Tbi swap build thread

[mcbassin]

Originally Posted by rfmaster

The are couple of issues that tend to pop-up when people switch from cast iron exhaust manifolds to headers in closed loop control car/trucks. The number one is being the fact that a single wire O2 sensor will run cooler if placed near outlet of the conventional long tube header. O2 sensor must be heated to about 600F for normal operation. Anything less and output voltage drops. A simple fix is to run 3 or 4 wire heated O2 sensor. Another problem that plagues headers are loosening header bolts and or a leaky exhaust flange gasket - causing exhaust leaks that O2 sensor is more than happy to pick-up! In both cases O2 feeds erroneous O2 levels back to ECM effecting commanded fuel delivery to intake.

Please do not get me wrong - I love the performance that headers offer over cast iron exhaust manifolds, but I had to replace 4 pairs of exhaust gaskets, flat surfaced header flanges (cheap dynomax headers), and went through couple set of exhaust bolts and thread locking compounds to keep things tight and in place.

//RF

I thought I was the only one that hated the down side of headers? I have had nothing with problems with them leaking at the head and the collector. How much horse does a decent set give you? Is it worth the problems? I know you can buy high dollar aluminum gaskets and retainers studs that don't back out.....but I'm a tight wad.

[68 TT]

It all depends upon how restrictive the stock manifolds are to the engine and if the tube size of the headers actually fits the way the engine is built.

If the tubes are too big or too small they won't work as well.

I have seen numbers as small as 5 hp for some smog motors and 50+ on high hp 60's muscle cars where they designed it with the intention of the owner putting on headers so the factory strapped the most restrictive passenger car manifolds on it they could find.

Our trucks probably only see 5 to 10 hp for headers without other engine mods to take advantage of them like a better cam, intake, carb, exhaust system, air cleaner, etc... Not really worth it in a fairly stock application for the headaches they typically cause.

[rfmaster]

Well, headers alone will not add significant performance gains. As 68 TT mentioned about 5-10 HP on a stock engine. From my experience you have to look at a complete engine in combination with drivetrain. Engine is nothing more than air pump which has finite volumetric efficiency. This discussion can go on forever, but a total package should be considered vs. individual pieces. Some parts work better than others when combined in engine package.

//RF

[250cows]

Well I got my motor fired up last night, and let it run for 30 seconds (I had to many wires laying around to much heat).

Now I'm still trying to finish up some wiring on 700r
My comp and wiring came from 89 truck and my motor and trans came from a 89 caprice. My harness does not have a c7 wire -- Can I re-pin c7 and it will work as the high gear wire, or will the comp need to flashed? Also what does TCC stand for torque converter control?
Thanks guys for all the help!!!!

[el phantasmo]

Wow I thought I was the only one to have bad luck with header leaks. My collectors would leak badly (too much frame flex) after every off road trip. I cut the collecter off and welded them straight to the exhuast pipe. No more leaks there but still had plenty at the heads. My block huggers are top of the line ceramic coated inside and out. I have used the same headers in a toyota v-8 swap with no leaks after two years. I just hope they will not cause the o2 sensor to read wrong.

250cows was your donor truck auto w/ overdrive? If not you may have to do more than pin c7 in, but I am no expert. I bet rf can tell you, he seems to be quite knowledgable about these systems. Torque converter control sounds right for TCC. It tells the converter to lock and unlock.

Have a good Friday the 13th everyone!

[250cows]

I'm assuming my comp donor was manual, because I dont have a wire in c7.

[rfmaster]

Originally Posted by 250cows

I'm assuming my comp donor was manual, because I dont have a wire in c7.

250cows

Can you post your ECM part number and broadcast code (BCC)??? Trucks equipped with THM400 did not use 4th gear indicator. You donor truck may have had either manual or THM 400 transmission. This explain absence of C7 wire - which addressed by inserting wire and pin into C7.

//RF

[250cows]

Here are the #
86asdx k391991245
16139481
If it is a for a 400 or manual, can I still have the tcc lock up option?

[250cows]

Can anyone answer the question above?

[FRENCHBLUE72]

I have no idea....

[Test Pilot]

Not to severly deviate the topic, but since all of this good info is here in one thread I thought I'd add this for those of us following along that are in 72 and older trucks.

