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New Member 1980 C3 Performance issues/ upgrades

Old 05-23-2018, 10:39 AM
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Grant Hollier
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Default New Member 1980 C3 Performance issues/ upgrades

New to the Forum as well as owning a 1980 C3 automatic Shes got 20,000 original miles and in great shape. I'm trying to wrap my head around everything on this site and have searched many things. Ive never worked on cars but It seems reasonable and I'm patient and have time. I'm going to start with some touching up of the interior dash pieces, change bulbs and painting panels etc. The car runs great and with the new battery it starts fine. Is it normal to have to give it some gas to be able to start? I hooked a jump starter pack up and it turns over without the added gas pedal support but with my new battery it usually needs a little gas. Is there a recommended cranking amps for an older car battery? Also the car seems to want to idle real low if I let off and will occasionally kill. Where should my RPMs be at idle speed? She seems to like at least 650/700. When in park its fine, just when in drive at a stop light i tend to worry. Are there any essential updates that you would recommend someone make on a new to them car? The info i do know is that The starter and alternator are both relatively new. Thanks in advance.

Last edited by Grant Hollier; 05-23-2018 at 10:44 AM. Reason: add photo
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Old 05-23-2018, 11:00 AM
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Originally Posted by Grant Hollier View Post
New to the Forum as well as owning a 1980 C3 automatic Shes got 20,000 original miles and in great shape. I'm trying to wrap my head around everything on this site and have searched many things. Ive never worked on cars but It seems reasonable and I'm patient and have time. I'm going to start with some touching up of the interior dash pieces, change bulbs and painting panels etc. The car runs great and with the new battery it starts fine. Is it normal to have to give it some gas to be able to start? I hooked a jump starter pack up and it turns over without the added gas pedal support but with my new battery it usually needs a little gas. Is there a recommended cranking amps for an older car battery? Also the car seems to want to idle real low if I let off and will occasionally kill. Where should my RPMs be at idle speed? She seems to like at least 650/700. When in park its fine, just when in drive at a stop light i tend to worry. Are there any essential updates that you would recommend someone make on a new to them car? The info i do know is that The starter and alternator are both relatively new. Thanks in advance.
First of all, WELCOME!!! I bought my 1980 L48 in 1997 and have enjoyed it ever since. Mine was a 'tired' 96k miler but had exceptional paint. That allowed me to focus on mechanicals and interior. 21 years later, there are FEW bolts or parts not removed/replaced.

Please advise if 305ci (LG4) or 350ci (L48 or L82). May just need a tune-up (cap, rotor, plugs and wires) and a fresh air filter. You can always bump the idle screw a partial turn to see if it will maintain idle.

What is state and condition underhood? Even with 20k miles, plastic connectors and hoses are rotted after 38 years. Vacuum lines can leak and affect idle and off-idle performance. Doc Rebuild sells complete sets (EGR, EFE, Cruise, Headlamp and Thermal sensor). Thermal sensors in your intake manifold can become defective and require replacement.

If you decide to go further:
  1. Get the Shop Manual for your year C3. Use it for the following checks.
  2. Check the timing; both initial and advance. My '80 did not have an adjustable advance so I swapped in an Accel Performance HEI and had advance set for performance. Verify you are maintaining at least stock timing. Most 80's will tolerate up to 10-12 initial advance (turning the distributor counter-clockwise while it is in the engine and running). You will know when it is enough when you start to get pinging under load (turn the distributor clock-wise until it does not ping under load). The initial timing is 6-8 degrees (check the sticker underside of hood). Mine likes 10-12 degrees.
  3. Examine and/or Have your carburetor rebuilt/refreshed. After 38 years, others may have altered the carb to solve other ills and made it worse.

Has the engine/drivetrain been updated/improved with performance parts?

Please report back on what you find/found.

