What is the BEST all around Carb for street and strip

[Clois Harlan]

I have an 750 HP Holley mechanical on my 427 and it performs well and at the dyno we churned out about 535 hp (about 40 hp more when we dropped a 950 on it). But, here is the question:

My Cobra is going to be relegated to less track time (maybe twice a year) and more street time and I am thinking of going with the Avenger Holley 770 with a vaccuum secondary for my all around driving. What are your thoughts?

Clois Harlan

[undy]

Clois, I think for max HP your 750 mech dbl pump will provide more top end power. I think the 770 will be too docile. With the 750 mech it would appear, at least you didn't indicate to the contrary, that it is a well match carb for your FE. You also didn't mention any drivability issues either. I honestly think you'll be under-carb'd with the avenger 770, especially in light of no admitted problems with the HP.

My vote is the 750 HP, without question.

Dave

[Hotfingrs]

Anything with the vacuum secondary will be fine for the street. You know what the other carbs can do, so when it's time to go racing, switch them over if you need to.

[Clois Harlan]

Jack that is exactly what I was thinking too. Dave the 750 has been flawless but goes thru a lot of gas in city driving. Some have told me of how difficult it was to drive a mechanical carb on the street but I have not found that to be true. The price is about the same for both carbs but I was just thinking of getting a little better gas mileage with the Avenger...actually the HP is about $100 more but as you said the HP is almost a perfect carb for the 427.


Clois

[vector1]

x2 on switching the carbs, one for street, other for track. if i see you at the track the street carb would prob work fine. i'll be running a 2 bbl.

[joyridin']

Maybe I'm missing something, but if you tune the 750 correctly, you should get about the same mileage as the 770 unless you are putting your foot to the floor all the time and kicking in the secondaries.

I have always had double pumpers and have never had a problem on the street at all. Put milder accelerator cams in the front and rear if it is coming on too hard. That will help the tip-in/tip-out if you feel it is too jerky. You can also change the squirter size, but for a 427, that shouldn't be an issue. Is it set-up for 4 bbl idle?

[sparks]

I just put on a m.demon825(from a H4160). The mech secondaries are fine for city driving. If the carb is tuned correct than there should be no problem. My car performes much better across the board than it did before..

[FUNFER2]

BG-Mighty Demon, is the best carb. I've ever used, if not going with a racing bluprinted carb.

[jhv48]

Originally Posted by joyridin'

Maybe I'm missing something, but if you tune the 750 correctly, you should get about the same mileage as the 770 unless you are putting your foot to the floor all the time and kicking in the secondaries.

I have always had double pumpers and have never had a problem on the street at all. Put milder accelerator cams in the front and rear if it is coming on too hard. That will help the tip-in/tip-out if you feel it is too jerky. You can also change the squirter size, but for a 427, that shouldn't be an issue. Is it set-up for 4 bbl idle?

Bingo X 2.

Keep your foot out of the DP and the mileage will be about the same if you tune the DP for street use and not top end.

[Clois Harlan]

Here is the deal. I have built a 408 stroker for HCS Coupe and I tried a Demon on that engine and it didn't perform very well so I pulled the HP off my cobra and put it on the engine and it dyno'd great. Now I need another carb (either another HP or something different) for one of the engines. They both run quite well with the 750 HP BUT, I was considering going with the Avenger just to not have two identical carbs.

Clois

[vector1]

leave the hp on the cobra and get a rr carb setup for the coupe. have heard good things about pro systems. if you put a bg on the coup you would prob have to tune it.

here's a good discussion

http://speedtalk.com/forum/viewtopic...=170557#170557

[Clois Harlan]

Thanks guys I appreciate your input...jury still out and no hurry to replace carb since coupe is still a couple of weeks away from completion and it is raining this weekend!

Clois

[Rick Parker]

If the balance of the engine was built for track usage such as intake, heads, cam etc you may find a vacuum secondary carb to be a huge compromise. One of the main reasons the HP and DP use more fuel comparatively speaking is because the idle circuits are dictated by the metering plates and their idle feed restictors which are intended to be much richer. Changing the main circuit jetting only limits the MAXIMUM fuel that will be allowed to flow. Do some research and check out the carb that was on the 425 HP 427 Chevrolet from the late 60's. The Metering plates control the show. You could contact a noted carb tuner such as Brasswell or Sean Murphy Induction and have the existing IFR's reduced in size and keep the same carb.

[greg schroeder]

I pur a Pro Systems carb on my Roush 427R. The double pumper I chose was a bit over 1000 cfm, not fuel efficient, but hammers all around.

[Silverback51]

I always prefer mechanical secondaries over vacuum.

I like my foot to control the secondaries, not a vacuum diaphram and a spring.

[patrickt]

Originally Posted by Silverback51

I always prefer mechanical secondaries over vacuum.

I like my foot to control the secondaries, not a vacuum diaphram and a spring.

... and I'm just the opposite. A properly adjusted vacuum secondary carb, that is the proper size for the engine, is a joy to drive both on the street and the track. But this is kind of like the BB v. SB threads....

[jwd]

Originally Posted by patrickt

... and I'm just the opposite. A properly adjusted vacuum secondary carb, that is the proper size for the engine, is a joy to drive both on the street and the track. But this is kind of like the BB v. SB threads....

I agree. I find it funny when people with DP's say they like the blast of power when the secondaries open when in reality, with any properly set up carb., the transition from primary to secondary should be seamless and not noticable at all.

Jim

[sparks]

Im just comparing one carb to another. I was stating how much better the car seemed to performed after the new carb was put on. I feel the mech secondaries are very manageable on the street. To each his own.

[vector1]

might be a good one to look at.

http://www.tmpcarbs.net/index.html