The below article (see link) has some info on how what the magazine guys did a 5.3 swap in a 68-72 C-10. Specifically what sparked my interest is what they did for the return line. I plan to take it a step further and make a line that attaches to the pipe thread fitting they welded in and dumps at the bottom of the tank and pointed away from the pickup.

I hope this helps someone.
Thanks to the OP and knowledgeable posters for adding thier info. I have yet to start collecting parts, but the TBI Swap is in my top 3 of my short list of things to do this thread will be invaluable when the time comes to start installing parts.


http://www.classictrucks.com/tech/09...all/index.html

[68 TT]

Originally Posted by 250cows

Here are the #
86asdx k391991245
16139481
If it is a for a 400 or manual, can I still have the tcc lock up option?

Is that the number off the chip itself or the ECM housing label? They are two different numbers.

[250cows]

Originally Posted by 68 TT

Is that the number off the chip itself or the ECM housing label? They are two different numbers.

On the housing label

[rfmaster]

Originally Posted by 250cows

Here are the #
86asdx k391991245
16139481
If it is a for a 400 or manual, can I still have the tcc lock up option?

Sorry - dropped the ball on this one.
From the limited information that I could find ASDX was used on 350 trucks (1227747 ECM) with manual transmission. For 350/700R4 (TBI) look BBC ASDZ calibration which was used in 1/2 - 3/4 ton C/K and G1 G2 (Vans) V1 R1 (old body style 1/2 ton truck). You can swap a chip or burn your own with a copy of ASDZ.

If you chose to burn your own Bin files visit

http://www.moates.net/

- for all the necessary tools, adapters and bin file images.

You'll need to add TCC enable output and 4th gear input to your harness - see schematic posted earlier in this thread.

//RF

[rfmaster]

Originally Posted by Test Pilot

Not to severly deviate the topic, but since all of this good info is here in one thread I thought I'd add this for those of us following along that are in 72 and older trucks.

The below article (see link) has some info on how what the magazine guys did a 5.3 swap in a 68-72 C-10. Specifically what sparked my interest is what they did for the return line. I plan to take it a step further and make a line that attaches to the pipe thread fitting they welded in and dumps at the bottom of the tank and pointed away from the pickup.

I hope this helps someone.
Thanks to the OP and knowledgeable posters for adding thier info. I have yet to start collecting parts, but the TBI Swap is in my top 3 of my short list of things to do this thread will be invaluable when the time comes to start installing parts.


http://www.classictrucks.com/tech/09...all/index.html

Welcome to the board and the TBI swap thread.

Firstly, I would advise you not to weld-in return line bung at the bottom of tank! The reason for this is that a stock TBI system is a relatively low fuel pressure system (stock TBI is content with 13 PSI give or take). TBI uses a spring loaded fuel pressure regulator (FPR) on top of the TB. For FPR to function correctly (i.e. steady 13 PSI) there should be minimum back pressure in the return line. By installing return at the bottom of the gas tank the return fuel must overcome the weight of fuel present in the tank. Soooo with that in mind install return line at the top of the gas tank as shown in the classic trucks article. In addition, I would also add a vapor line from the tank a charcoal canister. IFRC, early trucks did not have charcoal purge canisters, but it makes good sense and it does not cost any performance.

//RF

[250cows]

Would this be the best way for me to get torque converter lockup?
http://700r4.com/tech/tcc/relay_install/index.shtml

[68 TT]

Originally Posted by 250cows

Would this be the best way for me to get torque converter lockup?
http://700r4.com/tech/tcc/relay_install/index.shtml

Without TBI yes you would need that kit to have functional converter lock up, with a TBI conversion installing and wiring in the correct dual purpose brake switch and making the connections to the ECM are all you would need. The ECM will take care of the rest.

[250cows]

Originally Posted by 68 TT

Without TBI yes you would need that kit to have functional converter lock up, with a TBI conversion installing and wiring in the correct dual purpose brake switch and making the connections to the ECM are all you would need. The ECM will take care of the rest.

But will my manual shift ecm work -- can I just install a c7 wire and hook it to my tan/blk wire from trans.?

[68 TT]

Originally Posted by 250cows

But will my manual shift ecm work -- can I just install a c7 wire and hook it to my tan/blk wire from trans.?

The ECM & added pin wiring no problem. You will need a chip from an auto trans version with the 700R4 to work though. There are T-400 versions out there too that will be different programming so it needs to be a 700R4/4L60 version to work right and have TCC functional. Look for a half ton truck or Suburban and any Blazer as a donor.

