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I have questions…
have you had the carb off the car looks like you have a conversation plate I have seen people install them upside down also I would check the float level and power valve
Off hand, I'd say it looks like a Holley... Probably of the 600cfm variety. There is a stamping on the airhorn - visible in the 3rd pic down - but the resolution is too low to read it. That stamp will tell you the model number.
Just for discussion, the '67 427/390 engines came with Holley 600cfm carbs and they perform very well with that setup.
From: At my Bar drinking and wrenching in Lafayette Colorado
You took photos of every angle, except a photo of the angle showing the carb list number. What's the list number?
Without knowing anything about the carb, I can tell you that you have severe exhaust gas reversion soot staining up through the carb. This is indicative that your timing is way off. Before doing anything with the carb, you need to fix your timing. E-mail me if you need copies of my papers on how to set up your timing correctly. Remember this: Timing affects the carb. The carb does not affect timing.
Also, that carb, without knowing anything about it, is a little 600 or 650 cfm carb. Way smaller than your engine needs (your stock carb was 750 cfm, which you should consider re-installing). You do not need a smaller carb - complete nonsense. You need a bigger carb with a proper fuel supply and a proper setup.
Lars V8FastCars@msn.com
You took photos of every angle, except a photo of the angle showing the carb list number. What's the list number?
Without knowing anything about the carb, I can tell you that you have severe exhaust gas reversion soot staining up through the carb. This is indicative that your timing is way off. Before doing anything with the carb, you need to fix your timing. E-mail me if you need copies of my papers on how to set up your timing correctly. Remember this: Timing affects the carb. The carb does not affect timing.
Also, that carb, without knowing anything about it, is a little 600 or 650 cfm carb. Way smaller than your engine needs (your stock carb was 750 cfm, which you should consider re-installing). You do not need a smaller carb - complete nonsense. You need a bigger carb with a proper fuel supply and a proper setup.
Lars V8FastCars@msn.com
Sorry, totally new at this, and this vehicle. Never had a carb, never set timing, never had a corvette until last week. Once warm, the car really does cruise nicely.
The PO appeared to have taken great care of most of the items on the car. I’ll email you for timing stuff, and I’ll try to take a picture of the list number - thought I got one with a stamped number but maybe that’s something else.
I have questions…
have you had the carb off the car looks like you have a conversation plate I have seen people install them upside down also I would check the float level and power valve
nah that scares me at the moment, gotta build up confidence before wrenching on anything with fuel lines attached.
I’m seeing L6R1B and for what someone else indicated is likely the more important number,
80457-10 1223.
I started looking up used quadrajets, holy smokes are they spendy. I don’t mind putting it on the wish list but until then I’d like to get this one tuned up and running as nicely as it can.
80457-10 is the Holley model number, it's a 600 CFM carb. It's not to big for a 74 350, as Lars said it's more likely to small. It's an okay replacement for an AFB carb on a 64 327, but not for a 70's Q-Jet. It's also not a spread bore base carb and requires an adapter plate under it to mount on the stock intake, which doesn't help. Do yourself a favor and buy a rebuilt/restored correct Rochester Q-Jet from one of the companies that specializes in rebuilding carbs for collector cars (and not your local parts store).
I can't understand in the first place, why someone would use that carb on a stock intake? If they really wanted a Holley, Holley sells a spread bore replacement for the Q-Jet, that's a direct bolt on. I'd still look for a correct Q-Jet myself, and stay away from the Holley's. You can tune that carb up all you want and it still won't be right carb for your engine.
There is more than one good carb for a Small block Chevy…..no matter what folks say. Holley has been making and selling carbs for many years. And many car owners have successfully used them for years.
OP, any chance that you could get back in touch with the previous owner, and see if he might have the original carb?
oh I’ll ask, pretty sure we covered the topic but couldn’t hurt to see what comes of bringing it up. IIRC, he bought it in 2016 from a small dealer with this already installed. Of all the work he showed me he had completed, carb wasn’t it. But maybe he held on to some things for his 73.
Appreciate the other informative responses as well. Long term, I’d like to get the stock air cleaner set back up, with the factory designed hood insulation so I can pull cool air from the cowl. I just like the idea. I have a friend who has the factory air cleaner (and valve covers) so I’m already partway there. He runs a vintage restoration business so perhaps that’s another path to source a Qjet.
Long term, I’d like to get the stock air cleaner set back up, with the factory designed hood insulation so I can pull cool air from the cowl. I just like the idea. I have a friend who has the factory air cleaner (and valve covers) so I’m already partway there. He runs a vintage restoration business so perhaps that’s another path to source a Qjet.
You're going to have to change the carb before you try using the stock air cleaner, because the spacer under it will raise the carb up to high, causing the stock air cleaner to hit the hood. That's probably why the car has an aftermarket air cleaner on it now.
I’ll email Lars.
