Holley square bore
Thread Starter
Racer
Joined: Jan 2007
Posts: 427
Likes: 1
Holley square bore
I wish to go with Holley.
I am looking for the best application for my crate 350/290 hp, 1976, 4speed. I want vacuum secondaries and from what I can gather I would need a few ports for vacuum for the headlights, distributor, heater - A/C selection, power brakes, PCV and the likes.
I have heard a lot about the SA670 but am some what reluctant, what other models have you used and what success?
Dano,
I am looking for the best application for my crate 350/290 hp, 1976, 4speed. I want vacuum secondaries and from what I can gather I would need a few ports for vacuum for the headlights, distributor, heater - A/C selection, power brakes, PCV and the likes.
I have heard a lot about the SA670 but am some what reluctant, what other models have you used and what success?
Dano,
Tech Contributor
Joined: Aug 1999
Posts: 14,382
Likes: 6,402
From: At my Bar drinking and wrenching in Lafayette Colorado
The Street Avenger carbs have had issues with metering block calibration. If you don't mind doing a bit of tuning and tinkering, they can be made to run fine.
Holley recently did a lot of work to refine and redesign some of their metering blocks to run very well on today's pump gas formulations. These newly designed blocks are used in the new "Ultra" Series carbs. If you're going to spring for a new carb, throw a few more bills at it and step up to a well-designed carb that runs as it should on modern gasoline - the "Ultra" series is worth a serious look.
Lars
Holley recently did a lot of work to refine and redesign some of their metering blocks to run very well on today's pump gas formulations. These newly designed blocks are used in the new "Ultra" Series carbs. If you're going to spring for a new carb, throw a few more bills at it and step up to a well-designed carb that runs as it should on modern gasoline - the "Ultra" series is worth a serious look.
Lars
Thread Starter
Racer
Joined: Jan 2007
Posts: 427
Likes: 1
I thank you all for the advice. I looked into the 0-86670 Holley Ultra Street Avenger. It is $65.00 more that the Street Avenger. Thank you Lars, the money maybe worth it.
From what I have resourced the Ultra series has overcome some of the stumbling issues and problems of the Street Avenger Series.
Is there any experiance, good or bad out there using the 0-86670 Ultra Street Avenger 670 on a 350/290 HP crate GM engine or any other combinations?
Dano,
From what I have resourced the Ultra series has overcome some of the stumbling issues and problems of the Street Avenger Series.
Is there any experiance, good or bad out there using the 0-86670 Ultra Street Avenger 670 on a 350/290 HP crate GM engine or any other combinations?
Dano,
Pro
Joined: May 2003
Posts: 593
Likes: 0
From: London England
Racer
Joined: Apr 2006
Posts: 477
Likes: 43
From: Millbrae California
The metering blocks and the base plate are made by Bo Laws carburetion. The main changes are in the design of the idle well and the main well emulsion bleeds plus the jet spread from primary to secondary is in the 6 to 8 jet size range, from what i have seen the jet package is a lot closer to what it should be than the non Ultra series carbs have been. FYI, the weight of the Ultra series carbs is about 5 or 6 lbs lighter than a normal Holley carb.
The only thing i see that needs tuning is the accelerator pump duration spring is too soft when compaired to a 1960s era Holley carb so we are using a stronger duration pump spring like the one that is on a BG Demon carb. The pump squirt is a little lazy as the carb comes from Holley and i like to keep the pump squirter in the .031 to .035" range so the pump squirt will be easily vaporized thus the need for a stronger spring (a trick i learned when I was working for/with Barry Grant).
I hope this help Henry @ olescarb
The only thing i see that needs tuning is the accelerator pump duration spring is too soft when compaired to a 1960s era Holley carb so we are using a stronger duration pump spring like the one that is on a BG Demon carb. The pump squirt is a little lazy as the carb comes from Holley and i like to keep the pump squirter in the .031 to .035" range so the pump squirt will be easily vaporized thus the need for a stronger spring (a trick i learned when I was working for/with Barry Grant).
I hope this help Henry @ olescarb
Racer
Joined: Apr 2006
Posts: 477
Likes: 43
From: Millbrae California
The ethanol content does cause a 3 to 5% leaner a/f mixture shift plus the advance curve does need tuning (more initial, about the same total mechanical advance but less advance from the vacuum advance) since modern gasoline is less volatile than leaded gasoline.
Henry @ olescarb
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Thread Starter
Racer
Joined: Jan 2007
Posts: 427
Likes: 1
I made the leap of faith and ordered a Holley 0-86670 red in colour. I was tossed between red and blue; no that was not the motivating factor but rather your comments about the carb made my decision. I thank you all for your input.
I was hoping the red anodized base plate and metering blocks along with the polished aluminum would compliment the code 13 silver paint and Firethorne interior.
Dano,
I was hoping the red anodized base plate and metering blocks along with the polished aluminum would compliment the code 13 silver paint and Firethorne interior.
Dano,
