TBI Conversion Build

[big dump]

Well, I'm starting the conversion from carb to TBI on my '72 blazer, and have a few questions I'm hoping some of you guys can chime in give me some input here. I've searched extensively on here, and on thirdgen.org in their TBI section, but any other references would be helpful.

First off, the engine is a GM Performance 350 HO which has the vortec 64cc iron heads, and 9.0:1 compression. It was built in 1999, and has roughly 25k on it. P/N 12486041.

Link: http://www.gmpartsdirect.com/perform...ATID=1099.html

I bought all the parts from a '91 TBI from a fellow board member that include distributor, TBI unit, ECM, Harness, Map sensor, Knock Sensor Module, and Coil. ($200.00). I purchased separately from NAPA an 02 sensor, Water Temp Sensor, T-Stat, Knock Sensor, and Oil Pressure Switch. ($100.00)

I still need to purchase the Fuel pump, filter, hoses, block off plate, and relays associated with the fuel pump, as well as a VSS, and possibly a Park/Neutral Safety switch.

I'm running a TH350, which I will keep until I can afford to upgrade to a 700R4 in the future, but plan on running a VSS when I find one that will work.

So far, I've stripped the carb off the manifold, and tracked down an adapter plate through turbocity.com that I want to use, PN 635-600. ($60.00)

Link: http://www.turbocity.com/product_inf...products_id=12

My plan is to start bolting up the new parts, distributor, coil, TBI, and sensors, then start running the harness to see where everything ends up. I will probably save fuel for last (pump, filter, relay). Can anyone recommend a good affordable in-line pump for this conversion? Also are any of you guys running a pressure gauge, and which style relay would you recommend?



I circled a few things on the manifold here that I'm a little unsure of. First, there are two sensors on the manifold that I believe to be Temp on the left, and I'm not sure what the front is. Also, there is a vacuum tree on the back that has one line plugged. Can I just plug the MAP sensor in there? There should be consistent pressure throughout the manifold, so I shouldn't need a lone source for the MAP correct? Can anyone suggest where to plug the new temp sensor, and what I should do with the current sensors?

Also, do I need to hook up an ALDL, and if so, is it a plug in type of pigtail to the computer, or does it need to be spliced in somewhere?

Any help from anyone that has done this conversion before, or resources to this kind of swap would be very helpful. I'll keep posting on this as I go along.

Thanks in advance.

[OhNoJoe]

Here are a few site that may be helpful

http://www.hotrodlane.cc/
and
http://www.ls1.com/forums/index.php

[big dump]

Thanks Joe. Anyone else? Has this topic already been beaten to death? I really couldn't find much in the FAQ in terms of a comprehensive how to. BTW, I went with a TD Products adapter plate from Summit rather than the Turbo City. It was cheaper and I called Edelbrock, TD Products is what they recommended.

Link: http://store.summitracing.com/partde...5&autoview=sku

[kwmech]

Do not plug the map sensor into the T assy. There is a port on the rear of the throttle body unit itself that is specifically for the Map sensor. Keep the vac hose as short as possible and mount it with the vac port facing as close to down as you can. There may also be an issue with the T as that is where the fuel lines come into the rear of the Throttle body. I had a major problem with my big block and an edelbrock manifold

[68C15]

why not go with a stock or aftermarket TBI manifold?

I am also watching this in hopes someone shows what kind of fuel pump to use.

[clay68c10]

I used the inline pump Holley lists as a replacement for their TBI in Summit.
The ALDL in my setup was part of the in-cab harness, which I snagged when I helped part out the donor. I also got a wiring diagram for the donor and that helped a lot.
I'll second the above advice about the MAP, it will run weird without a nice original diameter vac line off the correct port.
I used the original fuel pump relay and fuse since I had the harness.
Did you get the distributor? If not, you'll need one since the computer controls the advance and reads RPM from it.
It looks like you have 2 temp senders in your intake now; the original style for your factory gauge is on the pass side and it looks like some aftermarket gauge type in the front. Take the front one out and put the TBI temp sender there.
I used the speed sensor from a generic cruise control kit. It has a magnet that you zip-tie to the driveshaft and a pickup sensor that you mount and wire in. One lead goes to ground and the other goes to the speed sensor input. I may switch to something more slick later, but this works for now.

