stock air cleaner is also the best cold ait intake you can get, as long as it is still plumbed into the intake horn beside the radiator.


Also, you will need that 87 engine to be complete, from the ballancer to the flywheel. It may not have the mechanical fuel pump provision, so you may need an electric pump.
 
Last edited:

89Suburban

Supporting Member
Supporting Member
Joined
Dec 7, 2010
Posts
24,811
Reaction score
6,752
Location
Southeast PA
First Name
Paw Paw
Truck Year
2007
Truck Model
Chevrolet Tahoe LT
Engine Size
5.3, 4WD
He won't have to certify anything here, just got to pass the sniffer if his area has that test. Some of the remote areas are exempt from the sniffer upstate.
 

usar17

Full Access Member
Joined
May 3, 2012
Posts
596
Reaction score
17
Location
PA
First Name
Shawn
Truck Year
1985/87
Truck Model
K20 Silverado
Engine Size
TBI350/700r4/NP208
Just has to pass a visual ;)

The 87 is complete. Windshield is missing so the interior has been exposed to the weather.....snow right now. Idk how well the ecm would hold up to that. I'm ok with wiring. Just didn't know how well it would match up. My 85 has cruise control. Do I have to worry about transmission or anything to that regard? Ei electronics, kick down, or lock up.
 

usar17

Full Access Member
Joined
May 3, 2012
Posts
596
Reaction score
17
Location
PA
First Name
Shawn
Truck Year
1985/87
Truck Model
K20 Silverado
Engine Size
TBI350/700r4/NP208
Only things missing from this c20 is the radiator, battery, windshield and bed lol
 

usar17

Full Access Member
Joined
May 3, 2012
Posts
596
Reaction score
17
Location
PA
First Name
Shawn
Truck Year
1985/87
Truck Model
K20 Silverado
Engine Size
TBI350/700r4/NP208
Here r some photos. I really don't want to spend $350 on a wiring harness. I'm good at labelling and rewiring. I have no fears about the engine compartment, I'm just nervous with how much I'll need to wire up inside the cab
 

Attachments

  • 2013-01-28_13-00-55_310.jpg
    2013-01-28_13-00-55_310.jpg
    97.2 KB · Views: 112
  • 2013-01-28_12-57-32_16.jpg
    2013-01-28_12-57-32_16.jpg
    99.8 KB · Views: 118
  • 2013-01-28_12-57-17_963.jpg
    2013-01-28_12-57-17_963.jpg
    95.1 KB · Views: 110

usar17

Full Access Member
Joined
May 3, 2012
Posts
596
Reaction score
17
Location
PA
First Name
Shawn
Truck Year
1985/87
Truck Model
K20 Silverado
Engine Size
TBI350/700r4/NP208
Transmission unknown. Im not properly dressed to crawl under this truck now in the snow. But here is a photo of the pan
 

Attachments

  • 2013-01-28_13-16-51_490.jpg
    2013-01-28_13-16-51_490.jpg
    95.9 KB · Views: 120

Jims86

Full Access Member
Joined
Aug 3, 2010
Posts
5,492
Reaction score
135
Location
Patterson,Ca
First Name
Jim
Truck Year
1986
Truck Model
K10 Suburban Silverado
Engine Size
5.7 TBI
Just has to pass a visual ;)

The 87 is complete. Windshield is missing so the interior has been exposed to the weather.....snow right now. Idk how well the ecm would hold up to that. I'm ok with wiring. Just didn't know how well it would match up. My 85 has cruise control. Do I have to worry about transmission or anything to that regard? Ei electronics, kick down, or lock up.

If you have the complete truck, thats great. the ECM is behind the glove box, and its associated mounting plate will bolt right into your 85. You can pull the wire harness out, and with the diagrams we have here, and a good digital volt meter, you can customize the harness to be stand alone, leaving the 85 starting and charging harness in place. I would also install new seals and gaskets in that engine before installation. Nothing more irritating than a shitload of leaks after a swap.
The 87 manifolds should work just fine with your current exhaust.
 

usar17

Full Access Member
Joined
May 3, 2012
Posts
596
Reaction score
17
Location
PA
First Name
Shawn
Truck Year
1985/87
Truck Model
K20 Silverado
Engine Size
TBI350/700r4/NP208
Any problems ill encounter with the transmission
 

Jims86

Full Access Member
Joined
Aug 3, 2010
Posts
5,492
Reaction score
135
Location
Patterson,Ca
First Name
Jim
Truck Year
1986
Truck Model
K10 Suburban Silverado
Engine Size
5.7 TBI
Any problems ill encounter with the transmission

Trans is a 400 in the 87.
you will have to use the wires and plugbfrom the 85 trans to make the computer control lockup....unless you swap the 400 in as well.
 

usar17

Full Access Member
Joined
May 3, 2012
Posts
596
Reaction score
17
Location
PA
First Name
Shawn
Truck Year
1985/87
Truck Model
K20 Silverado
Engine Size
TBI350/700r4/NP208
Ok which seals and gaskets do u recommend changing while the motor is out?

And which wires and plugs? I'm not very knowledgeable on the workings of transmissions. All I know off the top of my head is that there is a kick down linkage on the throttle and a vacuum sensor on the fire wall. Other then that you'll have to explain what is kept, rewired, or replaced.

Would it be easier to email back and forth?
 

Jims86

Full Access Member
Joined
Aug 3, 2010
Posts
5,492
Reaction score
135
Location
Patterson,Ca
First Name
Jim
Truck Year
1986
Truck Model
K10 Suburban Silverado
Engine Size
5.7 TBI
Ok which seals and gaskets do u recommend changing while the motor is out?

And which wires and plugs? I'm not very knowledgeable on the workings of transmissions. All I know off the top of my head is that there is a kick down linkage on the throttle and a vacuum sensor on the fire wall. Other then that you'll have to explain what is kept, rewired, or replaced.

Would it be easier to email back and forth?

All of them, get a kit....I would even do head gaskets, just to take that stuff off the list if you encounter any teething after the swap.
the plug that I am referring to is the 4 prong plug on the drivers side of the 700 r 4 above the pan. Or, depending on your truck's use, bypass all of that for the stronger 400 from the 3/4 ton. Or, you can just leave the Vac sensor keep it simple....which would make things a lot easier.
 
Last edited:

usar17

Full Access Member
Joined
May 3, 2012
Posts
596
Reaction score
17
Location
PA
First Name
Shawn
Truck Year
1985/87
Truck Model
K20 Silverado
Engine Size
TBI350/700r4/NP208
The 400 is shot. That's why I was given the truck for the motor.
 

usar17

Full Access Member
Joined
May 3, 2012
Posts
596
Reaction score
17
Location
PA
First Name
Shawn
Truck Year
1985/87
Truck Model
K20 Silverado
Engine Size
TBI350/700r4/NP208
So what do I do with the 700r4 plug? Cut and splice it in replace of the 400s on the tbi harness?
 

Jims86

Full Access Member
Joined
Aug 3, 2010
Posts
5,492
Reaction score
135
Location
Patterson,Ca
First Name
Jim
Truck Year
1986
Truck Model
K10 Suburban Silverado
Engine Size
5.7 TBI
So what do I do with the 700r4 plug? Cut and splice it in replace of the 400s on the tbi harness?

Run the wires to the ECM plug...we can walk you through that part. Will need to find a chip too. they are plentiful on ebay.
 

Latest posts

Forum statistics

Threads
44,458
Posts
958,356
Members
36,839
Latest member
UC1996
Top