Holley 870 street avenger help. - Chevelle Tech
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post #1 of 17 (permalink) Old Feb 24th, 09, 8:26 PM Thread Starter
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Holley 870 street avenger help.

Hello, i got a rich prolem with this carb 870 street avenger, i dont know anything about carbs but im learning, if the transfer slots are exposed to mutch will this be the couse of runing rich, here are some pics that i took fron the bottom of the carb.
The carb is out of the box, with the power valve is 4.5 and jets i think they are 78 primarys 82 secc.

My engine is a 454
3964290 heads 2.19 1.88 valves, flat top pistons, rpm air gap intake and cam is voodoo 60204 Duration 276/284, Lift .554/.572, msd 6al distributor and coil, i know this cam got to have a lot of timing advance for it to idle.
But any help is welcome.
Thanks.





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post #2 of 17 (permalink) Old Feb 24th, 09, 9:39 PM
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Frank Riley
 
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Re: Holley 870 street avenger help.

Is the power valve blown, first thing I'd check with a holley that has a rich condition, but I thought the Street Avengers were a new enough design to have a power valve relief check valve circuit... but just a thought...

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post #3 of 17 (permalink) Old Feb 24th, 09, 10:56 PM
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Re: Holley 870 street avenger help.

I have the same problem on a different brand carb...
looks like you might have a tad much slot exposed...try more timing at idle or lock your dist at you max timing. Has done this before? did you buy the carb new? If you can give us more info about the history behind the problem that would be a plus.

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post #4 of 17 (permalink) Old Feb 24th, 09, 11:20 PM
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Howard
 
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Re: Holley 870 street avenger help.

According to my holley catalog,you are correct with 78 primary,82 secondary jets with a 4.5 powervalve directly out of the box.I agree with others in saying that more info is needed as far as your "burning rich" history,whats your initial timing,total timing? Even though you do have a backfire relief valve built-in from holley...was there a backfire through the carb after the install of the 80870? Vacuum advanced distributor? What is your manifold vacuum reading? What type,CFM,primary jet size carb were you running before?

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post #5 of 17 (permalink) Old Feb 25th, 09, 1:08 AM Thread Starter
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Re: Holley 870 street avenger help.

The carb was new when i put it on the engine, and it was rich fron the first time.
My initial timing is 15 and total 36.
O and in the past i had maybe 3 backfires.(going to change the powervalve)

I have Vacuum advanced distributor, im going to lock the dist and see if it helps.
and change the primary jets to 76.
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post #6 of 17 (permalink) Old Feb 25th, 09, 1:36 AM
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Re: Holley 870 street avenger help.

changing the main jets won't help with an idle problem. Do you have a WBO2 meter hooked up? What exactly is telling you it's rich?

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post #7 of 17 (permalink) Old Feb 25th, 09, 5:40 AM
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Re: Holley 870 street avenger help.

If you get response from adjusting the idle mixture screws, it is not open too far. I played with a rich idle condition on another 870 and only relief I got was to drill two small holes in the primary butterflies. You can try cracking the secondary blades, but do not expose the transfer slot or it will suck in fuel from the rear.
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post #8 of 17 (permalink) Old Feb 25th, 09, 7:07 AM
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Re: Holley 870 street avenger help.

Is the choke engaged when taking that photo?

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post #9 of 17 (permalink) Old Feb 25th, 09, 12:01 PM Thread Starter
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Re: Holley 870 street avenger help.

What exactly is telling you it's rich? black smoke, smell fuel, and the plugs are wet and black.

and i get a response from adjusting a idle mixture screws, if in to far it will die, if i get them out to much it wil rev a little i think.
And i the remove the choke.
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post #10 of 17 (permalink) Old Feb 25th, 09, 3:58 PM
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Re: Holley 870 street avenger help.

Make sure the secondaries are not open too much also. Did you check the float levels? How about fuel filters? Sound to me like there could be something in the needle/seat - either front or rear. What fuel pump? Did you check the fuel pressure at idle?
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post #11 of 17 (permalink) Old Feb 25th, 09, 4:31 PM Thread Starter
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Re: Holley 870 street avenger help.

whith the clear sight plugs i can see the fuel just peaking, i have one fuel filter just after the fuel tank, another just past the fpr.
The fuel pump is an electric one and the fuel pressure is 6.5psi at idle, should it be 5psi?
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post #12 of 17 (permalink) Old Feb 25th, 09, 4:46 PM
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Re: Holley 870 street avenger help.

6.5psi is fine. You sure plugs are wet with gas and not oil?
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post #13 of 17 (permalink) Old Feb 25th, 09, 4:51 PM
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Re: Holley 870 street avenger help.

I had the same problem with a 780 Street Avenger and never did get it worked out. I sold it and bought a 4150 DP and never looked back.
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post #14 of 17 (permalink) Old Feb 25th, 09, 6:20 PM
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Re: Holley 870 street avenger help.

Quote:
Originally Posted by 90454SS View Post
Hello, i got a rich prolem with this carb 870 street avenger, i dont know anything about carbs but im learning, if the transfer slots are exposed to mutch will this be the couse of runing rich
yes, the transfer slots should be exposed no more than .020", when you expose too much of the transfer slot you effectively bypass the idle circuit..
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post #15 of 17 (permalink) Old Feb 25th, 09, 7:30 PM Thread Starter
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Re: Holley 870 street avenger help.

Yes the plugs are wet with gas not oil, i put one clean plug i run it for less then a minute and half of the plug was black and with the smell of gas.

And If oil was in there white somke will be out of the exhaust rigth?

Ok here is what im going to do, check for blown power valve, double check timing, float level and fuel psi, clean the carb and im thinking on locking out the distributor, and see if i can get the transfer slots to .020" or less ,but i will do this on sunday.
Thanks.
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