TBI conversion on a 472

R

restorencads

New Member
Joined
Jan 8, 2008
Messages
11
Reaction score
0
Points
1
Location
Gig Harbor, WA
Hello all,

Well I'm starting a new fuel supply project. All help would be greatly appreciated.  I've decided to attempt a tbi install on a 472 cad motor.  I've gone out to my favorite pick a part and gotten a tbi system from a 1995 Chevy 2500 pickup with a tbi 350. I've got the ECM-16197427, throttle body, and complete engine bay wiring harness with sensors.  I will be purchasing a 1981 FI 368 distributor for the project.  Any suggestions for fuel pump for this application (part# preferred)?

I will be taking this project step by step. I want to get all parts ready for install and then finally install.  I will be worrying more about programming later.  My questions for now are.  I'm looking at the huge pile of wires and thinking "I like wiring electronics, but what have I got myself into?"  I obviously won't be needing the part of the harness for the transmission and other lighting.  Could I use the manual to decipher what wires go where and remove unnecessary ones like transmission?  Basicly as I understand it, I will only need the wires going to the ECM that power it, ground it, go to sensors, throttle body, ignition, distributor, and fuel pump. Can't everything else go?  What about the knock sensor for the cad motor; I understand the knock sensor is engine specific, but won't it make the spark control go crazy? What is the remedy.  Next, to for warn you this is a later model '95 so it has the ESC inside the ECM.  What wire connections are required for connecting the 368 distributor?  I really didn't want to get involved with egr, it isn't on the engine now, and seemed like a lot more trouble.  But, what do you guys think?  If it were installed would I need the air pump reinstalled, flapper exhaust manifold, and egr manifold.

Well I suppose that is enough for now.  Sure to have more questions in the future.  Thanks in advance for any and all help!
Nathan
 
Can,t you get what they call a "metered drip can" to work for your car?
 
This is a stock low comp (71-74) motor?  Is it in a cadillac or at least going to be used like a cadillac with only occasional burnouts and such?  Also keeping the R's low (a typical cadillac did not see much over 3K very often)?

Fuel pump should be easy.  I have an inline holley that was around $130 IIRC and its quiet. The TBI's run in the 10-20 psi range and have a built in regulator so pretty much anything but a top fuel performance pump will work.  I remember reading about some late 80's F-150's that had frame mounted pumps that were reliable, cheap, and easy to mount. 

Have you found a way to do the tuning?  I am thinking that you are going to have to be able to tune it.  Things like you mentioned like the lack of a knock sensor and egr will cause issues.  I am 90% sure without a knock sensor it will go rich and retard the timing.  If its expecting an egr its going to be real lean at cruise (and thats on the 350) not sure what to expect on a 472.  I have heard even the hard to find 454 setup does not run worth a darn on a cad without some serious tuning.

One thing to look for at the junkyard or ebay (assuming you have the hood clearance) is the adapter plate for the TBI.  The early TBI 454's still used the Qjet manifold.  I like the look of those as far as even flow vs. the other options for a mounting plate.  In my car I dont have hood space so I have a holley flat plate that locates the throttle over the secondary holes.  I have never seen one in a yard but the are usually available on ebay.

I started out with a analog holley projection system on a 425 in a deville.  I got it dialed in so overall it ran pretty well.  I always had a few hiccups and flat spots but over all other than sucking gas worse than the carb it was totally drivable.  I then put the same system on my freshly rebuilt mostly stock 500  and pretty much could not drive the car at all.  I suspect the holley box was optimized for something around a 350 and there was just not enough range to run even a stock cad.  I then got a megasquirt and overall Im happy with it.  My TB is pretty much the holley version of the 454 one.  From what I read the 350 one was slightly smaller bore and has smaller injectors.  Mine has 85lb hr injectors and so far I have not seemed to hit any limits of fuel or air but I think thats just cause I am running a stockish motor at fairly low rpms.

Somewhere I think I have a bookmark with good info on the GM injectors and TB's. I will go look for it and post it if I can find it.
 
