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Keep my Quadrajet or get another carb for 350HO Vortec ?

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Old 02-01-2012, 07:05 PM   #1
waid1017
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Default Keep my Quadrajet or get another carb for 350HO Vortec ?

After a lot of research on the web, I am planning to replace the top end on my 350 V8 and replicate GMPP 350HO Vortec. Based on the Car Craft’s article, I should be at a minimum of 350hp (I hope ). I think this is the best bang for the buck.

http://www.carcraft.com/techarticles...e/viewall.html

http://www.carcraft.com/projectbuild...l/viewall.html


GMPP Stock Vortec Heads (#12558060)
GMPP Cam (#24502476)
The above heads & cam comes in the GMPP 350HO motor
Edelbrock RPM Air Gap or Performer Vortec.
Fel-Pro 0.15” shim head gasket to bring up compression to around 9.1-9.5 :1
Long tube headers

I rebuilt my Quadrajet and works just fine. Is it worth replacing it with a Holley 750 cfm or another Carb?

My 350 V8 is actually in a 1977 Olds Omega (Nova) so I dont know if there is any difference in post 75+ carburetor.

Thank you very much

Waid

Last edited by waid1017; 02-01-2012 at 07:22 PM.
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Old 02-01-2012, 11:14 PM   #2
Ben Lurkin
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I don't remember if anyone makes a spreadbore intake for vortec heads. If so, keep the qjet.
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Old 02-02-2012, 06:30 AM   #3
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Nope. Nothing else out there like a well tuned Q-Jet. These are very complex carbs, and may take some doing though. Guy's like Cliffs carbs and Lars Grimsrud can help you along. Well worth the effort, as you'll be showing most the other guy's tail lights.
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Old 02-02-2012, 08:39 AM   #4
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Quote:
Originally Posted by Ben Lurkin View Post
I don't remember if anyone makes a spreadbore intake for vortec heads. If so, keep the qjet.
You buy Performer spread bore intake for Vortec heads.
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Old 02-02-2012, 08:46 AM   #5
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Sounds like a good plan.
Keep your good-running spreadbore QJet.
Shortest vortec spreadbore intake is Professional Products cyclone 52007 ... it's very similar to EB2116 but a bit shorter; less $ too.

unless stock vortec heads are retrofitted with guide plates, '77 sbc rocker arms will not work (for long).

suggest a new set of pushrods (no need for race quality here) and a new set of "self-guided" aka "rail-type" aka "self-aligning" rocker arms as found on later heads (/350HO) ... maybe even 1.6:1 rar (no need for roller/roller tip rockers here).

like any brand new flat tappet cam, x476 also requires brand new lifters.
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Old 02-02-2012, 12:16 PM   #6
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When I did my vortec swap in my 77 zz4 I used GMPP vortec manifold 12486570 it will accept square or spredbore carbs. It also has an egr port. I stuck with a quadrajet and it work very well. I don't know if this manifold is still available. I have a spare new takeoff manifold on C/L
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Old 02-02-2012, 01:45 PM   #7
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Vanice, did you end up adjusting/changing anything on the Quadrajet?

What cam did you use?

Most likely, I will end up getting the Edelbrock 2116 - Edelbrock Performer Vortec Intake Manifolds Spreadbore which is cheaper than the GMMP and it too will accept both spreadbore and square.

Thanks
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Old 02-02-2012, 02:01 PM   #8
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The Q-Jet is a great carb - one of the all-time best street carbs.

I can't imagine that it wouldn't need a tune from the change, and there aren't that many folks around that have the knowledge and parts to do so - that's the only potential downside.
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Old 02-02-2012, 02:37 PM   #9
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What do I do about the choke heater tube?
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Old 02-02-2012, 03:39 PM   #10
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My 74 has a 78 q-jet. It came that way when I bought it, and as such, the manifold is setup for a divorced choke, and the carb has the hot air one, so I fitted an electric choke. Problem solved until a 74 auto q-jet pops up!

Last edited by mrmagrath; 02-02-2012 at 03:39 PM. Reason: Accuracy
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