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From: At my Bar drinking and wrenching in Lafayette Colorado
Whatever you do, don't buy a "rebuilt" Rochester. E-mail me for my "Commercially Rebuilt Q-Jet Problems" paper to get an understanding of why.
Be aware that you will need to change your intake manifold if you go to the Holley, and you will lose about 15hp versus a good Q-Jet if you go with the little Carter AFB (aka, "Edelbrock Performer").
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by vickv
So Carb on my L48 1977 corvette is basically done.
You'd be hard pressed to find a better carb than your original carb (properly set up and rebuilt). Unless it's not original or badly damaged, your '77 L48 Q-Jet is an outstanding carb that will perform better than anything else you can bolt on. Take a couple of pictures of it and post them up here (or e-mail them to me) and I can give you a good idea of whether or not your existing carb should be saved.
My 2 cents is that the Holley 4175 650 CFM Qjet replacement vacuum secondary carb which has been on my L-82 since 1985 has performed flawlessly with 2 rebuilds by me over those 33 years. The 4175 is a direct replacement for the Qjet, easy to tune both primaries and secondary vacuum springs, super easy to tune and rebuild, zero performance difference to the OEM L-82 Qjet and about the same fuel economy. Not sure why the 4175 is not mentioned more as a replacement for the Qjet as a direct replacement with similar performance but without unnecessary complexity..............
When you email Lars, make sure to ask him for all of his Quadrajet tuning white papers.
I really like that carb because it has APT (adjustable part throttle). If you were to get a wideband air fuel ratio gauge, with a little time, you could really dial that thing in. It allows you to have a very efficient cruising mixture like 14.5 - 15 to 1 and then a wide open throttle mixture of 12.5: with those larger secondaries. For sure keep it and rebuild it.
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by jb78L-82
My 2 cents is that the Holley 4175 650 CFM Qjet replacement vacuum secondary carb which has been on my L-82 since 1985 has performed flawlessly with 2 rebuilds by me over those 33 years. The 4175 is a direct replacement for the Qjet, easy to tune both primaries and secondary vacuum springs, super easy to tune and rebuild, zero performance difference to the OEM L-82 Qjet and about the same fuel economy. Not sure why the 4175 is not mentioned more as a replacement for the Qjet as a direct replacement with similar performance but without unnecessary complexity..............
The 4165 and 4175 Holleys can be set up to run very well. They are a near replacement for the Q-Jet in that they will bolt onto the spread bore intake manifold. However, they do not have the same vacuum ports as a Q-Jet, so attaching all vacuum and vent lines from the Q-Jet to the Holley will prove difficult, unless you want to strip the engine of many emissions and fuel vent lines. Throttle cable and bracket attachment is also not a direct replacement, and the fuel line inlet is slightly shifted from the Q-Jet, making it necessary to "tweak" the stock fuel line a bit. If a few mods and "creative" hose routing does not bother you, the spread bore Holley is a good alternative for a "new" replacement carb. Keep in mind that any new carb will not run perfectly "out of the box." Tuning and setup is required.
The 4165 and 4175 Holleys can be set up to run very well. They are a near replacement for the Q-Jet in that they will bolt onto the spread bore intake manifold. However, they do not have the same vacuum ports as a Q-Jet, so attaching all vacuum and vent lines from the Q-Jet to the Holley will prove difficult, unless you want to strip the engine of many emissions and fuel vent lines. Throttle cable and bracket attachment is also not a direct replacement, and the fuel line inlet is slightly shifted from the Q-Jet, making it necessary to "tweak" the stock fuel line a bit. If a few mods and "creative" hose routing does not bother you, the spread bore Holley is a good alternative for a "new" replacement carb. Keep in mind that any new carb will not run perfectly "out of the box." Tuning and setup is required.
Lars
Hi Lars!
I put my 4175 on my L-82 back in 1985 so it has been a few years BUT as I remember, I did not have any issues with the vacuum hoses that required any more than T fitting to work correctly and the the OEM throttle bracket hooked up perfectly to my 4 speed equipped car..no issues there as well. My only issue was the Fuel line had to be modified slightly to connect to the 4175 versus the Qjet. With my totally stock L-82 the 4175 ran perfectly requiring a primary adjustment to the lean 592 (emissions jet) to a primary 62 jet with the cat removed and true duals as well as the secondary spring kit to the lightest spring to operate the secondaries..all very easy.
