84 Crossfire to TPI conversion

[herzog]

I've been considering this for a bit now, and I'm curious to hear from any who have done this. I have the book "Chevy TPI Fuel Injection Swapper's Guide" and have thoroughly reviewed the site http://www.chevythunder.com , but I am a little concerned about clearance issues with the belt-driven accessories. At a glance, it looks to me like the power steering pump is going to be right in the way of at least the water neck and possibly the throttle body as well. I'm anxious to find out what brackets/accessories I will need to acquire. Also curious to know if an 85 or later fuel pump will be a drop-in replacement (I realize I have to upgrade the lines). Interested in hood modifications for the air intake, although I figure worst case I could put an air filter right on the end of the MAF sensor (I think I read somewhere that K&N makes one that fits there).

I should state that my car is completely stock, and will only be driven on the street. I am only doing this for a little more power/efficiency and, of course, the "fun" of it. Not too long ago, I acquired an '85 Corvette TPI setup from eBay (complete intake, injectors, fuel rails, sensors, ECM, wiring harness, relays, MAF sensor, air cleaner, distributor). Unfortunately, I'm missing the MAF controller (separate on 85). I'm considering looking for an 86 ECM and just buying an aftermarket harness, but I believe I'll then have to deal with the VATS issue. Thanks!

 

[Alloydude]

I know for sure that an 85 fuel pump will mount in place of the 84. Just have splice in the newer wire connector. As far as Hood clearance the stock 84 hood has ducting for the cross fire air cleaner so I think that would defiantly interfere with the tune ports throttle body. Not sure about the bracketry for the belt driven items.

 

[herzog]

Thanks for the reply. Great to know about the fuel pump. I thought it looked like the whole TPI unit was narrow enough to clear the ducting, although the front ducting (and possibly the radiator shroud) look like issues for the TPI air cleaner. I am having second thoughts about doing this now, mostly due to the effort involved overcoming clearance issues. Thinking it might be better to go with a complete stand-alone setup or just do the traditional CFI upgrades. Thanks again.

 

[Alloydude]

Surprised nobody else has chimed in. Yah. I’ve been considering the TPI swap my self. I have a TPI unit from an early Firebird but there is just so much involved it just seems easier to sell my 84 and get a newer model but I’ve grown attached to it so I’m just going to try and squeeze as much as I can out of the Cross Fire. Besides its really hard to get away with stuff like that in California. There is a site dedicated to the Cross Fire set up and it has been very informative with regards to modifications that can be done to get you up to TPI performance. It might be helpful to you http://www.crossfire.homeip.net/ I honestly gotta say that when I installed the newer fuel pump (85) in my car it ran sooo much better. Smoother idle and better acceleration. Good luck with what ever you plan to do with your Vette.

 

[Robert]

If it were me...and maybe it is, because I have a 1984 also. I just got it and am already thinking to the future.

In searching the web for info on the '84 before I bought it, I came across a site about XRam injection. It is supposed to replace the Cross Fire and still fit under the hood.

Check it out!

Robert

 

[MoeJr]

Herzog if all you want is a bit more power then keep the Cross Fire. Despite the naysayers it is a good system when set up right. You just gotta be smart and think things thru. Converting the car to TPI is a potential nightmare and you would be better off selling the 84 to someone who can accept it as it is and buy yourself an 85 or newer.

 

[nelson84]

I was going to swap out my crossfire for TPI, but at the price of an 85 vette right now, why not just leave your 84 a crossfire and buy an 85 to tinker with? Thats what I did, I bought a cherry 85 vette for $4300, all it needed was a throttle position sensor $99, and new carpet $400. The nice thing of having an 84 and an 85 is, you can swap targa tops and wheels and other crap like that. Now I mod both cars, its fun to mod the 84 to keep up with the TPI vette.

