1978 L48 carb/intake help
Thread Starter
4th Gear
Joined: Jul 2015
Posts: 4
Likes: 0
1978 L48 carb/intake help
Hello and this is my first post. This is the first Chevy I've owned and I'm not familiar with them. I found this corvette and fell in love when I drove it. It has 100k miles on it and is in excellent shape. They guy I got it from had it since 79 and kept it up. Everything except the cruise works as it should but in the past 10yrs it has sat covered in his garage due to his age. I have had it a month and love driving it. What a blast! It has true dual exhaust and as far as I can tell it doesn't have smog equipment on it. It has everything else stock. I want to replace the intake, carb and air cleaner right now and then this winter I'm going to pull the engine to reseal it, replace the timing chain, gears, etc. I do not plan on building the engine up. I just want to update those few items and drive the snot out of it.
What intake, carb and air cleaner can I buy and just bolt on this thing? I have looked at advances Website and they several in stock but I want to make sure I get something that works and that isn't overkill. I just want a nice daily driver.
Thanks in advance!
What intake, carb and air cleaner can I buy and just bolt on this thing? I have looked at advances Website and they several in stock but I want to make sure I get something that works and that isn't overkill. I just want a nice daily driver.
Thanks in advance!
Melting Slicks
Joined: Jun 2011
Posts: 3,116
Likes: 598
Hello and this is my first post. This is the first Chevy I've owned and I'm not familiar with them. I found this corvette and fell in love when I drove it. It has 100k miles on it and is in excellent shape. They guy I got it from had it since 79 and kept it up. Everything except the cruise works as it should but in the past 10yrs it has sat covered in his garage due to his age. I have had it a month and love driving it. What a blast! It has true dual exhaust and as far as I can tell it doesn't have smog equipment on it. It has everything else stock. I want to replace the intake, carb and air cleaner right now and then this winter I'm going to pull the engine to reseal it, replace the timing chain, gears, etc. I do not plan on building the engine up. I just want to update those few items and drive the snot out of it.
What intake, carb and air cleaner can I buy and just bolt on this thing? I have looked at advances Website and they several in stock but I want to make sure I get something that works and that isn't overkill. I just want a nice daily driver.
Thanks in advance!
What intake, carb and air cleaner can I buy and just bolt on this thing? I have looked at advances Website and they several in stock but I want to make sure I get something that works and that isn't overkill. I just want a nice daily driver.
Thanks in advance!
Drifting
Joined: Dec 2004
Posts: 1,714
Likes: 42
From: Austin Texas
Hey Fred!
Welcome to the forum. I guess I am curious why you are wanting to replace your carb and intake also. I have the same era Quadrajet on my car and love it.
You will get a lot of opinions on this but unless it is mechanically damaged and can not be rebuilt, an original Qjet is a desirable street carb and yours should have the APT (adjustable part throttle) screw adjustment. This means you can tune it to be a gas sipper while crusing around town and then when you punch it you get a roar of power.
Two names to get to know. Lars Grimsrud and Cliff Ruggles.
Do a search here for more info. Lars will email you his white paper for a diy project or he may even be able to rebuild it for you. Cliff has a book out on Amazon and rebuilds them also.
Good luck either way.
Best regards,
John
Welcome to the forum. I guess I am curious why you are wanting to replace your carb and intake also. I have the same era Quadrajet on my car and love it.
You will get a lot of opinions on this but unless it is mechanically damaged and can not be rebuilt, an original Qjet is a desirable street carb and yours should have the APT (adjustable part throttle) screw adjustment. This means you can tune it to be a gas sipper while crusing around town and then when you punch it you get a roar of power.
Two names to get to know. Lars Grimsrud and Cliff Ruggles.
Do a search here for more info. Lars will email you his white paper for a diy project or he may even be able to rebuild it for you. Cliff has a book out on Amazon and rebuilds them also.
Good luck either way.
Best regards,
John
Instructor
Joined: Jul 2015
Posts: 140
Likes: 7
From: Indiana
Howdy Fred.
I have a 76 that I just picked up a few weeks ago. One of the previous owners decided to replace the intake/carb on my vette. They used Edelbrock for both. Performer Intake and a 1406 Carb.
What has it got me? Well I had to fix a heat soak problem by putting in an insulator gasket (only a day or two worth of testing this fix so far but looks promising). I've also got a really cool clearance problem so I have a TINY air filter. Stock is what 3 inches? Mine is about 1 1/4 inch.
Now I'm resolving the issues with the throttle cable bracket that needs to be a lowered model in order to get a drop base air cleaner housing to fit.
With all of that in mind, will the parts look pretty when they are cleaned up? Yup, they sure do/will. However, I'm going to have to side with the other's opinions so far, if it's not broke and you aren't planning to re cam it, you might just want to clean up what you're working with instead of creating a domino effect issue that I get to clean up.
Well, that or watch my threads as I start them so you're ahead of the game and know what all to look forward to, ha!.
Welcome, and good luck!!
Nick.
I have a 76 that I just picked up a few weeks ago. One of the previous owners decided to replace the intake/carb on my vette. They used Edelbrock for both. Performer Intake and a 1406 Carb.