[250cows]

Thanks for the help.

[Test Pilot]

Originally Posted by rfmaster

Welcome to the board and the TBI swap thread.

Firstly, I would advise you not to weld-in return line bung at the bottom of tank! The reason for this is that a stock TBI system is a relatively low fuel pressure system (stock TBI is content with 13 PSI give or take). TBI uses a spring loaded fuel pressure regulator (FPR) on top of the TB. For FPR to function correctly (i.e. steady 13 PSI) there should be minimum back pressure in the return line. By installing return at the bottom of the gas tank the return fuel must overcome the weight of fuel present in the tank. Soooo with that in mind install return line at the top of the gas tank as shown in the classic trucks article. In addition, I would also add a vapor line from the tank a charcoal canister. IFRC, early trucks did not have charcoal purge canisters, but it makes good sense and it does not cost any performance.

//RF

I wasn't planning on returning it in the tank at the bottom. I was going to attach a tube to the part that gets welded into the top of the tank. This way the return line is submerged, but it will still enter the tank at the top.

[rfmaster]

Originally Posted by 250cows

But will my manual shift ecm work -- can I just install a c7 wire and hook it to my tan/blk wire from trans.?

C3 ECM (1227747 - you have a later service replacement p/n ECM) was designed to handle all drive train combination's. There are no ECM hardware differences between 'manual' and 'auto' ECMs. What sets them apart is the 32k EPROM chip which provides configuration tables and instructions to a microprocessor in the ECM how to handle different engine - trany combination. Different configurations stored in EPROM's are identified with GM lingo - aka broadcast code - BCC.

Before tying TCC line from transmission into ECM it is a good idea to verify the actual TCC lockup and release operation by manually enabling and disabling (i.e. pulling this line to ground). In some applications 700R4 were configured with positive logic vs. common negative logic - ECM pulls C7 low to enable TCC. For the life of me I do not know why GM did this, but it was done. As 68 TT mentioned you'll have to get a dual poll brake switch - GM 25524845. One set of contacts is normally closed (NC) this will be used with TCC wiring to provide +12 volts to the trany. When you step on the brake paddle NC switch contacts open and de-energize TCC circuit thus kicking out TC lockup. The normally open (NO) set of contacts will be used with brake light circuit in a normal fashion.

If you need a schematic - ask.



//RF

[250cows]

I'm a slow learner on elec. stuff.
A schematic would be great.
My wires coming from trans are purple, blue, tan/blk.
When you say pull c7 to ground to check, is this normally a ground or a voltage wire?
Also you're saying my ecm and chip will be fine.

[rfmaster]

Originally Posted by 250cows

I'm a slow learner on elec. stuff.
A schematic would be great.
My wires coming from trans are purple, blue, tan/blk.
When you say pull c7 to ground to check, is this normally a ground or a voltage wire?
Also you're saying my ecm and chip will be fine.

OK, here it is - the in CAB TBI conversion wiring. This schematic covers the following circuits talked about elsewhere in the thread: TCC with brake pedal disengagement switch (GM 25524845), VSS circuit using a standalone 2000 ppm inline VSS pulse generator from JTR (or equivalent), minimum ALDL connector wiring, SES light, P/N switch wiring using a relay and an isolation diode, and power for injectors. ECM power circuit is not shown.




Schematic was not closely reviewed - please check against references for typos. As always please perform a sanity check.

//RF

[68 TT]

Originally Posted by rfmaster

OK, here it is - the in CAB TBI conversion wiring. This schematic covers the following circuits talked about elsewhere in the thread: TCC with brake pedal disengagement switch (GM 25524845), VSS circuit using a standalone 2000 ppm inline VSS pulse generator from JTR (or equivalent), minimum ALDL connector wiring, SES light, P/N switch wiring using a relay and an isolation diode, and power for injectors. ECM power circuit is not shown.




Schematic was not closely reviewed - please check against references for typos. As always please perform a sanity check.

//RF

I haven't messed with the stock early TBI mechanical speedo dashes that have the optical sensor on them before. All my other EFI conversions were port injected so they used different setups entirely.

How would that three wire module coming off the back of the speedo interface with the ECM? I know one wire is a ground and one is ignition on power so I'm assuming the one remaining wire goes into the ECM at A10 like the JTR module. How does this interface with the DRAC and how is it wired in?