Here is the link:
http://www.diy-efi.org/gmecm/component_ ... ctors.html

That says that a 350 should be 43 mm bore with 2 55lbhr injectors.  Using the basic formula that comes out to around 187 HP at the stock 13 psi.  Even a stock 74 472 should make 200 hp. To get that you would have to go to 18 psi. To get to 250 horse you would have to go to 26 psi which I would not recommend.  I have heard that most of the TBI's start having issues around 18psi.
 
Hello Everyone,

First of all thanks!  Yes it is a 1972 Cadillac SD w/472.  Currently it is completely stock, but I plan to build a mild 500 in the future.  As for the tuning, I plan to put TunerCat/TunerPro on my laptop with  Moates Ostrich Emulator. To tune live and get all the bugs out and then burn a chip with the bin from program. I actually, already have the 454 adapter plate, but I'm concerned about clearance also. May end up with just a plate. So based on that information 2 80 lb/hr injectors at stock 13psi pressure would be a good match or way over kill.

I have a few more questions.  First of all did you (73eldoconvert) put new fuel lines in. I understand you need to use FI rubber hose where necessary, but will the stock fuel lines withstand the TBI pressure?  The car was originally AC equipped, thus it has the return line. Is it adequate for TBI? The car currently has dual exhaust.  How does that work with the O2 sensor? Can you wire a second one in?  When referencing this in the Hanes manual electrical diagram, I noticed it has the ppl wire connected to Oxygen Sensor HI and then it has Oxygen Sensor Lo (tan wire) grounded.  Could this tan wire be connected to a second O2 sensor?  To questions relating to transmission stuff. Is a speed sensor necessary and if so what is your options?  In the hanes manual it comments about the Neutral Safety Switch can cause problems.  It states, "Caution: The vehicle should not be driven with the P/N switch disconnected because idle quality will be adversely affected and a false Code 24 may be set." What did you do with our primitive P/N switch.  The ECM has three wires for P/N switch.  I'm really just jumping the gun here, because I could probably figure it out when I get there.  How is the '81 distributor connected to the ECM control? Does it have a coil and cap assembly like the HEI?

I'm concerned about the knock sensor also.  I read some where that in MS circuitry the KS is available, but isn't connected and isn't commonly used, why? But with GM ECM's it is very usually always recommend.  Is it be cause it is a closed system and is always trying to adjust for maximum performance?  Well in two different location there are ways of disabling the KS.  One says you can just disable it in the programming.  This next link says you can connect a resistor inline to ground. Which will fool the computer into thinking it is alright.  I was thinking that wouldn't be a bad idea, if you could limit max advance in a way so that it couldn't excede.  Like a distributor locks out at say 36 total. http://www.thirdgen.org/techboard/tech-general-engine/379504-knock-sensor-issues.html

The problem with EGR is in the tuning, correct?  It will require additional fuel at cruise.  Do you think it is important to add the EGR to a non-EGR car? I would rather keep it simple and leave it off.
Thanks, Nathan
 
I dont remember working on any gm TBI cars that had 2 o2 sensors.  The few that had duals were multiport.  Im running a dual exhaust system and only 1 o2 sensor.  Thats the way most of the older factory stuff worked, the sensor was at the end of one of the exhaust manifolds well before the crossover pipe.  Some o2's work to ground, some are isolated from ground, and some have heaters in them so be sure you know what you are dealing with.  They can easily be damaged and some are expensive.  Are you planning on a wideband? Most of them will output to a gauge and then simulate a narrow band for the computer.  Most people say tuning can be easier and quicker with a wideband.  I have one.  Knowing what I know now I may be tempted to try one without it but I already own the wideband.

