ok guys I've been searching and and didn't really find the answers I was looking for. What can I do to upgrade the '84 CFI engine? I already have to rebuild it and I will probably switch to carb in the process unless you guys give me a reason to stay CFI...I've heard good and lots of bad so maybe someone can shine some light on the situation.
thanks tim

 

There may not be a Cross-Fire sticky with a step by step photo journal of how to make a 10 second '84 CFI. but the one big issue for a performance CFI is covered in several threads: the small ports of the CFI intake manifold.

Get comfortable with grinding tools and spend who knows how many hours opening up the ports. When it can breath, the power will follow.

Hopefully the CFI devotees can help out with your question. In the meantime it would probably be helpful to know your budget, and what performance goals do you have?

Thomas

 

Hi Tim, welcome to our little corner of the forum. I see you are a new '84 owner, and already you want to ditch the crossfire injection. Oh boy.

First off, the crossfire L83 is simply a gen I small block Chevy, and will respond to the typical SBC mods(cam, heads, rocker arms, exhaust, etc). Now are you having problems with the crossfire setup, or have you been told that its worthless and are listening to some uninformed opinions? The crossfire injection is a very reliable setup when its tuned properly, we can cover that later. And lastly, what are your goals with the car? are you going to race it, either drag or road race? Are you just looking for a little more umph on the street? Or are you just looking for a reliable cruiser or daily driver? All of these questions have bearing on what sort of advise you'll be getting. The more specific you can be the more specific we can be with answers.

I really hope to see you keep the crossfire...oh yeah all n00bs must post pics of their vettes!

 

The intake is your biggest limiter...followed by 2 small throttle bodies and then by 2 small injectors...

It is entirely possible to Port the intake - it is the BIGGEST performance gain you'll get on the car short of heads/cam - best part is it's free minus the cost of beer & bits for the grinder...

You can also (and should...if you mod beyond this) upgrade the ECM and have the car tuned. When i had the CFI on my car i believe i had the 7747 ECM with the PROMinator setup. Not sure if this is still the defacto standard or not...

you should also modify the one TB and make the FPR adjustable. Modify an old distributor/carburetor tool with a flex shaft and you can make on-the-fly fuel pressure adjustments at the track or dyno...

You can also have the TB's bored out and install larger injectors out of a TBI truck if you need more air/fuel...

http://www.crossfire.homeip.net/

that site was the BEST POSSIBLE place to go with any sort of CFI issue/question/etc...i'm not sure how many people frequent it or if it's still heavily used...but i'd search there for your answers...

 

Like bench racing?
http://www.corvetteactioncenter.com/...D-more-hp.html

http://www.smokinvette.com/corvettef...ad.php?t=37638

 

http://users.swko.net/~lionsden/crossfire.htm
http://www.technovelocity.com/chevyh...rt_polish.html
http://www.digitalcorvettes.com/foru...&highlight=SY1
http://www.digitalcorvettes.com/foru...d.php?t=130759

 

All excellent advice given here. Take your time do some research and figure out your goals and budget first just like Green Rocket suggested.

 

**************
Ok guys ill give you a lil background info. I don't have the vette yet I'm buying it from a friend. I'm 16 so my budget isn't much. You already know its an 84 cfi and it is a project and I hope to have it driving by senior year next year, (I'm currently a junior n high school), thanks for the fast replied but I'm not sure I understand them if the intake and crossfire are the problem why not just put on a different intake and thow a carb on it? Which is what I had in mind. I'm not sure that I understand what you mean by porting it and such. I do know about the TB however as I have a 90 camaro with a tbi I drive to school. And to answer what I'm would be doing with it I would like to upgrade for a little more horse, enough that I could take it to the track every once in a while. I hope that gives you guys to answer a little better.
Thanks Tim

 

Let me ask you this.
Whats wrong with the intake? or are you referring to "its" restriction?
Why would you want to go to a carb and go backwards?

The CFI is the simpliest and easiest manifold to work with. Easiest mods made with the least amount of money. Extremely reliable and a perfect engine to learn on.