Last questions for now, does it harm the motor driving casually at current with the exhaust reversion Lars pointed out?
What is the proper Qjet for a 74 L48 auto? Hoping there’s a range of options that are “close enough.” I’m not trying to be concours correct or race anything, just addressing the issues previously mentioned.
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by Millie74
I started looking up used quadrajets, holy smokes are they spendy.
I have had several customers locate good, used rebuildable Q-Jets over the past month-or-so. One of them paid $45 for a nice Q-Jet, and two of them paid $75. Most good, used, rebuildable Q-Jets sell for under $200. There's a nice used, rebuildable '74 Q-Jet on eBay right now for $49.99 (it took me roughly 90 seconds to find it). If that's "spendy", you're in the wrong hobby... A new Holley spreadbore carb that properly fits your intake manifold, and that would run well, will cost over $700 (closer to $800).
Originally Posted by Millie74
I’ll email Lars.
Last questions for now, does it harm the motor driving casually at current with the exhaust reversion Lars pointed out?
What is the proper Qjet for a 74 L48 auto? Hoping there’s a range of options that are “close enough.” I’m not trying to be concours correct or race anything, just addressing the issues previously mentioned.
Your retarded timing won't damage the engine. It will cause poor fuel economy, poor performance, and elevated engine temperatures.
As for the Q-Jet, you can technically use any Chevy passenger car Q-Jet between 1969 and 1974. However, if you want to have the option/ability to hook up all vacuum hoses and systems, and if you want the throttle cable/lever system to be correct and easily installable on your car, you need to stick with a 1974 Chevy passenger car carb. The throttle lever was revised in 1974 from the design used up through 1973, and the '74 carb has vacuum hose connections unique to that year. There are a lot of those carbs out there in good, rebuildable condition for a very fair price - you just have to look. You can e-mail me for info on what to look for.
Hey Millie, welcome to the forum! It appears you are new to Corvette's, and maybe new to engines with carbs. You'll find lots of very helpful people here. And for Q-jets, timing, etc, Lars is extremely knowledgeable and always helpful to members of the forum.
You're in a hobby that can run up some $, but also but huge smiles on your face. Youtube videos will also help you get comfortable with doing some light wrenching as you gain experience and confidence. If removing the carb/spacer and replacing them with the right stuff intimidates you, just ask this forum for help. I guarantee you'll get the help you need. Nothing more satisfying than figuring out how to do stuff yourself! Best, Paul
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by Millie74
I’m seeing 80457-10.
That's a little 600 cfm 4160-series vacuum secondary carb - it's one of the smallest 4-barrel carbs on the market. Keeping in mind that the stock factory Q-Jet is 750 cfm, it's a big step backwards in terms of potential performance. Additionally, that carb, in its Holley-supplied configuration, has the "black" secondary diaphragm spring in it, which will prevent any operation of your secondaries. With a significant amount of work, you can make that carb run, but the end result, in the "best condition," will be far short of the performance you'll get from a properly set up stock factory Q-Jet. ...And the stock Q-Jet will allow you to use the stock air cleaner assembly for a very nice appearance.
A stock factory Q-Jet will require a bit of mechanical ability and work on your part. Your fuel line to that Holley is a dangerous rubber hose, and should be replaced with the stock, steel fuel line. Installation of the stock line assumes that you have a stock-type fuel pump on the engine, with the fuel outlet in the correct clocking position. You may have as little work to do to make your car run right...
You can make an immediate improvement by hooking up your distributor vacuum advance correctly: You're currently hooked up to ported vacuum, which is aggravating your retarded timing condition. Yank that hose off and hook it up to the manifold vacuum port on the carb and you'll see an instant improvement in idle quality and off-idle throttle response (you'll have to re-set your idle speed and idle mixtures once you do this). Make sure you suck on the hose before you relocate it to assure that your vacuum advance control unit is not ruptured - common problem.
Lars
You're going to have to change the carb before you try using the stock air cleaner, because the spacer under it will raise the carb up to high, causing the stock air cleaner to hit the hood. That's probably why the car has an aftermarket air cleaner on it now.
yep! I’ve felt pretty clueless at times here but figured that would be an issue
Don't let all the nay-sayers here curb your enthusiasm...... sometimes we can be a tough crowd. That carb will work fine on your engine....although not as well as a proper Q-jet. Definitely don't go any smaller....that's bad advise. You could start out by checking the fuel levels in the float bowls....fuel should just barely dribble out when engine is running and checking screw is removed. Also take apart the secondary diaphragm and check to and see what spring is there and to make sure it's in good shape. Those carbs are easily rebuildable, and you just have to watch a few videos to gather the info you need to tackle that.
Not sure of your experience and if your up to the task, but it's not that hard to work on those, you just need to watch for certain things. Get a book on Holley carbs and do some reading you'll learn something.
BTW...Just so you know, Lars is the go to carb guy on the forum and you should listen to his tuning tips. He's more than happy to help out and will freely share his information....just e-mail him.
