Hi
I own a 1984 corvette (crossfire injection). I am looking for performance modifications that would have a decent effect. (other than costly supercharger or turbo). Apparently, nobody makes any performance air intake kits for crossfire injection corvettes. K snd N only offers a replacement filter. The only chip I saw avaiable was hypertech. Would this be a good idea? What kinf of a difference could I expect with such a chip. Any suggestions or tips are welcome.
P.S: I previously owned a 1979 vette so Im new to the injection vettes.
Thanks for any tips

 

About $150.00 lighter in the wallet and a tenth of a second SLOWER in the 1/4 mile. Forget a chip, especially a Hypertech. I don't put much faith in the claims of air filter manufacturers as to the performance gains they are supposed to provide. However, the 1984 Corvette air filter fits nothing else. A serviceable filter element such as a K&N could save having to order or not being able to attain one. You can do general maintenance, cleaning, and tuning, etc. I found some performance playing with the fuel pressure and base timing. Underneath that misunderstood and oft maligned Crossfire intake lies the heart beat of America, a small block Chevrolet engine that responds to all the hop up methods as every other sbc The intake manifold is the engines namesake and it's albatross. Chevrolet deliberately choked the Crossfire with impossibly small ports in the manifold. The greatest single thing you can do for your performance is to port your intake manifold. Once it can breathe, other improvements will be able to function, to a degree.

RACE ON!!!

 

shorkey - CFI is spot on. Unfortunately the 84 is a bastard year. They can be made to run quite well and strong. The key is understanding them and not listening to the naysayers.

You may also want to check out http://www.crossfire.homeip.net for general Crossfire info.

 

Ok thanks CFI-EFI...I purchased a complete tune up kit that includes spark plugs and wires, stock air filter, pcv valve, cap and rotor...etc
So ill be doing the complete tune up.
For an intake manifold, do you have any suggestions?

 

For the best results on the tune up you will want to verify the fuel pressure, check the minimum air adjustment, and the TB balance. If you haven't done these before a FSM (Factory Service Manual) will be worth it's weight in gold.

As for the intake manifold, I covered that in my first post.

RACE ON!!!

 

CFI-EFI Said "Chevrolet deliberately choked the Crossfire with impossibly small ports in the manifold."

Why is this?

 

So they would be able to sell TPI powered cars three years after the 1982 introduction of the Crossfire.

RACE ON!!!

 

ohhhh ok I remember someone saying that a couple months ago. Actually it might have been you. Thanks!

 

im not done putting my car back together but heres my progress soo far on mods and stuff.

http://forums.corvetteforum.com/show....php?t=1846200

 

Probably. Think about it for a second. GM made the CFI manifold port opening about 2/3 the size of the port in the head. My CFI, stock other than the ported intake manifold is definitely faster than the iron headed TPIs. If GM made the ports in the CFI manifold the same size as the ports in all other SBC intakes and especially if they left some meat in there for porting, they couldn't have made the technically superior, and emissions friendlier, TPI as quick is it's predecessor, the Crossfire.

RACE ON!!!

 

Definetly check out http://www.crossfire.homeip.net. There a lot of info there on the Crossfire and bunch of free mods as well. You'll also find out more detailed information on whats available out there.

 

At the time GM had 4 things in mind. 1 low emissions, 2 high mileage, 3 drivability, 4 performance. The first 2 were mandated by the federal government. The easiet way to achieve the first 2 was to build an engine with good low rpm torque. Put this engine in a car with overdrive and high rear end gears and you get the desired results. One way to improve low rpm torque is to increase air charge velocity. GM did this by restricting the intake ports, its like putting your thumb over the end of a garden hose. TPI is simply a more efficient way of doing it. I'm sure CFI-EFI will tune in to tell you why I'm wrong
You can certainly increase the performance of your car. Porting the manifold is the key. Then build a 383

Paul

 

You aren't always wrong... Just often. I wouldn't say your theory is incorrect, just incomplete. GM needed better mileage and emissions than they could get, easily, from the existing (Quadrajet) carb systems available. The TPI was still in development and they had TBI injection in use on other, smaller engines. They stuck two 4 cylinder TBs on to the Crossfire manifold and voilà. They soon realized that unless they restricted the air flow available, they were not going to be able to follow up with the TPI as it was being developed. To anyone that has looked at the insides of various stock SBC intakes, even economy 2 bbl manifolds, it is clear that the restrictions in the Crossfire are more than just manufacturing inefficiencies. A Crossfire manifold, with ports the same size as the TPI ports, would have made the TPI impossible to sell as designed for 1985. Believe it...or don't.

