switching from carb to tbi info please

[1972BackInBlackC10]

so im thinking about switching my 1980 gmc to a tbi setup, i know that the 87 up blazer and burbs had tbi and the trucks in single cab for one yr and crew cab for a few yrs, im just wondering how hard it would be to change out the wiring harness, my main concern is the opening in the firewall for the harness is it the same size as my 1980?

also i know i need an electric fuel pump, however i just put a a new gas tank and sending unit in my truck a couple months ago and i really dont want to remove it again, is there any way i can put an inline fuel pump on my truck and where would be the best spot to mount it?

i already have a tbi intake manifold i still need a trottle body, id have to get the ecm as well can anyone think of anything else id need or im missing to do this swap? any info, tips, links, ideas would be appreciated

[1972BackInBlackC10]

well i found this thread it seems to have all the info i need http://67-72chevytrucks.com/vboard/s...light=tbi+swap

[gchemist]

You can buy an aftermarket wiring harness.
Checkout these easy to install kits.http://howellefi.com/gm-tbi-products...-tbi-kits.html

Harness only: http://howellefi.com/gm-tbi-products...sses-only.html

I would like dual TBI unit for my ZZ4.
http://howellefi.com/tbi-kit-chev-v-...n-tbi-kit.html

[D13]

Either have to change heads or complete engine. Intake bolts are at different angles. Throttle cable, wiring harness from anything but a square is different. You should not have an ECM on a 1980, you'll need to fab a mount, and get ALL the wiring from the donor. Donor needs to be a square or you'll have to adjust wiring lengths. Distributor is different.

[1972BackInBlackC10]

thanks guys, i was thinking of finding a square body from 87-91 to get my parts from

[spencer_41188]

how much hp is your engine putting out bacause the factry tbi only suports so much

i went with the fast ez efi it will suport 600hp. dont know how well it works due to a bad fuel pump dont take this the wrong way because the customer service was great... hopefully its in the mail tomarow lol and if that pump fails again im going Mechanical

there are Mechanical efi pumps out there. i would say thats the best way to go. a good exturnal pump will run 200 to 300 $

http://www.summitracing.com/parts/rp...make/chevrolet ... for small block
http://www.summitracing.com/parts/rp...make/chevrolet ... for big block

[1972BackInBlackC10]

its just the factory motor in the truck nothing special, if i can find the right deal i may switch gas tanks if the dnor tank isnt rusty, i dont really want to change my tank since i just put a new one in but i could always sell it

[BigBlocksRule]

Originally Posted by D13

Either have to change heads or complete engine. Intake bolts are at different angles.

No need to get radical on this, you can alter the center holes on the TBI intake to fit the head. The end bolts are fine. This isn't like a Vortec head where the ports are raised, just a bit different bolt angle for TBI intake.

Also, here's a link to a place that makes harnesses a bit cheaper than the one listed

http://www.fuelinjectionconnection.c...s-catalog.html

[1972BackInBlackC10]

yea i had a 69 chev that someone had put tbi on and the centre bolts were drilled on the intake to make it work

[Rich84]

Originally Posted by BigBlocksRule

here's a link to a place that makes harnesses a bit cheaper than the one listed

http://www.fuelinjectionconnection.c...s-catalog.html

I got a TPI harness from them..Great service and a real nice product.

[Jonboy]

I've bought 3 harnesses so far from Robert @ FIC. Nice pieces, great prices.

[rfmaster]

Originally Posted by D13

Either have to change heads or complete engine. Intake bolts are at different angles. Throttle cable, wiring harness from anything but a square is different. You should not have an ECM on a 1980, you'll need to fab a mount, and get ALL the wiring from the donor. Donor needs to be a square or you'll have to adjust wiring lengths. Distributor is different.

You do not have to change heads (or engine). The pre 85 cylinder heads had the four inner bolts were drilled at 90 degree angle to the head intake flange. Starting 1986 model year the same four inner bolts (two on each side) were machined at 72 degrees to allow easier assembly access angle. You can slot the holes in intake manifold to match the heads that you have and use 18 degree angled spacers like these (used on F-body TPI intake) :



You can make your own 18 deg spacers or use a stack of lock and flat washers. There are commercially available 18 deg spacers, but they are hideously expensive. Keep in mind that 2 out of 4 bolts holes protrude into inner valley and may pinch push rods. I forget which one one, but keep bolt length in check (1 x 3/8"-16).

The key to TBI swap while using with stock ECM EPROM is to use stock or RV cam shaft. As long as engine can idle around 650 RPM with at least 16 in-Hg of vacuum you'll have a very good chance of fine running TBI system. Aftermarket cam shafts with LSA of 110 or less and duration greater than 220 degrees at 0.050 should be avoided.

Happy Holiday (Xmas is over and Santa delivered!)
//RF

[1972BackInBlackC10]

i wonder if the tbi heads would work on a 1980 block

[BigBlocksRule]

Any SBC head will bolt to any SBC block.
As long as you're not calling the LS engines small blocks...

[1972BackInBlackC10]

maybe ill just put a set of tbi heads on it, would i have to change my pushrods?

[rfmaster]

Originally Posted by 1972BackInBlackC10

maybe ill just put a set of tbi heads on it, would i have to change my pushrods?