[big dump]

Thanks guys. 68, I'm somewhat limited in what manifolds I can use because of the Vortec heads. I called Edelbrock, and they recommended using an adapter plate by TD Products, so I figure that's the cheapest and easiest thing to do. Clay, I did get the distributor, I actually put that in last night. Pics to come. Any part number of the after market VSS you used? Also, does anyone know of where I can find an ALDL pigtail? should I try and get one from a yard?

Thanks

[big dump]

Does anyone know what this module/sensor might be?



It's a factory part off of the '91 that I got the rest of the parts from, but I'm not sure what it is. The PN is 2110B, and it says Made in Canada T2 on the left side. Looks to be missing a boss (arrow) that would match the other one coming out of it for a vacuum line. It also has a groove on the back that slides onto the MAP sensor bracket, so I assume that it would be mounted to it.

[clay68c10]

If you search Summit online for VSS you'll find a couple that should work, there's a year split but I don't remember what year. I do know the split has to do with how many pulses per mile the sender transmits to the ecm.

[bodydropped68]

Originally Posted by big dump

Does anyone know what this module/sensor might be?



It's a factory part off of the '91 that I got the rest of the parts from, but I'm not sure what it is. The PN is 2110B, and it says Made in Canada T2 on the left side. Looks to be missing a boss (arrow) that would match the other one coming out of it for a vacuum line. It also has a groove on the back that slides onto the MAP sensor bracket, so I assume that it would be mounted to it.

looks like the EGR solenoid.

[big dump]

Well I'm not planning on running the EGR because the intake I have doesn't have a port for it, and I don't need it for emmissions, so I probably won't worry about this part for now if that's what it is.

[68C15]

Originally Posted by big dump

Well I'm not planning on running the EGR because the intake I have doesn't have a port for it, and I don't need it for emmissions, so I probably won't worry about this part for now if that's what it is.

in that case you need to get the ECM reprogrammed to eliminate its function. this old OBDI system expects it to be there and adjusts fuel trim and timing to coincide with its function.

for the record an EGR system is not a bad idea. it has no adverse affect on performance as it closes when you reach WOT. it serves a VERY GOOD purpose by reducing combustion temps (keeps from burning rings and/or valves etc.)

[clay68c10]

I actually gained some fuel economy with the EGR. OK, it was only like .5 mpg, but at the 10-12 level every bit helps.

[Rust Buster]

I did this last year with my 72 K20. It worked great for the month I used it before I decided to completely restore my truck. I bought a Walbro (highly recommended) in line fuel pump with both pre and post filters from Arizona TPI. It was expensive at $185, but everyone and their mother pointed me in that direction. I still have it and it's basically brand new if you are interested. I also have a ton of other parts (brand new and slightly used) that are doing me no good. Feel free to pick my brain as I learned a ton when I did this conversion. BTW, it was a great mod, truck ran like a gem and cold starting was 100% better

[Rust Buster]

I used a Painless Performance VSS (direct plug and play) and experimented with it plugged in and not plugged in and I noticed zero difference. I was running a manual tranny. That's for sale too (VSS)

[incoma]

I'm glad you've got this thread going. I'm contemplating changing my truck to an injection system also, and the fuel system is the item I'm hung up on.

As Rust Buster said, we can use an inline pump, with a return line back to the tank, and it will work. I've been told by several people that an in tank pump will last for quite a long time as it has proper cooling and lubrication in the tank. My challenge is that I don't want to relocate my tank to the rear and I need to convert my in cab tank.

These in tank fuel pumps require baffles in the tank otherwise they'll run dry and burn out. Our in cab tanks have a flat area around the pickup tube, could we cut that out, install some baffles, and reweld that unit back in? I'd only do this to a new tank, but is there an easier way to accomplish the same thing? I think we could probably attach the fuel pump to the stock sending unit to utilize the existing plumbing and gauge sender...

Is there an easier way to do this? Am I over-thinking this?

