Rochester Q-jet carb vs Holley 770 cfm

kdsracing

Member
Mar 13, 2009
58
Apple Valley, CA
My holley is a squarebore and its just wasting gas. Ive had it for 14 years. I got the Q-jet for 150$ 10 years ago. Im reading about this carburetor as being a very good driver tool. Thats what I want. I want to save from having to buy a better street friendly holley.
I agree then. Especially if the manifold is spread bore and your current carb is squarebore. I’ve never seen that work well.
 

G72Zed

Veteran Member
Sep 8, 2015
4,084
Canada
Well, you have one of the "worst" Holley carbs in my opinion....80770 Avenger.....not surprised at all.

1980RS mentioned this right from the start.....reread post #4.
 

1980RS

Veteran Member
Jun 17, 2006
6,399
MN
I just realized the 4 barrel will not open on this holley when im on high speeds on the highway...Terrible.
Just like I though, all the ones I had were the same until I fixed my current 770 now it pulls as good as my old 3310. here's what needs to be added to make it work right.

770.jpg
 
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Fwyflier

New Member
Nov 8, 2019
22
If you really want to know about Qjets, the best thing to do is buy the book. There is a lot about these carbs that you won’t find here. I can’t find me book right now but I’m sure there is not a lot to chose from, it has a big carb on the front. I’ve been doing carbs for a long time and both Holley and qjets have there own quirks. I find it easier to “dial in” a Holley but once you get the qjet right they run like a champ. Good luck trying to save gas with a carbureted V8.
 

Francesco

Veteran Member
Well, you have one of the "worst" Holley carbs in my opinion....80770 Avenger.....not surprised at all.

1980RS mentioned this right from the start.....reread post #4.
Hi! Yes I know, Im putting in a 1980 Qjet in next week. This Holley is ok on the street but when you try and pick up speed it just feels like im going 80 km per hour on the highway...Wtf.
 

Fwyflier

New Member
Nov 8, 2019
22
Typical those 770 are jetted to lean. Have you looked at the spark plugs to see what color they are. It also sounds like your describing the vacuum secondary not opening. They make a spring kit to adjust how fast the secondary’s are opening.
 

tom3

Veteran Member
Aug 1, 1999
14,676
ohio
I'm not familiar with the Holley you have but used to put screw in the linkage to force the secondaries open a bit when the throttle is about half way open. Have to experiment some to get it like you want it. Did see a dyno test on TV where the guys did this and it picked up quite a bit of HP. A dialed in vacuum secondary does work pretty good on a big inch motor but can be hard to get it right. Had a 67 Ford Fairlane GT with the 390 and it, bone stock, would plant you in the seat from idle to about 6k rpm. Also 19 mpg on the highway, pretty good for the time.
 




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