Push rod length is critical to achieve correct valve train geometry. For a flat tappet cam shaft in a first gen SBC GM used 7.8" long push rod in production. However, whenever you 'piece' an engine together it is always a good idea to check push rod length with pushrod checker tool. Why? The block may have been decked previously, different head gasket compressed thickness, or heads have been flat milled or surfaced. All of these machine operations may have alter the stack and shorter or longer pushrods maybe required. There are also factory tolerances which can add up one way or another. Building an engine involves checking dimensions and tolerances. A push-rod checker tool is cheap insurance against nasty surprises.

Here is the link to an article:

http://www.carcraft.com/techarticles...ushrod_length/


In other words stock TBI heads should work fine with stock 1980 pushrods, but it is a good idea to check geometry.

//RF

[Oklahoma_k5]

I put tbi on my dads 84 Suburban about 10 years ago and when I was done I swore I'd never do it again. He had a 30,000 mile GM Crate engine we didn't want to give up. I bought a couple of donor vehicles, an 87 suburban for the fuel tank, fuel lines, and wiring, and an 87 Full size van for all the sensors, tbi, intake, Heads, and transmission wiring.

In the end he has an 84 that looks like an 87 except for the belts under the hood.

One thing we maybe should have done was had a custom PROM made but we kept the Idea that we were going to use stock chevy parts for the ability to replace them anywhere.

A few things that caused us problems.
*O2 sensors have a heat range, if the sensor is too far down the pipe even by inches it will not read right. Factory TBI is in the exhaust manifold at the connector.
*TBI heads have smaller combustion chambers which results in higher compression. ?9.4-1? vs Carbed ?8.6-1?
*Dad ended up working on this one so I don't know all the details except the Carbed 700r4 internal wiring harness was different than the TBI one. I think it had to do with the lockup of the torque converter. I pretty sure he didn't have to change any valves or any other hard parts.

Speed sensor was a big question that turned out to be really easy. 87 TBI get its speed from a sensor on the back of the speedometer in the dash. The speed sensor from the van attached like factory.

PCM mounted above the glove box and the only modification I had to do was make the hole in the firewall near the distributor a little bigger.

The main wiring harness on the Drivers side of the firewall was different somehow. I just remember that i ended up swapping in the underdash wiring from the 87 suburban as well as the underhood harness.

I know that it could have been done easier by cutting and splicing wires, but that was not what I was going for.

If I did somthing like this again. I'd put a TBI Motor and trans, wiring, and as much as I could from the donor in the truck. Certainly not put factory TBI on an old long block.

Have you priced low mile used LS Motors and Transmissions? My current project is getting one. I may swear that I wont use one of the next though.

Hope this helps.

[1972BackInBlackC10]

thanks rfmaster and oklahoma k5, my truck only has 56,000 original kms on it i believe that works out to 80 or 90,000 something miles, anyways i want to keep the motor because of the low mileage but want to go fuel injected, i was planning on pretty much doing what you and your dad did swap the harness in side and outside take anything tbi related off the donor truck, just havent decided if i should stay with the heads that are on my motor now or go with the tbi heads, im not ging for big hp its just going to be a daily driver

[Oklahoma_k5]

Originally Posted by 1972BackInBlackC10

thanks rfmaster and oklahoma k5, my truck only has 56,000 original kms on it i believe that works out to 80 or 90,000 something miles, anyways i want to keep the motor because of the low mileage but want to go fuel injected, i was planning on pretty much doing what you and your dad did swap the harness in side and outside take anything tbi related off the donor truck, just havent decided if i should stay with the heads that are on my motor now or go with the tbi heads, im not ging for big hp its just going to be a daily driver

We ran the carb heads for a few thousand miles and wound up switching to the TBI heads for better power and mileage. Not that a stock 80s 350 is a power house in a suburban but it was a real dog with the lower compression.
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[rfmaster]

Originally Posted by 1972BackInBlackC10

thanks rfmaster and oklahoma k5, my truck only has 56,000 original kms on it i believe that works out to 80 or 90,000 something miles, anyways i want to keep the motor because of the low mileage but want to go fuel injected, i was planning on pretty much doing what you and your dad did swap the harness in side and outside take anything tbi related off the donor truck, just havent decided if i should stay with the heads that are on my motor now or go with the tbi heads, im not ging for big hp its just going to be a daily driver

I think you got km to miles conversion wrong 56,000 km is only *0.621 = 34,776 miles. On the subject of heads. I have done 5 different TBI conversions - two 305, two 350, 383. TBI heads are not required for TBI system to work properly. I only install EFI related harness and remove unnecessary circuits from the donor harness as this makes for cleaner install. I leave original engine bay harness in place. VSS can solved by installing 2000 ppm in-line unit - there is a long discussion in the thread. This way original instrument cluster is untouched. The key to conversion is to have all parts in place before hand - changing directions mid-stream gets things unduly complicating. Planning ahead is a key.

//RF

[1972BackInBlackC10]

guess i was wrong but thats ok ill take 34,000 over 80 to 90,000 any day lol i still have the same plan as before just swapping out the complete harness, id rather not pick apart two harnesses to make one i have trouble with my hands so dealing with small individual wires would be very tedious for me vs just taking out the old harness and putting in a harness from an 87 and up. not saying it would be any quicker but it wouldnt be nearly as hard on my hands

[slammed427]

Originally Posted by rfmaster

VSS can solved by installing 2000 ppm in-line unit - there is a long discussion in the thread. This way original instrument cluster is untouched.

Can you give some more info on this? I'm getting ready to do this swap myself, and would much rather leave my gauge cluster alone.
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[mrolds88]

Even easier, GM used an adaptor on the 454's. Bolts to a qjet manifold.