secondary suggestions

[msc66]

Hey guys,

I'm about to rebuild my q-jet. I was thinking about copying larry70gs' set up which is 76 jets and 46B rods (mine had 73s & 48Bs) for the primary and BG secondary rods with a K hanger (mine had CT rods with an L hanger). Only problem is that the BG secondary rods are not available here http://www.carburetion.com/quadrajet.asp .

Anyone have any other sources for these or another combination that would work well for me? My set up is listed below.

Also could someone explain how the secondary rod and hanger letters apply to the amount of flow. That is, are BG rods smaller than CT? Does a K hanger open farther than an L?

My set up:

455 030 over, ported heads w/stage 1 valves, 9 to 1 comp.
cam 490 lift, 284 intake dur. 304 exhaust w/113 centerline
headers, poston intake, auto w/3000 convertor, 3.31 rear gears

Thanks for any help

[71GS455]

Mike,
The way the secondary rods/hangers work has to do with them impeding flow through a fixed size jet. The smaller the rod, the less it impedes flow (thus allowing more fuel through the "jet" and becoming a richer mixture.

There are some rods with a single step and some with two steps, IIRC. Holding them side by side, you can see the difference in size. The thinner rods will be richer. The step has to do with how early or late the part throttle enrichment happens. All sizes being the same, the one that is thinner "higher" on the rod will be richer earlier.

The hanger determines how deep in the "jet" that the rod hangs. If the hole in the hanger is high, you'll get into the thinner (richer) part of the rod earlier. If it's low, then the secondaries will have to be further open to get the richer mixture.

At WOT, they should be open pretty much all the way out of the gate so it wouldn't matter as much in a drag race. That is unless you adjust your secondaries to come in later because you want less power off the line for traction issues or whatever your reason would be.

I bought my rods and hangers from a local parts store. I used Edelbrock replacement parts and just gave them the part number to order. I don't have a catalog in front of me at this time, but a little searching may turn up those numbers.

[LARRY70GS]

Mike,
The Doug Roe book on Q-jets is a must have. It answers all your questions and more. This is an illustration that explains the secondary rod.

[LARRY70GS]

They also list all the secondary rods along with GM part #'s and dimensions.

[LARRY70GS]

There are alot of rods very similar to the BG's, you should be able to get one of them. The AU's at the bottom of the page are what came with the 70 Stage1 Q-jet. The AU's have a .0527 power tip, the BG's have a .0397 tip.

[msc66]

Thanks,
You know...I have the Roe book and didn't even think to look further into it for the size correlations between the secondary rods. Duh!

Thanks again