Tbi swap build thread

[1984 t type]

I have not put my automatic trans in yet but I did pull the manual out, it was a 456. I got my 700r4 and transfer case out of a 86 k blazer then sent the trans out to be rebuilt, I also made sure to get all the linkage. On another note picked up my parts truck yesterday and man is the interior nice, paid 450 for it and it actually runs but it needs new head gaskets. Should I send the center bolt heads out to the shop and use those heads and intake off the 91 or should I just use what's in my truck now with an adapter plate? I am trying to keep this a low cost swap but want to do it the right way. Not looking for power but reliability and mpg's as this will be my new daily driver.
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[rfmaster]

Originally Posted by 1984 t type

I have not put my automatic trans in yet but I did pull the manual out, it was a 456. I got my 700r4 and transfer case out of a 86 k blazer then sent the trans out to be rebuilt, I also made sure to get all the linkage. On another note picked up my parts truck yesterday and man is the interior nice, paid 450 for it and it actually runs but it needs new head gaskets. Should I send the center bolt heads out to the shop and use those heads and intake off the 91 or should I just use what's in my truck now with an adapter plate? I am trying to keep this a low cost swap but want to do it the right way. Not looking for power but reliability and mpg's as this will be my new daily driver.
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The center bolt heads on your donor are commonly known as a swirl (193) heads. If you look into intake port under intake valve you'll see a ramp that forces intake air to swirl.



Great concept except that it causes air flow restriction at higher RPM's which is not an issue for truck engines. IMHO, I would rebuild or fix 91 engine vs 85. The 91 block uses single piece RMS which almost never leak vs. split 2-piece seal used in 85 block. Also, the 91 block has provisions for a roller cam - cast bosses for the roller lifter retaining spider and machined cam thrust retention plate in front. If you ever choose to go to roller cam the conversion is matter of sourcing parts.

What you have to figure out why head gasket failed - most of the time it is due to head warping. These heads do not have enough material in right places and if subjected to prolonged high outputs tend to warp. If overheated they crack between two center adjacent exhausts ports. Before spending time or money on these heads have machine shop magnaflux them to make sure that there are no cracks. I have thrown out probably 3 or 4 sets of heads last year for cracks.

Older heads (from your 85) will bolt to your 91 block. 91 Intake manifold will require minor filing of 4 inner bolts - the angle changed from 45 to 72 degrees. Round file does the trick.

Stock ECM calibration can be used as a starting point to run this engine. However, as 68TT mentioned this will not be optimum due to spark advance (SA) and volumetric efficiency (VE) tables in your ECM setup for a 350 with swirl heads. ECM parameters can be easily changed by altering appropriate tables and burning new chip for your ECM.

Let us know what you find - do not rush into it - ask questions.

//RF

[1984 t type]

My 85 block runs like a dream and I'm on a budget so rebuilding the 91 block is not an option at this time. However I will take the heads to the machine shop and see if they are any good. Was planing on pulling my 85 block out to clean and paint the engine bay and block, so while it's out I will change all the gaskets and rear main seal also gonna check the freeze plugs. If I do use the 91 heads on the 85 block will I still have to get a new chip
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[68 TT]

Originally Posted by 1984 t type

My 85 block runs like a dream and I'm on a budget so rebuilding the 91 block is not an option at this time. However I will take the heads to the machine shop and see if they are any good. Was planing on pulling my 85 block out to clean and paint the engine bay and block, so while it's out I will change all the gaskets and rear main seal also gonna check the freeze plugs. If I do use the 91 heads on the 85 block will I still have to get a new chip
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You could put the tiny cam from the TBI engine into your 85 block with the 91 heads & intake on it then the ECM wouldn't know the difference. This would get you on the road for the least amount of money if the cam is in good shape and the heads were good. It will be a toss of the dice as to the condition of the TBI cam lobes though and with a blown head gasket or possibly cracked heads I don't think this is a budget frinedly approach for you.

If your cam is not too big in the 85 engine then it will end up being cheaper to just put a TBI adapter plate on the 85 intake and buy the stuff to burn your own prom chips rather than put out the cash to rebuild the TBI heads.

I would go with a new computer friendly cam & lifters with more lift & duration than the TBI cam if the one in your 85 is too aggressive. The stock TBI cam is ridiculously small and I wouldn't spend the money to buy a new stock replacement one.

The TBI intake does not flow well at all and will be a hindrance even compared to the stock 85 Q-Jet intake so don't waste your time or a set of intake gaskets to make the thing fit your 85 heads.

You will want an ALDL cable and the TunerPro RT software anyway just to monitor your engine so all you really need to buy above the basics is a chip burner like you will find on moates.net

A little quality time tuning the ECM to the 85 engine won't cost you anything but time and a bit of gas. The guys on thirdgen.org have documented all the tuning procedures very well so they are a great learning resource.