 

[topless82vette]

I've been considering this for a bit now, and I'm curious to hear from any who have done this. I have the book "Chevy TPI Fuel Injection Swapper's Guide" and have thoroughly reviewed the site http://www.chevythunder.com , but I am a little concerned about clearance issues with the belt-driven accessories. At a glance, it looks to me like the power steering pump is going to be right in the way of at least the water neck and possibly the throttle body as well. I'm anxious to find out what brackets/accessories I will need to acquire. Also curious to know if an 85 or later fuel pump will be a drop-in replacement (I realize I have to upgrade the lines). Interested in hood modifications for the air intake, although I figure worst case I could put an air filter right on the end of the MAF sensor (I think I read somewhere that K&N makes one that fits there).

I should state that my car is completely stock, and will only be driven on the street. I am only doing this for a little more power/efficiency and, of course, the "fun" of it. Not too long ago, I acquired an '85 Corvette TPI setup from eBay (complete intake, injectors, fuel rails, sensors, ECM, wiring harness, relays, MAF sensor, air cleaner, distributor). Unfortunately, I'm missing the MAF controller (separate on 85). I'm considering looking for an 86 ECM and just buying an aftermarket harness, but I believe I'll then have to deal with the VATS issue. Thanks!

Me personally I would just improvise your stock CFI harness if repinned will support a speed density TPI system with the addition of a IAT sensor and added wires. Then simply use 85-86 accesory brackets.

I think adding a 86 harness to your car to run a MAF based TPI system will be a nightmare. CFI harness is your best bet and just repin and run a 7730 F-body ecm and put it where the cfi ecm is.

Both efi system are MAP based batch fire system so your harness will run it fine, check out 3rd gen f-body owners who have repinned there TBI harness to run TPI a lot less hassles.

 

[nelson84]

I have a harness for an 84 to run TPI, its a speed density system and it comes with the ECM, and I have some homemade brackets to move you accesories. It was made by Howell. I was going to use it on my 84 but I ended up buying an 85 so now I have CFI and TPI. Could sell the ECM and harness and brackets and I will throw in a K&N cone air filter for $450 plus shipping if you are interested. I might try ebay to get rid of it.

 

[KANE]

...I should state that my car is completely stock, and will only be driven on the street. I am only doing this for a little more power/efficiency and, of course, the "fun" of it. Not too long ago, I acquired an '85 Corvette TPI setup from eBay (complete intake, injectors, fuel rails, sensors, ECM, wiring harness, relays, MAF sensor, air cleaner, distributor). Unfortunately, I'm missing the MAF controller (separate on 85). I'm considering looking for an 86 ECM and just buying an aftermarket harness, but I believe I'll then have to deal with the VATS issue. Thanks!

Since you have a TBI system (that is what CFI really is), why not re-pin the harness? Guys with TBI Camaros have re-pined their harnesses for TPI for years. Take a look on thirdgen.org - there are plenty of articles about how to do that.

Or, buy a sand-alone harness and tuck the CFI harness out of the way.

The question comes down to whether or not you want an exact OEM TPI system or not. If you want 100% OEM, then sell the 84 and buy a TPI car. Otherwise, the swap is the way to go.

Either way, the swap itself is straight forward. You should buy a copy of "TPI Swappers Guide". It has GM TPI troubleshooting procedures in it. Also, pick up the "Chevrolet Interchange Manual"- it has lists of thousands of parts and descriptions for what will bolt togther from plenums to base plates. I found both to be useful.

I've done two TPI swaps onto C3s. I would go with a speed-density system that uses a FBody ECM (mainly for cost reasons- why spend more $$ than you need to). Get a custom burnt chip with the VATS stripped out.

You'll spend about $1,300 for the whole swap and that covers little things like hose clamps, zip ties, intake gaskets, etc.

Here is wat I spent-

Item / Cost
Plenum, baseplate, fuel rail, TB $150.00
Fuel pump $90.00
EGR block off $10.00
TPS $20.00
Knock $44.00
IAC $70.00
MAT $12.00
MAP $45.00
IAT $12.00
CTS $12.00
Harness $245.00
O2 $25.00
Fuel hoses & AN fittings $100.00
Gaskets $25.00
Distributor $90.00
Injectors $240.00
Cables, clamps, bolts, misc $100.00
Fuel pump block off $10.00
Radiator hose, T-stat, housing $40.00
Total- $1,340.00

 

[CorvetteArchives]

BTW, on the TV show Two Guys Garage they did a TPI swap on an 84. Interesting show...and yes TPI did clear the stock 84 hood.

 

[bossvette]

the easiest way to go is speed density which the crossfire is already I'll bet you could modify the stock harness to work with a TPI the guy who has the chevy thunder website sells harnesses on E-bay under the name of chevytpi
why not shoot him an email and see what he has to say about it. He may be able to sell you the stuff you need. I have used two of his harnesses and have no complaints

 

[bossvette]

I just remembered I have an Accel power processor that piggybacks to the OEM computer and converts MAF TPI systems to Speed density and it can be programmed with a laptop if you mod your engine. Sent you a PM about it.

 

[WhalePirot]

So, how much is enough? A moving target, to be sure and for most of us, a bit more is the right answer. I wanted to do this once and 'go for it', so perhaps my work is more than your plan.

I admit that I learned a lot from the swap of a 406 (now 409) into my '84. It took three years and about $20k, including new leather and foam for the seats. I also went through the 4+3, the rear end ( which i still broke), the brakes, headers and 3", etc.

If I were to do it over, I'd follow the advice Dick Guldstrand gave me: "If you want TPI, sell your car and go with an '86 or later."

I run a PITA SuperRam, which clears the hood, but the air feed is crushed by the framework unique to the fwd part of the '84 hood. I am swapping into a later hood as we speak, because I lose a LOT of power when sucking hot air from behind the fan, through the cone K/N on the nose of the T/B.

I went with '87 accessories, which are probably 50/50 shared with the '84. The P/S res. and mount are different as is the AIR pump. I think the A/C, the alternator and the idler are the same. The rad shroud is different f/glass as the radiator mounts at a different angle. I run a '90 Camaro speed density ECM., with custom chip, through my modded harness, leaving the 'brain' in the stock site.

The MAF was hard to find and is for ducting purposes only with the SD vs MAF setup. I did not know if the later intake would fit.

It took me three years to get my car back on the road, tuned and reliable. It is a blast to drive, a beast and downright rude; perhaps too rude and loud.

 

[GO_VETTE]

I did an 84 TPI conversion. However I am also Turbocharging the car. So the benefit is that my piston compression is already 9.0:1, and my engine compression test was good.
So when you have an engine w/ 9.5:1 or 10.5:1(LT1), there are some considerations to the extent of boost.
Next, standard factory TPI's still have to be modified when running superchargers/turbos (if wanting fine tuner).
Even if you buy a high mileage 85,86,87,88, chances are you may have to redo fuel injectors down the line or your fuel rail may require new seals, or other air/fuel related items.
So I did it. If you ask me the best way to do it? YES, take it off ONE CAR.
1985 and 1986 wire harness do not interchange and work w/ ECM.
be prepared to reprogram chip. ESPECIALLY if you have VATS.
hood clearance issues (not really--->only worry about replacing the radiator shroud assembly)
fuel lines and pump( you will need to get a 255lb pump), lines no problem
belt driven accesories--yes must change
VSS retrofit plug(vehicle speed sensor) MUST NEED* * *
I recommend changing all sensors except MAF (usually lasts long, very expensive, if goes bad it is easy to change)
make sure get all parts from ONE vehicle and leep it that type.
not like me,
the TPI was from a Trans am
wireharness from PAINful
braided fuel line to fittings to fuel rail
ECM from Corvette
* and this costs more in end* stick w/ one car.
prefer MAF type, 1986 donor car or 1987 donor car * NOT 1988 because you will have to replace A/C compressor.