6 Pack Issues...

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2fine69s

2fine69s

69 340-6pak Rag Top
Joined
Aug 18, 2006
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Elm City, N.C.
Hey guys,
I need to pick your brains and beat another dead horse. I have a 340-6 pack that is an absolute fresh build, just ten years old. 372 ci, edelbrock heads, 10.25 Weisco pistons, ,530 Hyd Roller, MP 6-pack and ignition. Other than the dyno break in, I have just now started running the engine some since my car is almost finished. Other than running just a tad rich (carbs are out of the box and not adjusted properly) I had noticed that the accelerator pump had started leaking, probably dried out over time, so I decided to go ahead and change it and the front bowl gasket just to be safe. After all was said and done, I cranked it this afternoon and the choke engaged as should but the idle was higher than usual. I rapped the throttle to release the choke and it backfired from the rear carb. After checking, I had left a vacuum hose off. I reconnected it and fired it up again, it immediately started loading up and I noticed that when I put my hand over the air horn of the front carb, no problem, but when I put my hand close to the air horn of the rear carb, it would suck my hand quickly. Could it be that it busted the power valve on the rear carb when it backfired causing the excess vacuum and running rich on fuel? PS the picture is not today, it was a while back.
Martin

IMG_0126.JPG
 
Sounds like it to me. Could always temporarily block off the fuel to the rear carb and see if it fixes the problem.
 
I did not know there was a power valve in the front or rear carb. It sounds to me that the butterflies on the rear carb are not closing correctly.
 
Jadaharabi said:
I did not know there was a power valve in the front or rear carb. It sounds to me that the butterflies on the rear carb are not closing correctly.
Click to expand...
You very well may be right, I have only worked on the center carb. I'll check it out this weekend. I think Im going to re-check the linkage to the F/R carbs for bind also.
Thanks
 
Jadaharabi said:
I did not know there was a power valve in the front or rear carb.
Click to expand...
You know, your right, theres no metering plate on the F/R carbs, so nothing for the power valve to screw into. I really should have thought this through, instead of freaking out and jumping online...
Thanks
 
rumblefish360 said:
Pic 1, closed throttle, bad,
Click to expand...

The rear carburetors need to close down to their stops If that's too hard to understand I'm sorry but if they stick open you can adjust the idle screws all week long and it won't make a difference because they are not closed down to their stops.
 
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2fine69s said:
.........but when I put my hand close to the air horn of the rear carb, it would suck my hand quickly.....
Click to expand...
Sure sounds the rear is open more than the front

rumblefish360 said:
.....
Click to expand...


As I understood, the original outboards had a "sticking closed" issue. That wouldn't happen had they not been "closed" in the bores, would it? Maybe you can educate me rather than slam me?

I do agree, Mr. Shepard doesn't use the "totally" word..........
6PackExcerpt.jpg
 
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rumblefish360 said:
Daves69, Jada, you guys are telling me the front and rear throttle blades should totally close?

Yes or no?

If so, then why are there idle slots and adjustments screws?
Click to expand...


Nobody has said anything about the butterflys being totally closed except you, we are saying check to see if they are binding and not closing as they should.
 
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To get back on the issue.......

rumblefish360 said:
Daves69, Jada, you guys are telling me the front and rear throttle blades should totally close?

Yes or no?
Click to expand...
I've always taken "closed" to mean not open. But, I'm open to being taught.
And actually, I'm more in question if I'm not understanding the idle setup.
What I believe you are indicating is I should be backing out the center carb idle to closed throttle, adjust the rods for closed outboards, then bring up the idle with the center.
Is this correct?
 
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