Author Topic: qjet for 250 inline 6  (Read 1330 times)

Offline A.G.V.chevyfreak

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qjet for 250 inline 6
« on: July 16, 2018, 10:55:35 PM »
Good day everybody.
I'm from south africa and as my user name says a chevy freak.
Anyway, i'm building a hot 250 inline six (now a 266ci) and would like to use a quadrajet on it.  Been looking on the web for the pontaic ohc 250 quadrajet specs but only been able to find the jet and rod sizes.  I have a couple of spare qjets and would like to modify one to work on this motor.
Any help or info much appreciated.
thanks.
chevyfreak.
No luck on finding the airbleed sizes or idle tube size.

Offline Cliff Ruggles

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Re: qjet for 250 inline 6
« Reply #1 on: July 17, 2018, 03:32:15 AM »
That information is useless for what you are doing anyhow unless you were using a Pontiac OHC Q-jet.

Select a carburetor first, then tune it exactly for the 250 Chevy in line 6.  Without a carburetor part number I can't help......Cliff

Offline A.G.V.chevyfreak

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Re: qjet for 250 inline 6
« Reply #2 on: July 17, 2018, 09:21:22 AM »
Hi cliff.

The 2 carbs i have that i can use there is.
   7028212 that came off my 327. All still stock on this one.
 And then 7044233 that actually came off a caddillac, has small jets and needles.

Thanks.

Offline Cliff Ruggles

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Re: qjet for 250 inline 6
« Reply #3 on: July 19, 2018, 04:33:08 AM »
Both of those would do fine on a 250 six.  For the smaller CID you may have to reduce or eliminate any idle bypass air unless a larger than stock cam is used.

Stock jetting would be the best starting point and most likely no need to modify the idle system as both were pretty generous with idle fuel in stock form.......Cliff

Offline A.G.V.chevyfreak

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Re: qjet for 250 inline 6
« Reply #4 on: July 19, 2018, 05:49:37 AM »
Thanks for reply.   Will probably go with the 7028212.  Just wanted to know the pontiac specs to get a ballpark on where to start. Especially idle side. Wil fit carb and take it from there on tuning to suit.   
Bore is at 4inch now, head ported and comp ratio calculated at 9.45 ,Cam will be in 200 to 210deg duration. Still in discussion with the cam grinder on that. 
Would really like to run a qjet on this motor, best carb ever build.
4 of my motors is fed by qjets.  2  327 chevy motors , the pontiac 455 in my impala and have a newer style 1705  converted for boost ref on piston , on a 471 blower inline 292.   
Thanks for reply.
chevyfreak.

Offline Cliff Ruggles

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Re: qjet for 250 inline 6
« Reply #5 on: July 19, 2018, 07:54:51 AM »
The Chevy 7028212 is only similar to the Pontiac OHC 6 carb in appearance, completely different set up in every area so pretty much none of the set-up specs would be a good starting point if used with the Chevy carb.......Cliff

Offline A.G.V.chevyfreak

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Re: qjet for 250 inline 6
« Reply #6 on: July 19, 2018, 09:23:47 AM »
Will first try it as it is and see from there if it needs changes and where.
thanks for your input and guidance on this.