A few Holley Questions.
Melting Slicks
Joined: Oct 2001
Posts: 2,065
Likes: 1,395
From: Halifax, Nova Scotia, Canada
Matt you are lucky that you can get your car to cruise on the main jets at those low 1400-1600 rpm. Makes cruising tuning alot easier.
I have drilled my main body and installed jets in the transfer slots.
I also did at least 10 jetting changes in these transfer slots to get where I am today.
Another thing that most of us should do is enlarge the power valve restrictions in the meter block from about .060 to .070 for starters.
I have drilled my main body and installed jets in the transfer slots.
I also did at least 10 jetting changes in these transfer slots to get where I am today.
Another thing that most of us should do is enlarge the power valve restrictions in the meter block from about .060 to .070 for starters.
I have been running restrictions in my IFR for almost 30 years.
Barry
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
This is one reason why GM went accross the board with Spreadbores, smaller primaries allowing faster transitions to main jets.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Hole #4 in the top picture, the main body is the one I drill and tap 10 x 32 and install a 1/4 inch long set screw with a drilled metering hole of .058
This leans out the cruise while allowing the idle to remain rich for good idle quality.
This leans out the cruise while allowing the idle to remain rich for good idle quality.
Thread Starter
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Lots of information here.
Melting Slicks
Joined: Oct 2001
Posts: 2,065
Likes: 1,395
From: Halifax, Nova Scotia, Canada
Any improvement in fuel mileage is always a good thing.
Barry
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
Barry I use to shut my fuel off pulling in the driveway. I have a long long driveway to the shop and by the time I got to the shop I was feathering the throttle to keep it alive. I now shut the fuel off a block and 1/2 from home, still hit the shop with the car idling normal. No more feathering because the fuel bowls are running out.
My miles per tank have also gone up 50% at least.
My miles per tank have also gone up 50% at least.
Race Director
Joined: Oct 2000
Posts: 15,036
Likes: 79
From: central FL, near the beach.
norval
looking at my spare carb, it appears the slot is the jet.
how wide & long is your slot? i cant get a .025" drill in the 4165 slot!
i wonder if lowering the slot with epoxy would lower the transfer to main booster speed?
Also, to lower transfer speed, the back barrels should be shut tight, at least for a test. 2nd carb butterfly must be tight too. what do u think?
looking at my spare carb, it appears the slot is the jet.
how wide & long is your slot? i cant get a .025" drill in the 4165 slot!
i wonder if lowering the slot with epoxy would lower the transfer to main booster speed?
Also, to lower transfer speed, the back barrels should be shut tight, at least for a test. 2nd carb butterfly must be tight too. what do u think?
Last edited by Matt Gruber; Sep 26, 2007 at 09:34 AM.
Race Director
Joined: Nov 2000
Posts: 11,872
Likes: 12
From: Waterloo ontario Canada
norval
looking at my spare carb, it appears the slot is the jet.
how wide & long is your slot? i cant get a .025" drill in the 4165 slot!
i wonder if lowering the slot with epoxy would lower the transfer to main booster speed?
Also, to lower transfer speed, the back barrels should be shut tight, at least for a test. 2nd carb butterfly must be tight too. what do u think?
looking at my spare carb, it appears the slot is the jet.
how wide & long is your slot? i cant get a .025" drill in the 4165 slot!
i wonder if lowering the slot with epoxy would lower the transfer to main booster speed?
Also, to lower transfer speed, the back barrels should be shut tight, at least for a test. 2nd carb butterfly must be tight too. what do u think?
This jet then controls the idle mix until the main jet takes over.
Just like jetting the mains you can jet this slot doing it this way.
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Thread Starter
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
If you lower the secondary float level to 1/2 turn below the bottom of the sight hole that will solve the flooding out on a hard stop - it also helps a lot with bowl percolation in hot weather. I also run the primary float lower - 1/4 turn - again because of percolation.
If you have the idle screws too far in you will get lurching at slow cruise - 30-35 mph. I have mine set at 1-5/8 turns out from a soft stop. The difference between rich and lean is only about 1/8 turn. I run mine as lean as I can without lurching.
You also need your timing right on. For a better idle I use manifold vacuum instead of ported vacuum.
Guys like Norval are all-out power guys and may not agree with my ideas but they work real good for me.
If you have the idle screws too far in you will get lurching at slow cruise - 30-35 mph. I have mine set at 1-5/8 turns out from a soft stop. The difference between rich and lean is only about 1/8 turn. I run mine as lean as I can without lurching.
You also need your timing right on. For a better idle I use manifold vacuum instead of ported vacuum.
Guys like Norval are all-out power guys and may not agree with my ideas but they work real good for me.
Most all of the information you posted was related to the problems I was having.
I do run a one inch phenolic riser so percolation was not an issue but the float adjustments and idle screw adjustments got me running great on idle and cruise.
Now I need to play with the secondary circuit a little.
I had no idea that the idle screws were so sensitive.
Thanks to all for your help
Race Director
Joined: Oct 2000
Posts: 15,036
Likes: 79
From: central FL, near the beach.
if norvals' slot jet trick is combined with my pv trick, those poorly calibrated Holley's might turn into street friendly carbs.
The SA670 might not need slot jets at all, at least lars' success wih larger jets indicates it is not too rich stock.
Food for thought.
.
Lars: what is the stock transition A/F on your test engine?
The SA670 might not need slot jets at all, at least lars' success wih larger jets indicates it is not too rich stock.
Food for thought.
.
Lars: what is the stock transition A/F on your test engine?
Thread Starter
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
So I will say that it starts right off idle... 800 RPM and up.
So what does this mean?
Race Director
Joined: Oct 2000
Posts: 15,036
Likes: 79
From: central FL, near the beach.
good!
now turn the idle speed screw until it drips out. give it 10 seconds to stabilize.
if fuel drips out the booster 800-1000 then u have observed the carb problem;
> flooding.
high float, dirt on needle, high psi, etc
now turn the idle speed screw until it drips out. give it 10 seconds to stabilize.
if fuel drips out the booster 800-1000 then u have observed the carb problem;
> flooding.
high float, dirt on needle, high psi, etc