I still use this same carb on the rebuilt/upgraded 425+ Gross HP L-82 355 with 10.2 compression, AFR heads, and roller cam with only a primary jet of 68 now which needs to go to a 70 jet with the LTH 1 3/4 on the car now.
Pretty easy to tune and rebuild....
Last edited by jb78L-82; Oct 10, 2018 at 11:23 AM.
I have a 1977 L82 4 speed running a Quad Jet. I live in Houston TX. S&S Performance Carburetors was recommended for a rebuild. Just wondering if anybody has had dealings with them. My carburetor is seems to load up when I start and runs eratic until the temp reaches 180-190. After that it runs great. This car came from Bremeton WA. Thanks for any help.
I think I may bolt on a edlebrock with an adapter plate temporarily while I send my Rochester to my friend Jim Locke to rebuild. Jim is an old school racing mechanic who has done everything from forumla v's to Bonneville salt flats cars. He is doing me a favor since last time I needed to borrow tools at the track I repaid him with shotgun ammo and a round of sporting clays.
Will the edlebrock clear the hood with that adapter plate? Also 1400 or 1406?
You'd be hard pressed to find a better carb than your original carb (properly set up and rebuilt). Unless it's not original or badly damaged, your '77 L48 Q-Jet is an outstanding carb that will perform better than anything else you can bolt on. Take a couple of pictures of it and post them up here (or e-mail them to me) and I can give you a good idea of whether or not your existing carb should be saved.
Lars
pics coming in a few days. Thank you for the offer of your help! Much appreciated.
I sent my Quadrajet to Lars of my 77 Corvette, he rebuilt it, I mounted it, started the car, and it has been problem free for over 13000 miles. Best money you can spend, just send it to Lars.
There are lots of old guys that are good with quadrajets but finding one of them isn't easy and getting them to work on one is another.
You have Lars and he's willing I'd let him do it.
I've had great luck with the Holley spreadbore but I allways used thr double pumper version.with wonderful effect.
Had a few spreadbore Holleys they were reliable as a rock. Eddys are good, too.
Meantime have Lars set yours up. Best overall carb out there is a fine tuned Qjet on the street.
Look up HolleyPerformance on ebay, sometimes they have returns, overstock and remans cheap they stand behind. Other than that donot buy a used carb it aint worth it.
If Lars said to bolt on a Husqvarna leaf blower carb, that's exactly what I would do too. In spite of that, I'll throw this out there as well.
I put an Edelbrock 1411 of my '72 BB, mainly because that model EB has an electric choke, which would solve some choke linkage issues on my car, specifically. Right out of the box, it was lean and ran like total crap. It must have been jetted for Denver, but over a little bit of time, I experimented with different metering rods, jets, and springs, and now, the thing runs like an absolute warhorse. I have never ridden in a carbureted car that runs this close to perfect. I'd love to put a AFR meter on it just to see how close I got, but I probably wouldn't change a thing no matter what it said. No overheat issues (can occur when lean) and no fumes in the garage at all (can occur when rich). All that to say an Edelbrock would be a good choice, but it make take a bit of tuning to get it like you want it. Make sure you pick the model that's right for your CID.
From: At my Bar drinking and wrenching in Lafayette Colorado
Looks like a nice original carb in need of rebuild. It can be set up to run very well. Good luck with the process. If you have guy who knows how to set them up, that's great - let me know if I can assist.
Replacement Carb for 1977 L48?
The 4165 and 4175 Holleys can be set up to run very well. They are a near replacement for the Q-Jet in that they will bolt onto the spread bore intake manifold. However, they do not have the same vacuum ports as a Q-Jet, so attaching all vacuum and vent lines from the Q-Jet to the Holley will prove difficult, unless you want to strip the engine of many emissions and fuel vent lines. Throttle cable and bracket attachment is also not a direct replacement, and the fuel line inlet is slightly shifted from the Q-Jet, making it necessary to "tweak" the stock fuel line a bit. If a few mods and "creative" hose routing does not bother you, the spread bore Holley is a good alternative for a "new" replacement carb. Keep in mind that any new carb will not run perfectly "out of the box." Tuning and setup is required.