What has it got me? Well I had to fix a heat soak problem by putting in an insulator gasket (only a day or two worth of testing this fix so far but looks promising). I've also got a really cool clearance problem so I have a TINY air filter. Stock is what 3 inches? Mine is about 1 1/4 inch.
Now I'm resolving the issues with the throttle cable bracket that needs to be a lowered model in order to get a drop base air cleaner housing to fit.
With all of that in mind, will the parts look pretty when they are cleaned up? Yup, they sure do/will. However, I'm going to have to side with the other's opinions so far, if it's not broke and you aren't planning to re cam it, you might just want to clean up what you're working with instead of creating a domino effect issue that I get to clean up.
Well, that or watch my threads as I start them so you're ahead of the game and know what all to look forward to, ha!.
Welcome, and good luck!!
Nick.
Pro
Joined: Oct 2009
Posts: 664
Likes: 89
From: Marysville Ohio
How is the car running? If you don't have issues with the carb, I would agree with the others - most cost-effective approach for your goals are to clean up what you have - less overall work and cost.
Even if you have carb issues, I would look into a rebuild first. Lars and Cliff are both good, but also look into prices. A $400 rebuild vs a new carb is a factor to consider.
I also hear that the Chris's Carb Shop in Dayton is good (recommended to me by a local C2 owner).
A plus with keeping the QJet (aside from it is a great piece of hardware when properly calibrated) is that you can run your stock fuel lines with no hassle/modification. Most other carbs will require a bit of work to plumb them.
The only caveat I'll throw in is that modern fuel may boil easier than 70's era gas, so either a heat shield or return line might be helpful if you have hard starts immediately after driving on hot days - But I find that also seems to depend on the car. It your underhood heat is relatively low, it may never be an issue.
Even if you have carb issues, I would look into a rebuild first. Lars and Cliff are both good, but also look into prices. A $400 rebuild vs a new carb is a factor to consider.
I also hear that the Chris's Carb Shop in Dayton is good (recommended to me by a local C2 owner).
A plus with keeping the QJet (aside from it is a great piece of hardware when properly calibrated) is that you can run your stock fuel lines with no hassle/modification. Most other carbs will require a bit of work to plumb them.
The only caveat I'll throw in is that modern fuel may boil easier than 70's era gas, so either a heat shield or return line might be helpful if you have hard starts immediately after driving on hot days - But I find that also seems to depend on the car. It your underhood heat is relatively low, it may never be an issue.
Thread Starter
4th Gear
Joined: Jul 2015
Posts: 4
Likes: 0
Thanks guys. I will try the rebuild in the q-jet first. It is hard to start cold and has a low speed hesitation until the car gets to operating temp. The mid range is great and she wants to bog down/starve for fuel at 4500rpms.
Thread Starter
4th Gear
Joined: Jul 2015
Posts: 4
Likes: 0
No I didn't. The man started the vehicle every week and let it run and took it once a year to have it serviced. I tuned it up and changed the filters but did not pull the card, I added sea foam to the carb and tank.
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Instructor
Joined: Jul 2015
Posts: 140
Likes: 7
From: Indiana
I don't know how adding seafoam would compare to taking apart and cleaning. Have you made it through your full take of treated fuel?
Starting it up is good, but does nothing for the secondaries. And if it was a slow easy drive to get it serviced, that didn't touch them either. Now I don't know what was involved with the servicing that happened but I will tell you this, everything you have described as your issue all sounds like a dirty carb to me. So will a new carb/intake fix it, yup, sure will. But a little time and patience cleaning will save you **** loads of money and likely net you the same end result.
I'm new to vette's and honestly, new to old school carbs/etc that go along with them. Someone much wiser than I should be along shortly to provide you with some better answers/options.
Starting it up is good, but does nothing for the secondaries. And if it was a slow easy drive to get it serviced, that didn't touch them either. Now I don't know what was involved with the servicing that happened but I will tell you this, everything you have described as your issue all sounds like a dirty carb to me. So will a new carb/intake fix it, yup, sure will. But a little time and patience cleaning will save you **** loads of money and likely net you the same end result.
I'm new to vette's and honestly, new to old school carbs/etc that go along with them. Someone much wiser than I should be along shortly to provide you with some better answers/options.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
FWIW, Lars's rebuild prices are far more modest than $400, IIRC. If you're still running the OE intake manifold, your only options are another Q-Jet or a spreadbore Holley. I have an intake that supports spread and squarebore patterns but I'm happy w/ my Q-Jet. It does "OK". 
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Make sure the accelerator pump and power piston move smoothly in their bores. The power piston bore can be smoothed up with a .223 rifle brush if it doesn't move well. I haven't done an accelerator pump well yet, but I'm told you can use a brake piston hone for this.
Pro
Joined: Oct 2009
Posts: 664
Likes: 89
From: Marysville Ohio
FWIW, Lars's rebuild prices are far more modest than $400, IIRC. If you're still running the OE intake manifold, your only options are another Q-Jet or a spreadbore Holley. I have an intake that supports spread and squarebore patterns but I'm happy w/ my Q-Jet. It does "OK".