I am installing a new 350 GM Goodwrench and I was planning on using my stock intake and carb from my 86 iroc, I know they will fit, but with a larger engine will the stock carb be able to feed the new engine properly.

 

Which engine? Unless it has Vortec heads, it won't be a problem. In that case, just get a Vortec intake manifold.

The stock intake isn't the best out there, but it's not bad. With a performance cam, good-flowing heads and exhaust, you might reach its peak. Now would be a good time for a Performer or Action +.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/LB9 block, ZZ3 cam and intake, WP 305 heads ported & polished, Hooker headers & y-pipe, hi-flow cat).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

it's a basic engine rated at 249 hp w/ headers, hei dist. which i have both. My brother said he would give me his 750 vacuum secondary, would this be good, but I don't want to kill my mpg.

 

If you go with anything other than the factory q-jet, you're going to have to replace the distributor with a vacuum/mechanical advance unit (which it sounds like you have), and your SES light will come on at all times. Basically you've taken the computer out of the loop, so your torque convertor will no longer lock up (this can be handled by an aftermarket kit). Also, the computer keeps the mixture as lean as possible, and without the CC distributor, you won't have a knock sensor. All the things that happen when the computor is disabled will have the effect of reduced mileage.

As for the stock q-jet, it will flow as much or more than the Edelbrock I have on my 396. Admittedly, I'm at a rather high altitude, but that q-jet feeds my big block just fine, thank you.

A lot of guys complain about them, but the q-jet is a great street performance carb. The CC type takes it one step further by being fuel effecient as well. To say nothing of running cleaner.

Any idea what I'm suggesting?

 

Oh, another thing. By "750 vacuum secondary", I assume you're talking about a square-bore Holley. That won't mount to your stock intake manifold without an adapter.

 

Mark,
It sounds like your getting some good advice here already. A Q-jet or Holley vac/secondary will do fine on fuel mileage if they are in good working order (kind of rare to find one like that IMO).
It is likely that your stock intake will provide more off-idle torque and be better for fuel mileage than an aftermarket dualplane.
You never said anything about disabling the computer on your car, so I suppose your original question was if the computer will feed the larger 350 enough for good fuel mileage. I would say no problem on the fuel mileage, but possible problem at full throttle.
For the record, I have personally seen substantial gains on the order of 30+ horsepower by just swapping a factory iron intake with an Edlebrock-RPM (on the 305 engine). So if you're going for power then I'd say replace both intake and carb with more performance oriented models. I have also seen Edlebrock intake/carb combinations produce great fuel mileage results as well, and that includes the combo on my car. My 383 gets 24mpg (highway) with the same carb settings that I race with.
The mods I do to the carb effect both power and fuel economy because I do controlled tests for both. I like the drivability and fuel economy too.

hope this gives you some useful ideas



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*I do custom performance mods on Edlebrock Performer carburetors (dualplane intake mods in the works),
White 1986 Irocz, 305/383 with Edlebrock Performer-RPM intake and Performer #1407 carburetor, +110hp shot of crack, 700R-4 tranny, 3.25:1 rear, Mcreary Road-Stars, SLP-stainless 1.75" shortie headers & Y-pipe, single 3" Borla exhaust, Linginfelter-TPI camshaft part number 74216 pulls 17" vacuum solid. Cam specs 213/219 @.050 114-LSA, .462/.470 lift @1.5:1 ratio. MSD-6AL, billet distributor, multi-retard, blaster-3 coil, and RPM switch.
N/A runs 10.9 @124,
Crack-runs 10.3 @135
haven't run at track since Oct-99