i want to tpi my stock 77 ..i have read about and seen many of these units for sale ...pros and con on both...the speed d. units are suposed to ne more reliable..and the maf is suposed to be an simplr bolt on ..i would like to here from some who have done these upgrades on there c3's......please try and keep it simple ..i just would like to get some input on the swaps an how they worked not ...and your thoughts on the one that works the best pros and cons on the install and the performance.. thanks

 

Speed Density

Pros:

Easier to install in a C3 because you can bolt a air filter straight to the throttle body.

Cons:

Harder to find used and a little more expensive because of that.

But cheaper in the long run because your not dealing with the maf sensor. They can cost several hundred dollars to replace.

Maf

Pros:

Easier to find

Cons:

Harder to install because you have to fabricate some sort of air cleaner system because of the maf sensor.


Actually years ago people used to prefer the maf system with engines that weren't stock (383, large cams etc) because they adjusted better to the new engine. But these days we can fine tune the 90-92 Speed Density systems to the non-stock engine by data logging and custom chips.

For a C3, the best way to go is Speed Density due to the air cleaner system needed on Maf.

 

Here's a link that will explain the difference in more technical terms...

http://www.carcraft.com/techarticles...ion/index.html

1982CorvetteDude is correct in saying a speed/density system is a better choice for a C3.

 

ok let me try to be clear-r....i am not going to use a throttle body system tBi.......tpi ...tpi is all im intrested in.......sorry and thanks

 

This will be good research, read this and if you have any questions let us know

http://chevythunder.com/

 

I am looking at the same thing TPI on my 80. I found a computer from Megasquirt, It looks like you can by-pass some of the sensors. It is cheaper than GM computers, and they say it is very versitile.

 

Not sure what the megasquirt costs, but you can get by with a $30 - 50 junkyard ecm and a custom chip with whatever sensors you need taken off for $65

http://tpiparts.net/inc/sdetail/657

 

I will look at it.

Thanks

 

GM computers can be had for $20 in the salvage yards if you know what to look for. I have six of them now. The speed density computers that were mounted in the engine compartment were also used on many other GM models (Cutlass Supreme, Grand Prix and Luminas). This setup is using one (pictured). It will be for sale shortly as I've built four different styles of EFI setups now.

 

If you have the ability to do a wiring harness on your own...IE solder it up and insulate it....read a wiring diagram.....and can get junkyard connectors....

I have all the mechanicals and air cleaner, and stuff you need for a conversion....I did my first one on my '72 some 16 years ago...not hard at all, really just takes time and somewhat of a learning curve....

Stick with the stock computer and use speed density, the chips/calpaks are available for 150 bux....all setup ready to fly, no need to program a 500 buck computer project when your 20 bux junkyard computer can do it, along with connectors and wiring and do it better, for a total of 200 bux....

 

You have a unit
First you have to determine whether you want mass air flow or speed density. The C3 is more conducive to speed-density due to space issues.
Mass-air flow is easier to make engine changes without PROM changes.
If you are technically proficient enough to make a Camaro harness work they can be bought for $100 or less. I have been told that you can also use a 3.1 Corsica or Cavailier harness with a little work, it uses the same 7730 Speed-Density ECM. Aftermarket harnesses range from about $300 for Painless to $500 for Howell to $700 for Street and Performance.
Howell makes a great harness, but for a Tuned Port they do not make one that will control the converter lockup on a 200R4/700R4/4L60 transmission. If you are running a manual or non-overdrive-automatic transmission I highly recommend them. I have heard great things about Street and Performance harness, but do not have first hand experience with them. I also have a Fuel Injection Specialties (FIS) harness and it is OK. The ECM can be had used for $10-50. A good external fuel pump will cost at least $100. I use an 88 Ford Truck external pump,
$114 from CarQuest, made in Texas by Airtech. If you have a 78-82 you can use your fuel tank with an 82 sending unit and a TPI pump. An aftermarket PROM with VATS and Emissions codes removed will be $100-200 depending on source and complexity. You will have to add an oxygen sensor to your exhaust, $20 for the sensor, $5 for the weld-in bung, and say $25 for an exhaust shop to weld it in if you can’t. Some harnesses use VSS and some do not. An auxiliary VSS sensor is around $75. To install a TPI I say figure at least $800 plus the TPI unit and whatever repairs are necessary to bring it up to useable status. I have
TPI/700R4 in my 69 Corvette (Howell harness) and an 83 Pickup (FIS
harness) and I love it. Starts good, great torque, good fuel mileage, easy to swap onto stock engines (although both of mine are complete engines out of 90/91 ‘Vettes).

