84vetting

Just bought a 84 Vette, and I am sorry to say, but its a dog when it comes to get up and go, I have no emissions here in Maryland to worry about, so I would like to increase the hp and get it in the 300 range, besides the Renegade Intake , what cam can I run with the stock computer , like to get something with some nice chop to it at idle, any other mods I can do , looking to keep budget under $2000

divotdug

In my mind I'm not sure it is possible to get another 100 horses out of that engine for 2k. Horsepower just isn't cheap.

I have an '84 but am fine with it as is. To be honest, if I wanted another 100 horses I would sell my '84 and buy a '96....but that is just one old man's opinion.

Buccaneer

The manifold change or a good port job on the stock manifold is a very good move to more power. Do you know what your fuel pressure is? This is very important on a CFI motor. Set it at 13psi and it will run great. If your fuel pump can not support the higher flow, replace it with the 85-87 corvette pump and regulate it down to what you want.

Be careful with a cam change and a stock ECM. A pretty choppy cam will wig out the MAP sensor and not run right. Stay closer to stock duration with more lift and you should be fine. The closer your LSA is to 114, the more ECM friendly the cam will be.

Good luck with the mods.

Tom400CFI

What or how much can you do yourself? What is your skill level here? If you want 300 hp, you can get there with good (or ported) heads, a MILD (near stock duration) cam, a heavily ported or aftermarket intake manifold, CAI mod, headers and dual exhaust, optimized timing and fuel pressure. You could do it all for less than $2k if you can port yourself. In fact, I feel that head and intake porting, 1.6 rockers and springs, LT headers and proper dual exhaust would get you there and would cost you less than $1k.

If you want a "choppy idle" just for the sake of "sounding cool"...., you can do it and you can probably do it on a stock ECM, but you'll be giving up power, driveability and mpg. It would be dumb. If it's really important to you, IMO, you'd probably want to get a different (easily tunable) ECM, get that "big choppy cam" and then tune it to run on that cam.

So...what's really important to you?

blackozvet

here's something I found in the Summit catalogue, dont know how good it is tho !

https://www.summitracing.com/int/par...-100/overview/

Buccaneer

Mmmmm... That looks familiar.

mrfeeney

I'm a new 84 Crossfire owner and have been reading a lot of posts, what you say here makes a lot of sense to me but one thing in your post is not clear to me, what mods to the CAI? it already has it stock, what mods need to be made?

SELLC

Back in the early 80's crossfire was cool...

Now days, well.... Let's just say it's antiquated.

Tom400CFI

No it doesn't. The inlet for the stock stock air intake is in the hood, right above the radiator shroud. I'm sure that you've seen it and the hood ducting if you've opened the hood. That area, right above the radiator, is not "cold air". It's warm or hot air as it's part of the "engine bay"/underhood area. Many '84 owners use a hole saw or a die grinder to cut holes in the radiator shroud, then use some kind of weather stripping to seal the hood/air inlet to the radiator shroud. Set up this way, the air is drawn from in front of the radiator/ac condenser, and is kept segregated from heated under hood air from the system inlet, to the TB's. Does the mod do much? Probably not, but it's something and it's hard to imagine that it would be worse than drawing under hood air.

Here is one that has been modified; see the hole cut in the radiator shroud and surrounded by foam? That hole wasn't there, from the factory; it's almost as if GM set up the car for racing...then left the inlet blocked for street use durability concerns. Someone else though so too....

BlueTwoToneCorvette

With the crossfire you are wasting your money to try to get a big power improvement. Even if you are a home mechanic you are talking a big money rebuild and parts swap.

I would do it as cheaply as possible. Remove obvious intake restrictions. Open up the exhaust. Remove air pump.

For 32 year old car that you are having fun with, something is going to break soon enough and you'll need cash for that.

Tom400CFI

Warning, Will Robinson...Warning!

Are you speaking from experience? I'm guessing not, since you left out the biggest single item for improvement on a CFI car; porting/replacing the intake. In reality, modifying a CFI car is a DYI endeavor on the CFI specific parts. That = CHEAP TO MOD. The rest of the engine that isn't CFI specific is no different than any other stock SBC of the era except that the '84 CFI came with forged pistons.

