Holley Set-up Questions
Thread Starter
Racer
Joined: Feb 2001
Posts: 405
Likes: 15
From: Minneapolis
Holley Set-up Questions
My son-in-law just bought his first 'Vette. A '75 with a 4165 or 4175 Holley on it, which isn't set up right. It won't run right unless it's at 1000 RPM. The vacuum advance is plugged directly into the intake manifold (I know that's not right)
Being a Quadrajet person, I know nothing about Holleys, and my son-in-law knows even less.
So, what's the deal? Should the vacuum advance be connected to the tube near the passenger side top of the air horn?
When I block off the advance, I am able to bring the idle speed right down to where it's supposed to be. However, then it wants to kill when you put it in gear.
Next issue is that adjusting the idle mixture screws don't have any effect on idle quality.
Any of you Holley people out there have any advice? A vacuum hose schematic would be real nice, if someone could send one.
Help!
Being a Quadrajet person, I know nothing about Holleys, and my son-in-law knows even less.
So, what's the deal? Should the vacuum advance be connected to the tube near the passenger side top of the air horn?
When I block off the advance, I am able to bring the idle speed right down to where it's supposed to be. However, then it wants to kill when you put it in gear.
Next issue is that adjusting the idle mixture screws don't have any effect on idle quality.
Any of you Holley people out there have any advice? A vacuum hose schematic would be real nice, if someone could send one.
Help!
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
not a holley person... but put the vacuum advance for the distributor in a port that has no vacuum at idle... where is the EGR plugged into????
Advanced
Joined: Jun 2004
Posts: 89
Likes: 0
From: St. Charles IL
The reason your idle screws wont do any thing is your butterflies are too far open and get out of the idle circuit, move your advance hose to the pimary metering block (tube on the passenger side). Check your base timing, close the butterflies as much as possible, (you might even need to open the secondary butterflies a little more, check float height also. NOW you can adjust low speed screws (in untill it slows, out till it goes away then add 1/3rd of a turn). But I am no expert either.
Pro
Joined: Dec 2002
Posts: 560
Likes: 1
From: Mooresville NC
My holley has the advance hooked the carb above the throttle plates. If idle mixture screws have no effect, there may be a couple of problems.
1. the fuel bowl levels are not set correctly
2. the inlet fuel needles are dirty and are staying open
3. blown power valve
4. check motorpsycho502 comments.
1. the fuel bowl levels are not set correctly
2. the inlet fuel needles are dirty and are staying open
3. blown power valve
4. check motorpsycho502 comments.
Advanced
Joined: Jun 2004
Posts: 89
Likes: 0
From: St. Charles IL
Originally Posted by MILO
My holley has the advance hooked the carb above the throttle plates. If idle mixture screws have no effect, there may be a couple of problems.
1. the fuel bowl levels are not set correctly
2. the inlet fuel needles are dirty and are staying open
3. blown power valve
4. check motorpsycho502 comments.
1. the fuel bowl levels are not set correctly
2. the inlet fuel needles are dirty and are staying open
3. blown power valve
4. check motorpsycho502 comments.
Thread Starter
Racer
Joined: Feb 2001
Posts: 405
Likes: 15
From: Minneapolis
I checked the timing and it was at 8 BTC, which is close. Primary throttle plates were shut tight, but didn't check the secondaries. Will do that next.
A blown power valve sounds plausible, because when he wheeled the thing into my garage, and shut it off, I noticed fuel generously dripping into the main venturis on the primary side.
Now where the heck is the power valve and how much trouble is it to replace? Guess a Holley manual is in order.
Thanks to all for the ideas.
A blown power valve sounds plausible, because when he wheeled the thing into my garage, and shut it off, I noticed fuel generously dripping into the main venturis on the primary side.
Now where the heck is the power valve and how much trouble is it to replace? Guess a Holley manual is in order.
Thanks to all for the ideas.
Advanced
Joined: Jun 2004
Posts: 89
Likes: 0
From: St. Charles IL
timing should be 12 with no vac connected. you sure the butterflies are really closed, if it kinda whistles at idle you are leaving the idle circuit. but the drip in the primaries has to be either the float level is too high on the front bowl (should be at the bottom of the inspection hole) to adjust, loosen the screw and turn the nut tighter to lower the needle seat)or blown power valve, when you remove the primary float bowl the power valve will be screwed into the metering block (the piece with the jets screwed into it) power valve: (big round thing screwed in above the jets) to test it: it is basically a diaphram with a spring, a backfire can cause the diaphram to rupture. if you dont mind the taste, your mouth can develop enough vacuum to test it. what I would do is check the float level before you take it apart because too high fuel level and it will just bubble right out of the venturi, if that s not it, have a new valve to pop in there, tell em you want a 6.5 (which is standard BTW)
Advanced
Joined: Jun 2004
Posts: 89
Likes: 0
From: St. Charles IL
I have been having carb woes lately, luckily I have a few different new or almost new auto and marine holleys of different sizes to play with. my vette 650 mech. DP had acouple stripped bowl screws on the primary, could not get it right even after total rebuild, put a marine 600 mech DP i had layin around on the other night and big difference, off idle stumble went away, no more drippy, good response. a little fat I think, WFO power is not quite as good though cuz now it wont bark second, but progress is still progress.
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Instructor
Joined: Jul 2000
Posts: 173
Likes: 0
From: Pumpkin Center CA
Go to www.holley.com for some excellent tech articles. I agree with the blown power valve - fix it first then all these other tips will very likely get you a very crisp throttle.
Thread Starter
Racer
Joined: Feb 2001
Posts: 405
Likes: 15
From: Minneapolis
This Holley has no obvious float adjustments or inspection plugs on the side of the fuel bowls. So, can't dial them in, as has been suggested. I've been to the Holley site, too, and that wasn't a whole lot of help other than to identify the carb as a 4165 or 4175.
Maybe notching the timing to 12 degrees will help some, but there still is a definite fuel delivery problem.
Maybe notching the timing to 12 degrees will help some, but there still is a definite fuel delivery problem.