RACE ON!!!

 

Faint praise, but probably the best I can hope for The info I stated was what I was told back in the 80s, when I first started working on Vettes. It may have been spin, but it still seems plausible. Could GM have gotten 230 hp from an 84, sure. Did marketing influence engineering, wouldn't surprise me. Maybe you have info I'm unaware of, but here's where you lose me. Chevy sells Corvettes, not injection systems. Let's say its 1985, you walk into your local Chevy dealer to buy a new Corvette. You notice it has a new injection system, but it makes the same hp as last year. Are you goinig to say "Fugiddaboutit" and walk out? I don't think so. But hey, I'm just an old mechanic not a marketing guru.
Here's something I noticed looking on the poster I have I here in the shop. 82-200hp @ 5200 rpm, 84-205hp @ 4300, what's up with that?
Have you ever posted pics of your ported intake, might helpful to other crossfire owners.

Paul

 

lets not mislead people please. i doubt stock 84s came with dual exhaust, drag radials, or higher stall speed converters like your car now has

there is more to your 13.8 sec crossfire than simply a ported manifold, and comparing it to a stock TPI is kinda apples to oranges without similar supporting mods on the TPI car

 

Maybe, when you walk into your local Chevy dealer and you find out that the "new and improved" 1985 is slower than last year's stop gap engineering exercise, which is a compromise, waiting for the final approval of the TPI, you might decide to wait until Chevy provides an upgrade that is quicker than the fill in model. New Corvette sales are not "must haves, for basic transportation. Most are second or third, or more cars, the purchase of which is highly discretionary. If the car isn't right, the buyer is under little pressure to "settle". He can wait until next year. Besides, there is a natural progression. There is an expectation of improvements from one year to the next. I am not a marketing guru, either, but take a look at a few SBC intake manifolds, and then tell me that Chevy made an error, that they miscalculated, on the Crossfire manifold.

Knowing what I know, that poster showing Crossfire HP at 5200 rpm has to be a misprint. The 205 HP @ 4300 IS the 1984 spec.

I never took any pictures of my manifold, but except for having been thorough, there is nothing to see or anything special about it. I matched the ports to a gasket, which was a mistake, because the heads aren't. Like the rest of the long block, the heads are untouched. I have an undesirable port mismatch at the junction with the heads. It is nothing more than an amateur, home grown porting job, easily duplicated by any other like, hobbyist.

RACE ON!!!

 

There is no misleading going on. The post is about the Crossfire engine. My Crossfire engine is ALL factory stock, with the exception of my ported intake manifold. And by FACTORY stock, I mean that it has never, in 165000+ miles, even had any repairs, even to factory specs. It has never had a head off. The drag radials, the true duals, and Vigilanti converter are no secret. If they were, YOU wouldn't know about them to keep bringing them up. I have done some tuning and other minor adjustments, too. Am I cheating, lying, or mislead people if I don't disclose every tire pressure adjustment?

Apples to oranges? Maybe you feel it is an unfair match up, but both participants have been clearly defined. There are no secrets. I have raced several similarly modified, and more, TPIs and beaten them too, but the point was how a properly factory built CFI would compare to the factory TPIs as introduced and released. This isn't the first time you've brought up that my car has more than just a ported intake. I sense a note of jealousy.

RACE ON!!!

 

I have the Xram set up and it disappointing at best. The last owner did a lot of work to get my 84 to run better than the stock crossfire set up. Wealand promised him 50 horsepower with the xram set up , I can can testify Im not sure its any faster than a stock Crossfire.It uses a 4bbl manifold instead of the restricted crossfire with the crossfire TBs. He also has a 85 pump and a ecm from a Camaro. The car runs smooth and is very responsive but my 0 to 60 times with the roof off and a stop watch was 7.3 seconds. Lets suppose that I was not overly accurate and a little slow pressing the stop watch button. That would leave me Im still running about the the stock 6.7 0 to 60 stock time Car and Driver suggested on their 84 road test. Im thinking of porting the old crossfire I was given with the car in the box that the 4bbl manifold cam in.

 

tried to open that forum,,, i can't see any section's etc. ???

 

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