I'm very curious about the vacuum set-up you have. Normally, Holley carburetors have an internal passage that provides vacuum to operate the throttle blades. Why is this hose and valve necessary?
Six pack tuning help needed, please
- Thread starter 69 GTX
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Meep-Meep
дворянин
That hose IS what provides the vacuum signal to the outboards because of their remote nature (separated from the center carb).
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OK, I'm seeing this valve, which is not stock at all. Seems it's purpose is to bleed off some vacuum signal to ATM so the outboards don't open so fast. But Holley thought of that too! If you remove the vac diaphragm you will note the bleed off hole that passes right into the main venturi. I have seen two sizes. Approx .067" and .043" and the larger of the two holes will slow the opening of the outboard carbs. Also in my experience the outboards don't open in a linear fashion. It's quick until about half way then very slow to not at all depending on the diaphragm springs. Seems it should be reversed and perhaps the PO of your setup was onto this, hence the addition of the bleed valve.
- - - Updated - - -
OK, I'm seeing this valve, which is not stock at all. Seems it's purpose is to bleed off some vacuum signal to ATM so the outboards don't open so fast. But Holley thought of that too! If you remove the vac diaphragm you will note the bleed off hole that passes right into the main venturi. I have seen two sizes. Approx .067" and .043" and the larger of the two holes will slow the opening of the outboard carbs. Also in my experience the outboards don't open in a linear fashion. It's quick until about half way then very slow to not at all depending on the diaphragm springs. Seems it should be reversed and perhaps the PO of your setup was onto this, hence the addition of the bleed valve.
66Satellite47
Well-Known Member
Meep & Colorado
Sorry I got this off track. The valve is a vacuum bleed, just adds a little more adjustability to the end carb opening. I ran my other setup very near stock & worked great. Modifying end carb jet plates & drilling holes got my first setup off track. Got back to nearly stock & problems solved. The setup in the picture was done by a fellow around here that did the carb & ignition work on several of the hard running Stock/Super Stock guys in the early & mid seventies. The pitured stuff ran perfectly.
Meep-Meep
дворянин
Didn't I just write that!? But thanks for confirming.
Well finally going to get back to the 6pak RR tonight.
We tried closing up the .073 holes and retuned. We came to the conclusion that we need to close the .073's and are going to put .030's in. I think this will be the last step in getting it correct.
Oh forgot to mention a problem solved. on the previous tune session he noticed when he would put the air cleaner back on on it would pick up 200 rpm. Turns out the base was hitting the vent arm on the center carb bowl opening the throttle a little, to we modified the arm to get more clearance. Hope this helps someone down the road.
Well the RR is finally street ready now. Idles pretty smooth at 850 (idle varys 30 rpm due to cam) with 13 vac. Shuts off without dieseling or use of idle solenoid. No gassy exhaust. Idles good in gear at stops, owner is very happy! Way better than the 950 idle standing on the gas & brake at the same time to get it to idle at stop lights. With a very choppy idle.
So we ended up with .040 holes in outer carbs & .090 in center. Timing at 16 at idle & 34 all in at 2200rpm. Timing was the biggest help with this car, was 8 btdc Thanks Lew & Meep for your help! Now I can't wait to do mine when it's done!
So we ended up with .040 holes in outer carbs & .090 in center. Timing at 16 at idle & 34 all in at 2200rpm. Timing was the biggest help with this car, was 8 btdc Thanks Lew & Meep for your help! Now I can't wait to do mine when it's done!
I did notice last night while fondling my 71 carbs that the outer carbs had .085 holes already in the blades. When did holley start doing that? Was this standard on 71 carbs or an revision done by Holley later in the run?
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