#81  
Old 12-09-2019, 05:04 PM
Formula jg Formula jg is offline
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Thanks for the pics, that's some cool looking setup.

  #82  
Old 12-14-2019, 06:21 PM
Formula jg Formula jg is offline
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I went ahead and elongated the sec. T-slots to just below the plates but winter is here so can't road test for awhile.

First 2 pics are before and 3rd pic is after.

Unfortunately I stripped one of the base plate to main body threaded holes, pice 3 and 4. What's the best way to repair this?
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  #83  
Old 12-14-2019, 06:36 PM
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A slightly longer screw? Or, drill & tap to a larger screw size and install a threaded rod the same material as the main body (or aluminum), and re-drill and tap to the correct screw size.

I do this occasionally on Rochester 2G's.

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  #84  
Old 12-14-2019, 07:10 PM
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Some main bodies have enough room for a long screw and put a nut on top.

I'd try a longer screw first to see if there's more threads to catch. Some have plenty extra and some don't on those outer corners.

And you've helicoils as an option

Clay

  #85  
Old 12-14-2019, 08:12 PM
Formula jg Formula jg is offline
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Is it 12-24 thread?

  #86  
Old 12-16-2019, 02:35 PM
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I want to think Tom seeing an article on the 4224s where Grumpy Jenkins ground the slot out to delay the secondary openings also.

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  #87  
Old 12-16-2019, 07:05 PM
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That is where I got my information for the Holley #4224 carbs modifications years ago.
Grumpy came to Holley a couple of times to talk to other Engineers about his race program with Chevrolet.
Rest in Peace, Grumpy. Grumpy and Wally Booth both used to hang out at Holley Engineering at times and Zora Duntov consulted at Holley Engineering in Warren Michigan on the Holley "Z-manifold"

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  #88  
Old 12-16-2019, 11:09 PM
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Quote:
Originally Posted by Tom Vaught View Post
That is where I got my information for the Holley #4224 carbs modifications years ago.
Grumpy came to Holley a couple of times to talk to other Engineers about his race program with Chevrolet.
Rest in Peace, Grumpy. Grumpy and Wally Booth both used to hang out at Holley Engineering at times and Zora Duntov consulted at Holley Engineering in Warren Michigan on the Holley "Z-manifold"

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Guys that know an awful lot about cars still seek out guys that know more in specialized areas. A lesson for us all. You may think you know. But maybe you just don't know that you don't.....

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  #89  
Old 12-17-2019, 09:41 AM
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I personally try to take what info I heard from "old timers" like Dave Austin, Ken Duttweiler, Gale Banks, Smokey Yunick, and Homer Perry and pass it on to people whenever I can. Be it Carb stuff, Boost stuff, Flow Bench stuff, or even NACA stuff.

Most of the is still as good as when it was first spoken.

I am just the messenger, nothing more. Maybe I diagnose occasionally.

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  #90  
Old 12-25-2019, 11:37 AM
Formula jg Formula jg is offline
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Merry Christmas and Happy Holidays to all.

The journey to solve this stumble issue has me doing a lot of technical research along with working on different areas and circuits of the carb that may or may not be connected to the problem, but now I hope to bring this carb to the next level.

That said I came across a couple of older Innovate and other carb related forum threads where they talked about eliminating the kill bleed on annular booster carbs. Can someone explain the dynamics behind this type of alteration and if there is any benefit (or harm) in doing it?

  #91  
Old 12-30-2019, 08:18 PM
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Update.
Road test revealed no improvement to the stab and stumble at cruise below 2300rpm.
Changes were as follows:

High flow PV’s
Block middle E-hole (1 and 3 at .026)
Elongate sec. T-slot to approx. .010” below closed plates

Not sure of my next move, its been suggested to increase IFR from 31 to 33 and retune IAB and mix screws accordingly.

What was a common IFR size for an old Holley 850 mech. sec. DP?

I’ll try anything at the point, weather permitting.


Last edited by Formula jg; 12-30-2019 at 08:29 PM.
  #92  
Old 12-30-2019, 10:03 PM
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Quote:
Originally Posted by Formula jg View Post
Update.
Road test revealed no improvement to the stab and stumble at cruise below 2300rpm.
Changes were as follows:

Block middle E-hole (1 and 3 at .026)

What was a common IFR size for an old Holley 850 mech. sec. DP?

I’ll try anything at the point, weather permitting.
(HOW MANY EMULSION HOLES DO YOU HAVE ON ONE MAIN WELL OF YOUR METERING BLOCK? 3, 4, OR 5 EMULSION HOLES.) STOCK WAS 2 ON ONE MAIN WELL AND 2 ON THE OTHER MAIN WELL.?


STOCK IDLE FEED RESTRICTION ON THE 4781 850 CFM CARB was .038".

Tom V.

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  #93  
Old 12-31-2019, 09:06 AM
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Hi Tom,
This carb was designed with 3 E-holes and currently have it set up with 2 (blocked off the middle).

Thank you for the specs, do you have any more details for the 4781 such as MJ size, IAB AND HSAB?

Also did that carb use a 50cc accelerator pump on the sec. Side?

  #94  
Old 01-02-2020, 10:57 AM
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I've got an 830 annular DP. I had a lean stumble similar to yours too. I tried some things but what finally fixed it was the big brown cam on the 50cc pump up front. The 50cc pumps don't pump any more than the 30cc pump unless you use the 50cc pump cam. Sorry if you already knew this. Jon

Ps I played with the IFRs too to no avail as far as the lean stumble. Mine are currently. .029". I want to try 028 when I get a chance. My carb is working fine now. No stumble thenks to the brown cam. I just want to lean out the cruise a bit more if possible w/o causing other issues.

