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Old 09-02-2012, 12:09 PM
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Street Avenger

Good Day...

I have a GM 350 built prior to me purchasing the truck. The only thing I know for sure is it has a nice sounding cam lope. The engine has an Edelbrock Performer RPM manifold with a Holly Street Avenger 670 on it with pre 1980 cast Chevy heads. I am attempting to set up the carburetor according to Lars Grimsrud's article and have created problems.

1. According to Lars, you set the throttle plates at .020 of the verticle slot showing. Also known as the transfer slot. I have adjusted the rear throttle plates to that spec and the primary throttle plates will not close far enough to get to the .020 measurement. The idle adjust screw is adjusted back to where it is not even touching the linkage stop. About half to the transfer slot is visible at that point. The choke fast idle cam is not in the way of this issue. According to Lars, both transfer slots should be adjusted equal for proper operation. When I install the carb with the transfer slots as noted, it will idle too high and can not be adjusted lower.

2. I have noticed a strange burn pattern on the spark plugs. The plugs are showing half of the plug white and the other half light brown. The color difference is NOT up and down of the porcilin, but back and front on the porcelain. It appears that the plugs are light brown on the side closest to the valves and white away from the valves. Why?

Your comments are appreciated.

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Old 09-02-2012, 07:53 PM
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1. You have something holding the throttle blades open, Bent shaft, linkage or throttle blades not centered in the hole. Hold the carb up to a light and llok through from the bottom, should see equal distance all around. Would be the first time I had to loosen the throttle blades and readjust them.
2. Can you post pictures of the plugs? They sound like you are ok. Slight brown is good.
I dont remeber, is there a small throttle stop screw underneath holding the plate open?
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Old 09-05-2012, 09:07 AM
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Hello I have that same carburetor and I tried to do the .020 on both primary and secondary and it caused my engine to idle over 1100 rpm and adjusting the primary would not let it idle down.

The transfer slot on the secondary side sits up higher then the front ones and that is part of the problem. What I did to fix this problem was readjust the primary to about .020-.030 and no more then that and close the secondary up all the way and then turn the secondary screw to where it makes no contact with the throttle shaft part on the side on the base plate adjustment area and then slowly turn it to where it just starts to make contac and opens the secondary butterflys and then give it about one full turn and that should be close to where it will work good and you should have good idle adjustment on the front.

You might have to go on full turn and a half more on the secondary if you have a big cam. That is what worked for me without it having the high idle problems like your having. Now if you have a big cam with 230 @ 50 or more then you will have to open the front as per above and the secondary's more.

Also the street avenger carbs have a very lean idle circuit and you might have issues getting it to work with a big cam but since you don't know the specs that could make it harder to tune correctly.

Also how is your timing and where is it set at? That can also make carburetor tuning easier if your timing is set right for your engine.

The street avenger carburetors are for mild engines and not engines with radical cams with a big lope to them and without making metering block adjustments or air bleed changes which you can do but once its done it can't be changed. Engines with lopey cams will take a lot more fine tuning of the carburetor along with correct timing to get it right.

Also on your spark plugs that is how mine are they are a nice tan color where it is firing and white elsewhere so that is a good burning plug in my opinion.


Eric
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Old 09-05-2012, 09:36 AM
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Quote:
Originally Posted by 1brewmaster1 View Post
Good Day...

I have a GM 350 built prior to me purchasing the truck. The only thing I know for sure is it has a nice sounding cam lope. The engine has an Edelbrock Performer RPM manifold with a Holly Street Avenger 670 on it with pre 1980 cast Chevy heads. I am attempting to set up the carburetor according to Lars Grimsrud's article and have created problems.

1. According to Lars, you set the throttle plates at .020 of the verticle slot showing. Also known as the transfer slot. I have adjusted the rear throttle plates to that spec and the primary throttle plates will not close far enough to get to the .020 measurement. The idle adjust screw is adjusted back to where it is not even touching the linkage stop. About half to the transfer slot is visible at that point. The choke fast idle cam is not in the way of this issue. According to Lars, both transfer slots should be adjusted equal for proper operation. When I install the carb with the transfer slots as noted, it will idle too high and can not be adjusted lower.

2. I have noticed a strange burn pattern on the spark plugs. The plugs are showing half of the plug white and the other half light brown. The color difference is NOT up and down of the porcilin, but back and front on the porcelain. It appears that the plugs are light brown on the side closest to the valves and white away from the valves. Why?

Your comments are appreciated.
Here is the Holley manual on the 80670 Street Avenger. It has the tuning specs in it. http://www.holley.com/data/Products/...0219-3rev3.pdf
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