Welcome, Guest. Please login or register.
May 28, 2017, 12:34:40 pm

Login with username, password and session length
TRADER Feedback System
IS NOW AVAILABLE
* SBFTECH Membership Required *
433491 Posts in 37081 Topics by 9458 Members
Latest Member: Rich351
Search: Advanced search
Advertiser Inquiries
+ SBFTECH.com Experienced Small Block Ford Tech
|-+ General Tech
| |-+ General Tech
| | |-+ Old Holly Carburetor...to rebuild or not...that is the question
0 Members and 1 Guest are viewing this topic. « previous next »
Pages: [1] 2 Go Down Print
Author Topic: Old Holly Carburetor...to rebuild or not...that is the question  (Read 1627 times)
FORD93GTFREAK
Stroked Small Block
****
Offline Offline

Posts: 336


Location: Griffin, Ga

« on: February 20, 2017, 07:55:30 pm »

I have this holly carburetor sitting around in the shop. I think it was professionally built at one time by a shop, since there is a tag "Carburetor Shops" on it

To rebuild or not rebuild is the question...

I thought I would consider using in on my 93 Mustang instead of the Summit Racing 750 Dp?

I don't really know what size it is or model. It looks like there are some parts missing and where the secondary pump was there is some epoxy of glue over the hole.

I would appreciate some info, good or bad.

thanks!



Logged
juiced coupe
Six figures worth of don't give a f*ck
Global Moderator
Big Block
*****
Online Online

Posts: 8091


Location: Pascagoula, MS
The land mass between New Orleans and Mobile


« Reply #1 on: February 20, 2017, 08:12:51 pm »

Its a vacuum secondary, no secondary accelerator pump.

For whatever reason, it could have developed a leak on the rear bowl. That is likely the reason for the epoxy. Or someone may have put a DP bowl on a VS carb and needed to seal the location.

Its likely a 3310, 750 cfm version. Very common, but not a bad carb.

If your Summit carb is a mechanical secondary version, I wouldn't even consider swapping over to a VS carb unless there was a problem.
Logged

Doing more with less, or something like that.
http://sbftech.com/index.php/topic,20009.0.html

Quote from: Monte Smith
Bottom line, if it was the hot ticket, the fast guys would do it.............they don't

You might need some Titanium rods and a flow bench!  LMAO on floor

I honestly don't get it.

I'm sweating, my heart is racing, my clutch foot is twichin', and my right arm punched the computer screen doing an involentary 2-3 shift while reading all that. 
FORD93GTFREAK
Stroked Small Block
****
Offline Offline

Posts: 336


Location: Griffin, Ga

« Reply #2 on: February 20, 2017, 08:56:21 pm »

Its a vacuum secondary, no secondary accelerator pump.

For whatever reason, it could have developed a leak on the rear bowl. That is likely the reason for the epoxy. Or someone may have put a DP bowl on a VS carb and needed to seal the location.

Its likely a 3310, 750 cfm version. Very common, but not a bad carb.

If your Summit carb is a mechanical secondary version, I wouldn't even consider swapping over to a VS carb unless there was a problem.
thanks for your information. I appreciate it!

I do have vacuum secondaries on the Summit racing carburetor 750 DP. If this Holley carburetor would be a good performer? I would consider rebuilding it, however I still may have more carburetor that the 302 needs
Logged
FORD93GTFREAK
Stroked Small Block
****
Offline Offline

Posts: 336


Location: Griffin, Ga

« Reply #3 on: February 20, 2017, 08:57:19 pm »

Its a vacuum secondary, no secondary accelerator pump.

For whatever reason, it could have developed a leak on the rear bowl. That is likely the reason for the epoxy. Or someone may have put a DP bowl on a VS carb and needed to seal the location.

Its likely a 3310, 750 cfm version. Very common, but not a bad carb.

If your Summit carb is a mechanical secondary version, I wouldn't even consider swapping over to a VS carb unless there was a problem.
thanks for your information. I appreciate it!

