1974 Chevrolet Corvette L-82

**jiveass** · 12-21-2009, 11:30 AM

Originally Posted by 402 Wifey

If you are hearing metal on metal !! Then you might need to rebuild the differential .. My hubby just had to rebuild is whole butt end !! and we herd the same noises .. and what had happened is his yoke had some play in it and was bent .Also his drive chaft bearing had to be pressed !!! lots of money . My advice is do not keep driving on it !!
DO YOU HAVE A STICK SHIFT !! BECAUSE IF THIS IS THE PROBLEM THEN YOU WILL ONLY HEAR THE METAL ON METAL WHEN YOU LET GO OF THE GAS .. AND YOU ARE in a low gear .. BUT WHENYOU GET INTO HIGHER GEARS SAY ON THE FREE WAY !! YOU WILL NOT HEAR IT! very dangerous

it sound like if you were to take a hammer and ding it against a pole or somethin...its not really a clunk...more like "ding"........this car is my daily driver....i have to drive it.

**pajeff02** · 12-21-2009, 11:59 AM

Originally Posted by needls1again

this is kinda scary to me...as i am experiencing strange clunking at times in my 81.....more like a clang....like metal is hitting metal..hmmm

Put a jack under the differential and get the rear tires off the ground -- then grab the tire and see how much slop you have. There should be some play, but not excessive. As to the clunking noise -- it would not surprise me if the exhaust is hitting on the tunnel in the crossmember. Each pipe goes through a hole in the crossmember that supports the transmission. Before I replaced the entire exhaust system, ours had a fairly good "clunk" in it that was a metal on metal sound. Grab your tailpipes (make sure they are cool first) and wobble your exhaust around a bit -- see if that reproduces the sound.

**jiveass** · 12-21-2009, 12:06 PM

Originally Posted by pajeff02

Put a jack under the differential and get the rear tires off the ground -- then grab the tire and see how much slop you have. There should be some play, but not excessive. As to the clunking noise -- it would not surprise me if the exhaust is hitting on the tunnel in the crossmember. Each pipe goes through a hole in the crossmember that supports the transmission. Before I replaced the entire exhaust system, ours had a fairly good "clunk" in it that was a metal on metal sound. Grab your tailpipes (make sure they are cool first) and wobble your exhaust around a bit -- see if that reproduces the sound.

i actually had the exhaust replace from the cat back this weekend...i looked under the car while it was on the lift and all the pipe from the front to the back is outside of the frame, so i dont think that is the issue...although i suspected it before i had exhaust fixed...(on a side note, it does sound damn good now with 2 1/2" pipe with no mufflers)..but i think i may have a bad shock on the drivers rear. maybe the half shaft is hitting something on that side from it sitting too low?

**pajeff02** · 12-21-2009, 12:09 PM

Could also be a lower shock mount that has broke or worked itself loose. Lots of stuff can bang around underneath -- keep looking and I am sure you will find it.

**jiveass** · 12-21-2009, 12:26 PM

Originally Posted by pajeff02

Could also be a lower shock mount that has broke or worked itself loose. Lots of stuff can bang around underneath -- keep looking and I am sure you will find it.

yea the rear setup looks complicated compared to most...guess ill have to lay under it and stare at it for a while to get a concept of how it all works

**jiveass** · 12-21-2009, 12:47 PM

hey jeff you got any pics of the underside of your car? and the engine bay? id like to check that out.

**pajeff02** · 12-21-2009, 12:48 PM

Originally Posted by needls1again

hey jeff you got any pics of the underside of your car? and the engine bay? id like to check that out.

Have to look on the home computer -- I'll see what I have this evening and post it up.

**langss** · 12-21-2009, 01:04 PM

Originally Posted by pajeff02

He had the spindle let loose and he almost lost a wheel -- we were discussing how much fun it is to service the rear wheel bearings in Corvettes.

Thank you for your clarifacation. I only owned that car for three years and it spent most of that time in the air.The "Posi" was another issue as was the Radiator,Steering Control Valve,Emergency Brake Assy,Half Shaft U-joints,Drive Shaft U-joints,Tilt Telescope Steering Colume.The list is almost endless.To me it was lucky that I can do my own work,otherwise the labor alone would have killed me.It was fun,but when the time to dump the "Money Pit" came,I had no regrets.I replaced it with an 84 Z-28 that I still own today.

