Swapping out a Holley to ?

[Formula400]

Hi!

Just wanted to ask what you would do to improve power and economy concerning a carburator equiped Pontiac 389.

Current engine speccs.

Pontiac 389+0,30
Edelbrock RPM kam and intake
Headers
Iron cast heads with 1.92/1.66 that has had some porting work done to em
Compression ratio is around 10.5 to 10.75.
Automatic 200r4 (very soon anyways)
Rear ratio 3.73

Currently I have a Holley 700 DP (4150) and I've been trying to get it economical while I'm crusing on the highway and to work but whatever I do isn't working at all and after some reading I understand that 4150 = not good milage.

I'd like power when I step on it but at the same time I want good milage when I'm not.

Currently it is taking 11,82 miles per gallon witch way to much IMO.

So what would you swap too? (Carburator wise sense a Fuel injection is a bit out of my reach at the moment)

Quadrajet or Edelbrock?

How much would I gain in miles per gallon if I swapped?

Thanks in advance for any help!

//Sven

[deuce_454]

the brand of carb matters less than the tuning... you should be able to improve that with a wbo2 meter and some jet changes... a dp isnt however the greatest milage carb.... for best milage my money is on efi..

if you have somone who is REALLY good at quadrajunk carbs it will outperform both the holley and carter (edelbrock) in milage

the OD tranny will help greatly, as will forcing it in lockup while cruicing

[Formula400]

Originally Posted by deuce_454

the brand of carb matters less than the tuning... you should be able to improve that with a wbo2 meter and some jet changes... a dp isnt however the greatest milage carb.... for best milage my money is on efi..

if you have somone who is REALLY good at quadrajunk carbs it will outperform both the holley and carter (edelbrock) in milage

the OD tranny will help greatly, as will forcing it in lockup while cruicing

Hi!

Have a LM-1 that is currently using a Wideband O2 sensor but the problem is that if I jet lower I get a problem at light loads.

As far as I understand it the Powervalve restrictions and the jet size should always be the same area when combined so if I put in lower jets I need to drill the power valve restrictions so the area in the jets and the restrictions match again or I will run lean at light loads.

I had 60 jets from the original 66 jets and an earlier powervalve (8hg one and my car has 9.5 at idle) and still I could get it to way past 16:1 in fuel air ratio with the following splutter.

but when I got up the speed (slow as hell so I wouldn't run too lean) it ran fine at 14.5:1 witch I loved. but again it wasn't funny to drive like that and the milage didn't improve overly much for some odd reason.

//Sven

[72blackbird]

I have a Holley 750 vacuum secondary on top of an e-performer sitting on my 406 Poncho- I could get 14/16 mpg with a light foot, and this is with 72/80 jets, a TH-350 and a 3.08 posi. The DP's are good for racing but not daily commuting- run vacuum advance on your distributor as well and your fuel economy will improve.

Geno