I do have vacuum secondaries on the Summit racing carburetor 750 DP. If this Holley carburetor would be a good performer? I would consider rebuilding it, however I still may have more carburetor that the 302 needs
Logged
FORD93GTFREAK
Stroked Small Block
****
Offline Offline

Posts: 336


Location: Griffin, Ga

« Reply #4 on: February 20, 2017, 08:58:45 pm »

sorry for the double post and this thread may need to be moved to the Carburetor Tech section?
Logged
CDW6212R
Big Block
*****
Offline Offline

Posts: 2438


Location: Knoxville, TN.

« Reply #5 on: February 22, 2017, 03:00:36 pm »

Look at the model number printed on the front of the air horn, that will let you look up all of the parts it should have, and the rebuild kit you'll need.

That size of a vacuum secondary carb can work fine on a 302, the VS is adjustable to make the back open sooner or later, or less etc.

Better question though, how much of the idle/transition slot is visible now with the throttles closed? I see the front has holes already in the butterflys, which suggests someone did tune it for an engine at one point. If they did it right then it shouldn't take much to get it to idle right at least.
Logged

Don

1991 Mark VII LSC Special Edition, soon to be OBDII and 4R70W, then GTC body kit and 347.
1998 Mountaineer, plans for A4WD and KB 2200 blower later, XP8 parts, paint and a 332.
1973 Ranchero and 72 Sport front end ...will be a 351 Clevor, EFI and 4R70W.
FORD93GTFREAK
Stroked Small Block
****
Offline Offline

Posts: 336


Location: Griffin, Ga

« Reply #6 on: February 22, 2017, 07:26:43 pm »

Look at the model number printed on the front of the air horn, that will let you look up all of the parts it should have, and the rebuild kit you'll need.I appreciate the info, however there are no numbers on the air horn anywhere

That size of a vacuum secondary carb can work fine on a 302, the VS is adjustable to make the back open sooner or later, or less etc.thanks for the info. I have a Summit Racing 750 DP I'm using now, with VS however I was thinking this old Holly would be a better choice?

Better question though, how much of the idle/transition slot is visible now with the throttles closed? I see the front has holes already in the butterflys, which suggests someone did tune it for an engine at one point. If they did it right then it shouldn't take much to get it to idle right at least.I saw that there are holes in the butterflies, however I wasn't sure why, you answered that thought. The idle/transition slots I would have to use feeler gauges to check. If this carb was tuned? I wonder if it will work for my engine, provided I can rebuild it
Logged
knucklefux
Adv_SBFTechie
Big Block
****
Offline Offline

Posts: 4287


Location: leesburg, ga

« Reply #7 on: February 22, 2017, 10:57:08 pm »

Stick with the double pumper.  A 750 carb is just right for a 302...don't let the needs of the Chevy boys affect what you need.

The ONLY reason to mess with that VS holley is if you have problems with the carb you're running.  Also, you're probably going to have to plug the holes in the butterflies to get your junk to idle worth shit.
Logged

95 gt-R.I.P.
2004 cobra-needs more boost
CDW6212R
Big Block
*****
Offline Offline

Posts: 2438


Location: Knoxville, TN.

« Reply #8 on: February 25, 2017, 08:49:56 am »

I thought the Summit carb had vacuum secondaries.

The slots I mentioned in the bores of the Holley carb are where the fuel comes from for both idle and transition to the main boosters. Those are slots, open the throttles and look at them inside all four bores. When the carb is tuned ideally, only a "square" will be visible of those slots when the throttle blades are at the idle stop.

Typically when you first run a carb on an engine the first time, you'll adjust the idle screws to get the idel you want. That moves the throttle blade along the slot, exposing more or less of the slots. If the blades are too far from the ideal location(visible square(the slot width matches the slot length visible)), then too much or little fuel comes from the slot. That affects how much idle fuel comes from the slot, which affects how useful the idle screws are. The idle screws only control the idle bleed holes, which are a tiny round hole located nearby but always under the throttle blades.

