C3 Rochester Quadrajet Jets and Metering Rods

[Chuck S.]

Anyone know an internet site that has the jet and metering rod sizes specified for seventies era Corvettes?

I plan to rebuild the old Quad that came on my 70, and would like to confirm the jet and metering rod sizes during the process. It's a rebuild of a 7029207 replacement (71 build date), but I will be using it on my 70 350/300hp base engine with manual transmission and AC.

[Clem Z.]

Re: C3 Rochester Quadrajet Jets and Metering Rods

pri rod #36,pri jet #66, secondary rod #7034822, stamped BG. parts www.weber-carburetors.com/quadrajet.asp

[Jeff W.]

Re: C3 Rochester Quadrajet Jets and Metering Rods

Chuck, I got all of my parts for my 72 at Swap Supply, swapsupply@swapsupply.biz, pretty decent pricing as well.
Jeff

[Scott Marzahl]

Re: C3 Rochester Quadrajet Jets and Metering Rods

Can anyone help me out with setting up a '76 Q-Jet I am currently rebuilding for a 350, 10:1 with a "151" cam installed with an automatic trans. There are no emissions on the car, just dual exhaust.

The primary jets are size 76 with 48K metering rods. The secondary metering rods are CH's. I have a set of new BE secondary rods that are a tad bit richer I could use for this application, however I do not have any primary rods or jets.

Should I bump up the primary jets to maybe a size 78 for this application, change the metering rods or both?

Thanks,
Scott

[Patrick H.]

Re: C3 Rochester Quadrajet Jets and Metering Rods

Chuck,

In addition, if they're not available from GM, they "have" been available through Edelbrock. I think I bought some from Summit.

http://store.summitracing.com/egnsearch.asp?N=700+115+300519&D=300519

I'll send you an answer to your other e-mail question. I haven't been home long enough to answer anything this week.

Patrick

[Chuck S.]

Re: C3 Rochester Quadrajet Jets and Metering Rods

Clem, I did a little more digging on the internet, and found an article on Quadrajet tuning by Lars Grimsrud at the link below under "carburetors".

Over the years, he cataloged jet and rod sizes for many Quadrajet carburetors. It appears the jet/rod sizes you gave me are for the original 7029207 carb which is for a 69 350/350hp Corvette, and I want to set the carb up like a 7040213. I wasn't thinking...you would need that carb number.

He doesn't show the jet and rod sizes for the 7040213, but shows a couple set-ups for the 7040503 (70 Corvette 350/300hp MT ECS carb). Will there be a big effect on engine performance from the ECS carb specs versus the standard 7040213 carb? He gave these specs...I'm thinking the first one is the better match to the 7040213; it is also coincidentally the same set-up as the 70 Corvette 350/350hp MT Fed.

7040503 Camaro 350/300hp: PJ=#76, PR=44, SR=BA, cruise jet=3.0159, WOT jet=4.0055

7040503 Chev 350/300hp (best tuned): PJ=#74, PR=#43, SR=AK, cruise jet =2.8486, WOT=3.7699

http://www.buickpartsdirectory.com

[Chuck S.]

Re: C3 Rochester Quadrajet Jets and Metering Rods

Gee, it must be tough being busy with work responsibilities...I can't remember anymore. I suppose my rehab must be complete.

Thanks for the reference, Patrick. Is the jet number used by Rochester and other sources, e.g. #66 or #74, the size of the drilled opening in thousandths of an inch?

[Clem Z.]

7040213 Q jet

pri jet 76,pri rod 44, sec rod 7034337 stamped BA

[Clem Z.]

rochester yes, holley not always *NM*

[Chuck S.]

Outstanding! Thanks For The Help, Clem. *NM*

[Patrick H.]

Re: C3 Rochester Quadrajet Jets and Metering Rods

As Clem said.

Do you have the Rochester carb book?

Patrick

[Chuck S.]

Re: C3 Rochester Quadrajet Jets and Metering Rods

No, I don't have the book, but planned to buy if I needed it.

I have the Helm 70 Chassis Overhaul Manual which covers the 4MV Rochester, and there are numerous basic overhaul articles on the internet. Some of the internet procedures are easier than the Chevrolet manual. With the jet and rod specs that Clem supplied, I'm thinking I can skip the book.