I just put a holley 670 street avenger on my car. And when i was at the local hangout everyone was telling me the street avenger is a piece of junk and sucks for performance. Is it that bad of a carb? I have a 750DP i can put on if it would make that big of a difference.

 

It's not "that bad of a carb". However, with your setup, it may be a mis-match.

With a manual transmission, especially one of the T5 type, what happens between WOT shifts is important. You shouldn't speed shift a T5, which means you have to let off the throttle between shifts. When you do this, the vacuum secondaries may start to close, but that won't happen, most likely, until you've shifted and have let the clutch back out and are on the throttle again. Not the ideal situation.

With mechanical secondaries, the throttle blades open and close with the accelerator. No doubt about what they're doing. This is a much more desireable situation.

All you need to watch is the minimum RPMs at which you go full throttle. This is dictated by engine displacement and carb size. Holley has a chart on their website Tech Info link, mechanical secondaries section. The smaller the carb for a given engine size, the lower the RPMs at which you can go full throttle.

 

I have the same carb you do and haven't had any problems. It ran awesome as soon as I bolted in out of the box. Right now I'm just trying to get it tuned in for my specific application, but besides that I think its great.

 

dittos. Mine worked great right out of the box. I've run a 13.85 on a stock ZZ4 crate and get 20+ mpg.

I think it's a good compromise between a 650 and a 750.

I bet those guys dissing the carb have never used one.

 

Well when i bolted mine out of the box it was really lean. But now we have went up 6 sizes on the jets and it is running better but still needs tuning. When i have read about similar setups to mine they all recommend a 750cfm carb but i think they are refering to a VS carb and not a DP. I guess i will do some more tuning and see what it does.

 

I have a 570 Street Avenger on my 305 powered S10 Blazer. I had to tune mine some for my application but runs great. I'm runnin high 14's in the low 90's in a 3800# suv with all options, overdrive, and 3:42 gears. By the way it is a very mild 305, every day driver. My old Carter NEVER ran this well!

 

Well, coming from a person who did run a 670, I think it sucked. Had it on my 305 for over a year and never seemed to be that wonderfull. Sure it was an improvement over the Q-jet but it just felt lazy to me. Tried different springs, different jet sizes and never got it like I wanted. Started buying parts again for my 350 and picked up my current 750 Speed Demon w/mechanical secondaries. Thought I'd put the 750 on the 305 for a giggle and what do you know, it ran awesome and still got 20-22 mpg on highway. Sold the 670 shortly after getting the 750 dialed in on the 305.

 

I haven't had a problem out of my 770S/A.

good enough to run 12.6 with a manual trans.

dyno'd 350HP at the wheels and still get 22MPG highway with 3.42 gears and .63OD.

Personally I like the VS carb. I've never tuned a MS but they sound a bit trickier to me.

 

ok, here's a word from someone who made 433hp on one...


had a 670... th eonly time i ever had an issue with it was at the track with some traction... it would hook, then as the rpms came up, it would spin, i'd let off, it'd flip the secondaries closed and as soon as i got back to the floor, it'd bog bad...

still, the carb made the power and it did perform ok... however, after 5 years of use, it gave up the ghost, and just ran rich....

i have since upgraded to a 4150hp, i like it much better, but its still not a bad carb for the money and being a vac secondary....