Last edited by TedH; 05-23-2018 at 11:08 AM.
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Old 05-23-2018, 11:46 AM
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Originally Posted by TedH View Post
First of all, WELCOME!!! I bought my 1980 L48 in 1997 and have enjoyed it ever since. Mine was a 'tired' 96k miler but had exceptional paint. That allowed me to focus on mechanicals and interior. 21 years later, there are FEW bolts or parts not removed/replaced.

Please advise if 305ci (LG4) or 350ci (L48 or L82). May just need a tune-up (cap, rotor, plugs and wires) and a fresh air filter. You can always bump the idle screw a partial turn to see if it will maintain idle.

What is state and condition underhood? Even with 20k miles, plastic connectors and hoses are rotted after 38 years. Vacuum lines can leak and affect idle and off-idle performance. Doc Rebuild sells complete sets (EGR, EFE, Cruise, Headlamp and Thermal sensor). Thermal sensors in your intake manifold can become defective and require replacement.

If you decide to go further:
  1. Get the Shop Manual for your year C3. Use it for the following checks.
  2. Check the timing; both initial and advance. My '80 did not have an adjustable advance so I swapped in an Accel Performance HEI and had advance set for performance. Verify you are maintaining at least stock timing. Most 80's will tolerate up to 10-12 initial advance (turning the distributor counter-clockwise while it is in the engine and running). You will know when it is enough when you start to get pinging under load (turn the distributor clock-wise until it does not ping under load). The initial timing is 6-8 degrees (check the sticker underside of hood). Mine likes 10-12 degrees.
  3. Examine and/or Have your carburetor rebuilt/refreshed. After 38 years, others may have altered the carb to solve other ills and made it worse.

Has the engine/drivetrain been updated/improved with performance parts?

Please report back on what you find/found.
Thanks for the reply! just what I was looking for. Ill take some pictures under the hood for you to check out as well as get the other info.
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Old 05-23-2018, 02:43 PM
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Originally Posted by TedH View Post
First of all, WELCOME!!! I bought my 1980 L48 in 1997 and have enjoyed it ever since. Mine was a 'tired' 96k miler but had exceptional paint. That allowed me to focus on mechanicals and interior. 21 years later, there are FEW bolts or parts not removed/replaced.

Please advise if 305ci (LG4) or 350ci (L48 or L82). May just need a tune-up (cap, rotor, plugs and wires) and a fresh air filter. You can always bump the idle screw a partial turn to see if it will maintain idle.

What is state and condition underhood? Even with 20k miles, plastic connectors and hoses are rotted after 38 years. Vacuum lines can leak and affect idle and off-idle performance. Doc Rebuild sells complete sets (EGR, EFE, Cruise, Headlamp and Thermal sensor). Thermal sensors in your intake manifold can become defective and require replacement.

If you decide to go further:
  1. Get the Shop Manual for your year C3. Use it for the following checks.
  2. Check the timing; both initial and advance. My '80 did not have an adjustable advance so I swapped in an Accel Performance HEI and had advance set for performance. Verify you are maintaining at least stock timing. Most 80's will tolerate up to 10-12 initial advance (turning the distributor counter-clockwise while it is in the engine and running). You will know when it is enough when you start to get pinging under load (turn the distributor clock-wise until it does not ping under load). The initial timing is 6-8 degrees (check the sticker underside of hood). Mine likes 10-12 degrees.
  3. Examine and/or Have your carburetor rebuilt/refreshed. After 38 years, others may have altered the carb to solve other ills and made it worse.

Has the engine/drivetrain been updated/improved with performance parts?

Please report back on what you find/found.

