Topic: Holley Carburetor Initial Setup

[Angela]

I'm looking for help with initial setup advice for a Holley 4150t. Specifically, I need help with the following:

(1) How do I set the secondary butterflies before putting the carb on the engine? I know there is a set screw accessible from underneath the carb, but I'm not sure how to know when the butterflies are open the correct amount. The following link seems to imply use of a 0.020" feeler gauge, yet to me that seems ludicrous... Twenty thousands!?!? No way.

(2) Tips on setting the fuel floats? I've read that one should remove the inspection screws and adjust the floats with the engine running. But, really? With all the vibration I can't imagine I'll be able to turn those float adjustment screws. Does someone make a clear inspection screw I could temporarily install so that I could see the fuel level?

[J_Speegle]

The instructions in the rebuilt kit provides all the bench settings. Do you have a copy of that sheet?

Once on the engine the float setting can be fine tune There are clear plugs but never been able to see the fuel level in the bowl once they are installed. Always bench adjusted them low, then once on the engine and running pulled the plugs then with a wrench and screwdrivers (two hand job) adjusted the float upward until you get just a little flow at the bottom of the opening. Done it hundreds of times and 10's of thousands of others have been successful at doing the same. Place a rag under the bowl and base on the end your working on to catch the small amount of fuel that sill drip down. If you get fuel on anything - IMHO pat dry don't wipe  

[Bob Gaines]

The instructions in the rebuilt kit provides all the bench settings. Do you have a copy of that sheet?

Once on the engine the float setting can be fine tune There are clear plugs but never been able to see the fuel level in the bowl once they are installed. Always bench adjusted them low, then once on the engine and running pulled the plugs then with a wrench and screwdrivers (two hand job) adjusted the float upward until you get just a little flow at the bottom of the opening. Done it hundreds of times and 1o's of thousands of others have been successful at doing the same. Place a rag under the bowl and base on the end your working on to catch the small amount of fuel that sill drip down. If you get fuel on anything - IMHO pat dry don't wipe

  +1 .

[rockhouse66]

A good starting point for setting the secondary butterflies is to adjust the screw so that the transfer slot is visible on the intake manifold side of the carb as a square - same width as height.  This is basically just barely exposed or barely open.

You can hang the float bowl upside down and get the float level in the ballpark before you install the bowl on the carb.  Just guess where the float would ride in the gas - maybe if it is a used float there is a discoloration line at this point - and adjust until that float point is at the bottom of the level adjustment hole.  As mentioned, adjusting this on the car is not difficult, just potentially messy.

[WT8095]

Here's an illustration of what Jim is talking about.

Borrowed for a post on jalopy journal: http://www.jalopyjournal.com/forum/threads/holly-carb-adjustment-a-f-ratio-screws-dont-change-idle-wassup.617498/

[Angela]

"The instructions in the rebuilt kit provides all the bench settings. Do you have a copy of that sheet?"................................ No, I do not. Could you provide a copy? I have no idea what you're talking about.

[jwc66k]

"The instructions in the rebuilt kit provides all the bench settings. Do you have a copy of that sheet?"................................ No, I do not. Could you provide a copy? I have no idea what you're talking about.

And therein lies the problem. I did a search on Yahoo using "Holley carburetor tuning" and was overwhelmed by the number of websites that have text, books and videos on the subject. Try it.
Jim

[Angela]

Wow, thanks for your nice comment Jim. You thought I didn't know how to use yahoo or google to search on this or any other topic?

My response, to Jeff, was such that I had no idea to which specific rebuild kit instruction sheet he was referring to. I indeed have a genuine holley rebuild kit (for the 4150), which contains an instruction sheet (which I have read) and it does not mention anything about how to adjust the secondary butterflies.

Yes, there is tons of info on the web about this carb..... which I can easily find. In fact, my initial post mentions one such link I found using google (yet failed to include the link.... my bad). However, I questioned most of the info I found, include the 0.020" gap specified in that link. It was my understanding that one of the purposes of this forum was to post questions concerning new and existing research and address related questions.

To all, here is the link I forgot to provide in my original post:     http://www.lbfun.com/warehouse/tech_info/fuel%20&%20intake/Holley%20Carb%20Paper.pdf

[WT8095]

I don't have a '67 shop manual, but it presumably would contain the same procedure as the '68, shown below.

Section 10-10 in the '68 manual specifies the secondary throttle setting as "1/2 turn after screw contacts lever".

[Angela]

Dave, thanks, that's interesting. I checked my '67 shop manual yet didn't notice that information. Experimentally, I have to turn the secondary adjustment screws approximately two turns (after screw contacts the lever) to get the butterfly open enough to expose the section of the transfer slot as shown in the picture you provided. Hmmmmmm..... I'll re-read both pieces of info and repeat the procedure.

[WT8095]

I checked my '67 shop manual yet didn't notice that information.

Not easy to find. It's in Section 10-1, "General Fuel System Service". It's not in Section 10-6 with the rest of the 4150C-specific information.

[Angela]

Thanks again Dave. This info is spread across two different sections in the '67 shop manual.... but I finally found the info. As you indicated, the shop manual says to fully close the secondary butterfly, turn the set screw until it *just* touches the adjustment arm, then turn the screw an additional 1/2 turn.

Now, concerning the picture you posted of the transfer slot (referring to Jim's comment)..... I think I get it now.... that figure you posted is referring to the *primary* transfer slots, NOT the secondaries. That explains why one would need to turn the adjustment screw much more than 1/2 turn to get the secondaries to look like the figure you uploaded. :-)

So, I think I'll leave the secondaries adjusted per the 1/2 turn described in the shop manual and see what happens when I start the car.

Back to Jeff's comment that many, many people have adjusted the floats with the car running. I believe you -and I'll give it a shot myself. For what it's worth, however, I noticed the shop manual states never to adjust the floats with the engine running. :-)

[WT8095]

Now, concerning the picture you posted of the transfer slot (referring to Jim's comment)..... I think I get it now.... that figure you posted is referring to the *primary* transfer slots, NOT the secondaries.

Glad to help. I posted the pic to help illustrate what Jim was describing, and I didn't notice it was for the primaries. I've heard that too about the "square" setting for the transfer slot, but perhaps as you pointed out it doesn't apply to the secondaries. I'm anxious to hear you results, as one day I'm going to have to make the same adjustments   if  when I eventually get my car together. 

[rockhouse66]

It applies to the secondaries.  As a matter of fact, I would say it doesn't apply to the primaries at all except possibly for the initial setting before installation.  The idea is to expose enough of the secondary transfer slot so that the secondaries are functional at idle (as they are supposed to be).  Then the primaries are adjusted with the idle screw on the linkage to obtain the desired idle speed.  The initial slot opening is irrelevant for the primaries because you are changing it as required with the idle screw.  If you just changed the title of that illustration from primary to secondary, it would be right.

If you find that the ported vacuum has vacuum on it at idle, then the primaries are too far open and the cure for this is to adjust the secondaries a little more open so you can turn the idle screw down to get the same idle speed as before but without activating a signal at the ported vacuum.  It can be a trial and error thing for your particular engine based on cam used and probably other factors as well.  Which makes it sort of a PIA because adjusting the secondaries requires removal of the carb for each adjustment.

[Mike_B_SVT]

Great info!

I set my secondaries to the "touching, plus 1/2 turn" setting, and then I ended up getting secondaries that would stick closed :-/