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  #1  
Old Apr 4th, 08, 03:30 PM
dubs68camaro dubs68camaro is offline
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Default Holley 4 corner idle question

Are the main bodies of a Holley 4 corner idle different from the 2 screw model? Also, If a metering block has the power valve part not drilled from the factory but does have the air/fuel screws, does that make it a rear 4 corner metering block? Where there any Holley double pumpers that didn't have a primary power valve? I have some metering blocks as described and I want to build a couple of 4 corner carbs and take an 850 I already have and make it a 4 corner jobby. Just needed this info to proceed. Thanks guys!!!
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  #2  
Old Apr 4th, 08, 03:39 PM
zdld17 zdld17 is offline
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Default Re: Holley 4 corner idle question

4 corner metering blocks are specific. They each have their own circuits. Don't think you can just add on as the secondary air horn will have to have transfer slots , I believe. As well as secondary squirters off the airhorn. What are you trying to do? Make a 4 corner DP out of a single squirter?
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  #3  
Old Apr 4th, 08, 03:56 PM
dubs68camaro dubs68camaro is offline
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Default Re: Holley 4 corner idle question

no...no....no..... I'm trying to turn some of my 750 and 850 double pumpers into 4 corner idle carbs. That's why I trying to line out the questions in some kind of order. It suck because there still seems to be no master reference guide out there that will allow you to take a metering block number(s) and figure out what carb it should be on based on the restricter sizes. I just talked with Holley tech last week and they confirmed that there is no real way of knowing with just a metering block in your hand. I have a 4 corner carb coming to me next week. I'm going to try and study the relationship of that block to main body relationship and see if I can prove my theory right. It would sure be easier though if someone could answer these questions and save me some time.

As always Don, thanks for the reply!
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Old Apr 4th, 08, 05:28 PM
Z15CAM Z15CAM is offline
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Default Re: Holley 4 corner idle question

9 time out of 10 a 4 corner idle is useless unless you're running insane compression and a 4000/8000rpm cam other words NASCAR or Pro Strip. It does not mean you can not run one on the street running lower compression and say a 2000/5500rpm cam but you will usually find that you will be setting the rear idle screws on their seats, that is closed, as the front idle adjust is sufficient.
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  #5  
Old Apr 4th, 08, 05:34 PM
zdld17 zdld17 is offline
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Default Re: Holley 4 corner idle question

First , Any idea what your carb #'s are on the air horn? I have an old Holley book with old stuff as I am old enuff to have bought it new.

Second, my thinking is that as long as you have the plate and bowl to do this as well as the secondary squirter stuff in the air horn( you need this as you will have a dp carb), it should work. As when you try to close off secondary plates with the little allen head screw on the right side near the throttle plate link, you are basically opening plates some off the transfer slots , that does draw fuel from the secondary bowl. So seems to me all you need is the metering block with adjuster screws and floats as well as "squirters for the secondary part of the air horn.. Don't hurt to trial and error.
Sounds like your are trying to make a 4779-1 ir a 4781-1. Remember now the 750 has 1 11/16" bore plates and the 850 has 1 3/4" bore plates. two differant animals.
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  #6  
Old Apr 4th, 08, 05:43 PM
dubs68camaro dubs68camaro is offline
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Default Re: Holley 4 corner idle question

This is strictly for selling purposes on ebay. I'm trying to turn 4779-2's into 4779-8's. Don, I have 4776, 4777, 4779, 4780 AND 4781's. The people on ebay love to pay more for a 4 corner idle because it's more bells and whistles. These are not performace issues. I also don't want to rip people off by putting an 1850 series 600 front plate on the rear of a double pumper and call it a 4 screw idle. If there is function, then fine. I have a 363 perfect 100 rating on ebay and want to keep it that was. Just thought I'd run it by the "experts".
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Old Apr 4th, 08, 06:02 PM
zdld17 zdld17 is offline
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Default Re: Holley 4 corner idle question

