Carb ?
Safety Car
Joined: Mar 2002
Posts: 3,780
Likes: 442
From: Southwest MI
Re: Carb ? (sting73ray)
i'd do a "performance rebuild" of your Q-jet. it's all you'll ever need for that 350. jetting/different metering rods, etc etc.....
:seeya
[Modified by 66427-450, 11:17 AM 5/5/2003]
:seeya
[Modified by 66427-450, 11:17 AM 5/5/2003]
Race Director
Joined: May 2000
Posts: 12,712
Likes: 2,264
Re: Carb ? (66427-450)
Agree. Your Quadrajet flows 750 CFM at 1.5" Hg. and a "high performance" carb is not going to buy you anything. There are a lot of minor Q-jet mods to improve performance such as modifying the linkage to open the secondaries earlier and maybe some jetting changes along with backdating the ignition map to a pre-emission configuration. Get all the centrifugal in by 2500 with total initial plus centrifugal equal to 36-38. Select a vacuum can with about 16* at 12-15" and run the signal line from a full manifold vacuum source that has manifold vacuum at idle. Since the L-48 only has 8.5:1 CR and was designed for 87 PON fuel, at worse you might have to run mid grade to keep then engine out of low speed detonation, but it will have dramatically better throttle response and low end torque.
Any of the various Rochester Quadrajet books should give you some ideas on how to improve performance. If you really want to wake up the engine at medium to high revs, install an L-82 cam advanced four degrees, but then you'll need a vacuum can with the full 16* advance at 8-10"
Duke
[Modified by SWCDuke, 11:49 AM 5/5/2003]
Any of the various Rochester Quadrajet books should give you some ideas on how to improve performance. If you really want to wake up the engine at medium to high revs, install an L-82 cam advanced four degrees, but then you'll need a vacuum can with the full 16* advance at 8-10"
Duke
[Modified by SWCDuke, 11:49 AM 5/5/2003]
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Re: Carb ? (sting73ray)
The stock Q-jet is a very good carb but very complicated. I just don't have the time to debug mine. I picked up a Holley 4175 spreadbore for $20 at a swapmeet and plan to give it a try. New 4175's go for ~$300 at Summit or Jegs. Uses electric choke though and best install for that is witha relay off the oil press light sensor. I've gotten tired of all the linkages and tricky parts to adjust on the Q-jet. :(
Safety Car
Joined: Aug 2001
Posts: 3,683
Likes: 201
From: Waterford Mi
Re: Carb ? (cardo0)
I switched to the Holley 4175. Spreadbore replacement. Some tunnig of the accereator pump cam and discharge nozzles but it works real good. Check out my home page for pics. I did have to get a spacer for the air cleaner to sit right. I changed the manifold after I ran the stock one for a while. Then I kept adding to the mods. :yesnod:
