uhhh.... I have personally worked on an 84 a few times in my life. It was on a customer's car and those ports as cast are total crap for airflow. I was even offering to port it for him, but he refused and wanted to convert over to carb. My dad and I did a carb conversion and put a nice cam as requested and he told us that the car feels so much better than it ever did. Even I believe it was worth the $800 he spent on it. So in reality, stock CFI intakes as cast are pretty much useless for performance unless you think a 15 second quarter mile is fast. I dunno if you originally understood what I said or not, but that being said, performance suffers with the stocker as cast. Now, if you port them, that is a whole different story within itself. I'm sure you ported your stock manifold so it didn't suck ***** on performance anymore. Great, awesome, cool, good job on improving GM's crappy ports as cast. Seems like the airflow is more than adequate for your 400 if you are running 12s as what your avatar says. So anyways and again, congrats on that and to eachs' own.

 

Wow Tom, mid-low 13's and 24 mpg hwy?! That sounds great! I mean, I know that 13's isn't the fastest, but I don't plan on taking her on the 1/4 mile, and I'm really digging the 24 mpg bit. I'll be living in a part of Houston where everything is far away, so having a moderate-high performance car that can save some gas would be the best of both worlds for me!

And thanks for helping to clear the part about the ECM. From my viewpoint, it's something less to worry about; I just want to make sure it won't damage the engine. Don't have stacks of money lying around!

And js292, thanks for the link to Vette Tech's Tri-Y's. Matching those up to the X-pipe and dual cats from Melrose would make for a wicked exhaust combo, I think.

So I guess the two things left that I'm not so sure about are the heads and the gear ratio. What would be a good recommendation regarding cylinder heads? As for gears, some people say 3.73's and some say 3.54's. Which ones would give more of that SOTP feel and still be comfortable on the highway?

 

No problem in the info. I do want to point out though just so we're clear, that the ECM doesn't just "adapt" to the changes you've made. It's dumb as rocks. You need to make the mechanical changes to the fuel and ignition system to get optimal performance, driveability, and fuel economy out of the stock ECM. You need to "feed the engine what it wants".

In MY case, w/the 400 engine, ported intake and 224/234 cam, I started w/90 pph injectors meant for the 454 TBI engine. Through trial and error, I found that my engine "liked" 15 PSI the best w/those injectors, and that netted me the best 1/4 mile times. Unfortunately, it was a little rich at idle (likely due to the cam being a more radical profile than the stock one). I solved that problem by buying a vacuum referenced fuel pressure regulator, meant for marine TBI applications. Using the stock-to-the-CFI regulator spring, I set the new regulator to 15 psi (w/no vacuum) and that resulted in ~10 PSI at idle w/17" of vacuum. It worked out extremely well, IMO. As good as a custom ECM tune? No, but good enough that no one would know the difference, and good enough to meet the criteria? Certainly. Point is, you'll still have to figure out how to "feed the engine what it wants" and there will be some trial and error, just like if you were re-jetting a carb after the same type of mods on any motor.

 

Hes not running 12's in a CFI car, he doesn't even own one! He is running a 2006. Ya gotta read what this guy puts out VERY carefully!

 

Maybe YOU do. It is no secret that I have a C6 now, and that is the car that is what's running 12's.
1. A VERY quick search will turn up that info, not to mention a glance at my profile.
http://forums.corvetteforum.com/member.php?u=167177
http://forums.corvetteforum.com/show....php?t=1738556
http://forums.corvetteforum.com/show...5&postcount=74
2. Not once have I EVER said or implied that my CFI car ran 12's, b/c it didn't. Go back, put you reading spectacles on and actually READ my posts; they all claim 13's for the CFI car.

No "Big secret" for anyone of average intelligence. I post on this board sometimes b/c these gen cars interest me still, AND I have actual experience w/the subject at hand (bigger cube CFI), unlike yourself. You sure like to try to make something out of nothing. I'm running some BIG CONSPIRACY here! lol

 

I read all that but you write so vaguely, mixing the past and the present, that some don't pick up on it. I didn't have to search to find out about the 2006, it's in your profile. Some don't pay as close attention as I do. I don't think it's a conspiracy, simply fuzzy writing reporting things From your past possibly not well remembered.

 

Show me where I've "mixed the past and present" relative the topic at hand. Where, in a CFI thread (or any thread for that matter) did I talk about my C6's 1/4 mile times as if they were my old Trans Am's times?? Post it up for me please.

I don't write vaguely. I state the facts and if someone is interested enough to want to know "why" or "how" they can ask. (you should try it). I don't need to type the "why" or "how" if the OP or person asking the question already knows...or doesn't care. I'm perfectly willing to divulge everything about anything that I've done. No "secrets" here. All anyone needs to do is ask.

As for "remembering the past", you're RIGHT! NOW you're on to something. Perhaps it's my memory that's the problem with this thread!! Thanks for pointing that out. Gee....now I wonder if I actually ever did OWN a Trans Am? Maybe it was all just a dream.... Der.

Do I need to start pulling up posts from 3rdgen, and the CFI forum from that time frame?

It's a beautiful day in Utah and I'm off to Lake Powell for the weekend. Have fun on your 'puter this Memorial day weekend Ducky. Hmmm, now I'm beginning to wonder if I even own a boat?....maybe that was a dream too! I'll have to run down to the garage and see if there's a boat in there...

Have a great weekend everyone, and YES, you can run a CFI on a 383 w/the stock ECM...to get this back on topic!

 

I think to a large degree, you have been led astray. With your performance goals and a limited budget, you can piece together a really good performing DD without spending a lot of money. First, for a non racer, driving on normal tires, not drag radials, you don't need a Dana 44 carrier. It is highly unlikely that you will have any problems with your D36.

With the added torque, you really don't need any more gear, either. Right now, 70 mph is 2000 rpms. With 3.54 gears it will be closer to 2300-2400, and with 3.73s more like 2500+. The comfort level is highly subjective and personal. Try cruising in 3rd, instead of OD, to see how you like it. Driving in 3rd is worse than with the gears, but it may help give you a feel for what it would be like. Fuel mileage will suffer with the gears, also. On the highway it will be proportionate to the ratio you select. FYI, there are quite a few people swapping TO the 3.07 gears that you now have.

A mild cam aimed at under 5000 rpm performance will not require ECM modifications. A few mechanical adjustments maybe, but not a major chip re tune.

Big aftermarket heads are for high rpm horsepower. Match port your lousy "624" heads and do a little bowl work and they will work well with your ported crossfire manifold on your 383.

RACE ON!!!