[rfmaster]

Further to 68TT point

If you have a factory cam (or even a mild RV cam ) in your 85 350 stock TBI calibration is robust enough to run that engine. Once you get it going and driving you'll want to dial in the combo for a better performance which will require, as 68TT put it " Quality time with TunerPRO ". You'll be surprised how much performance can be attained after you are done with it. Just keep this in mind stock TBI cam has 179/194 deg duration at .050" and maximum valve lift with 1.5:1 rocker ratio is .350/.384 - pathetic for all practical purposes.

For a factory or mild RV builds my basic rule of thumb is - if it idles STEADILY around 650-700 RPM with 14 to 16 in-Hg (or better) stock calibration - (ASDU) is good enough to start with and run. The biggest hindrance to TBI is large overlap camshafts with tight LSA <112 deg. Tighter LSA and large overlap throws too much unburned intake charge into exhaust, at idle, causing false lean condition.

If you are looking for a mild flat tappet camshaft MT-2, CS-1014R, Crane CRN-113904, Edelbrock Perfomer 3702 and many others have been tried and are known to work with basically stock TBI calibrations.

//RF

[1984 t type]

Ok so I'm going to go with the adapter plate with the 85 intake and heads. Is there going to be a special bracket for the tv cable ? Just trying to get my parts lined up
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[rfmaster]

Originally Posted by 1984 t type

Ok so I'm going to go with the adapter plate with the 85 intake and heads. Is there going to be a special bracket for the tv cable ? Just trying to get my parts lined up
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There are couple of ways of solving TV cable bracket issues.

I have used Edelbrock 8036 kit - I do not know why Edelbrock designates for pre 78 intakes?

Existing throttle - trany kick down bracket (with spacers) and adjustable TV cable. Works OK if TBI to Carb intake adapter is 1/2" or less. Taller adapters screw up TV cable - throttle arm geometry - you have to raise bracket to maintain TV cable geometry, hence spacers.

Bowtie overdrives kit - expensive, but very nice kit. Works with carbs or if adapter plate is thin.

Carb brackets of various flavors are also known to work.

Correct TV cable - throttle arm geometry and correct adjustment of TV cable is a key to 700R4 longevity. Just my 2 cents.

//RF

[68 TT]

Originally Posted by 1984 t type

Ok so I'm going to go with the adapter plate with the 85 intake and heads. Is there going to be a special bracket for the tv cable ? Just trying to get my parts lined up
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You should be able to shim up the one from the 91 donor vehicle and make it work on your 85 intake with the TBI adapter.

Take some pictures & measurements of it on the 91 before you make the swap and shim it as needed to get the same distance from throttle arm and the same height relative to the base of the throttle body. This will get the proper amount of cable motion and the correct angle so everything works the way it is supposed to.

[1984 t type]

Who do u guys recommend that I get my Tbi adapter from ?
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[rfmaster]

Originally Posted by 1984 t type

Who do u guys recommend that I get my Tbi adapter from ?
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Probably the nicest CNC machined TBI plates that I have seen:

http://www.tbiparts.com/

He also carries a full assortment of TBI related parts.

//RF

[68 TT]

Originally Posted by rfmaster

Probably the nicest CNC machined TBI plates that I have seen:

http://www.tbiparts.com/

He also carries a full assortment of TBI related parts.

//RF

That one also addresses the common problems with many of the cheap adapters. Vacuum leaks because the TBI unit is partially over an intake mounting bolt location and insufficient flat area around the TBI unit to seal the IAC passage ways.

It is well worth the extra money to get the tbiparts adapter rather than try to save a couple bucks on a cheaper one and having to deal with problems.

[1984 t type]

Ok gonna order that one. New problem, went to start removing the harness from my parts truck and it's not worth saving so who do you guys recommend for a aftermarket harness? Also what parts do I still need off the parts truck? I allready pull the computer and tbi unit
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[rfmaster]

Originally Posted by 1984 t type

Ok gonna order that one. New problem, went to start removing the harness from my parts truck and it's not worth saving so who do you guys recommend for a aftermarket harness? Also what parts do I still need off the parts truck? I allready pull the computer and tbi unit
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Can you post photos - it is tough to make recommendations without seeing the harness. Locally, in SoCal, due to the heat connector bodies crack, but these can be easily replaced. It is cheaper than R&R the whole harness. If there is a wire damage - that can be fixed with a solder joint and heat shrink. I come from electronic background and fixing harness issues is not a hard task, just requires some patience and correct materials.

If you are set on replacing your harness check out Fuel Injection Connection dot com on Ebay. Personally, I have reworked every single donor harness - I have never used aftermarket harness before. Perhaps someone else can chime in and suggest other sources.

You'll need all sensors
CTS - cheap to replace
O2 sensor - get a new one.
ESC module - works with knock (KS) sensor
KS - get a new one keep old one as spare.
Distributor & coil - 85 may have vacuum advance which does not work with EFI
MAP Sensor
EGR control valve
VSS - part of trany

TPS and IAC are in TB
FP relay

Do not forget to remove ALDL connector - driver side under dash.

