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Carb selection advice: SBC Mild cam

4K views 17 replies 6 participants last post by  ap72 
#1 ·
Here are the specs

350 SBC 4 bolt main
.040 overbore
76CC heads from 74-80
9 to 1 compression
Performer RPM intake manifold
Hugger headers
manual trani

Currently I have a 600cc holley single pumper 4 brl that seems to run OK, but just doesnt have the power or response that I am looking for. I used to have a throttle body fuel injection setup (Holley) that made substantially more power and torque and performed flawlessly until the ECU died and I had to go back to carbs.
I have had the carbs dyno tuned a couple of times in the past by a very good tuner extremely familar with holleys and I am not happy with them, The power breaks up substantially in the upper rpm's and the torque down low is just not what it should be (half what it should be..). The latest dyno a year ago was 235rwhp and 295rwtq (Power valve changed and some other stuff, still broke up in top end and just felt sloppy). The same dyno 4 years prior was 245rwhp and 275rwtq with about 25% drivetrain loss. When fuel injection was used it had 50more hp and 100 more tq to my butt dyno which has been very accurate to date :)

Im looking for a carb that will let me tune it better and fit my performance needs better.

I do road racing very occasionally but mostly mountain runs and drift days in the car, but it is 90% a street car.

I was thinking a holley 670 street avenger, can anyone confirm this would be good?
 
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#9 ·
Tech inspector, Mild cam. Here are the details on it. If I remember it was an RV style cam. (We tried to eliminate low end torque, trani does not fair well with high torque)

It's an Elgin "Pro Stock" Cam
These are the specs on the box.
DURN DUR. @ .050 CAM LIFT Valve Lift Lobe Centers
IN Ex IN Ex IN Ex IN Ex IN Ex
291 291 218 218 0.303 0.303 0.455 0.455 105 115
 
#12 ·
I agree with f-bird,a 4779 holley or HP series or,,,if you can build the carb yourself? I really like using a 4777 holley as is except,,change the base plate to a base plate off a 4781(850). Build that carb,it will flow785 ish.The throttle response is excellent,small venturi Vs 850 Base
plate. If you modify the 650 add replace able air bleeds
 
#13 ·
F-bird,

Its so bad right now I am thinking that I have some other issue.. It feels like 100hp right now. Im going to start with the fuel filter and see where that gets me, and then pull the plugs to see what it looks like.

Again, when I had fuel injection it felt amazing.. Like I could break the tires loose at 50mph by just stomping on it.
 
#18 ·
Go back to efi. You'll never get the consistent performance efi can give from a carb. Carbs are great for track cars but they require continuous fiddling.

Plus the cost is about the same or less.


Then I'd change the cam to something like a voodoo 262. Maybe even the 256. They're both plenty big for your combo and will give you a lot more mid range power.

Heads would be nice too but may be too expensive. People often forget that talk is cheap but parts aren't. No offense but your car doesn't look like a high dollar combo. Upgrading to some good used heads may be an option though so watch Craigslist. A mildly ported and milled set of double hump heads would fit what you already have and can be found rebuilt for 300 or less if you keep an eye out.

Those small changes will all add up to a much stronger mid range with minimal cost.

For the ecu I like mega squirt but other options are available.
 
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