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  #95  
Old 01-02-2020, 11:04 AM
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This one.....
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'78 Macho T/A DKM#95, 460cid, SRP pistons, KRE 310 D ports,
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  #96  
Old 01-02-2020, 11:30 AM
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Quote:
Originally Posted by Formula jg View Post
Hi Tom,
This carb was designed with 3 E-holes and currently have it set up with 2 (blocked off the middle).

Thank you for the specs, do you have any more details for the 4781 such as MJ size, IAB AND HSAB?

Also did that carb use a 50cc accelerator pump on the sec. Side?
80 square on the jetting.
Power Valve in the front and rear metering blocks was "6.5".

Stock IFRs was .070" on the first 4781 carbs (2 corner idle)
(We increased the Primary IFR on Cliff Ruggle's Carb to .074"
and it liked the change).
You have a 4 corner idle carb so rear IFRs should be about .068 or .070 in size on the rear.

High speed Air Bleeds have typically been .028" and .025" on the old 4781 carbs
but you have a 3 hole emulsion circuit which screws that up vs the 2 hole used in
the old metering blocks. The 3 hole metering blocks was a bad idea all around.
Better to use the upper two holes and plug the bottom hole vs what you have done.

Tom V.

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  #97  
Old 01-02-2020, 01:38 PM
Formula jg Formula jg is offline
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jonmachota78, When I added the 50cc with brown cam to the sec. side there was literally no improvement, never tried it on the primary side so I will definitely give it a shot.
Do you recall how large you went with IFR before determining this was not the solution for you?

Tom,
Quote
"Stock IFRs was .070" on the first 4781 carbs (2 corner idle)
(We increased the Primary IFR on Cliff Ruggle's Carb to .074"
and it liked the change).
You have a 4 corner idle carb so rear IFRs should be about .068 or .070 in size on the rear."

I think you may have intended to type in IAB in lieu of IFR in that statement, but please correct me if that presumption is wrong.

My current E-hole setup is as follows:

Top (high above float level) - 0.026"
Mid (right at float level) - plugged
Bottom (well below float level) - 0.026"

Where were the 4781 Holley 2 E-holes located relative to the average float level setting?

  #98  
Old 01-02-2020, 03:02 PM
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Correct Idle Air Bleeds. These 3 letter names get muddied up when you are looking up the specs in the Holley Red Book, I prefer the actual names. Emulsion Holes, Primary Idle Air Bleeds, Primary Idle feed Restrictions, Power Valve Channel Restrictions, Secondary High Speed Air Bleeds. In some cases Secondary Idle Feed Restrictions.

You have to make sure that you are not calling the Upper Kill Bleeds and Emulsion Hole.
Emulsion Kill Bleeds are typically slightly smaller and them Emulsion Bleeds are typlcally the same from Holley. Some tuners on circle Track applications make the Bottom Emulsion Hole on a 3 hole Emulsion metering block about .040".

Tom V.

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  #99  
Old 01-02-2020, 04:27 PM
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Quote:
Originally Posted by Formula jg View Post
jonmachota78, When I added the 50cc with brown cam to the sec. side there was literally no improvement, never tried it on the primary side so I will definitely give it a shot.
Do you recall how large you went with IFR before determining this was not the solution for you?
I don't think you need two 50cc pumps so I would move your 50cc pump/brown cam from the rear to the front.

Going by memory, I think I went back up to 035" IFR, but then the cruise AFR was back up to pig rich status and was unacceptable to me. (038 is stock if I remember correctly)

In my opinion, you should not have to calibrate your carb to run overly rich is a cruise situation in order to cover up a lean stumble when the throttle is moving. That's the job of the accelerator pump. You should be able to have an acceptably lean cruise AFR AND cover up the lean condition when the throttle is moved with an adequate pump shot in both volume AND duration. In conjunction with the brown cam, you need the pump shot nozzles to be larger enough to get volume right away to prevent a stumble but also small enough to provide enough pump shot duration to last long enough to cover the duration of the lean period when the throttle is moved.

A correctly calibrated pump shot along with a correctly sized IFR provides the best of both worlds with minimal compromise. Reasonably lean at cruise, but then the pump can "give her the beans" when the throttle is in motion in order provide both economy and seamless drivability.

I love quadrajets and I was determined to make this holley perform close as possible the my old quad. I'm pretty happy with how it runs now, it's still a tad rich a cruise (even with IFRs down to 029). That's why I still want to try 028s,but its livable the way it is now. Seems we're always chasing the dragon in this hobby!

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Last edited by jonmachota78; 01-02-2020 at 04:35 PM.
  #100  
Old 01-02-2020, 05:56 PM
Formula jg Formula jg is offline
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Tom,
I believe the Kill Bleed is also known as a Siphon Break, correct?

The pic shows all 3 E-holes open however I currently have the middle blocked.

What I would like to know is where the 2 E-holes for the 4781 Holley are located relative to typical float level on that 850 Holley?

jon,
I tuned mine for a lean cruise (easily into the 15's AFR) and solid 12.6 at WOT and I want to keep it that way if I can.

I'll flip the pri. and sec. pumps before increasing the IFR.
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