Hello All,

I'm fairly new to the Corvette ownership. I have a 75 c3. I was wondering if an early c4 tpi intake /fuel injection system would bolt on to a stock c3 set up? I know there would be more to it then just unbolt the old intake c3 and bolt on the c4 intake. Just wondering if it would bolt directly on. And if so, has anyone done this top conversion before? Would it be complicated to get it all working?

 

OK, you will need a computer, a wiring harness for the computer to run the engine, you will also need a different distributor and an electric fuel pump. I am n the process of building up a motor now to go into my 78 and although it is a lot more work than just bolting on an intake, it's doable, depending on your mechanical skills. THere are some stand alone fuel injection set ups that can use your existing manifold, but they are in the $2K range. There is a lot of info on this forum and the C4 tech forum that can clue you in to what is involved, just do some searches for L98 into C3. If you decide to go further and have some specific questions, please just PM me. As I said, I have gone through a lot of this but still have a few months to go before I try and fire it up. SEARCH IS YOUR FRIEND.

 

I had one in a '63 many moons ago...

 

I have refurbished a TPI system off an IROC Camaro to put on my 76, computer, harness, sensors and all. I am probably going to install it next summer when it gets too hot to drive it.

 

I see you're from texas so it makes sense now.

 

There were 2 types of TPI on the C4 - Mass Air Flow (Early) and Speed Density (Late).
*The MAF system has an air flow meter in the duct leading air to the throttle body, and measures the amount of air directly and supplies fuel accordingly. It is more adaptable to internal changes to the engine.
*The Speed Density system uses manifold vacuum to CALCULATE the amount of air the engine is using and then supplies the appropriate amount of fuel. Much more development work was done on this system (by both GM and the aftermarket).

Take a look at the Street & Performance website http://www.hotrodlane.cc . It has a lot of info and everything you may need.

 

If you are using your original heads you will have to modify the runners that bolt to the head. At a minimum the center bolt on each side is at a different angle than what is on your heads.

 

Basically the fellows nailed it. '85-'86 will have the older style intake bolt pattern and the '87-'91 cars have the newer style. You can mod an older intake base with a Dremel, grinding bits and (if you want to go fancy) a set these:

http://www.jegs.com/i/Professional+P...52112/10002/-1

The '85-'89 were MAF systems and the '90-'91 were SD systems. Both have their pluses and minuses and you would do well to research the differences between the two.

Best bet is to get the complete intake and associated parts off of a donor car. If you get an F-Body (Firebird or Camaro) system keep in mind that the fuel rail fittings come out at the rear of the drivers side head and the C4 rail fittings on the passenger side at the front of the motor.

Pay close attention to cam selection with a TPI. Personally, unless you have a seriously ported and reowrked setup (or run a Super Ram intake) I'd recommend 1.5RRs and bypass the 1.6s as the extra lift gets you next to nothing on a stock or lightly modded TPI setup. They don't breath well on the big end. Also, TPI cars respond very well to smart exhaust mods. Long tube headers and a high flowing exhaust perk up a TPI like no other mod does. Take a peek on the C4 section...you'll see that is the 1st thing C4 owners recommend to newbie C4 TPI owners.

Mods I would recommend are as follows:

Ported TPI base, runners and plenum
52mm throttle body (no bigger)
1.5RRs
Exhaust mods as mentioned
Cam swap (look for TPI grinds...don't just stab any old cam in)
MAF systems need an EPROM chip burned. You should have this done with a speed shop that dyno tunes or you can check out buying a custom mail-order chip. Keep in mind that there are some chip burners out there that just 'mail it in'. You need to have someone who will at least burn the chip with the proper mods done to your car. Let them know every specific mod done to the motor and your rearend gear ratio. If you have an automatic they need to know your stall speed.

For a fuel pump I do recommend either Racetronix or Holley. The factory '85-'91 TPI pump will work fine for a stock or lightly modded TPI motor.

Utilizing the TPI engine harness and computer will make it a breeze to convert your C3 to an electric fan setup. Again, your donor car (F-Body or Y-Body) should be able to supply exactly what you need and it will work fine for your C3.

That's the quick and dirty info from my end. Keep us posted! Every C3 owner I have talked with or has posted their TPI swap were very happy with it.

Later,

Lee

 

Been at this conversion on my '72 for some years now, Have tons of parts, but no intake manifold base.....I have plenum/runners/gaskets/injectors, but no throttle body went larger to 52 mm some years ago, but I do have a K/N air cleaner that will fit the stock T-body.....even have a dizzy cover....

have all the sensors too, and a spare computer, but Alvin Anderson can set you up with a chip/cal-pac.....sorry no wiring/connectors.....

but junkyards can provide that stuff in an afternoon......

I also have wiring diagrams.....

lemme know if interested.....PM, please.....

GENE SLATER