Quote:
Originally Posted by dubs68camaro View Post
This is strictly for selling purposes on ebay. I'm trying to turn 4779-2's into 4779-8's. Don, I have 4776, 4777, 4779, 4780 AND 4781's. The people on ebay love to pay more for a 4 corner idle because it's more bells and whistles. These are not performace issues. I also don't want to rip people off by putting an 1850 series 600 front plate on the rear of a double pumper and call it a 4 screw idle. If there is function, then fine. I have a 363 perfect 100 rating on ebay and want to keep it that was. Just thought I'd run it by the "experts".
es ta bueno con migo.
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  #8  
Old Apr 4th, 08, 09:55 PM
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77wolf10.85 77wolf10.85 is offline
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Default Re: Holley 4 corner idle question

Quote:
Originally Posted by Z15CAM View Post
9 time out of 10 a 4 corner idle is useless unless you're running insane compression and a 4000/8000rpm cam other words NASCAR or Pro Strip. It does not mean you can not run one on the street running lower compression and say a 2000/5500rpm cam but you will usually find that you will be setting the rear idle screws on their seats, that is closed, as the front idle adjust is sufficient.

ditto, and well said.

psst Dub, go ask at speedtalk.com. There's dudes over there that could maybe tell you if you can drill the body, where, how large a hole etc, or if you are wasting your time. I have either 2 or 3(maybe 4? heck Idunno) four-corner carbs but I never did a body comparison from a 2 to 4. I am curious what you learn, please keep us informed.
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  #9  
Old Apr 5th, 08, 06:20 AM
dubs68camaro dubs68camaro is offline
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Default Re: Holley 4 corner idle question

That's fine Tim.....but you have to keep it just between you and me. I don't want others getting a cut of the action!!!!!
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  #10  
Old Apr 5th, 08, 07:35 AM
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77wolf10.85 77wolf10.85 is offline
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Default Re: Holley 4 corner idle question

oops we forgot to talk about it in stealth mode now everybody knows

Fun game Dub, glad to play. Got me a little smile going while I try to get my body limbered up a little... I worked a 16 yesterday to get a 1500hp machine up and my back and junk is ......junk.
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  #11  
Old Apr 6th, 08, 07:51 AM
lluciano77 lluciano77 is offline
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Default Re: Holley 4 corner idle question

Here is the real deal with 4 corner idle. It will improve idle on any engine by making the un-adjustable secondaries adjustable.

It is up to you wether you want a secondary block with a powervalve. The important part is to have the mixture screws obviously. If using a powervalve, you will possibly need to resize the PVCRs, (power valve channel restrictions) but this can be done later and will not effect idle.

This is what you need to do:
-Get a primary metering block. Any carb will do, but the best thing is one from the same carb you have now. I have bought broken or core carbs off Ebay to get them. Thank god for the torque monsters breaking their baseplates. A core carb will help too because you can practice everything that I mentioned in this post before drilling the carb that you will run.

-Drill the baseplate on the secondary side to match the primary. You will see how the primary idle circuit is routed. It is kind of tough, but you have to drill the baseplate from the underside so the the passages meet up through the baseplate. Use your baseplate gasket as a template. You need two holes to intersect. One from the top and one at an angle from the bottom. There is usually a bump just under the throttle plate where they need to meet. Try and match the primary side hole sizes. You will notice on the baseplate that the primary only has one hole and the secondary has two. That is where you will be adding the passage from the top. Don't drill either hole too far. Go a little on each until they meet. Use a drill bit to check the angle that came stock on the primary side.

-Block the old secondary crossover channel in the baseplate using JB weld. It is a channel between the primary and secondary on the sides looking from the top. I plug it about 1/4" and use a file to carefully machine the JB weld flat.

-Look at the carb main body. There are holes where the idle circuit passes through on the primary side that aren't on the secondary side. They will intersect the top of the baseplate on the secondary side where you just added your new holes. Looking at the bottom of the main body, again use you gasket as a template and mark where the new hole needs to be. Now this part is critical just like the last intersection... On the side of the carb at the secondary side of the main body, there is a hole that needs to be drilled that will intersect the hole you drill from the bottom. Use the primary side again as a reference. The depth of these hole must meet up the same. I go a little at a time until they meet. Makes sure you are drill straight and level when drilling both holes. Don't go too far. Sometimes the hole from the side has been started for you as on some 1850s I have done. Most carbs you will need to start from scratch though.

