Bassman616

Hello all,
Im new to the page and im hoping some of you can help. I have a 1974 L-82 and i keep running into more and more problems. The main issue right now, is that my dad and i started it in mid-late spring this year and it was running a bit rough, so we had our mechanic come by, and he determined it was the spark plugs and wires and maybe the coil. Turns out the spark plugs were fried, the wires were burned and and pinched between the headers and the frame. So we got all that changed out, still ran really rough. Our mechanic tried adjusting the idle but didnt do much so he suggested it was bad gas. My dad and i drained out the old gas, and got a couple gallons of premium and a gallon or two of Turbo Blue (108 octane) and now it wont hold an idle at all. The last we heard, the mechanic suspected the carb was off in some way or another, yet he hasnt been able to do any more work on it in about a month or so. If anybody has any ideas of what could be going on, or any suggestions of what to check, it would be greatly appreciated

-Troy

caryb78

Have you tried adjusting the idle speed located on driver side of engine at base of carb. on side where the linkage is. You will see the adjustment screw right next to carb. pointing from front to rear. Turn it in a turn or two and see if that makes a difference.

7t9l82

What was the status of the car before you started it, how long had it been sitting before that? Is the firing order correct? What type of carburetor does it have? It may be the carb is gummed up and should be gone through, if so send it to Lars.

Bassman616

I believe that is what our mechanic was adjusting, it didnt seem to make much, if any difference

Bassman616

The car had been sitting since fathers day of last year, it had stalled out due to a bad battery, which have since replaced. The firing order is correct, and the carburetor is a Weber/Edelbrock (online i saw it going by both) 600.

Sand71

Could be the distributor is off...did you remove it as part of your tuning?

Easy Mike

In all of this, you do not mention having tuned the car. Why not do a complete tune up, to include timing.

Revi

Have you tried contacting a local Corvette club? Perhaps one of their members could help you out?

No disrespect to your mechanic, but a lot of "todays" mechanics have no clue when it comes to older cars. My buddy had to have his 78 S/A inspected when he brought it in State. They failed it because there was only one spring in the rear suspension. Obviously the other one had fallen off. Jeesh!

my 76 ray

Is the choke closing? On these old cars you press the gas pedal to the floor one time to set the choke before you start it when the engine is cold. If the choke doesn't close the engine will not idle when it is cold.

dochorsepower

Start with a compression check, that will tell a lot. Make sure everything in the distributor is in good condition. Then there is the possibility of a cam problem, timing chain could have slipped a tooth, or some worn cam lobes. Start with the simple stuff first. One more thing, check the engine electrical ground strap.

Gazehound

I would also look for something as simple as a vacuum hose that fell off or is leaking.

Bassman616

We did not remove it, and we had no problem with it last year

Bassman616

We were having our mechanic go through a tune up bit by bit, but just recently found out that he talked up his skills more than he actually knew. My dad and I would do it, but we're not the most, for lack of a better term "mechanically inclined" lol so are trying to find a reputable mechanic to come help us out

dochorsepower

Forum members may be able to recommend help if we knew your location.

Bassman616

We are located about 20 miles north of Detroit, Mi

Bassman616

My dad and i poured a couple gallons of midgrade into the tank today to dilute the high octane a bit, and it has seemed to help a small bit. It did idle, roughly, for a few seconds upon the initial start up today. But we have gas spraying out of a small tube just to the left of the butterfly (if sitting in the car, its to the left of it). After a dozen or so cranks of the key, it just seemed to backfire a bit as to spray gas out. Should we try diluting the octane a bit more or is there something else we should try? Could it be the points?

Thanks, Troy

Revi

Until you or someone that understands what a proper tune up is, diluting the gas is not accomplishing anything.

You are really just chasing your tail unless you understand the carb, ignition system and vacuum system. You may have a problem with one or all of them. It could be the choke or the idle screws or fuel filter or fuel pump or points or timing or vacuum leak or slipped harmonic balancer or float height or plugged metering rods or a flat lobe on the cam or blah, blah, blah, ........................................ ........

You don't know what you don't know. Find someone that understands these systems, perhaps a local Corvette club member that is willing to help. Trying to diagnose a problem with 100 variables on a forum isn't the easiest way to go about things. Between you and the mechanic who knows how many items have been adjusted correctly or incorrectly.

https://search.yahoo.com/search;_ylt...yfp-t-901&fp=1

LS4 PILOT

When a car gets this old , there are hundreds of major and minor issues .

The plugs wires and plugs were a good start. A new distributor cap and button is called for too.

Did the plug wires GET back on the right cylinders, if they changed wires, that always is a possibility....no matter how many years experience , people screw up.....make sure they are 100 % correct??don't guess ....be sure !

I went behind mechanics found lots of issues. Maybe in all the confusion a vacuum line got pulled off , cut , mis connected....

Your 74 originally came with a points distributor ...is it still a points system or has it been converted to HEI?

If it is still points ...I'd do a tune up next...use new points , set dwell and timing with a timing light. ..

Has the engine been rebuild before?

Vacuum leaks are common with all cars . You need to inspect and replace , or cut and reconnect all junctions . Leaking vacuum can't cause ruff running.

Might want to replace the fuel filter , just for good measure . It's cheap ...but could be gummed up .

the carb ultimately may need an PROFESSIONAL overhaul....few people I d trust to do this . Lars is the one I'd use ...if it gets to that point.

You might take pics of the engine post them here , so guys here can see what you got...somebody might spy a loose wire, vacuum problem , etc.

It's really hard , without seeing exactly what you have.

Pics are the best ......sound video even better

Finally ....I d find a old guy ...somebody retired from a GM dealer who worked on these old style cars everyday . Call your corvette club , get recommendation of a local person who specializes in old motors .

A good old school guy could knock this out in a few minutes.

Unforgiven1

This is the best idea. It is unfortunate but, as an automotive technician, I see it a lot. It is as difficult as it has ever been to find a technician familiar with older, carbureted vehicles. I'm sure some of the members on here can get you on the right track to finding someone competent in your area. You will no doubt benefit from being in the Detroit area!
Best of luck!

TheSkunkWorks

While the interweb - and the CF in particular - can be a great resource, I too concur that you really need someone there on the ground with you who actually understands (remembers?) how to go about tuning a car that doesn't have OBD. And, no, we're not all dead yet.