WTB - QuadraJet Carb for 1968 Riviera

[kreed]

Need a good rebuildable QuadraJet for my 1968 Riviera project.  Any help  appreciated . Thanks KReed ROA 14549

[Craig Balzer]

There's one on eBay for $550

 

https://www.ebay.com/itm/176478605240?fits=Year%3A1968|Model%3ARiviera&_skw=QuadraJet+carb+for+1968+Riviera&itmmeta=01J8DM696RNS6NPFVWCETKFQSG&hash=item2916f1cfb8:g:HUkAAOSwj8JmmYyo&itmprp=enc%3AAQAJAAABAHoV3kP08IDx%2BKZ9MfhVJKm6p2DktV77k7PgRtucSNJEiH54DuhYVanDEelYhINZsXmFZgL7WyU66umVyesQmNgI8Usp7kHsZ2Ul14P1MR%2B8sLq6ezoq5WX6QiAiOllFZsDjzZGTKdLc9beuqD2hQCCjFp07U3RlT%2BFxrusRpeE6a4938GvEgwEIkreNwzpDO6FdEVajB5WFsHk2SV321Gz1euVS14Mu%2FlamkgAaXKO9CMLOYZK3FgsWozeDPlM9qh7qAnBMIQfDXfgwEHfs%2Fjbt4WuBA9IJ%2Boql3SvwTucqCYZ0xiErQJ3GbUSgjn6IwXyKBJeVw0MvRD1AbXlxQt4%3D|tkp%3ABk9SR7qTmbTDZA

[RivNut]

7028240 from a 1968 Buick. Says it's rebuildable

 

https://www.facebook.com/marketplace/item/3612473942416323/?ref=search&referral_code=null&referral_story_type=post&tracking=browse_serp%3A565f8b11-b8f9-4785-8db2-8b981d0559b5

[jj5794]

Ken,

 

Please be aware that there are early and late Quadrajets for 1968 Buick 430's, 7028240 and 7028248, respectively.

 

Jim Vesely ROA # 7437 BCA # 39477

[RivNut]

Here’s what I’ve found.

 

First discussing the early and late 1968 8-430 carbs (7028240 -> 7028248). The only difference in these carbs is that Rochester made a modification to the float to improve fuel control; all calibrations are identical.

 

Perhaps Jon at the Carburetor Shop could explain what the differences are and make a suggestion to bring the ..40 up to ..48 specs.

[RivNut]

On Jon Hardgrove’s website for his The Carburetor Shop, he shows both carburetor numbers and a different kit for each. This goes for early and late carbs for both the 400 and the 430.  What are the chances that ordering a late kit for the early carb would bring it up to the later specs?

[telriv]

All involved,

 

MAYBE a call to Jon is warranted in this case to help solve/get more Clarencey on the differences.

 

Tom T.

[carbking]

Ed sent me a PM, that I looked at about midnight, and answered off the top of my head, which is often a bad idea.

 

Somewhere in the 1968, 1969, 1970, and 1971 models, Rochester changed the placement (machining) of the float pin, which required a different float, and I mentioned this to Ed as the possible difference. These were NOT changed at the same time across vehicle or model lines, hence the year range above.

 

Further research this morning shows this to be untrue.

 

Checking the specifications one by one, the ONLY difference in the two carbs is the float. I have a new old stock from the early carb, but not from the late. The late number supersedes the early number, which was then no longer available.

 

Further research shows the aftermarket float manufacturers use the exact same replacement float for both, as well as 4 other Rochester float numbers used in other GM vehicles.

 

Why the different numbers? 

 

I don't know, but will speculate.

 

This was close to the beginning of the "foam" (I cannot spell the chemical name and too lazy to look it up) float. The float manufacturer (no, Rochester did not make the floats) changed the sealing float "skin"  formulae several times trying to prevent gasoline from permeating the skin, thus causing the float to absorb fuel, become heavy, and no longer function as desired.

 

GUESSING the late float is the exact same float shape with a different skin.

 

So the newer float WOULD bring the early carb up to the later carb specs.

 

One of the aftermarket float manufacturers made a brass variant of these floats, which is what I always used when I was still restoring carbs. I still have a small quantity of these NORS brass floats.

 

Now, Ed mentioned that I show different kits for the early and late, and he is correct.

 

WHY?

 

When I first started the manufacture of carb kits, I used the original (in this case Rochester) overhaul (not the less expensive power) kit application list to correspond to my application list where possible; and then added items to the original bill-of-material which I feel either should be replaced, or saves a trip to the parts house for those using my kits. In the case of the Rochester Q-Jet, I add the secondary air-valve spring and secondary cam (both of these should ALWAYS be replaced) and a length of hose for the choke pull-off (convenience), plus a clip to retain the power piston bracket because the plastic retainer is generally bad.

 

So my kits for the early and late carburetors are identical; simply because they were ordered from the original Rochester application list.

 

As to which carb to use?

For the "driver" either, with the later foam or the brass float.

For the "show car", one would need to coordinate the build dates of the carburetor and the vehicle.

 

Jon

Edited September 25 by carbking (see edit history)