I just bought a camaro and it has a 305 in it that is not stock, the guy before me did all the work but i am just trying to id everything. Cannot find this part number anywhere but know it is a q-jet. Any info would be great. Also did the q-jets ONLY come 750 or 830cfm??? 1704985 thanks
uzzled: Interesting...nothing I can find matches this number. It doesn't decode right. Are you 100% sure on the numbers?
As far as i remember. but mainly im try to find the size (cfm) of it. I think it may be too big. Just wanna check up on it. If not i gotta clean and check jets etc. It bogs and doesn't have the power it should
big block buicks came with either 750cfm (71 and earlier) or 800cfm (72 and later). i don't know where you're getting 830cfm from. except that i have seen sources that claim that the rochester rating was, how you say, 'optimistic'? they give the ratings as 750cfm designation/730cfm actual and 800cfm rated/770 cfm actual. YMMV. http://dyeager535.topcities.com/qjetdecode.html example: 17080243 170 - general rochester production code 8 - tells what year frame to use, 8 means 1980s, 4 designates 1970-75 and 5 designates 1976-79 0 - last digit of production year, in this case 1980 2 - type of carb, in this case a 4v quadrajet 4 - division, 4 = buick, 0/1/2 = chevy, 5 = olds, 7 = pontiac 3 - trans type, odd #s mean manual, even #s mean auto 17049285 so basically, none of your code past 170 decodes according to online sources. ah, you added a new digit. well, that would put the 2 in the quadrajet designator spot and 5 might be possible for a manual transmission car but the 8 still doesn't decode as a valid GM marque and 49 might not be a valid year.
so what am i doing, confusing the year for the oversized oil pickup tube with the carb upgrade??? could be. :error:
http://www.taperformance.com/newpage1.htm TA says 72 and up for the 800cfm claimed/780cfm actual although i seem to have forgotten how to subtract. :shock: :ball:
When you look into the primaries, is the bore smooth all the way down or does it step out some towards the bottom? If its smooth then its a 800, if it steps out its a 750.
Are you sure about that number ? 80's Rochester carburator starts with 1708**** (8 digits) 1976 - 1979 Rochester carburator starts with 1705**** (8 digits) All 1955 - 1975 Rochester carburators are starting with 70***** (7 digits)
As I recall, the 800 cfm unit was actually an 830. The easiest method of determining the size is to look carefully at the primary barrels. If the interior has a "bump' visible on the inside of the primary barrel, it is an 830. If the bump goes all of the way around the primary, it is a 750. Over the years, the capacity of these carbs has "changed," but I believe that the correct sizing, from my GM days as a driveability tech, the correct sizes were 750, and 830, the only difference being the primary sizing. If the 305 in question is not stock, I suggest tuning the carb to work, as the original unit was as I recall, electronic, unless it came from a truck. If there is question, I suggest looking at the truck line as well, as it used different metering, for truck emissions. Good luck... Ray
