who here is actually running the l83 or fbody variant in basically original condition?

i have an 84 c4 that is all original, the car starts right up when drizzling gas in the throttle body, but has sat so long probably needs new pump, throttle bodies rebuilt, synced and new injectors car only has 79k on the odometer. i would like to get it running, maybe do some porting on the anemic base manifold, and would like some insight from thos that have substantial experience with this setup.

and yes, i have a dual plane along with 4778 holley sitting here, but i want to make the car run and run good, then i will look into modifications.

 

mine still going strong-corvette L83 in an f-body.You probably only have stuck injectors,possibly rotted foam rubber pump hose or pump ruined by bad gas.decent chance it will run ok or even good once injectors unstick.With only 79K, nothing should need rebuilt except some aged gaskets may need replaced.Once up and running,plenty of increased performance potential-starting with intake porting If exposure to fresh gas does not free stuck injectors,gently tapping on top of injector with a hard object usually gets them going again.

 

What insight are you looking for, specifically?

It sounds like two things, to me:
1. Getting it running (right)
2. Adding power

1. Diagnose the fuel delivery system. Check fuel pressure first, then if good, the injectors. If it needs a pump, get a MPFI pump as the CFI/TBI pump is marginal.

2. Set the fuel pressure (by adjusting the regulator on the rear TB) to 13-14 PSI or so. Spec is 9-12 and that is weak. CFI "likes" 13--14.
Advance the base timing as much as it will take w/o detonation; typically 10-12* is about what these like.
Engine responds well to exhaust improvement (like any F-bod) or early C4
Port the bejeezus out of the intake...until the walls/ceilings/floors are paper thin. If you "window" it, just fix it with a mold-able epoxy. The runners are too small so you can't go "too big"...the bigger you port them, the more power it will make.

^That should get you to somewhere in the 270-280 hp range, and be FUN to drive.

 

Does all the porting require a new tune to the base fuel and timing maps?

 

No. While a tune would likely help, it's definitely not required. I'll share my experience with you to back this up:
My CFI car was an '83 Trans Am...so it was the 305 CFI. I did these mods to it:
*Edelbrock "headers", Y pipe, deleted cat and 3" cat back
*160 stat
*advance timing
*Electric fan (your 'vette already has that)
*Raised fuel pressure
*Tied the Cowl induction open
*Swapped the 700R4 for a Borg Warner T5
With air filters removed, car ran 14.5/95 mph in the 1/4 mile. How many hp does it take to make a 3300 lb car go 95 in the 1/4? About 230 hp. Remember, this was starting with a 170hp 305...not the 205hp 350 that you have.

I swapped in a 350, added more fuel pressure (fed it what it wanted) and ran about the same times in the 1/4.

I swapped in a small block 400 and did the following:
*Ported the bejeezus out of the intake
*Bored the TB's out to 53mm
*Ditched the "swirl plates and radiused the lid-hole
*Roller Rockers
*244/234 cam
*90 PPH injectors + Vacuum referenced fuel pressure regulator set at 15 PSI (Vacuum pulled it down to ~10 PSI at idle/closed throttle)
*Underdrive pulleys
With ^that engine, same exhaust as the 305 (Edelbrock headers & Y with SLP cat back), same trans/rear everything else about the same, the car went 13.20's @105.

I never tuned, altered or touched the ECM throughout that entire journey. How did it run? It ran awesome; It idled like stock, started quick, had fantastic drivability and wicked throttle response, and gave me over 24 mpg on trips. By all objective and subjective measures, it worked very well. The take away here, is NOT that "you can do what you want" on the stock ECM...but rather, as long as you keep the cam "proportional" to the stock cam...or in other words as long as you don't radically change the shape of the torque curve from stock (flat), then it's easy to "tune" it with basic methods, such as injector sizing and fuel pressure and it will work pretty good. So the long answer to your question is that no, you don't need to re-tune the ECM for a ported intake. One more example is a great guy (CFI-EFI on the forums) had an '84 'Vette. With a heavily ported intake, exhaust and a converter, he was running mid 13's. He never touched his ECM either. Port it...and don't hold back!

 

Dart "Iron Eagle" 165 runner/67cc chamber heads work great on the L83 350 and a big upgrade over the old 76 cc '624 heads cheap too-$300 for bare US made heads,machine work/valve jobs were perfect .

 

i have a set of 113 vette heads, was thinking them or eq 200cc vortec heads, something cheap

 

If you get Vortec heads, you'll have to drill the intake heads for for standard bolt pattern intake, then "raise" the intake by stacking gaskets. "CFI-EFI" and I did this to his car ('84 'Vette) and while it seemed hoakie, it ended up working fine. Personally, I'd port the 113 heads and use those:
Decent performance, when ported
Lighter weight
Compatible bolt patterns and port height.

 

driving season back to my area,and have noticed gas mileage using the Iron Eagles has improved a decent amount vs the old ported '624s

 

That's a pleasant surprise.

 

better chamber design and higher compression does the trick