**pajeff02** · 12-21-2009, 01:10 PM

Originally Posted by langss

Thank you for your clarifacation. I only owned that car for three years and it spent most of that time in the air.The "Posi" was another issue as was the Radiator,Steering Control Valve,Emergency Brake Assy,Half Shaft U-joints,Drive Shaft U-joints,Tilt Telescope Steering Colume.The list is almost endless.To me it was lucky that I can do my own work,otherwise the labor alone would have killed me.It was fun,but when the time to dump the "Money Pit" came,I had no regrets.I replaced it with an 84 Z-28 that I still own today.

^^ Exactly why I replaced EVERYTHING when I did the restoration on ours, so I would not have these issues. Well, at least for a while anyway.

Don't know if it still shows, but "402 Wifey" had posted some nonsense and this is what I was responding to.

**langss** · 12-21-2009, 02:03 PM

Originally Posted by pajeff02

^^ Exactly why I replaced EVERYTHING when I did the restoration on ours, so I would not have these issues. Well, at least for a while anyway.

Don't know if it still shows, but "402 Wifey" had posted some nonsense and this is what I was responding to.

Yes thats what I was thanking you for.If you ever have any questions,feel free to ask,even though you have already gone throught the car,I spent a lot of time on mine and found a few shortcuts that saved me a lot of time and money.Regards.

**pajeff02** · 12-21-2009, 03:00 PM

Here are the only two decent underhood pics that I have. I am fairly new to the whole digital camera thing, so the majority of the restoration pictures are on print film. First pic shows the engine after I pulled the intake back off to powdercoat it. Decided to make it a mix of "new" and "old" as it now has Vortec heads. Second pic is from this spring after the new radiator unexpectedly took a crap on my garage floor. That was not a lot of fun, but it allowed me to clean up a bit more of the overspray from the paint job. I don't have any good pics of the undercarriage I can post.

**jiveass** · 12-22-2009, 12:33 PM

i like the powdercoat...hey so is there a certain header that fits in the c3's or is it just a general longtube header? also is there a way to rebuild the headlight setup or what? mine go up in very slow motion...i suspect a vaccum leak but i checked the hoses and they look ok.

**pajeff02** · 12-22-2009, 12:42 PM

Originally Posted by needls1again

i like the powdercoat...hey so is there a certain header that fits in the c3's or is it just a general longtube header? also is there a way to rebuild the headlight setup or what? mine go up in very slow motion...i suspect a vaccum leak but i checked the hoses and they look ok.

The headers are Dynomax ceramic coated, made to fit the C3 -- I had to slightly clearance the bracket for the shifter interlock on the firewall to get them in from underneath -- other than that, they fit great.

Headlights are a PITA on these cars. Your vacuum source is located on the back of the intake manifold and probably includes a check valve and filter. The most probable leak is at the canisters - there is a rubber boot on the rod that is not too bad to replace. Also check the hoses where they attach to the canisters and to the diverter valves (which are mounted under the front header panel. I have a new switch for ours -- on startup our headlights go up and down all by themselves.

**jiveass** · 12-23-2009, 04:09 AM

one other question...how much power are you makin? and does the stock drivetrain hold up well to a lot of power?

**pajeff02** · 12-23-2009, 04:15 AM

Originally Posted by needls1again

one other question...how much power are you makin? and does the stock drivetrain hold up well to a lot of power?

We did the build ourselves and it's never been on a dyno -- best estimate would be somewhere just north of 300 hp. The weak link is apparently the half shafts, more so in a manual transmission car with sticky tires.

**langss** · 12-23-2009, 05:02 AM

Originally Posted by needls1again

also is there a way to rebuild the headlight setup or what? mine go up in very slow motion...i suspect a vaccum leak but i checked the hoses and they look ok.

Check the little manual switch that's under the steering column.With mine,a previous owner must have used it a lot and it would leak in just one position.So the headlights would go up really slow and retract the same.If you manually left them up on mine,eventually one then the other would retract because of the leak.

