TBI swap - (Engine)

springer · January 6th, 2008, 09:19 PM

I have a chance to but a complete 87 blazer for 200.00. Runs good. the reason I am thinking about it is to take the TBI off of that motor and put it on mine. I know I will need an adapter plate which I can get at summit,but what else will I need

. I dont want to start this and then need some high dollar chip for the computer or something.

**3 on the tree** · January 6th, 2008, 09:26 PM

PM Cricket. He just did this last year.

I think he has recovered by now, from it.

**James** · January 6th, 2008, 09:46 PM

You won't need a reprogrammed chip unless your cam profile lobe separation is too great. Getting a chip is not a big deal.

I put 90 TBI on a 77 and it went well except for a repetitive code 32 and fueling problems. Never have eliminated the 32 at cruise but I think it's been narrowed down to low MAP pressure due to open flowing exhaust. It doesn't affect how it runs, but I spent a lot trying to figure it out. I ended up dumping my saddle tanks in favor of a TBI tank. A non-tbi tank can cause overpressure problems unless you run your return line into the filler neck. Also they lack a baffle and it's possible to starve your electric pump.

You'll need to add a VSS signal speed sensor between your speedo cable and transfer case. Also need to add an oxygen sensor to your exhaust - be very careful where you place it.

Howell is a good place to get information and they have a kick-butt aftermarket system that uses the GM set-up. Howell Engine Developments Inc. - Throttle Body Complete Kits

CDA 455 · January 7th, 2008, 05:04 AM

Quote:

Originally Posted by Cricket

I put 90 TBI on a 77 and it went well except for a repetitive code 32 and fueling problems. Never have eliminated the 32 at cruise but I think it's been narrowed down to low MAP pressure due to open flowing exhaust. It doesn't affect how it runs, but I spent a lot trying to figure it out. I ended up dumping my saddle tanks in favor of a TBI tank. A non-tbi tank can cause overpressure problems unless you run your return line into the filler neck. Also they lack a baffle and it's possible to starve your electric pump.[/url]

Ooo! Ooo! Ooo!

Semi hijack.

Can you elaborate on this point, please

?

My buddy mentioned this when I told him I was installing a Ram Jet 350 in my '72 Blazer.

I have the stock tank and sending unit mounted now.

What do you recommend?

springer · January 7th, 2008, 06:30 AM

Mine is not driven on the street at all. I also have a 22 gal fuel cell. I dont know how it will work. I thought about an external fuel pump with a return line. Do I need the vss because I havent had a speedo in years. Also did you use the wireing from the TBI truck or did you go with aftermarket stuff. Who reflashed your chip.

**James** · January 7th, 2008, 10:19 AM

Here's a couple more good links that explain TBI.

TBI

How to install GM TBI on any Chevy V8

Clem, the fuel injection system requires a constant, consistent fuel pressure. You must have the proper fuel pump and if "off camber", a baffled tank in order to meet those standards. The EFI fuel system runs in a loop, excess fuel is returned to the fuel tank by means of a return line. The return line AND the tank return port must be large enough to accommodate that fuel. Some people who retain their stock tank route a return line from the TBI throttle body into their fuel filler neck to get around the overly small fuel tank entry port and avoid back pressure.

So imagine your using your stock 72 Blazer tank with a frame rail mounted pump. The rail pump is not cooled in any way and can become hot causing vapor lock. The stock tank return line is too small for the larger volume of fuel that the EFI pump generates causing a back pressure, then overpressure in the tank = vapor lock or fuel boil. If you got off camber with a 1/4 tank or less the fuel pick-up might suddenly suck air which can starve the EFI pump leaving you in a bad situation. The Ramjet 350 is a TPI motor IIRC, you need a very high output fuel pump to keep up with that motor. That means your going to have to modify the fuel system to fit the engine requirements.

Springer, you can use a fuel cell but you need to make sure the tank has a baffle around the pick-up or at least a sump. If it doesn't you need to get a tank that does. I ran my unbaffled saddle tanks for a little while and found out the hard way that Non-EFI tanks do not work well with an EFI system. Ask mrk5 about our Bangs Canyon trip and the fuel boiling out the filler neck of my truck.

Eventually I found that a TBI tank with fuel-cooled in tank pump worked the best.

You have to have a speed sensor, I don't believe there's any getting around it. I used a painless wiring aftermarket harness. I did not need a chip reflash because I bought a new TBI motor and had it installed. The TBI has much better low end torque and performed better than the stock carbed 77 motor for what I do.

DISCLAIMER: I am by no means an expert on the subject so if anyone else can add to this please do so.

CDA 455 · January 7th, 2008, 11:48 AM

So I need to update my wiring too? Or just part of the wiring?

Can I get a fuel tank and pump from a '90 or '91 Blazer and call it good?

Is the '90-'91 Blazer fuel pump an in-tank or out-of-tank pump?

**James** · January 7th, 2008, 12:26 PM

Ramjet install into a 65 impala: Installing The GM Ramjet 350

If you Google "Ramjet 350 installation" it will bring up several pages of installations. You might ask Greg72 over on CK5, he has done some advanced swaps on 1st Gens. It wouldn't hurt to PM him for advice.

**MrK5** · January 8th, 2008, 04:39 PM

Quote:

Originally Posted by Cricket

Springer, you can use a fuel cell but you need to make sure the tank has a baffle around the pick-up or at least a sump. If it doesn't you need to get a tank that does. I ran my unbaffled saddle tanks for a little while and found out the hard way that Non-EFI tanks do not work well with an EFI system. Ask mrk5 about our Bangs Canyon trip and the fuel boiling out the filler neck of my truck.

Eventually I found that a TBI tank with fuel-cooled in tank pump worked the best.

No, don't ask me! I'll never confess to anything. I was never there!

The other thing you have to watch on factory NON-TBI tanks is the return line. They are usually too restrictive for TBI setups.

FYI, tbichips.com is a good source for custom chips. He sells through ebay. I've chatted with him about a TBI swap and he gave me some good pointer for modding the motor to run better with the TBI & custom chip.

I think B_to_C was able to get away without his VSS hooked up for awhile. The computer is just going to think your idling and revving the motor in park.

Badbowty75 · January 8th, 2008, 09:10 PM

Quote:

Originally Posted by CDA 455

So I need to update my wiring too? Or just part of the wiring?

Can I get a fuel tank and pump from a '90 or '91 Blazer and call it good?

Is the '90-'91 Blazer fuel pump an in-tank or out-of-tank pump?

the two different types of fuel injection have(TBI and MPFI) have completely different needs that is why i asked you in the other post what you where going to do for wiring and fuel supply. A TBI i believe runs at like 14 psi or so where a MPFI is some between 45 and 60 psi or i believe that is the range i know it is high. Any blazer or full size truck up to 92 is going to be TBI and have an in tank pump but i dont think the pump will flow enough PSI for you Ram Jet. If you could find a tank out of a truck, van, or suv with with a vortec motor i think you would be on the right path. The spec sheet that came with that motor should have a min and max fuel preassure listed on it. I know aero motive makes external pumps and regulators but they are spendy. Hope some of this helps.