-A good drill index will help for this part. You need to check the sizes of your IFRs (idle feed restrictors) and IABs (idle air bleeds). Use the butt end of the drill bit for this. When you feel a snug pull and the next size up won't fit you know you found it. The IFRs are on the metering blocks. They are brass restrictions about 1 1/4" up when looking at the main body from the side. They are on either side of the powervalve at about the same height to center. On top of the carb, the IABs are the outer bleeds at the entrance to the venturi next to the fuel bowl vents. They are brass restrictions. The IABs are the larger diameter holes on the outside. Don't touch the HSABs (high speed air bleeds) which are located on the insides closest to the fuel vents. They have nothing to do with the idle circuit for the most part.

I would shoot for .033" on the IFRs both primary and secondary. For the IABs go with .070". This is just a baseline. The main thing here is the IABs on your carb will be the wrong size for 4 corner idle. You can get brass hex head setscrews to make you IABs and IFRs adjustable. You will need to drill and tap the IFRs and IABs. I would use 10-32" for the IABs and 6-32" for the IFRs. Get the 1/4" length or 3/16" if you can find them.

This step is what 99% of people miss in doing the secondary conversion. The IAB/IFR relation makes or breaks the benefit of 4 corner idle. A wideband 02 sensor is your best bet at fine tuning everything when you are done. That will help find the timing and tuning of your bleed ratios.

Once you get all the conversion finished and the restrictions done, set your transition slot to .020" on primary and secondary if possible. If you can't get the idle you want you can close down the secondary some. It is more important to get the primary set right. I always adjust my idle speed at the secondary and leave the primary at .020"

Your advance curve must be set right. I like 18-20o initial on my engine. I wouldn't go any lower than 14o. Make sure your mech. advance is set up for proper total. This will be somewhere in the 32-36o range approx. Vacuum advance can help a street car too. Just don't overdo it. Make sure the starter doesn't kick back and that you don't detonate at cruise or under load.

This website will help more than anything else out there. Do some searches for drilling and tapping bleeds. This is the best info on carbs I have found anywhere. http://www.innovatemotorsports.com/f...isplay.php?f=7

There are plenty of books out there showing how to add 4 corner. Most of them miss one or two steps though. You can look though to see where the passages are that I am talking about.
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  #12  
Old Apr 6th, 08, 08:04 AM
lluciano77 lluciano77 is offline
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Default Re: Holley 4 corner idle question

Quote:
Originally Posted by dubs68camaro View Post
Are the main bodies of a Holley 4 corner idle different from the 2 screw model? Also, If a metering block has the power valve part not drilled from the factory but does have the air/fuel screws, does that make it a rear 4 corner metering block? Where there any Holley double pumpers that didn't have a primary power valve? I have some metering blocks as described and I want to build a couple of 4 corner carbs and take an 850 I already have and make it a 4 corner jobby. Just needed this info to proceed. Thanks guys!!!

The main bodies are different because of the IAB/IFR relationship. Also, the passages on the secondary side are not drilled for the adjustable circuit.

I do not run a secondary PV (powervalve). The secondary PV will get uncovered on a hard run in a fast car. Think about it, they make jet extensions for the secondaries. If the jets get uncovered what happens to the PV? A PV can however be good in a road race carb. It will allow a smaller main jet for cleaner cruise and still richen at the top under high load. Figure out which is more likely to ber what you need. This is one reason I like the 4010 carbs. They put the PV at the bottom of the bowls.
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  #13  
Old Apr 6th, 08, 08:08 AM
lluciano77 lluciano77 is offline
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Default Re: Holley 4 corner idle question

Quote:
Originally Posted by dubs68camaro View Post
This is strictly for selling purposes on ebay. I'm trying to turn 4779-2's into 4779-8's. Don, I have 4776, 4777, 4779, 4780 AND 4781's. The people on ebay love to pay more for a 4 corner idle because it's more bells and whistles. These are not performace issues. I also don't want to rip people off by putting an 1850 series 600 front plate on the rear of a double pumper and call it a 4 screw idle. If there is function, then fine. I have a 363 perfect 100 rating on ebay and want to keep it that was. Just thought I'd run it by the "experts".
I wouldn't start selling these until you have a much better understanding of carbs. Read as much as possible on the site I gave the link to.