**jiveass** · 12-23-2009, 09:29 AM

Originally Posted by langss

Check the little manual switch that's under the steering column.With mine,a previous owner must have used it a lot and it would leak in just one position.So the headlights would go up really slow and retract the same.If you manually left them up on mine,eventually one then the other would retract because of the leak.

i was not aware of this switch...guess im still learning about this car..

jeff- yea the half shafts seem to be whats makin the clang sound im hearing...perhaps some new u-joints in those......i plan on replacing the shocks this weekend....maybe that will tell me more....also i would like to find a few parts at a decent price....anyone know where to find the instrument cluster/radio housing fairly cheap? i have aftermarket radio in mine which i dont mind but id also like to have and uncut origional. also need a driver side t-top...i know those aint cheap for sure....but a tree limb fell on it during the hurricane and cracked it..its leaking....also some goood replacement window motors....center cap for the stock wheel...carpet, door panels ect....my interior isnt bad but id like to switch to black interior..and also looking for stock steering wheel.....damn thats a lot of stuff i want and didnt realize until now.

**pajeff02** · 12-23-2009, 10:39 AM

Originally Posted by needls1again

i was not aware of this switch...guess im still learning about this car..

jeff- yea the half shafts seem to be whats makin the clang sound im hearing...perhaps some new u-joints in those......i plan on replacing the shocks this weekend....maybe that will tell me more....also i would like to find a few parts at a decent price....anyone know where to find the instrument cluster/radio housing fairly cheap? i have aftermarket radio in mine which i dont mind but id also like to have and uncut origional. also need a driver side t-top...i know those aint cheap for sure....but a tree limb fell on it during the hurricane and cracked it..its leaking....also some goood replacement window motors....center cap for the stock wheel...carpet, door panels ect....my interior isnt bad but id like to switch to black interior..and also looking for stock steering wheel.....damn thats a lot of stuff i want and didnt realize until now.

I always forget about that switch too. We lucked out and have a Corvette restoration place and salvage yard about 20 miles from my house -- Gee's Corvettes. The owner has been great to deal with and has always come through for me on whatever I needed. Too funny -- we had a tree branch fall on ours during a storm and it put a good size hole in the top of the right front fender. Took care of that when the car was painted 3-4 years ago.

**langss** · 12-24-2009, 06:25 AM

Originally Posted by pajeff02

^^ Exactly why I replaced EVERYTHING when I did the restoration on ours, so I would not have these issues. Well, at least for a while anyway.

Don't know if it still shows, but "402 Wifey" had posted some nonsense and this is what I was responding to.

I read it on another thread.... I guess she/he had multiple id's, but all her posts have been deleted from this thread....How funny....

**pajeff02** · 08-22-2011, 06:04 PM

Trying to get the idle issues sorted out on the Corvette this week so we can put some miles on her this year. When I started the restoration, the engine was adorned with a Holley Q-jet replacement carburetor. I quickly found that neither a regular Holley or Carter style carb would fit under the stock air cleaner. I really wanted to retain this air cleaner as it is a cowl inducted piece and just looks mean with the seal ring setting in place. Not having any spare Q-jets laying around the garage, I ordered a Jet Stage II from Summit. So far, I have been less than impressed with it. On the run in stand, the engine ran and idled great with a Holley handling the fuel delivery. I switched over to the Jet Q-jet after installing the engine in the car and have had issues with wandering idle, stalling, lean mixtures, and backfiring. Interestingly, the mixture screws really do not seem to do a whole lot for helping matters. We even pulled the intake back off the engine to make sure we did not have a vacuum leak causing issues.

Prior to tonight, I had only removed the top of the carb to check things over. During that tear down, I noticed light shining through the dome next to the primaries and found what appeared to be a gouge in the casting. I epoxied that shut, made some adjustments to the height of the primary metering rods and tried running it last year. Although the engine idled better, it still exhibited signs of being lean and wandering. After removing the carb this evening and taking it about 85% apart, I have found a loose epoxy plug in a well to the side of the primaries and quite a bit of dirt and grime in the base, as pictured. Also, the primary throttle shaft on the passenger side appears to be a bit too loose. I inspected the base and it does not have a bushing kit installed. To say that I am less than impressed with the quality of Jet's rebuilds is an understatement -- I would have been better off starting out with a junkyard carb and building it myself.