Grant,
Are you checking the RPM using the tach. in the car? (a 38yr. old tachometers can easily be off) Idle with an auto. trans. should be 800 RPM. Also check the idle stop solenoid. (I've seen them stick and shut the idle down)
Bob
P.S. Nice looking car.
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Old 05-23-2018, 02:45 PM
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Old 05-23-2018, 02:47 PM
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Originally Posted by Pa'svette View Post

Grant,
Are you checking the RPM using the tach. in the car? (a 38yr. old tachometers can easily be off) Idle with an auto. trans. should be 800 RPM. Also check the idle stop solenoid. (I've seen them stick and shut the idle down)
Bob
P.S. Nice looking car.
how else would I check RPMs? And where is the isle stop solenoid located?
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Old 05-23-2018, 03:04 PM
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I bought my '80 new and still have it. It's an L82 automatic. Out of the dealership it always idled low when cold. I used to have have to keep a little pressure on the gas while holding the brake at stop lights to keep it from stalling. Once it warmed up it was OK. I tolerated it for several years. Finally figured out that it needed a little adjustment on the cold idle screw on linkage on the passenger side of the car. That said, I see there is a lot of aftermarket stuff on the engine including the carb. I never worked with an Edelbrock so I'm not certain of the locations of its adjustments, but I assume they're in similar locations. But if you do adjust something, write down how much adjustment you put in (e.g. 1/2 turn CW). It's easy to tinker with this a little and that a little and suddenly things are worse and you don't know how you got there.

Concerning the RPM, 600/700 RPM warmed up, in gear, with the brake held is pretty typical. If it's warmed up and it still seems like it might quite, the base idle can be adjusted up a little for now. But as others have noted there are a lot of things which can cause a poor idle on a 38 year old car. It can be an adventure.
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Old 05-23-2018, 03:12 PM
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Default l48

Itís the l48 engine by the way.
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Old 05-23-2018, 03:24 PM
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how else would I check RPMs? And where is the isle stop solenoid located?
[/left][/QUOTE]

Just saw your pictures. Since your carb. is not stock it may not have a stop solenoid, but if it does it would be left side of the carb. Any mechanic should have a portable tach. or a digital timing light with a tach. Some parts stores may loan you one.
Bob
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Old 05-23-2018, 07:55 PM
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Welcome aboard! A member of this forum, Lars Grimsrud, wrote an ex ellent, easy to understand paper about timing. I'm not in front of my computer but found a link to it - and several other good articles.

http://www.corvette-restoration.com/how-to-articles/

The specific one i am referring is the Timing for Peak Performance.

I followed his write-up and it really helped wake up my 78.

Enjoy the club!
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Old 05-23-2018, 09:38 PM
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Originally Posted by Matt81 View Post
Welcome aboard! A member of this forum, Lars Grimsrud, wrote an ex ellent, easy to understand paper about timing. I'm not in front of my computer but found a link to it - and several other good articles.

http://www.corvette-restoration.com/how-to-articles/

The specific one i am referring is the Timing for Peak Performance.

I followed his write-up and it really helped wake up my 78.

Enjoy the club!
Thanks. Yíall are all very helpful.
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Old 05-24-2018, 09:26 AM
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Originally Posted by Grant Hollier View Post
...Itís the l48 engine by the way...
Or was when it left St. Louis. The engine code 8 in the VIN confirms the L-48. Have you checked the block stamps?

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Old 05-24-2018, 09:44 AM
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Originally Posted by Easy Mike View Post
Or was when it left St. Louis. The engine code 8 in the VIN confirms the L-48. Have you checked the block stamps?

I figured this with the 8 in the VIN. Where would I find the block stamps?

