Hi Guys,
Looks like I'm getting a little bit of money out of workers comp (finally! after 4 1/2 years!), so I want to get my MR2 sold and get into a Corvette.

There are a lot of 84's around for pretty cheap. Yes, I know the CFI system isn't nearly as good as the TPI, etc. I don't expect it to handle 500hp or anything, BUT, I'm wondering how the computer handles mods like a larger (but still mild) cam, better heads (maybe L-98 or Vortech heads), improved exhaust, etc.

I really don't want to wait a few more months till it's all finally settled - I want my Corvette and I want it NOW Or, should I just hang on till I can get a 90+ car like I prefer?

As a side question - anyone know if you can drill the L-98 heads for a heat riser? I'm in California, so the EGR system still needs to function.

 

Do you like to "tinker" and "own" your cars' performance? Or would you rather keep your hands clean, and spend money on proven mods or performance?

If it's the former, get the '84. If it's the latter, get a LT1 ('92) or newer.

I like to tinker, and I had a CFI fed car for ~12 years; an '83 Trans Am that started off as a stock 305 CFI/auto trans car. When I sold it, the car ran low 13's @~105, idled like stock, and got over 24 mpg highway -all through the CFI intake, using a stock ECM and "chip". That car, everything that I did to it, and experience is what qualifies me to speak about the '84 'Vette.

You can keep the computer stock if you keep the cam shaft's duration-to-displacment ratio ABOUT the same as stock. As you increase duration, the engine will want more fuel, higher in the RPM range, and less fuel (than stock) down low. That is a change to the fuel CURVE, and you can only accomodate some of that, mechanically. I think that 215* would be the limit on what you could "band-aid" mechanically, and still have stockish idle, driveability and fuel economy.

Having said that, you can get much larger gains than a cam-only can provide, other ways:
*Ported intake, when done right is the single biggest gain you can get short of forced induction or NO2.
*Exhaust; the '84 exhaust is restrictive and upgrading it -same as you would on an '85-'91- is going to help.
*Fuel pressure and base timing adjustments will gain you a LOT by themselves.
*"Cold air intake" -making the hood induction system functional
We have a guy here at our local track that has run in the 13's w/his '84. His mods are: ported intake, bored TB's (did nothing), "free mods", cat back exhaust, and a torque converter.


Other comments on your post:
*"L98 heads" aren't going to show much improvent over the stock CFI heads. A bit, due to higher compression, but flow wise, there isn't much gain there.
*If you need EGR in California (as opposed to having an EGR there for visual), you would have to fabricate a remote EGR system w/L98 heads. I don't think that it is practical to drill/port the L98 head for EGR.
*"Vortec" head ports won't line up w/the CFI intake's runners.

So short answer is YES, you can go far, on the stock computer. I did. Part of my solution though, was displacement. But pleny of evidence exists to show that you can have dramatic improvements even on the 350 CID. I can tell you that opening the hood to reveal a stock looking CFI engine, that runs even w/LS1's at the strip...it's fun. People's reactions are fun too.

 

Hi Tom,
I think you and I talked on the phone last year.

Yes, I like to tinker and "own" my performance - as you can see by my current car at www.marcmedina.com/MR2.html

If I can find a Vortec engine in the local junkyards here I can get the heads complete for under $100. I could certainly re-drill the intake bolt pattern to fit them.

For a cam I was thinking of the old 350hp 327 cam (222/222 and .447/.447), maybe with 1.6 rollers.

Yes, I'd certainly do an exhaust upgrade, as well as ignition, etc.

If it was you that I spoke to, I'm still interested in doing some serious internal porting work on a CFI intake. Where would the problem come in the mis-match between the CFI intake and Vortec heads?



EDIT: Doing some searching on Summit and foudn this Lunati that looks reeeealy nice: http://www.summitracing.com/parts/LUN-60102/
and here is the next one down: http://www.summitracing.com/parts/LUN-60101/

The smaller one is power from idle (1000 rpm) to 5500, which would probably be fine, but something about that 1400 to 5700 of the larger one just gives me wood

 

One other question - in the pics I'm seeing online, I don't see where the EGR system is picking up the exhaust gas for the CFI system. It looks like there is no crossover in the intake. Can I get more info on this?

 

The egr only picks up gas from one side, the pass. side head. I think the vortec heads are a slight mis-match at the intake ports. But GM sells those fastburn alloy vortec heads that have a dual bolt pattern. So it cant be that bad of a mis-match. Stock vortec heads need to have some prep work done to run higher lift cams. Vortec heads do not have the egr passage to feed the intake. Sounds like a cool project.

 

Thanks for the info! I guess I really need to get my hands on an intake so I understand it better.

What I've been thinking though is to take out a lot of the runner length completely. Since the LT-1 and HSR type intakes go down to under 4" runners, we know the engine can sustain a short length. I think that cutting down the runners will also help (hopefully) the fuel distribution.

We'll see what happens I guess

 

On the crossfire intake, there is a coolant channel that runs in the middle of the valley. I think this was added to improve fuel atomization. I don't know if it is the reason for the small runner ports though, 2 things fighting for the same space? If I ever get a cross fire manifold cheap, I'd like to disect it to see how thick the runner floors are.

 

If youre dying for a 90 then wait and get it. They also used EGR
Not sure if that old school cam would be the best choice for your EFI

 

You can re-drill for sure, but you MAY run into this problem:



That cam is too big, IMO....and out dated. You can get a more modern cam like the one in the Summit link, that gives you more lift for your duration. I think the Lunati cam is too big too though. Get your power from improving the intake, heads and exhaust, like GM did w/the LSx engines, and keep your cam closer to 210*-215*, and the computer will be easier to work around.


I wouldn't downgrade the ignition w/aftermarket stuff. The stock stuff gets the job done; cheap, reliable, proven. I've had nothing but trouble w/MSD, Jacobs ignition, etc.



You can extend your RPM with manifold work, heads and valve lift w/high ratio rockers on a modern cam profile; just like GM did w/LSx engines. The LS2 has a stock cam under 210*, but makes peak hp at 6000 RPM. The local guy I mentioned above w/the stock long block CFI; he has found the BEST results by shifting over 6000 RPM at the track. That is on the stock cam, heads, rockers, exhaust manifolds, etc. Evidence that you don't need much cam duration for a long pull, w/the right intake system.

Last, I wouldn't shorten the runners. You'll loose low/mid tq and won't gain much up top. The runner length as it stands now, is a great, mid-length runner.

I do recall speaking w/you. I am glad to see you're moving on a 'Vette!

 

The two don't fight for space. The runner floors are 1/8" - 3/16" thick.

I chopped and closed off that coolant channel to try to lower intake temps. Waste of time. No improvement from that experiment.

 

Lot's of great info Tom, thanks MUCH! I'll take your advice on the heads, cam profile, etc.

I autocrossed my MR2 today and that was the final nail in the coffin for it. Getting to see how well other cars (with torque) get from one corner to the next showed me how much I need to change cars. My times were within a second of a couple of dead stock C4's, but they were more composed (or at least looked like they were) than my laps were. Anyways, I'm going to wax it up and get it advertised this week. Party's over, time for a C4!

It's good to know that the CFI setup will rev up to 6K plus - I do like to get the revs up