BlueTwoToneCorvette

I just put my 85 L98 back together again, so I know the complexity that you have to deal with to get things right. You guys here are great help, and very supportive, but I think it would be easy to get in over your head replacing the intake and sorting the fueling/tuning issues unless you had help.

Tom400CFI

O.K...I'll buy that. But the CFI intake is way, way simpler (and cheaper) to take off and on or replace, than a TPI...and all that^ is way different than what you originally said; that it would be super expensive and therefor a waste of money to try. As far as "sorting fueling", on a stock or stockish engine it's very simple; just make sure there is sufficient pressure. I'd say that modifying an '84 CFI is easier and cheaper than your '85 TPI.


.

Hot Rod Roy

One of the best things about this forum is the encouragement we can give to each other! I think this comment, although well intentioned, may be discouraging to those looking for better performance from their '84. Opening up the CFI intake manifold ports takes a lot of patience, but it can be a rewarding DIY project, and there are no "fueling/tuning issues"! No changes are needed in that department. You get the reward of the improved performance with that first drive! Even if that's the only thing you do to your '84, you'll notice the difference!

Buccaneer

I saw the top post from BlueTwoToneCorvette and had to sigh a bit. I wondered to myself the same thing that Tom mentioned...Do you have a CF or have you ever owned one, are you speaking from experience to make that statement?

Not to stomp on anyone or anything...But, The one thing that I always cringe a bit at is, when someone with all the good intentions in the world try's to help says...that they heard from a friend who heard from a friend or my dad had one or knows a guy who had one and try's to help and in effect delivers mis-information and never really owned a CFI car.

From the TBs to the intake, it's a bit of a quirky setup (non-standard carb/FI), but from there down its a 350 is a 350. The only other thing that comes into play is the ECM, it's very limited in stock form, but once you get away from that and can tune via a laptop, that's when things change and open up for real performance gains as long as you do it correctly, you will spend cash though, no way around that. Again, that's not to say you won't get any performance gains by what has been already mentioned. The intake is a huge stumbling block with CFI and you will see good gains by just that change whatever means you choose to get there.

Thanks Tom, I did get a little chuckle from your "Warning, Will Robinson...Warning"!

I think for the most part, most people on the forum do try and help others with their CF which is what the forum is really about, but sometimes it goes wrong.

Tom400CFI

Glad someone did. I think I went and dated myself there, though.

SELLC

IIRC the crossfire was only offered for two years right? The last year of the C3 and the first year of the C4? If GM only ran with it for two years, then it's safe to say the aftermarket offering isn't going to be as strong as engines that had 4-7 year runs.

I know they also used the crossfire in the Camaro of that era. I have driven quite a few crossfire injected vehicles and calling it a CFI is not really fair given the fact it has twin CFI throttle bodies.

It's a totally different feel, but even still they are tumbling fuel and air down an intake runner. I don't think it's being mean to say that a "ported" design is much more efficient. It's like trying to compare ported injection to direct injection. Progress just happens!

mrfeeney

Wow Tom your correct, I saw the ductwork going to the air cleaner housing and just assumed it was ducted outside the engine compartment. Thanks for the pictures of the mod, I'll put that on my "to do" list. I also see I'm not the only one that got "Danger"

Gibbles

Its not to hard to get more hp from the crossfire.
First and biggest thing holding you back is the intake.

I went for a renegade intake, heads, camshaft, full roller rockers, full exhaust system with long tube headers, topped off with larger fuel injectors and a new computer that can be programmed to make use of the changes (ebl flash).

Intake was about 500, exhaust was 1100, heads were about 1100, camshaft kit was about 230, rockers were about 250, mufflers (flow master 40), were about 200, rj11 injectors were about 120 for the pair...

The car drives amazing now, however i'm still building the computer program.

BlueTwoToneCorvette

The OP stated that he wants to go from 205 HP to 300+ HP and spend less than $2000. I'm just trying to keep it real. Of course you can get huge horsepower from a CF. I'm just trying to give good advice from personal experience of having a project car and having the costs creep up past what you were expecting going in.