Looking at my carb options when it comes to the 350 swap.

1- Get my qjet rebuilt or go with a SMI Level 2 build optimized for a L98
With polished 083 heads, LT4 cam (slightly hotter than stock), flat top pistons, hooker 2055's, PROM chip for the 350

Or


2- rip out all of the computer stuff, go with vacuum advance dist. and a Holley or edlebrock.


Looking for 280-320 hp. Excellent driveability . Easy tune ability.

Chuck

 

If you're going to be running a cam in it, I'd say go with non computer controlled QJet and HEI (unless necessary to pass emissions in your area). The cc-QJet system WILL work with a modest performance cam like the HotCam, but it will likely not deliver optimum performance esp. in part throttle/transition situations and the idle may be a little flaky (WOT will be just fine, though, believe it or not).

 

^^^This

I think your better all-around option of those you listed, is to get Sean Murphy to rebuild it. May not be cheeeeep up front, but within a coupla tanks of gas, it'll start paying you back. At the price of gas these days it doesn't take much to turn you from penny-wise to pound-foolish. Although actually, the cost of replacing all that other stuff, is on the order of $700; and THEN, use MORE gas, every single instant the car is running. Your vendors' cash registers go cha-ching more often on YOU. Not a wise way to spend money: use your own money to increase your own expenses FOREVER.

 

Damon & Sofa-

Thanks for the input. I am most likely leaning towards a Sean Murphy rebuild now.

 

If you're only planning on the production lt4 cam, the ccc will run it no sweat.
I think it is 203/210? 206/210? Something like that...
no prom needed, your l69 has the hotter spark curve.
I'd swap to a 350 knock sensor and esc though.

currently swapping out my l69 for an l31, will be adding cam later with the ccc setup.

 

I just talked to the machine shop that's working on my engine and they didn't think that the ccc qjet would run well. I think he probably thought that the computer was as touchy as the TPI computer... In fact he thought at first I was going to run a TPI setup. Doesnt sound like he might have good knowledge of carburetors. They are going to add a custom grinded cam to match up with 083 polished 3-angle heads with new springs and new hypereuatic pistons.

Thought about vortec heads as well.....

 

Here's a good read
https://www.thirdgen.org/forums/carb...t-capable.html

lt4 oe is 203/210
zz4 is 208/221
lt4 hot is 218/228
all have been used in CCC combos, Monte Carlo SS owners also have some nice CCC combos try their boards too.

 

Thanks Anthony!!!

 

The vortec heads/lt4 OEM cam (not hotcam!) should be good for just about 300hp.
factory lt4 heads flow just a bit better than vortecs and have more compression, 330hp

if your ported 083's flow vortec numbers you should reach your goal. Although you miss out on the efficient chambers.

I was going to run this combo, but damn the lt4 oe cam seems scarce these days.
good luck with your swap!

 

Thanks!
My main priority at this point is getting the bottom end of the engine solidified with quality parts, then at some point in the future go with Vortec heads.

But I am definitely going with the Sean Murphy Stage 2 setup and keep the L69 computer unless there's issues.

 

I swapped out my L69 for a 350 when my L69 lost a bearing. I'm running a Lunati Voodoo cam (P/N 60121) with 270/278 duration .515/.530 intake/exhuast, World Sportsman II Heads and Edelbrok Performer intake and my CC Qjet runs it just fine. I had mine Qjet rebuilt by Cliff Ruggles though I've heard good things about Sean Murphy.

In stock form, the Qjet wasn't happy, especially at idle. The bigger cam pulls less vaccum and the carb didn't like that at all. I was having to bump the idle up out of "idle" to keep the fuel flowing since the carb using the vacuum singnal for idle fuel flow. Once it was rebuilt,, I considered a modified stage 2...not quite stage 3 but more than stage 2 build based on my own research of what is commonly considered a stage 1,2 or 3 rebuild fot these carbs and I haven't had any issues in the past 3 years.