That's why the first thing done to tune a carb, is to get the throttle blades adjusted to expose the proper amount of those transition slots. Then the other tuning works much more predictably, the idle screws mainly, and the pump nozzles, jet sizes etc.
Logged

Don

1991 Mark VII LSC Special Edition, soon to be OBDII and 4R70W, then GTC body kit and 347.
1998 Mountaineer, plans for A4WD and KB 2200 blower later, XP8 parts, paint and a 332.
1973 Ranchero and 72 Sport front end ...will be a 351 Clevor, EFI and 4R70W.
FORD93GTFREAK
Stroked Small Block
****
Offline Offline

Posts: 336


Location: Griffin, Ga

« Reply #9 on: February 27, 2017, 08:05:08 pm »

Stick with the double pumper.  A 750 carb is just right for a 302...don't let the needs of the Chevy boys affect what you need.Yes, I know. I also know that I'm only running off of 375 cfms primary and I also know (thanks to joel 5.0) that the carburetor is a tune-able device and the 750 DP will work

The ONLY reason to mess with that VS holley is if you have problems with the carb you're running.  Also, you're probably going to have to plug the holes in the butterflies to get your junk to idle worth shit.I have decided to just keep the old Holley until needed. I just thought maybe it would have been a better carb all the way around for tuneability? I have had plenty of carbs in the past years, however it's been a while since I've fooled with one on a vehicle.

Thanks for your input I appreciate it! and btw I was in Columbus, Ga with my wife a few months ago, it's a really nice place and the river walk area was cool also.
Logged
FORD93GTFREAK
Stroked Small Block
****
Offline Offline

Posts: 336


Location: Griffin, Ga

« Reply #10 on: February 27, 2017, 08:10:44 pm »

I thought the Summit carb had vacuum secondaries.

The slots I mentioned in the bores of the Holley carb are where the fuel comes from for both idle and transition to the main boosters. Those are slots, open the throttles and look at them inside all four bores. When the carb is tuned ideally, only a "square" will be visible of those slots when the throttle blades are at the idle stop.

Typically when you first run a carb on an engine the first time, you'll adjust the idle screws to get the idel you want. That moves the throttle blade along the slot, exposing more or less of the slots. If the blades are too far from the ideal location(visible square(the slot width matches the slot length visible)), then too much or little fuel comes from the slot. That affects how much idle fuel comes from the slot, which affects how useful the idle screws are. The idle screws only control the idle bleed holes, which are a tiny round hole located nearby but always under the throttle blades.

That's why the first thing done to tune a carb, is to get the throttle blades adjusted to expose the proper amount of those transition slots. Then the other tuning works much more predictably, the idle screws mainly, and the pump nozzles, jet sizes etc.
O I gotcha! I really need to take off my Summit carb and do exactly what your talking about. I probably will check it out this weekend. I have a spacer I need to install.

thanks for the input. I appreciate it!
Logged
FORD93GTFREAK
Stroked Small Block
****
Offline Offline

Posts: 336


Location: Griffin, Ga

« Reply #11 on: February 27, 2017, 08:32:28 pm »

I thought the Summit carb had vacuum secondaries.

The slots I mentioned in the bores of the Holley carb are where the fuel comes from for both idle and transition to the main boosters. Those are slots, open the throttles and look at them inside all four bores. When the carb is tuned ideally, only a "square" will be visible of those slots when the throttle blades are at the idle stop.

Typically when you first run a carb on an engine the first time, you'll adjust the idle screws to get the idel you want. That moves the throttle blade along the slot, exposing more or less of the slots. If the blades are too far from the ideal location(visible square(the slot width matches the slot length visible)), then too much or little fuel comes from the slot. That affects how much idle fuel comes from the slot, which affects how useful the idle screws are. The idle screws only control the idle bleed holes, which are a tiny round hole located nearby but always under the throttle blades.

That's why the first thing done to tune a carb, is to get the throttle blades adjusted to expose the proper amount of those transition slots. Then the other tuning works much more predictably, the idle screws mainly, and the pump nozzles, jet sizes etc.
I hope this pic is of what your describing about the square?
Logged
CDW6212R
Big Block
*****
Offline Offline

Posts: 2438


Location: Knoxville, TN.

