Tbi swap build thread

[pancake]

Hello All,

Sorry it has been soooo long. I have been realy busy with work.

I did have some time to go to the local yards and find a 25 gallon gas tank for my TBI swap. I also found some of the relays off a Caddy that RF was talking about.

I had a question about the relays RF:

How do I know what wire of the bottom corelates to the number on the top.

EX: relay #85 is the 12 gauge solid red wire, or the 12 gauge purple and black wire?


I am using the relay for a 4 wire O2 sensor.

I beleive I read in the post that you used and adapter plate to mate a TBI to an older manifold. This could save me a lot of time and work. Did you like the adapter plate, or would you modify the stock manifold to fit the older heads?

Thanks again for all you help guys and good to see new posts.

[rfmaster]

Originally Posted by pancake

Hello All,

Sorry it has been soooo long. I have been realy busy with work.

I did have some time to go to the local yards and find a 25 gallon gas tank for my TBI swap. I also found some of the relays off a Caddy that RF was talking about.

I had a question about the relays RF:

How do I know what wire of the bottom correlates to the number on the top.

EX: relay #85 is the 12 gauge solid red wire, or the 12 gauge purple and black wire?


I am using the relay for a 4 wire O2 sensor.

I beleive I read in the post that you used and adapter plate to mate a TBI to an older manifold. This could save me a lot of time and work. Did you like the adapter plate, or would you modify the stock manifold to fit the older heads?

Thanks again for all you help guys and good to see new posts.

Hey Pancake - welcome back.

On JY relays you'll have to get very friendly with a DVM, but most BOSCH style SPDT relays follow the numbering sequence:
PIN 85 Coil (usually negative or ground connection)
PIN 86 Coil (usually positive connection)
PIN 30 Common pin
PIN 87 Normally Open (NO)
PIN 87A Normally Closed (NC)

With a socket it is a bit of work, but coil wires almost always use smaller gauge wires - e.g. 16 AWG pink/black for +12 source and any color for a control switched circuit. For power relay contact look for large gauge wire - for example 10AWG red or orange color wire.
You can (blindly) determine which wires lead to relay coil pins with a DVM - any pair of wires that you can measure 70-100 Ohms is your coil circuit wires.

To verify relay contacts you can always power up relay with a 12V source while having DVM measuring the three power wires. But first you can find NC pair, then power up relay. It is basic electricity checking - sorry if I went to basic I just do not know what your comfort level is.

On a manifold Q
I went to a TBI specific manifold, but you can use adapter plate. I am currently looking to build 383 with Vortec (L31) heads using early 70's block I got from my colleague. I am looking into using Weind 8121 with 4150 adapter plate for TBI. I am guessing that you have ubiquitous Q-Jet intake - Transadapt makes a series of adapter for Q-Jet intakes. Look for a rear #2206 mounted plate as this will move TB bores over the larger secondaries and keep throttle cable length close to stock. You still may have to experiment with rear cable bracket - I had to that because of 1" spacer I used.

//RF

[rfmaster]

BOSCH relay with contact labels on its side




This one only uses NO contacts for SPST function.

This is my relay stack (old photo - taken during summer of 07)



Left to right O2 heater relay, Fuel pump 2, Fuel Pump 1 - bracket of my favorite electrical donor - 4100 Cady!

//RF

[brontotx]

Originally Posted by pancake

I beleive I read in the post that you used and adapter plate to mate a TBI to an older manifold. This could save me a lot of time and work. Did you like the adapter plate, or would you modify the stock manifold to fit the older heads?

Pancake: I modified the stock TBI manifold to fit the older heads and it was a pain in the azz. The only advantages I see to using the stock manifold are that it is available everywhere and dirt cheap (usually included in a "system") and makes the throttle linkage line up. If you are using a 700R4, it also ensures the TV cable is in the right spot.

To modify the stock manifold, the two center holes on both sides of the manifold need to be oval-ized to allow the different bolt angle to line up with the holes in the heads. I tried using a cutter in a die grinder to enlarge the holes, but the cutter I was using quickly loaded up with aluminum and was worthless. I didn't have any other suitable cutters for the die grinder, so I used a coarse rat-tail file and filed the oval holes by hand (15-20 minutes per hole - phew!). Second, you need to compensate for the different bolt angle and how the four center bolt heads seat against the manifold. The shims you showed in Post #172 will work - that is what I used on the passenger side. On the driver's side, I could have also used the shims, but instead used a 4-1/2" cut-off wheel in my grinder and carefully changed the angle of the manifold so that the center bolt heads would seat flush.

[rfmaster]

Originally Posted by brontotx

Pancake: I modified the stock TBI manifold to fit the older heads and it was a pain in the azz. The only advantages I see to using the stock manifold are that it is available everywhere and dirt cheap (usually included in a "system") and makes the throttle linkage line up. If you are using a 700R4, it also ensures the TV cable is in the right spot.

To modify the stock manifold, the two center holes on both sides of the manifold need to be oval-ized to allow the different bolt angle to line up with the holes in the heads. I tried using a cutter in a die grinder to enlarge the holes, but the cutter I was using quickly loaded up with aluminum and was worthless. I didn't have any other suitable cutters for the die grinder, so I used a coarse rat-tail file and filed the oval holes by hand (15-20 minutes per hole - phew!). Second, you need to compensate for the different bolt angle and how the four center bolt heads seat against the manifold. The shims you showed in Post #172 will work - that is what I used on the passenger side. On the driver's side, I could have also used the shims, but instead used a 4-1/2" cut-off wheel in my grinder and carefully changed the angle of the manifold so that the center bolt heads would seat flush.

100 percent in agreement with brontotx- its a royal PITA. Get carburetor to TBI base adapter plate and save the headache. You have to take a look at your current TV cable brackets very closely (especially if you have 700R4, geometry must be right!)

TV cable geometry is critical - incorrect setup you can kiss your trany goodbye. I had to do some minor fabing (I used Holley 300-49 intake with 1" spacer). Throttle cable bracket came off some early 80's carbed car.

Rear view


Driver side back


TV Cable side view


//RF

[pancake]

Thanks RF for the pictures. I did pull the 3 relays off the strut tower on a cady. 2 are Bosch and 1 is ?.

Do have a part number for a AC Delco 4 wire 02 sensor?

I will be getting an adaptor plate for the TBI and that should help with the install.

The 31 gallon fuel tank was way to big for my 4x4 rig so I found a 25 gallon one from a 87 Blazer. Should work great.

Will keep ypu all posted.

[rfmaster]

Originally Posted by pancake

Thanks RF for the pictures. I did pull the 3 relays off the strut tower on a cady. 2 are Bosch and 1 is ?.

Do have a part number for a AC Delco 4 wire 02 sensor?

I will be getting an adaptor plate for the TBI and that should help with the install.

The 31 gallon fuel tank was way to big for my 4x4 rig so I found a 25 gallon one from a 87 Blazer. Should work great.

Will keep ypu all posted.

Pancake
4-Wire NBO part numbers
AC Delco #: AFS75
GM #: 25312184
Delphi #: ES10006

//RF