[clay68c10]

The biggest problem with the fuel system sucking air on an EFI setup is that it moves a lot more fuel than a carb setup. There is always a good quantity of fuel being pumped back to the tank unless you are under heavy load and/or WOT. If a carb setup sucks air for a second, no biggie- you have fuel bowls to make up for that. If EFI does the same thing, you get a lean miss since there's no 'buffer' in the fuel supply. That being said, I don't let my stock in-cab tank get below 1/8 so that I don't starve the pump. I've got the inline pump under my cab and haven't had any fuel starvation problems yet. This is an ideal setup for an external pump, you have a nice gravity feed as long as the tank doesn't go dry. I suspect an external pump for a rear tank setup would be more prone to losing it's prime under the right conditions.
As a side note, in 7 years as a professional mechanic I've replaced 2 external fuel pumps. I couldn't count how many internal pumps I've done, but I bet it's been over 50.

[Tx Firefighter]

Mount the pump in the convenient spot for your application. That fuel flow will keep it cool enough.

That deal about the fuel pump being better off in the tank since it's cooled by being submerged in fuel is a myth.

All of that fuel going through the pump cools it, not the outside being submerged.

[big dump]

Thanks for all the info guys! I just got off the phone with Affordable Fuel Injection, in MI, and they have a deal where they'll send you out a new chip calibrated to your application if you buy a harness with them. I decided to go this route after hassling with the stock harness and trying to piece it together for the last two days. Total with all of the jumpers that I need along with the chip was $365.00. I figure it's well worth it to pony up for it and make sure that I get the right chip that's calibrated for me and a harness with zero gremlins. Anyway, he did tell me that I'd be better off with the larger bore TBI from a 454 for my application because the engine is a fairly beefy crate engine with 330hp. But I'm gonna run it for now with the 350 TBI and even though I might not get ALL the power I could have, I'm sure it will be a world of difference over the carb. BTW Rust Buster, I'll PM you about some of your extra parts, do you have any sort of write up on the one you did? I think this could be a nice thread to put in the FAQ when we're all through here. I'll try to get some more progress pics up tonight.

[big dump]

Got a few more things done this weekend, I didn't really have much time to work on it but here she is...

TBI unit mounted onto manifold with the Trans Dapt adapter plate. I was slightly disappointed with this plate, only because it's just lazer cut steel that was unfinished. I suppose they count on it just not rusting because of fuel and oil getting on it, but most of the competitors that I researched were aluminum. Anyway, it bolted up perfectly and is tapped in the right spot to receive the TBI hold down bolts or studs, and also included nice gaskets.



I also drilled the hole for the O2 bung to be welded into the down pipe on my exhaust. I went to weld it in, but realized I had left my bottle open after the last time I welded. My welder is old and has a small internal gas leak, so long story short, I'll be welding tonight after picking up a full bottle today. It's gonna be very tight getting up in there to weld, but I didn't want to mount it in the front in harms way which was about the only other option.



More later...

[watahyahknow]

nice tread keep my eye on this one

[skchevota]

Just an FYI from personal experiance, make sure you run a leed to your fuse box for your ignition sorce, if you had a points style distributor and try to run off of the existing ign. wire it only puts out like 8 or9 volts. The EFI will not function correctly at that voltage. And if you dont have the overdrive tranny or EGR you dont need the VSS. it will through a truoble code though, but so will no EGR.

[big dump]

Thanks for the response. I'm having a chip burned without the VSS code or the EGR. If I had the ports on the manifold, I would opt for the EGR, but I don't think it's worth getting a new manifold just to run the EGR. Also, I'm going to run the distributor out of the 91 donor truck which has an external coil. I have a pigtail from the harness to the distributor, then one from the distributor to the coil. I had to purchase another jumper from the coil out to the power and tach. With this type of setup, how should I plan on hooking up the ignition?

[djracer]

I ran a stroker motor on tbi with vortec heads! make sure you mount your map sensor higher than the port on the tbi unit and don't allow it to drop enroute to the sensor or the vacuum line can fill with fuel and cause issues!

[big dump]

TTT Waiting on parts to get here from Summit, and AFI (Affordable Fuel Injection). Should have more to post Thursday. Purchased a return line kit from Summit,

Link: http://store.summitracing.com/partde...5&autoview=sku

and still searching out the best deal for the fuel pump. My father is a Napa sales rep, so I get good deals on most things, just trying to save as much as I can. More later.