« Reply #12 on: February 27, 2017, 11:06:12 pm »

Yes, you're looking for that slot from below the carb. Often you first look at a carb and see either a lot of that slot, or almost none of it. Too much showing pulls more fuel from it at idle, which means less from the idle circuit, and the screw doesn't do as much to adjust the idle. Too little of the slot or none can mean little or no flow at idle from the slot, and you get a stumble when the throttle is opened, needing more(too much) accelerator pump nozzle size etc.

That transition slot is the starting point to adjust a carb. You get the engine to idle with the throttle blades where they are intended to be at idle, and then adjust the rest without moving the idle stop screws. That's the tricky part, setting the idle stop screws before installing the carb, and getting the proper air and fuel to make it idle there. That's where drilling the holes in the blades comes in. I hope you don't need to make the holes smaller, it's not easy. You can remove the blades and use steel balls to hammer the holes smaller on a flat steel surface. That's a trick from auto trans VB work, fixing a hole you drilled too large. You can flatten the metal at the hole and make it a little smaller, carefully.
Logged

Don

1991 Mark VII LSC Special Edition, soon to be OBDII and 4R70W, then GTC body kit and 347.
1998 Mountaineer, plans for A4WD and KB 2200 blower later, XP8 parts, paint and a 332.
1973 Ranchero and 72 Sport front end ...will be a 351 Clevor, EFI and 4R70W.
FORD93GTFREAK
Stroked Small Block
****
Offline Offline

Posts: 336


Location: Griffin, Ga

« Reply #13 on: February 28, 2017, 07:30:03 pm »

Yes, you're looking for that slot from below the carb. Often you first look at a carb and see either a lot of that slot, or almost none of it. Too much showing pulls more fuel from it at idle, which means less from the idle circuit, and the screw doesn't do as much to adjust the idle. Too little of the slot or none can mean little or no flow at idle from the slot, and you get a stumble when the throttle is opened, needing more(too much) accelerator pump nozzle size etc.

That transition slot is the starting point to adjust a carb. You get the engine to idle with the throttle blades where they are intended to be at idle, and then adjust the rest without moving the idle stop screws. That's the tricky part, setting the idle stop screws before installing the carb, and getting the proper air and fuel to make it idle there. That's where drilling the holes in the blades comes in. I hope you don't need to make the holes smaller, it's not easy. You can remove the blades and use steel balls to hammer the holes smaller on a flat steel surface. That's a trick from auto trans VB work, fixing a hole you drilled too large. You can flatten the metal at the hole and make it a little smaller, carefully.
Ok, now I will follow those instructions above. I believe I have a decent idea on what it involves, however I don't remember seeing any holes in the blades on the Summit Carb I'm running? I will know Saturday though.

again, thanks for all the info. It will give me a good starting point.

I do have one issue with this carb though. The secondary fuel bowl sight glass is always full and I have adjusted it once but didn't seem to make much of a difference in the fuel level that I can see. I wonder if I even need that extra rear pump?
Logged
Jeff351w
Big Block
*****
Offline Offline

Posts: 1214


Location: Imperial, MO
393 build & new trans in progress


« Reply #14 on: February 28, 2017, 10:53:26 pm »

I do have one issue with this carb though. The secondary fuel bowl sight glass is always full and I have adjusted it once but didn't seem to make much of a difference in the fuel level that I can see. I wonder if I even need that extra rear pump?

The fuel level is affected by the float bowl height.  Adjusting this by the screw and locknut on top of the carb will set it correctly. 

If it didn't work the first time, try it again.  Loosen the locknut then hold it in place as you adjust the screw.  Retighten the locknut when the correct fuel level is reached (just above the bottom of the sightglass commonly).
Logged

Quote from: mighty mouse

I often have tires with just too much tread or a fuel tank that is just too full. Accept no substitutes!
Pages: [1] 2 Go Up Print 
« previous next »
Jump to:  



Powered by MySQL Powered by PHP Valid XHTML 1.0! Valid CSS!
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines



408 Stroker