As for the knock sensor I think it is because they are pushing it a little.  If you ended up with some bad gas (easy to do with all the alcohol now days) and got a hot day you would be in trouble but instead of just killing all the performance they push it a little because they have the sensor to pull it back if you get in trouble.  What I read about the sensors is they have to be located in a pretty specific location and 'tuned' to work correctly.  Sometimes on older motors its just not possible.  It would at the least take a bunch of trial and error.  Most people that are using them seem to be using blocks that are new enough to have a factory location and sensor.  If you get it in the wrong spot it will pick up things like lifter noise and not detonation.  Thats likely why even Megasquirters dont use them, no port on the blocks.

For fuel line I just bought regular gates xl hose at my parts store.  Its rated to something like 45 psi which I figure is plenty of headroom for a 15 psi system.  I used the factory return line.  I think the books say that you should be running less than 3 psi on the return.  On my car with the engine not running its close to that but running the needle just bounces off its stop.

The 81 dizzy looks just like the 74- Hei's with the coil in the cap except there is no vacuum advance can and the cap is held with screws instead of those clip screw things.  The GM TBI cars used a smaller cap with or without an internal module and an external coil.  I think electrically they are the same as the 81 but the connectors will be different.

The PN switch came up here recently and I had never run into it before.  The mid 70's cadillacs used a mechanical interlock so they did not have the extra contacts on the switch but the earlier and later ones apparently do fit so you can swap them out.

As for the EGR dont have mine hooked up because MS is not really designed to use them.  I want to find a way to use it because I am having detonation problems that I think are heat related.  Egr cools things and I think would help my problem.  I had the car running pretty good with the carb and recurved dizzy.  I had drivability issues in the transitions with the EGR hooked up so I unhooked it.  I then had to add a ton of fuel and started the detonation problem after a long high speed cruise.  AS for your problem making the computer think its there will be the first trick and then tuning will be the second issue. 
 
Hi Nathan,

I have a '74 472 and have been doing research into the different EFI options, especially the GM TBI ECM's and Megasquirt.  Difficult to make up my mind as both have their pro's and con's.

Wiring:  ftp://ftp.diy-efi.org/pub/gmecm/manuals/16197427/

368 distributor wiring.  I have one of these too. :) Maybe some one will post the 1981 Cad wiring diagram.  if not take a look at the Megasquirt Megamanual.  It's a wealth of info and probably has enough info for you to figure this out.

Throttle body.  I agree with 73eldo that the 350 TB isn't a good idea.  Not only are the injectors on the small side, but the lack of CFM will cost you top end power.  I would use the GM 454 TB with it's 2" bores and 80-90# injectors.  From what I've read the 4.3/5.7 TB's have 1 11/16" bores with 520 CFM and the 454 TB's flow 670 CFM. GM didn't publish CFM numbers so take it for what it's worth. I believe you can run 454 injectors with your 7427, but you should research that.

O2 sensor.  You won't be able to piggyback 2 sensors off the same circuit.  I wouldn't worry too much about just reading one bank. That was the normal setup on OBD1 engines. If you don't have a heated sensor you should put it as close to the exhaust manifold as possible or it may not run hot enough and will take forever to warm up.  If you have a heated sensor I would put it in the cross-over tube.  Again, the Megamanual has a ton of info.

Fuel Pump. I don't have a part number, but the in-tank units are nice. Less noise and they last longer. The extra work to install is worth it in my experience.

Knock sensor.  I wouldn't think that GM installed knock sensors so they could run timing at the ragged edge. More of a solution to all the variables that can cause a motor to detonate: low octane fuel, extra heavy load, or any number of mechanical or cooling issues. All us old timers remember turning back dizzy's on pre-computer vehicles.  Anyway, a knock sensor is a very nice to have feature, but not mandatory. You can set the knock retard enable temp to maximum to trick the computer into not using it.  The dataloggers do count knock sensor hits though so it can be quite useful for tuning.  Getting the sensitivity right will take some effort, but it's very feasible.

Fuel return line.  What size line does your Caddy use?  5/16" should be fine, but 1/4" will most likely have too much back pressure.  Might be a good idea to check the back pressure with a t-fitting and gauge regardless.

EGR.  Not needed to make your engine run properly IMHO.

