holley spreadbore gm replacement carb..
Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
I have heard knowledgeable people say that the Holley spreadbore is not a very good carb. It doesn't have some of the nice tuning features of a Quadrajet, and lacks some of the nicer things about regular squarebore Holleys, too. This is just what I have heard.However, if you use one, and it does what you need it to do, and your happy with it, then God love ya! I am actually thinking about getting one myself.
Scott
Scott
Last edited by scottyp99; Jan 8, 2011 at 11:26 PM.
Le Mans Master
Joined: Oct 2007
Posts: 7,451
Likes: 974
From: RI, Now Franklin/Nashville TN
I have heard knowledgeable people say that the Holley spreadbore is not a very good carb. It doesn't have some of the nice tuning features of a Quadrajet, and lacks some of the nicer things about regular squarebore Holleys, too. This is just what I have heard.However, if you use one, and it does what you need it to do, and your happy with it, then God love ya! I am actually thinking about getting one myself.
Scott
Scott
That is why I keep repeating my experience with my 4175 over the last 25 years. I have heard the same from people but just as many people say the 4175 is great and the Qjet sucks, so I call it a draw and default to my personal experience with the Holley 4175 and the OEM Qjet on my 78 L-82 over 33 years. The only caveat is that my experience is on a mostly stock lightly modified L-82. It does not pertain to high HP extensively modified engines. As a good basic reliable 4 barrel carb, the 4175 has the tuning features that one would need: Idle adjustment, electric choke, vacuum secondary spring tuning, and easy primary jet replacement, and easy rebuild ability. I believe that the 4165 squarebores have external float adjustment-I have never needed that adjustment and it still would be easy to do on the 4175-take the float bowl off (easy), adjust, put float bowl back on (easy). Many of these issues are just NOT easy to do on the Qjet-that is all I am saying and once a qjet's calibration is off, the fun really begins! Isn't it funny that to rebuild a qjet correctly, you have to send it to a specialist?-it's a carb for pete's sake.
Last edited by jb78L-82; Jan 9, 2011 at 09:28 AM.
Pro
Joined: Aug 2000
Posts: 503
Likes: 17
From: Jacksonville FL
Holley Spread Bore conversion
Did anyone have throttle linkage problems?
My '69 (bought used a few months ago) came with a cobbled together bracket which I remade out of nice materials, so...the geometry may not be stock. Thats' the opening disclamer!
I find the cable attaching ball on the Holley is much closer to the fixture on the bracket which holds the carb end of the cable. This results in very little carb opening. In addition, I measured the length the ball moves from closed to WOT; on the Q jet it moves 2 5/16", on the Holley it moves 1 3/16".
Assuming I could get the cable end far enough away from the ball stud on the Holley, I'm guessing it will get alot more throttle for much less pedal movement.
The Holly throttle bracket, part number 20-32, did not work for me as it is designed for the newer square plastic clip on the end of the cable as opposed to the older round end that clamps in place.
Did any of you have simular problems? Maybe I just need to find a stock throttle cable bracket.
Locke
My '69 (bought used a few months ago) came with a cobbled together bracket which I remade out of nice materials, so...the geometry may not be stock. Thats' the opening disclamer!
I find the cable attaching ball on the Holley is much closer to the fixture on the bracket which holds the carb end of the cable. This results in very little carb opening. In addition, I measured the length the ball moves from closed to WOT; on the Q jet it moves 2 5/16", on the Holley it moves 1 3/16".
Assuming I could get the cable end far enough away from the ball stud on the Holley, I'm guessing it will get alot more throttle for much less pedal movement.
The Holly throttle bracket, part number 20-32, did not work for me as it is designed for the newer square plastic clip on the end of the cable as opposed to the older round end that clamps in place.
Did any of you have simular problems? Maybe I just need to find a stock throttle cable bracket.
Locke
Le Mans Master
Joined: Nov 1999
Posts: 5,768
Likes: 3
From: San Diego CA
Carb was good at WOT and idle.
Burning Brakes
Joined: Oct 2001
Posts: 911
Likes: 5
From: TN
6210's
I modified my 68's air cleaner drop base when I installed the Holley 6210. I removed the vent tube and covered the hole with a freeze plug using silicone sealant to attach it. In 1973 I did not know if I would move the tube back to install the original QJet. Moved the tube to a more rearward position on the air cleaner base and brazed it. Works great for me using the original drop base 68 air cleaner.
Navigator
Joined: May 2004
Posts: 9
Likes: 0
From: N. Smithfield RI
Air cleaner fit
I have a 76 with the holley spreadbore. I am using the complete air cleaner setup from the 78 dual snorkel on it on a Weiand manifold. No problems with clearances. I had the single snorkel one first.
The only modification was to cut the breather tube to the valve cover and extend it using a piece of rubber hose.
This is a manual transmission.
The only modification was to cut the breather tube to the valve cover and extend it using a piece of rubber hose.
This is a manual transmission.
Melting Slicks
Joined: Aug 2005
Posts: 2,683
Likes: 34
From: Working on the car NY
. I tried Getty premium and ended up draining the tank it ran so rich. I think I tried another brand and it did the same thing. Obvioulsy the carb wasn't set up right (I guess). I put a Q Jet on and haven't looked back in 37 years
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Le Mans Master
Joined: Mar 2008
Posts: 5,948
Likes: 72
From: Oxford MA-----You just lost the game!!!!
yes, it goes on and on my friends.
Some people posted on it, not knowing what it was,
and they'll continue posting here forever just because
this is the thread that never ends.............
Keep the shiny side up!
Scott
Racer
Joined: Sep 2000
Posts: 457
Likes: 0
From: Overland Park, KS USA Kansas
Lars......THE Quadrajet Man!!!
This thread never dies.....and one of our very own (Lars) can rebuild and engine test a Quadrajet for a very reasonable fee....I used his services to rebuild my 1974 Quadrajet to keep everything "numbers matching" (for future owners because it makes no difference to this driver), but his expertise and ability along with reasonable fees should be mentioned in all Quadrajet threads. I'll admit that the Quadrajets are far more complicated to rebuild than a Holley, but when you have an experienced mechanic with the proper tools, man do they perform well. Just thought I should mention one of the great contacts we have here on our Forum.
Le Mans Master
Joined: Oct 2010
Posts: 6,936
Likes: 848
From: melbourne florida
2023 C3 of the Year Finalist - Modified
i used the double pumper version on a couple different corvettes one manual one automatic and i liked that carb on both. the fact is no mater what carb you put on a car some adjustment will be needed. i prefer a mechanical secondary.
Tech Contributor
Joined: Aug 1999
Posts: 14,379
Likes: 6,390
From: At my Bar drinking and wrenching in Lafayette Colorado
Racer
Joined: Oct 2008
Posts: 475
Likes: 3
From: Windham NH
Lars did a great job on my Holley Spread bore. I bolted it on and was ready to drive..