Differences in years
All Corvette TPI intake manifolds work with the older (through 86) iron
heads and the factory aluminum heads through 91. F-body TPI intakes
use the upright center bolts on 87-92 and thus fit all 87-95 iron heads (non LT1). Either can be swapped to fit the other with some drilling.
F-body has the fuel lines come out on the drivers side and has a central port for EGR. Corvette has fuel lines that come out on the passenger side and has an external port for EGR. Corvette fuel rails fit F-body intakes and vise-versa. The runners are all the same through the years, but the LH runner has a hole for a 9th injector in the 85-88 runners.
This can be plugged off if you get a nice LH runner and don’t want the 9th injector or decide to run speed-density. The plenums all physically interchange, but 90-92 have an extra vacuum port for the MAP sensor used with the speed-density computers and wiring. 89 is an odd year, it is mass-air flow but without the 9th injector. 89 up throttle bodies can be used on all years, but a 85-88 throttle body requires a ½” hole be drilled in the front of a 89-92 Plenum for idle air. 89-92 Throttle bodies have a bit more desirable cable attachment. The cable attaches around a circular linkage which has a smoother actuation than the straight linkage on the 85-88. The Corvettes have an aluminum plenum extension over the distributor, the F-body extensions are plastic. The Corvettes use an HEI coil-in-cap distributor for 85-91 (Delco 1103680).
85-86 F-body also used a big-cap distributor. 87-92 F-Body used a small cap distributor with an external coil (Delco 1103479). This same distributor is used in the 87-95 5.0/5.7/7.4 TBI injected trucks. The F-body intake gets it's exhaust for EGR from the center passages in the heads like most SB Chevys. A Corvette intake gets it's EGR exhaust from the RH exhaust manifold/header through a flex-tube to an opening near the distributor-no center passages in the intake. If you are required to keep EGR and you have a Corvette intake, I recommend getting the C4 exhaust manifolds. They are like mini-headers, and have a 2 1/2"
outlet. I have them on my 69 and like them.

As far as a throttle cable to use, on my Vette, I used a TPI Corvette cable, 1990 I think (about $20 new GM) but you have to cut the end off inside the car and use a hood-release-cable end (Corvette Central 342138 "cable stop") to get it the correct cable length (the housing is OK).
You must use a cable from the type car your throttle body came from if you want to have a chance of not cutting it. Again, 85-88 use a straight pull, while 89-92 have a circular attachment for more smooth actuation and so the inner cable is longer. On my 83 truck I used a TPI F-Body cable and it was OK, but I had to coil it up into a loop in the engine compartment because the housing was so long. I also TPI'd a 72 Chevy truck and used a 90 350 TBI truck cable for it. It was 1/2" short outside if anything, but I was pretty pleased with it all told-I didn't have to shorten it. In a Vette it might be about right. In all vehicles I've done you need a die grinder to square the firewall hole off a bit. All vehicles I've done used the late throttle-body.


I would look into a TPI. They start immediately in winter, have great vacuum, and will get great mileage. I can open the headlights and the wiper door at the same time with no hesitation at all-solid wooomp. With 3.70 gears (and a 700R4 overdrive) I get 18mpg city and 22+ highway.
With 3.55 or 3.36 it would be even better. You can probably find a used Corvette TPI engine for $1000 and with an $800 harness/computer/fuel pump you would be set. On a 78-82 you can use the stock fuel tank with an 82 sending unit and TPI pump and be in better shape than 68-77 with an external pump. With the Vette TPI you would have aluminum heads that would remove weight. Even with an F-body iron-head TPI 350 it will be less weight than a stock intake. It will bolt up to everything in your car, use stock accessories, use your transmission, and the visual appeal is awesome. Don't be afraid of fuel injection, it really works.

As far as websites see:
www.corvettefaq.com

 

Do not buy a harness from Howell. They are no help if you have problems.

 

Really? I had great support from them. Had several questions answered later and they sent me a 4th gear switch for my 700R4 lockup kit no questions asked. I just wish they would do a harness and PROM for a 700R4 so i didn't have to use the separate kit. Their harness is much more professional looking and robust looking than FIS or Painless.

 

speeking of 700r4....when i started this maf/speed-d thread i started thinking about getting a comlpete motor with a 700r4 speed-d tpi wireing hrns and computer...(complete un seperated) then i would have all the correct components and the tranny that i am going to change also...what are your thoughts on that?? thanks

 

That would be the easiest and cheapest route to get a complete running engine / tranny combo out of a donor car. If your trying piece everything together it get's expensive. Swapping to 700r4, your going to have to modify your driveshaft.

I would purchase this book, it covers pretty much everything you need to swap to TPI (or fuel injection) for any car. Lots of pictures and information.

TPI Swappers Handbook by JTR (Jags That Run)

 

I recommend these guys for a harness: http://www.eficonnection.com/eficonnection/gallery.aspx The "TPI 727" harness is what you want with the weatherproof ECM that can be found in the salvage yards for $20. Scroll down to the link to the 73 corvette they did with a LS1 engine. The ECM was mounted in the rear storage comparment.

 

I've done several TPI engines. I would recommend a harness from Street & Performance. They offer good advice, great support and every TPI part and service you could possibly need.

The TPI Engine Swapping book by Jags That Run is definately a worthwhile reference book for anyone considering any TPI conversion (My first TPI/700R4 went into an 85 Jag XJ6 that my wife drives)

 

Markdtn,
What did you use for the VSS in your '69 with the 700R4? I'm doing a speed density setup (ZZ4 with a Camaro ECU) on my '70 and I'm using an '88 Vette 700R4. Did the TPI Vettes use a cable driven speedo with 4K pulse VSS (I think speed density is a 4K pulse)? If not, where did you get the VSS setup? Part number? Not trying to steal the thread but this seems to be as good a place as any to talk TPI turkey.

 

I can answer this one! The Corvettes didn't use a cable drive speedo(84 up). Here are your two options if you want to retain the cable driven speedo and have a VSS.........http://tpiparts.net/82_92_sensors?start=25. The first one "sensor 802" is your best option. It was originally used on police intercepter cars.

 

That's what I'm using on my set-up...