Keep us posted on your project.  :thumbup:
 
Just found this regarding the heated 02 sensor:

http://www.tbichips.com/faq.htm

http://motors.shop.ebay.com/_Car-Truck-Parts-Accessories__AFS74-HEGO_W0QQ_nkwZAFS74Q20HEGOQQ_fxdZ1

Ebay ad:    This is a GM AC DELCO AFS74 3 wire heated 02 sensor.  I have decided to start selling these as many of my chip customers are now doing heated 02 sensor conversions on there older GM vehicles that originally had single wire 02 sensors.  Most autoparts stores primarily carry Bosch or some other brand 02 sensor and I just haven't had as much success with those 02's as I have had with the actual GM 02 sensor.  This 02 has a purple wire on PIN C which is the feed to the computer and both A and B pins are brown and either one you can go to the chassis for a ground and the other wire goes to 12volt hot that is hot when the key is on.  Whatever fuses or relays used to accomplish that 12v hot is entirely up to you just that is how I wire these things.  These allow you to place the 02 further down the exhaust than the old 1 wire 02 sensors because they are heated they stay at proper operating temp for a more accurate 02 reading for the computer.  Also, since they are heated they allow the computer to go into closed loop faster for better fuel economy.

Any questions or if you wish to use a credit card to pay for your auction while avoiding  your credit card info being passed on the internet. Give me a call 336-471-2827.  I do not put credit card info on any computer system for security reasons.
 
The narrows can be heated or not.  All the wides I have seen are heated.  Wides are not that common until more recently on OE stuff.  All wides need some extra computer bits to interpret the signal, often times this is external to the main ECU or gauge.
 
Most of the wide band kits you can buy have multiple outputs that can be configured to what ever you want.  What most people do is config one to be a narrow band for the ECU and then use the other for a gauge or data log system.  If you are using one with a MS you can set it for a 0-5 output and then MS MT will display and use it as a wideband.
 
That configuration would be narrow band. (above sensor on ebay)

Wideband needs several signals to the controller.

You need at least 2 signals from the sensor to the controller, since the way it works is by controlling the current into the device and watching a sens voltage. The value reported is derived from the current. There's also a calibration signal. The Heater need to be controlled as well instead of just applying 12V.

http://wbo2.com/lsu/lsuworks.htm
 
Yes, narrowband is correct.  I'm not sure how effectively the hacked GM computers can use a wideband?  Even so a wideband sensor and gauge would still be a great tuning aid.  Unfortunately, even the Megasquirt II doesn't fully use wideband from what I've read in the Megamanual.
 
scout said:
Unfortunately, even the Megasquirt II doesn't fully use wideband from what I've read in the Megamanual.
Click to expand...
What do you mean?  And what do you expect it do to that you dont think it does?  Im running one on my MS2.  If you wanted to (but its not recommended) you could give a wide band 100% authority over the mixture.  I think for the most part you end up setting it so its just a little bit more range than a NB gives you but it does give you the wb display on megatune and logs which is both a comfort and handy for initial tuning.

I would agree about the GM ecus not gaining anything from one since I imagine you have to configure them to look like a nb but like you said having a gauge is a big help especially if you do not live and breathe tuning.

A warning about anyone thinking about using a wideband.  They are not perfect!  The also tend to be easy to damage and most of them require periodic calibration.  When you are first starting out with an engine that is barely running dont bother looking at the gauge, misfires will mess up the readings.  Just start out tuning the old way.  Get the thing to have a decent idle and rev up nice.  That should get rid of the misfires and then you should start getting good readings from your WB and can start to dial things in.
 
I would also like to add that my WB has been flaky so I was thinking of trying a NB.  If I ever get around to doing it I will be sure to let you guys know how different it is.  With what I now know I think its not going to be a problem and its sure a lot cheaper.  Maybe if I was looking for cutting edge performance or working on a dyno a WB would be needed but Im starting to think a NB will be plenty for my basic street driver needs.
 
You must log in or register to reply here.
Back
Top