//RF

[1984 t type]

Can someone post a schematic of the sensor locations. I may have jumped the gun saying the harness is shot it was in the 90's today and I was frustrated but I do have a couple of connectors that are ruined some were not even hooked up. Will post some pics later today or tomorrow. Thanks for the help
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[critict1gc]

ok so i need a heated o2 sensor for my hooker headers is there one in specific that i should get? can i just get any 3 wire bosch sensor off jegs. if there is a good one on jegs can someone tell me wich one

[Jonboy]

I used the FIC harness in my swap. The harness I had was pretty hacked up, so it was worth saving $245 of aggrivation to me to go with a new one. Not exactly shoestring budget, but not rediculously priced, either.

[rfmaster]

BOSCH makes fine O2 sensors, but GM ECM PID algorithm does not match very well with BOSCH S curve. Most of the time it will work OK, but sometimes you get funny close loop cycling between rich -lean condition. When I switched from BOSCH to AFS-74 problem resolved itself. AFS-74 heated 3 wire O2 sensor was used in a 95 S10 4.3L V6 GM part number 25312179 or 19178959 or ACDelco AFS-74 (or 213-632).

Rock Auto has 19178959 (AFS74) for about $50

//RF

[bagged74]

this is a great thread!! tons of info.
Do you guys have any experience with the 16197427 ECM? I am using the engine, trans and harness from a 94 truck. I have all the wiring sorted out except for one wire that doesnt seem to match the pinout diagram or the service manual that I have.

[rfmaster]

Originally Posted by bagged74

this is a great thread!! tons of info.
Do you guys have any experience with the 16197427 ECM? I am using the engine, trans and harness from a 94 truck. I have all the wiring sorted out except for one wire that doesnt seem to match the pinout diagram or the service manual that I have.

Which wire? We had a one gent that have transplanted 7427 PCM into 70 with 4 speed.

[bagged74]

the wire in question is in pin F8. the pinout and service manual show it should be gray/blk, but the wire I have is blue and runs down to a 2 pin weatherpak connecton that has a purple wire in it as well. the purple wire the runs to a plastic box with two diodes inside and two other purple wires coming out. i have no idea where these were connected as they were cut when i got the harness.
pin F8 shows to go to the 4wd indicator, but the truck was 2wd and had no 4wd indicator. any ideas?

[rfmaster]

GM used one harness design for both 2wd and 4x4 drive-trains. In 2wd application F8 is unconnected (gray/blk) wire. The box that you are describing is most likely an anti-lock diode module. This module should have two purple wires fed into Pin A. One of the two purple wires should be tied to TCC/Brake switch, while the other purple should be tied to Pin E13 of the PCM. The B port of the diode module is tied to 4x indicator and antilock module.

If you are doing 2wd transplant - leave this wire unconnected.

//RF

[bagged74]

Well I finished up my tbi swap today and drove it for the first time. It runs great, but I'm pretty sure the 3.07 gears are gonna have to go.
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[68 TT]

Originally Posted by bagged74

Well I finished up my tbi swap today and drove it for the first time. It runs great, but I'm pretty sure the 3.07 gears are gonna have to go.
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If you find a rear axle donor with gears you want and TBI then the DRAC will be right for the axle swap too. Vans came with 3.42 & 3.73 gears pretty commonly.

[Cruz]

I have also posted this at the 3rd gen board....
Looking for thoughts or ideas on intake manifolds.

“75” 4 bolt block 9.5:1 compression (non TBI RV Cam can't remeber the specs currently)

194 cast iron heads ported and polished gasket matched.

89 TBI 7477 ECM running EBL with 14 psi fuel pressure

Currently running the 89 TBI intake modified to bolt to my cast iron heads.

I have recently acquired an RPM Air Gap manifold and was wondering if anyone has used this with the EBL and were there any performance gains/loss or other issues using this manifold? Since the Air Gap does not have a provision for an EGR will this affect anything with the GREAT mileage I am now enjoying?

Since converting my truck to fuel injection from a carb…… I have doubled my MPG from 10 to 21 MPG. All I can say is wow…. This is with running the TH400 in it now….. looking for a good 700R4 for the next project just to see what the mileage will end up…………..

Thanks for your input

Cruz

[dropd80s]

Finally got my CCSB pulled out of the shop under its own TBI'd power yesterday! Shes an 86 with a 90 sub TBI 350/700 and complete harness swap. Everything stock. My problem is she seems to be running very rich. I have considerable black smoke at idle. I have let the truck warm up to operting temp, and still have no codes stored. Everything is clear.

I am curious if the higher pressure fuel pump I ran (E2000) is overloading the FPR?
I know I need to check and make sure the 5/16" return line I ran is not kinked.
Also, I have no exhaust on the motor, only a few inches of pipe on the manifolds. Could this be cooling my 02 and not letting it read properly?
I assume this could also be a CTS problem or Vacuum leak?

Any ideas you guys have or how I should go about ruling things out would be a huge help. Thanks in advance