jimbow

I've found out how to decipher the numbers. For instance, my carb no. is decoded as follows:
17081218 is: 170 is for "after 1976"
8 is for Decade , 1 is for year,
2 is for QuadJet as Model of Carburator
(0= Monojet,1=2 brl, 6=Varijet, etc.)
1(or 2) is for Chevy Div. (4=Buick,5=Olds, 6,7=Pontiac)
8 is for automatic transmission (Even No.=auto, Odd No.=Manual)
My Question is:
The last number which signifies automatic or for manual transmission... does this mean there is a difference in the carb itself depending on the transmission????

I don't believe it is, but why the differentiation? jim

TOM B1

The automatic would have kick down linkage.

hunt4cleanair

Yes and emission control as well. For example, it could have been specified for Federal (48 states), California or high altitude.

Underneath the part number is reference to the broadcast code and date code...like 3057 BHT or built the 305th day of 1977 and code is BHT or L48 automatic.

Your carb was specified for a 1981 L81 motor with automatic transmission delivered in California. So...it's configured for california emission control.

kend414

That's good info. My Quadrajet's numbers are 8904 1901.
Underneath those #'s are #3556 W.
WTF?

lars

kend -
Looks like you have an Edelbrock 1901 - a Q-Jet built under license by Edelbrock.

kend414

Hey Lars! Thanks! I'll be seeing you this Friday. I wondered if the Edlebrock sticker (no other manufacturer ID)was for real but didn't see these carbs listed on their website.

lars

They have discontinued the Q-Jet carbs and no longer show them on their web site.

jimbow

what exactly is different on the quadrajet made for automatic transmission applications, and the quadrajet made for manual transmissions....?? Thats the 64,000 hollar question! jim

lars

The auto trans carbs have provisions for the tranny kickdown linkage on the throttle arm lever. The auto trans carbs often have provision for the vacuum hose for the vacuum modulator. The auto tranny carbs are sometimes jetted differently in order to avoid off-idle hesitation with the tranny in "drive." I have seen factory-correct/original cars with auto tranny/manual tranny carbs switched right from the factory: The carbs are close enough that you can install an auto-tranny carb on a manual car with no problem. I believe when the factory ran out of carbs in one barrel-O-parts, they simply installed carbs out of the other barrel-O-parts rather than stop the assembly line. So the 64,000 hollar answer is, "not much."
Lars

coach79

17059216
0599 cma ???
if the 170 is after 1976 and the next two are decade and year then I'm confused I have a 78

petronix

While we are on the topic, I've been wondering the origins of my carb. The carb came on my 72 L-48, but I am pretty sure it is not the original and I have not been able to match the code with any sources of information that I have come across.

Here are the code numbers:
Quadrajet R-4 # 17054927 2811
stamped on back of carb 70456n9

When I disambled it for rebuild, I read the stampings from Jets/Needles/Hanger as follows:
Main Jets 74
Main Needles 43B
Secondary Needles DA DA
Secondary Hanger 33797 O
According to the stampings the car seems to be set up for an early 70's Chevy 350 pickup truck.

The motor is original ,except for a 327/350 spec cam swap and has 56,000 miles. It seems to be running a bit lean with the carb and the idle screws don't do too much, except make it stall if screwed to far in.

lars

pet -
Carb number 17054927 is the GM Service Replacement carb for a 1972 350 Vette, Camaro, and GMC. It should be jetted 74 jets, 43 primary rods, and DA sec rods. It has the "170" prefix since it was manufactured after 1976. But it's identical to a 1972 carb.

coach -
Carb 17059216 is not the original carb for your Vette. It's a '79 Q-Jet off of a 305 & 350 Camaro with air. It should be jetted 72/40/CH.

Lars

1979L82

http://www.chevellestuff.com/generic...r_decoding.htm

also alot of good info, including Lars stuff, on corvettefaq.com

petronix

Thanks for the info Lars. I thought this was probably some type of GM replacement. The one thing I believe is different from the original is that it has an adjustment screw for the power piston on the front of the carb between the idle adjustment screws (instead of on the top of the carb). The rebuild kit I bought from Napa seemed to match up to the 72 carb specs.