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CarburetorsCarb discussion and questions. Upgrading your Third Gen's carburetor, swapping TBI to carburetor, or TPI to carburetor? Need LG4 or H.O. info? Post it here.
So I know it's a Rochester carb but on identifying website is says that the number has to be 2 for a 4bbl but it says 3 so apparently it's a monojet but I'm sure it's a 4bbl since it looks like one. Not sure if website is wrong or my identifying number is wrong.
Neither the website nor your carb # are "wrong". The website isn't exactly "accurate" but it has the beginnings of some of the right info.
1708 = model E4ME (E = electronic control, 4M = Q-Jet, E = electric choke)... that part of the # doesn't necessarily stand for the decade of production although it's somewhat close to that except that 702 #s continued to be used at least until 70, and 704 and 1705 carbs were both built in the 70s
7 = a year ending in 7, which would be 87 in the case of that model, was the year that specific configuration was introduced; could have come off a later year car but wouldn't be by much since carbs were eliminated altogether well before 90
306 = the code for the specific application... those for Chevy car engines (regardless of "brand" of the body) usually but not always start with 2, and even numbers are for auto trans, for example
A photo showing THE WHOLE CARB from above would be helpful. Many of the details that vary by application are visible externally, fuel line configuration for example.
Telling us what you want that info for would also help. For example, it's not necessary to know anything at all about "identification" to buy the right rebuild kit.
An interesting fact not touched on by the article (the visible part of it at least) is, Carter didn't exactly produce Q-Jets "under license from GM". While somewhat true, that's not exactly what the relationship was.
What really happened was, the Rochester plant had a fire, that wiped out most of its production capability. GM contracted with Carter to fill their needs and shipped what tooling survived to Carter, who had most of the rest of what it took. I don't know the dates of any of this. I DO know that there are A SHIPLOAD of "Carter Q-Jets" in the world, mostly from the early to mid 70s as far as I can recall seeing. As far as I'm aware there's nothing really "different" about them from Rochester-produced ones, in the sense of one being more "desirable" or "better" or anything like that.
"Desirability" mostly derives from the model:
702 & 703 = original 4Mx where x described the choke, either C for integral hot air or V for divorced
704 = smogger version of original, still called 4Mx
1705 = M4Mx where the 1st "M" stands for "Modified", this model had the cast-in provisions for the aneroid baro compensator although only a few actually were equipped with that, most had a plastic "filler" cup in that place, and C chokes
and of course 1708 = electronically-controlled.
The 702 is the series most friendly to hot-rodding. 703s were mostly on California cars so there's not all that many of those around. 704 and 1705 have very small drilled passages leading to the metering parts, especially in the idle system, and therefore are relatively much more difficult to make work with low-vacuum cams. 1708 is the same way but is a bit more flexible within a certain range because of the way the IAB valve works.
Last edited by sofakingdom; Jul 21, 2017 at 08:04 AM.
What really happened was, the Rochester plant had a fire, that wiped out most of its production capability. GM contracted with Carter to fill their needs and shipped what tooling survived to Carter, who had most of the rest of what it took. I don't know the dates of any of this. I DO know that there are A SHIPLOAD of "Carter Q-Jets" in the world, mostly from the early to mid 70s as far as I can recall seeing.
I believe my dad's '69 Impala 300 horse 350, which he bought new, had a Carter-built Q-jet on it. Either that, or it was my brother's '66 Impala Super Sport 275 horse 327, which he got in '72, I think it was. Been awhile, details are getting fuzzy. May have been both.
At any rate, those were the first Q-jets to which I was exposed. For years I actually thought the Q-jet was a Carter design. After all, the WCFB on my '57 283 was a Carter. The only Rochesters I had seen were 2-barrels on pickups and trucks.