I have had several customers locate good, used rebuildable Q-Jets over the past month-or-so. One of them paid $45 for a nice Q-Jet, and two of them paid $75. Most good, used, rebuildable Q-Jets sell for under $200. There's a nice used, rebuildable '74 Q-Jet on eBay right now for $49.99 (it took me roughly 90 seconds to find it). If that's "spendy", you're in the wrong hobby... A new Holley spreadbore carb that properly fits your intake manifold, and that would run well, will cost over $700 (closer to $800).
Your retarded timing won't damage the engine. It will cause poor fuel economy, poor performance, and elevated engine temperatures.
As for the Q-Jet, you can technically use any Chevy passenger car Q-Jet between 1969 and 1974. However, if you want to have the option/ability to hook up all vacuum hoses and systems, and if you want the throttle cable/lever system to be correct and easily installable on your car, you need to stick with a 1974 Chevy passenger car carb. The throttle lever was revised in 1974 from the design used up through 1973, and the '74 carb has vacuum hose connections unique to that year. There are a lot of those carbs out there in good, rebuildable condition for a very fair price - you just have to look. You can e-mail me for info on what to look for.
extremely helpful. I did a half assed 30 second search and saw a couple eBay listings for $750. I’ll email you for more guidance.
Originally Posted by Hopper12
Hey Millie, welcome to the forum! It appears you are new to Corvette's, and maybe new to engines with carbs. You'll find lots of very helpful people here. And for Q-jets, timing, etc, Lars is extremely knowledgeable and always helpful to members of the forum.
You're in a hobby that can run up some $, but also but huge smiles on your face. Youtube videos will also help you get comfortable with doing some light wrenching as you gain experience and confidence. If removing the carb/spacer and replacing them with the right stuff intimidates you, just ask this forum for help. I guarantee you'll get the help you need. Nothing more satisfying than figuring out how to do stuff yourself! Best, Paul
if anything, yes, tons of response here. Correct on both accounts, I just got the car last week and it’s a first on both accounts. I’m a quick learner but I have not wrenched on a car much in the last 20 years. Looking forward to getting back into it, but there are a lot of things people assume you know when giving advice that takes me a little longer to figure out. I have a couple friends of family I can lean on if needed. One has restored an early c3 corvette and is a retired mechanic. The other runs a restoration shop but specializes in Fords. Though he’s extended an invitation to check it out, they are a small shop that would rather take on full restoration than just repair or tune up type jobs.
I’m trying to balance enjoying the car as is while the weather is still nice and save some things for when PA breaks out the salt and I need to keep it garaged.
Originally Posted by lars
That's a little 600 cfm 4160-series vacuum secondary carb - it's one of the smallest 4-barrel carbs on the market. Keeping in mind that the stock factory Q-Jet is 750 cfm, it's a big step backwards in terms of potential performance. Additionally, that carb, in its Holley-supplied configuration, has the "black" secondary diaphragm spring in it, which will prevent any operation of your secondaries. With a significant amount of work, you can make that carb run, but the end result, in the "best condition," will be far short of the performance you'll get from a properly set up stock factory Q-Jet.
A stock factory Q-Jet will require a bit of mechanical ability and work on your part. Your fuel line to that Holley is a dangerous rubber hose, and should be replaced with the stock, steel fuel line. Installation of the stock line assumes that you have a stock-type fuel pump on the engine, with the fuel outlet in the correct clocking position. You may have as little work to do to make your car run right...
You can make an immediate improvement by hooking up your distributor vacuum advance correctly: You're currently hooked up to ported vacuum, which is aggravating your retarded timing condition. Yank that hose off and hook it up to the manifold vacuum port on the carb and you'll see an instant improvement in idle quality and off-idle throttle response (you'll have to re-set your idle speed and idle mixtures once you do this). Make sure you suck on the hose before you relocate it to assure that your vacuum advance control unit is not ruptured - common problem.
Lars
can’t wait to suck on a hose. I’ll check over the fuel pump situation, and what clocking position means with that. And I’ll check out getting a steel fuel line.
Once upon a time, I pulled apart my 87 Honda prelude and changed out the fuel rail and injectors. I’m not completely clueless, but I am definitely not a mechanic.
After reading the forum sticky on timing, it’s information overload but theoretically sounds like something I can work through. Going to have to read about idle speed and mixture adjustments.
As for the black secondary spring, if those aren’t opening am I correct in associating that with the issue on WOT, it’s getting more fuel but not enough air. Unless it’s been modified from the factory-supplied setup, as you noted, I can’t look at mine and tell north from south on it.
I do hope I’m not annoying anyone or wasting anyone’s time here. I’m enjoying diving into this.
Name that carburetor
Probably of the 600cfm variety. There is a stamping on the airhorn - visible in the 3rd pic down - but the resolution is too low to read it. That stamp will tell you the model number.
