[jhein]

Yesterday I got my new carb. It looks good. It's going to replace my current carb which is a likely fake 7040273 Frankenstein carb. I can't wait to get it on the car.

[SD455DJ]

Very nice! What date is on it?

Dennis

[jhein]

Originally Posted by SD455DJ

Very nice! What date is on it?

Dennis

Thanks! It's 3409

[jhein]

[padgett]

Just for S&G, 273 is a RA carb, 263 is a 350hp, both with manual transmissions

[jhein]

Originally Posted by padgett

Just for S&G, 273 is a RA carb, 263 is a 350hp, both with manual transmissions

Yeah, I know. But since there aren't many of those around, I guess I'd rather have a real 263 than an obvious fake 273.

[SD455DJ]

Originally Posted by jhein

Thanks! It's 3409

Jhein, Thanks! Have you checked out what it has for jets & metering rods yet? My 7040270 (auto carb) had it's original 69 jet/37 rod primaries and DA (.044 M) and 'N' hanger on the secondary side. With today's fuels, it seems a tad lean, so will jet up a little bit after some more shake-out driving.

Dennis

[unruhjonny]

incase this helps - taken from my 1970 Rochester book (secondary hanger part number translated thanks to Cliff's book):

jets / primary rods / secondary rod

7040270 = 70 / 37 / CC
7040273 = 70 / 37 / CC
7040263 = 70 / 41 / CC

I believe that the '263 was a smidge leaner on the primary side because of the POE (used on all non-RA Pontiac airhorns that year) which would introduce a smidge more fuel on light or part throttle.

Also incase it's helpful;

7028270 = 72 / 41 / BE
7028273 = 72 / 42 / BE
7029270 = 69 / 38 / BP
7029273 = 69 / 36 / BP

[padgett]

I recall using 70 primaries in just abut everything. 37 rod will cruise richer than a 41. Was just looking for my main Rochester book, black binder withChev/Pont label. Know where within about 300 sq. ft....

[SD455DJ]

Originally Posted by unruhjonny

incase this helps - taken from my 1970 Rochester book (secondary hanger part number translated thanks to Cliff's book):

jets / primary rods / secondary rod

7040270 = 70 / 37 / CC
7040273 = 70 / 37 / CC
7040263 = 70 / 41 / CC

I believe that the '263 was a smidge leaner on the primary side because of the POE (used on all non-RA Pontiac airhorns that year) which would introduce a smidge more fuel on light or part throttle.

Also incase it's helpful;

7028270 = 72 / 41 / BE
7028273 = 72 / 42 / BE
7029270 = 69 / 38 / BP
7029273 = 69 / 36 / BP

Thanks Jonny. My RAIV (7040270) original jetting was 70 /39 /CC. Does the Rochester book differentiate between the RAIII and RAIV? It's entirely possible all the metering was changed on this (RAIII 7040270) carb.

Dennis

[unruhjonny]

@ padgett - well, now you don't need to look

@ Dennis - I would wager the metering was adjusted at some point;
These carbs were setup as per application;
I have heard that when these cars were new, it was common for dealerships to perform metering changes to remedy customer complaints ect - and while I don't know if there was a TSB which suggested a metering change, but that's another possibility.

I so would have loved to be around when these cars were new... I'd would have probably always been broke too

[jhein]

Originally Posted by unruhjonny

incase this helps - taken from my 1970 Rochester book (secondary hanger part number translated thanks to Cliff's book):

jets / primary rods / secondary rod

7040270 = 70 / 37 / CC
7040273 = 70 / 37 / CC
7040263 = 70 / 41 / CC

I believe that the '263 was a smidge leaner on the primary side because of the POE (used on all non-RA Pontiac airhorns that year) which would introduce a smidge more fuel on light or part throttle.

Also incase it's helpful;

7028270 = 72 / 41 / BE
7028273 = 72 / 42 / BE
7029270 = 69 / 38 / BP
7029273 = 69 / 36 / BP

So what are the differences between the 270 and 273? Just the linkage for the tranny kickdown or something else?

Also, so then I can change my primary rods and get closer to the RA calibration?

[padgett]

I was around when these were new and was always broke. But was a GMI student on the GI Bill, and had access to Many Things.

(Like an unchromed Buick bumper, Flint glommed onto some of my ideas).

ps in front was my SCCA B/P Z06 FI split window.

[unruhjonny]

Originally Posted by jhein

So what are the differences between the 270 and 273? Just the linkage for the tranny kickdown or something else?

Also, so then I can change my primary rods and get closer to the RA calibration?

shoot me an email (as opposed to a private message please);
I'll see If I can be of help.

[unruhjonny]

Originally Posted by padgett

I was around when these were new and was always broke. ...

LOL - thanks for that

[johnta1]

So what are the differences between the 270 and 273? Just the linkage for the tranny kickdown or something else?

No vacuum port for the automatic kickdown.
(no throttle kickdown on automatic linkage)

[johnta1]

BTW, Padgett used to have some good Qjet info on the web.
(not sure if it's still up)

[padgett]

You mean this ? Jon is the expert, I just play at it.

[johnta1]

You mean this ?

Yep!

[TA455HO]

I have Cliffs book - but on Padgett's "How to speak rochester" site he mentions Doug Roe's book. I looked it up on amazon and was surprised to see it was published on January 1, 1672! Lol! Had to share that one. Hopefully that was supposed to be 1972...

https://www.amazon.com/Rochester-Car...6366251&sr=8-3