 

nothing is wrong with it that I know of, I cant start it because theres no timing chain, cover, and who knows what else has been taken off. I do know it needs a rebuild and my friend who has 30+ years of auto expirience suggested I use carb and I wanted to anyways. I figured If i'm rebuilding might as well upgrade and hope to find some way of passing emissions. Plus I don't want to have to use a computer that needs tuning and such like a tpi or something. Could just swith the intake if that does have restriction problems and keep the crossfire?

after I get the car I'll know more about what it needs and I put up a restoration thread to keep everyone posted.
thanks tim

 

Here's some intake photos, the top is unported, you can see how the ports are much smaller than the following pics, which are just a couple of ports I did this winter. I won't say its an easy job, but it is definitely doable. and is inexpensive. If you have someone who has the tools to borrow, you could do it for free.




You can see I actually went through on one of the ports, not a big deal, sealed it back up with an epoxy and it works like a champ. It just goes to illustrate how much material needs to be removed.



So a few more questions: How many miles are on it? How are you determining that you need to rebuild the engine? What condition is all the rubber in (hoses, belts, tires) these things could need to be replaced and may eat a lot of your budget up.

If the timing chain has come off, you may be really asking for trouble. the heads may need to be rebuilt as well as the engine, especially if the chain broke under load. Bent valves and broken springs and possibly dinged up pistons, etc.

Carb is not an upgrade, and the crossfire computer isn't really a tunable one. If you just put it back together in a stockish configuration, you shouldn't have a problem with the computer. Plus passing emissions with a carb may be a bit of an issue.

Sounds to me like you've really got a money pit there, there are plenty of C4's out there do yourself a favor and find one that runs.

 

So a few more questions: How many miles are on it? How are you determining that you need to rebuild the engine? What condition is all the rubber in (hoses, belts, tires) these things could need to be replaced and may eat a lot of your budget up.

If the timing chain has come off, you may be really asking for trouble. the heads may need to be rebuilt as well as the engine, especially if the chain broke under load. Bent valves and broken springs and possibly dinged up pistons, etc.

Carb is not an upgrade, and the crossfire computer isn't really a tunable one. If you just put it back together in a stockish configuration, you shouldn't have a problem with the computer. Plus passing emissions with a carb may be a bit of an issue.

Sounds to me like you've really got a money pit there, there are plenty of C4's out there do yourself a favor and find one that runs.[/QUOTE]

not sure on the miles i can tell you tomorrow, the timing chain was taken off before my friend purchased it from his friend and was gonna rip the engine out anyways to put his monstrous big block in it. which we might do before I buy it from him and if thats the case Ill post us swapping the engines and then me swapping them back if not rebuilding some of it. I'm not planning on a complete rebuild more of replacing older parts with a few preformance ones i.e. cam, timing chain, mabye intake, ect. but if I can just get the thing to start after putting a new chain on it I'd still be happy and upgrade as I go.
thanks tim

 

Like Kangi says a carb is not a upgrade. In many cases mechanics YES mechanics recommend the carb mainly because they don't fully understand the crossfire. Its not rocket science and is very easy.
You have a restricted intake with 2 throttle bodies and a couple of injectors. Add in a few common sensors and thats all there really is to it. Like stated before its very reliable as well.
Anyways if you do a Bigblock you may have to beef up the front suspension to hold the extra weight. Headers would be a pita to put on. Best way to go small block IMO. Just to give you a idea. Basic common known mods are a set of Dart ss heads ($625 pr), 2040 cam ($140), 1.6rr's ($185), Hedmen headers ($150), 2500 stall ($200 and up). True dual exhaust ($250). Not all mods have to be done at one given time. You start with the free ones Ported intake, cold air mod. For little money you'll have a fun car. All this and you stick with a more modern version of fuel injection rather than a carb. Don't worry about having to "tune" with the 84, leave the ecm alone you can't do much with it anyways. You can get by if you do need to "tune" just by adjusting FP up or advance the timing. Once again both free to do.
84 is a fun car to learn on..... thats what I've done...

 

Sixteen and a project Corvette - now THAT'S a combo!

Worried about passing emissions testing - but doesn't want a computer/fuel injection. Just to make the preceding more fun, has thoughts of a big block conversion. All of which will be done on a "not much" budget.

