General Category > Quadrajet Carb Talk and Tips

2x4 Oldsmobile 455

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Marx3:
I am planning an Olds 455 build and came across this
http://www.ebay.com/itm/Offenhauser-Big-Block-Oldsmobile-2x4-Dual-Quad-Alum-Intake-Offy-B-B-Olds-/191438784361?pt=Motors_Car_Truck_Parts_Accessories&hash=item2c92a40769&vxp=mtr
on ebay. I would love to have a 2x4 Qjet setup, I know I could tune it to run as good as possible.
The thing is, this intake is not a great performer for real power... Olds builders advice against it for serious powerapplications.
I plan to build my 455 relatively mild for starters, but up the road I would like to enter the 12's, maybe even the 11's in my ´78 Trans Am, so I am going to build it to make pretty serious power.

Question is, would it even be possible to make a 2x4 Qjet setup work flawlessly on a powerful 455 Olds ?
I would use 750 units for the job... that would give me about 500 cfm combined on the primaries as far as I know.
Too much?

Cliff Ruggles:
Nice looking intake, and it may have enough material to port it for a spread bore carburetor so you don't need an adapter.

I'm not a big fan of 2 x 4bbl set-ups, since a single q-jet can easily support 455 cid to at least 750hp, but they look cool and make for great conversation at car shows, cruises, etc.

I've helped several customers set up q-jets to work on similar set-ups, I would use and prefer the early Chevy carbs for those applications, as they are side inlet and sit nicely on those intakes without crowding.  They are also very common carburetors, zillions of them from the 1971-1974 period floating around on E-bay, swap meets, etc........Cliff

Marx3:
I am only thinking of doing it because it would be cool to make it work flawlessly. Very few people are running 2x4 setups here in Denmark. I would not be going for the coolfactor as much as the satisfaction in making it work.
I have plenty of cores lying around, I can easily find 2 late 70's 750 unbits with side inlet.

I am undecided as to stroking that 455 to 495, but I have no doubt I could build a 849cfm unit to feed it plentifully wether it stays at 455 or gets bigger.
Well, thanks for your reply, I will keep on thinking about it.

von:
IMHO the key to making it work well would be to make a progressive linkage so that at below say one third to half throttle it would operate on the primaries of the rear carb only, then at about one third to half throttle the front carb primaries start to open and progressively open faster than the rear carb until both are fully open at WOT. The secondaries of course open as normal on their own in response to air flow requirement.

Marx3:
I hear ya... I wonder how the factory 2x4 setup is on, say a nailhead with AFB's for instance... A good friend of mine has a true 2x4 Riviera. I gotta check with him.

I agree with the idea of having just one pair of primaries operate at normal light throttle application, but I dont know if the rest would work. I imagine it would be dificult to control the fuel metering at wot. The secondaries would open at a pretty fast rate. Some thought and some trial and error would have to be put into the project.
I am getting more and more hooked on the idea, mostly because it would be cool to make it work as flawlessly as a single unit always do.

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