Originally Posted by cobalt327
Hi Norman. I had a '68 LeMans w/the 215 hp Sprint engine. Actually ran pretty good for only 250 cid.
Pontiac OHC Q-jet carb numbers:
1969- 7029260(AT), 7029261(MT)
1968- 7028260(AT), 7028261(MT), 17054906(?typo prolly?)
1967 (230cid) - 7027268(late, AT w/o AIR), 7027269(late, MT w/o AIR), 7037268(late, AT w/AIR), 7037269(late, MT w/AIR)
The following is from High Performance Pontiac
7027260 (early, AT w/o AIR), 7027261 (early, MT w/o AIR); 7037260 (early, AT w/AIR; 7037261 (early, MT, w/AIR)
1966- 7026260 (AT), 7026261 (MT)
Before going further, are you actually working with a Pontiac Sprint or Sprint clone, or are you tuning a different but similar set up?
Sorry I forgot to mention this earlier. Actually, the application is for a '75 Mercedes 280C, DOCH with in-line 6, high revving (6500 RPM), 2.8L engine. The carburetor (Std.) used by Mercedes for this application was a spreadbore, Solex 4A1 which is a poor and disappointing copy of a Quadrajet in every respect and leaves much to be desired. I will need to replace this carburetor as it is beyond repair (severely warped) and leaks fuel and air/vacuum making it un-tuneable (is that a word?), and miserable to drive. In any case, I would prefer to invest my time, money and energy into finding a permanent cure to the Solex issues; thus my inclination into staying focused on converting/modifying a Q-jet to suit this purpose.
In terms of air flowing capabilities, I have no idea what the Solex's CFM raitngs are; though I have searched in vain for this information. However, from what I can tell, the venturis and bores look to be substantially equal if not identical, as well as the exterior appearance. I have managed to gleen from extensive searches, that the carburetors that comes very close to matching the Solex, in terms of air delivery are the ones found to have been fitted to the Pontiac Firebird Sprint. Thus, my search for additional information on these carburetors begins here. Those who have managed to successfully make the Q-jet adaptation to the Mercedes 280C appear to be quite happy with the results, but are no longer available to offer/share the finer details.
I have Webers 32/36 and 38/38, Autolite 4100 and Holley 4175 carbs available to me in my stash of good-to-haves. The only one of these I would spend time attempting to convert would be the Autolite 4100 (1.12 venturis); failing my ability to make the Q-jet work. That said, it may be my last resort but only because of the availability, simplicity and low cost of these old 'shoe boxes'. Converting to a Q-jet is quite a daunting challenge, no doubt. But isn't that what hot-rodding is all about?
I have recently ordered a couple of books on the subject of tuning and servicing Rochester Q-jets, but nothing like being able to bounce ideas off of kindred spirits in one's pursuit of knowledge. I did not mention that I have a well equipped home workshop with machining and welding capabilities; if nothing else, it may come in handy to machine a set of bushings for those pesky worn out throttle shaft bores.
Thanks for the info you have provided, I very much appreciate it. I look forward to any additional thoughts and information you may have and be willing to share.