Keep on reading as much as you can on the forum and other resources. Not only will you learn things like that porting is the process of opening up the ports for more airflow, but you will also learn from the collective wisdom of guys who have done all of the car repair things that you want to do.

If you get the car post some pics so we can see what you are starting with. With a very limited budget it would likely be the best use of your money to repair what is broken and get it running once again. Building a carbed engine, big or small block, that will legally pass emissions is not realistic. If you lived in an area that was free of emissions testing it would be different, but from your statements that is not the case.

Good luck, I hope you get the car.

Thomas

 

thanks I mostly just finished my 90RS that I bought when I was 15 (half a year before I even had my permit) now it just needs adjustment here and there. My friend owns the corvette and the big block which has been sittin in his garage for ten years and he's is confident that it'll fire on the first try, simply amazing, he'll be helping me with the swap but i'll be doing the restoration mostly myself with maybe a little help from my dad he has nonperformance experience. so it should be alot of fun I'll definatley keep you guys posted on the situation and tomorrow I'm going to see the car and work out our deal. so hopefully it'll work out and be drivable by the upcoming school year. Thanks for everyones support I could really use it.
thanks tim

 

You mean "Downgrading" to a carb??

You are taking two steps back in time.....your friend with 30 years experience.....experience with working with pre-80s autos...maybe not a good source for this particular application

And going to Carb, you'll never pass the visual inspection for Smog. You'll have to go to a CARB judge and get a sticker.

 

Not only will you fail visual inspection with a carb, you'll destroy your catalytic converter because your O2 sensor won't be able to adjust the fuel mixture like the EFI would, so you'll fail the sniffer test, too. Unless you've got some major bucks, skip the big block idea. With the ideas you've mentioned, you will just destroy the car, and then you'll have to try to find another "friend" to sell the very frustating money pit project to! It sounds like your previous "friends" might be looking for a sucker, too!

 

as for car tech my friend is great with old school tech and methods but those are the methods I first learned and prefer them to some new school stuff, its a matter of opinion, as for me I really don't even like newer cars in general, thats just how I am both sides have their advantages and disadvantages, But thats why I came to the board to find find more info on computer contolled engines and the such. so don't be trying to dis people you dont know or will ever meet. Its rude. And as for emissions I just want to get the car running and I'll worry about emissions later I wont be throwing anything away so I can hopefully reattach the old setup if I decide not to use it. For now I'm keeping it and am worrying about mods later I'm trying to figure out what I can do later on.
thanks tim

 

For those wanting to set Tim down the right path (fuel injected small block), just remember that you are dealing with teenage logic (no disrespect meant).

So, the very best thing you can do is to encourage Tim along on the mechanical adventure and let him learn along the way. I see two possible outcomes no matter the initial plans: 1) he surprises all of us with a beautiful big block installation (maybe except for the big hole in the hood and the high rise intake/carb setup protruding another 5" or 6"), or 2) Tim gets part of the way into an unsatisfactory big block conversion before he shifts gears towards a fuel injected small block.

What I am convinced of is that Tim will follow it through to completion. He has already proven himself on his '90 RS project, so this is not his first project car. I overhauled my first engine when I was 12 with the help of my dad (a '65 Dodge Polysphere 318), so I appreciate the tenacity of a teenage mechanic. A lot of my teenage ideas on cars and hot rods didn't work out and I had to change my plans, and I suspect that Tim will go through that as well. But at the same time the whole process will give Tim a fantastic real life mechanical experience.

My mother, bless her heart, would even let me drag car parts into the house. Later, I once assembled an engine for her car in the family room. It was quite shocking for her friends to see, but she told them it was okay because it was for her car!

Who knows how Tim's '84 Corvette will turn out, but I think we should all cheer him along.

Thomas

P.S. Tim, no matter what you have read about big block C4 conversions, it is much more of a messy project than you might think. There really is no good way to get a decent header design into a street big block C4. Many street conversions end up using the heavy and restrictive cast iron manifolds. You may, or may not know, that big blocks are very sensitive to exhaust flow: a proper header is often worth 70 hp vs. the cast iron manifolds on a performance big block. There are other issues, but I'll hold back and wait to see if you start a thread on a big block installation.

 

This might help.
http://www.gmhightechperformance.com...tte/index.html