By the time you get all the tools, rebuild kits, etc. You will not make much profit. Believe me, I have already tried and it just aint worth it. People have no idea what they are doing and will complain and want to send the carbs back. I had one guy drill the crap out of the PVCRs because he thought that was part of the 4 corner conversion. He ruined the carb and I had to battle with him and Ebay for a month.

The other problem is once you start to tune your carb and learn how it really works, you will start to see how hard it is to guesstimate what someone else's engine will want. The only way to custom make a carb for someone that performs like the carb gurus want you to think would be to hook an AFR gauge up to their car and tune. Otherwise they will go toward the rich side to make sure you don't complain and send the carb back. That is why Holleys are always on the rich side. The lean side will run worse so they err to the rich. It is kind of like the movie "The Matrix". Once you take the red pill and find out what is really going on, you will never look at carbs and tuning the same again.

A metering block is a metering block. There are differences obviously between 3 circuit Dominator metering blocks and there are some spreadbore style blocks that won't interchange with the 4776-4781 line. The differences are in the IFRs, the PVCRs. Generally the E-holes (emulsion holes located on the vertical channels in the blocks) are around the same.
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Old Apr 7th, 08, 07:10 AM
dubs68camaro dubs68camaro is offline
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Default Re: Holley 4 corner idle question

lluciano,

I was really hoping that someone would reply with some good, detailed information.

Either you are a great poser, or you really know your stuff!!!! I am going to do just what you said with the different main bodies I have. I will not get into the drilling part because I'm not a carb tuner for the general public and DO NOT sell my carbs as rebuilt. I clearly sell them as cores or rebuilders and alway list that altitude, HP and a million other things will need to be put into the core they buy from me to make it work for their application. I really love the info you shared with us though and thank you. I think I now know why a 4779-8 is a 4779-8 and a 4779-2 is a.....well, you get the idea.

Tim,
You need to go back to the detailed instructions you got out of the Lucky Charms box and re-read the secret agent "code of ethics" that came with your "Sandarian 4" utility belt. It clearly states that YOU MUST NOT enter stealth mode, thus secretly communicating with another Sandarian 4 warrior, unless you post the symbol. Please do not allow this to happen again or I will have to report you to the Quazar 16 Board of Directors. You have been warned.

LMAO.....my wife is asking what's so funny and I had to tell her that I just peed my pants!!!!!!!!!!!!!!!
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  #15  
Old Apr 7th, 08, 05:06 PM
lluciano77 lluciano77 is offline
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Default Re: Holley 4 corner idle question

I have been modding Holleys for years and tried just about every style they have made including the 2 barrel 650 with no boosters. I prefer not to make a business out of it more for the reason that the I could make more in labor at work then I would working on carbs. Most of the shops out there that deal with customers, warranty their work, buy all the tooling needed and maintain new bits etc., gaskets, or whatever else all adds up. I would suggest maybe modding carbs as a trade off with someone else that is good with welding or other things you may need.

Again, there are a lot of books out there that will help. Go to your neighborhood bookstore and look through all the Holley books. Its free and you can get the info you need with pics of what I am talking about. I would pull some pics off the Innovate site, but I should ask them first before using them. Of course you could go on that site and register and see for yourself.

I am not claiming to be all knowing about carbs, in fact I am still learning a lot. Read through the Innovate site and you'll see how much there is to learn. I run an Autometer wideband Sport Comp gauge, but the best knowledge base is the Innovate site.
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