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Carb for my 350 Chevy

 
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64 C-10
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PostPosted: Wed Mar 30, 2011 2:48 pm    Post subject: Carb for my 350 Chevy Reply with quote

Here's the deal. The Carb on my 350 is running rich. It's a 570 Holley Street Avenger on a new stock GM crate motor. Nothing fancy..just an Edelbrock Performer EPS intake and headers. I'm getting 20 mpg highway which isn't bad for a daily driver.
I have tuned on this carb until I'm sick of it. I'm starting to think the Street Avengers are junk although this is my first one. It works as it's supposed to. I have adjusted the floats and tuned on the Fuel / air mixture screws til I'm tired. It just always seems to smell rich and has since it was new.
What I'm looking for is another Holley to replace this one since it's still under warranty. No Edelbrock. No way, no how.
I also Llike the 20 mpg. And I do want to stay with the duel line.

So, can I go to a 650 cfm and maybe keep the mileage or something smaller ?

Thanks. Smile
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SMOKEmUP
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1979 Chevrolet Camaro

PostPosted: Wed Mar 30, 2011 5:33 pm    Post subject: Reply with quote

A 600 or 650 should be fine. MPG should remain the same with a vacuum secondary carb provided the go pedal is used the same way.

Not sure I follow where you can't tune it. You make changes but it still runs the same?

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64 C-10
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PostPosted: Wed Mar 30, 2011 6:35 pm    Post subject: Reply with quote

Smoke, what I mean is that after setting the float level, a week later the float was too high. That made no sense to me and I've never had that happen before. Probably something sticking in the new carb. Maybe ?? I have set the air /fuel mixture a couple of times also.

It seems like I smell gas at times after driving but that may be going away after the last float adj.

I drove the car to Fl on a vacation and got 20 MPG down and back. I could have done better coming back but had emergency surgery while I was down there and wanted to get back home after a week in the hospital. Some vacation, huh. lol.

I really think the carb is a factory defect but I can't pinpoint just what.

OH, and it is a vac secondary , elec choke carb.
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10sec.et
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PostPosted: Wed Mar 30, 2011 10:28 pm    Post subject: Reply with quote

Holleys dont exactly have the best surfaces on the main body. some tend to start leaking in weird places after a while. i always touch up the surfaces with a file when i rebuild. maybe the carb just needs some attention to detail. although, i know what its like to be sick of screwing with a carb only to have it do something else weird the next day. i tossed a complete 850 in the trash once after spending over a month and not being able to get it to run right. it kept leaking down into the intake. i tried everything to fix it but it wasnt happening. that was the last time i bought a swap meet carb.
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64 C-10
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PostPosted: Thu Mar 31, 2011 10:36 am    Post subject: Reply with quote

This carb was new in the box !!

That's what confuses me so much.
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PostPosted: Thu Mar 31, 2011 11:11 am    Post subject: Reply with quote

Is the fuel pressure consistent?
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Paul P
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PostPosted: Thu Mar 31, 2011 12:57 pm    Post subject: Reply with quote

Good point on the fuel pressure. Electric or Mechanical fuel pump?

I would have to assume the floats are not junk but if they are brass that would eliminate them as an issue. They are likely nitrile black plastic floats which are well less than optimum and could be affected by the ethanol in the fuel these days.

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64 C-10
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PostPosted: Thu Mar 31, 2011 2:34 pm    Post subject: Reply with quote

Fuel pressure in a consistent 6 lb. And the floats are brass.
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jeep_406
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PostPosted: Fri Apr 01, 2011 12:21 am    Post subject: Reply with quote

Are you able to monitor fuel pressure during driving conditions?
If the fuel Pressure and floats are fine, I'd think there's a problem in the needle and seat. Do both bowls fill up higher?
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64 C-10
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PostPosted: Sat Apr 02, 2011 10:19 pm    Post subject: Reply with quote

The problem had to be the needle and seat........I thought. But now, everything seems normal. Before if I parked on a slight side to side grade, the engine would try to flood. The last time I adjusted the float level, the problem was corrected and it hasn't acted up since. But, the engine still seems to run a little rich, even with the small carb. Go figure.

I'm unable to monitor the fuel pressure while driving but I'm sure that would show something.

I'll probably replace the 570 with a 650 cfm Holley. I just think I got a dud.

The one thing I haven't done is check the primary jet size. I don't know what I should be running but I'm thinking maybe a #67 or #68. Maybe that's the problem.

Oh and BTW, the engine has a mechanical fuel pump.
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64 C-10
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PostPosted: Wed Apr 06, 2011 10:38 pm    Post subject: Reply with quote

I was WAY off on the jet sizes. Looks like #57 and #58 is the recommended size. I'll remove the float bowls as soon as I get healed up from this surgery as I really hate to just give up. lol

Just not able to do the work yet.

Thanks and I'll keep you posted on the progress. Smile
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64 C-10
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PostPosted: Fri Apr 08, 2011 12:55 pm    Post subject: Reply with quote

This just keeps getting better. The warranty is now out on the carb. I went out this morning and removed the air cleaner, looked closely at the part #, then to my Summit catalog.
Yep, you guessed it. 670 Street Avenger. WAY too big for this engine. So, I'm stuck with the 670 at present.

I got on the phone to Holley. They suggested I jet down from a #65 to a #62 and I shouldn't be running too rich and my mileage should improve. The spray nozzle is a #31 so if I have any problems, I can drop down to a #25.

I really can't afford a new carb right now. I had figured the 570 would have been perfect for this engine. The supplier messed up and ordered the wrong carb and my dumb azz didn't check the #. So, I guess it was my own fault. Embarassed
I guess I'll just have to live with it. I have a Holley Street Avenger that is just out of warranty too big for my engine.

Oh well, I have probably done worse in my years of playing with hot rods.

Thanks for all the help guys. Smile Sorry I supplied the wrong info. Embarassed
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