My aunt was the original and only owner before me and I seriously doubt she swapped the engine. But it is possible I suppose.
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Old 05-25-2018, 03:59 AM
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Correct cold starting of an GM carbed engine was to step on accel pedal 1 and 1/2 times to start engine. The fast idle cam should hold idle at 1400rpm until engine warms up, a quick jab at accel pedal releases the fast idle linkage and allows engine rpm to drop to normal idle rpm. Being a 1980 chances are it has A/C and originally had an idle solenoid, yours having an Edelbrock carb most likely is missing the solenoid but still needs to run at the OEM specified rpm which should be on the emission label under the hood. The purpose of the solenoid was to hold the rpm up higher than the throttle stop, when the key was turned to off the solenoid lost voltage and the linkage dropped to the idle stop so there would be no engine run on. [dieseling]. T

RUBBER FUEL LINES GOTTA GO BYE, BYE

Last edited by terrys6t8roadster; 05-25-2018 at 04:02 AM.
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Old 05-25-2018, 10:42 AM
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Originally Posted by terrys6t8roadster View Post
Correct cold starting of an GM carbed engine was to step on accel pedal 1 and 1/2 times to start engine. The fast idle cam should hold idle at 1400rpm until engine warms up, a quick jab at accel pedal releases the fast idle linkage and allows engine rpm to drop to normal idle rpm. Being a 1980 chances are it has A/C and originally had an idle solenoid, yours having an Edelbrock carb most likely is missing the solenoid but still needs to run at the OEM specified rpm which should be on the emission label under the hood. The purpose of the solenoid was to hold the rpm up higher than the throttle stop, when the key was turned to off the solenoid lost voltage and the linkage dropped to the idle stop so there would be no engine run on. [dieseling]. T

RUBBER FUEL LINES GOTTA GO BYE, BYE
Great explanation even to someone that knows zero about this car. What would I replace the rubber fuel lines with? Im trying to start out doing small things like that.
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Old 05-25-2018, 10:47 AM
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Originally Posted by Grant Hollier View Post


I figured this with the 8 in the VIN. Where would I find the block stamps?

My aunt was the original and only owner before me and I seriously doubt she swapped the engine. But it is possible I suppose.
The pad stamps are on the flat surface of the engine block, just in front of the passenger side head. The machined surface the head is bolted to, extends ahead about 3/4in past the front end of the head. The engine code and a partial vin number are stamped into it.

Last edited by DB Cooper; 05-25-2018 at 10:49 AM.
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Old 05-25-2018, 11:00 AM
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Originally Posted by Grant Hollier View Post


Great explanation even to someone that knows zero about this car. What would I replace the rubber fuel lines with? Im trying to start out doing small things like that.
I would see about having a metal fuel line fabricated. If you were running the q-jet, it would be an item you could just order. However, the Performer carb inlet position is different. An alternative could be to purchase an original fuel line and splice/adapt a short run of hose and in-line filter at the carb into a shortened OEM fuel line. Long runs of hose are not recommended (ie. length between pump and carb).

Just a thought... I may have 1-2 spare fuel lines that I removed from my car after the flared end at carb inlet split. They were good fuel lines otherwise and since that end would be cut off to add the short length of hose and in-line filter, one would be perfect for your use. Let me know if interested and I can get a shipping estimate to ship one to you (you pay just the shipping as I have the box it arrived in...). I tend to save most of the parts I use/remove but have parted with some of my stuff over the years as I tend to run out of shelf space.

Let me know if you are interested.

Last edited by TedH; 05-25-2018 at 11:59 AM.
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Old 05-25-2018, 11:18 AM
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Bring it over, I have all the stuff to make up a proper fuel line. You bring the beer. T
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Old 05-25-2018, 02:04 PM
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Beautiful 80, welcome to the forum.
Looking at your engine pictures, I would make sure the Edelbrock carb is the correct unit for your 80 L48 and ask your Aunt if she has the documentation for it and any other equipment added to the engine, like a camshaft replacement etc. If the carb has been on the engine for a while it might be in need of a rebuild. I also see there have been a number of vacuum lines and smog equipment removed so I would also look to see if everything has been terminated properly and if the vacuum advance to the HEI distributor is connected to a proper port.
The rubber fuel line needs to go.
Another safety concern on low mileage classics is the tires.
Check the manufacturers date stamp on the side wall to determine how old the tires are.
Anything over 5 to 6 years should be replaced even if the tread is in excellent shape.
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