Help! 78 Vette Engine issue
Thread Starter
Instructor
Joined: Jul 2008
Posts: 167
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Help! 78 Vette Engine issue
Hi all,
I had taken my Vette to a specialty corvette shop back in April for some repairs on wiring in my dash.
After close to 6 months, and picking up the car twice due to sloppy work I finally got my car back.
They repaired and overhauled the carburetor, however my car was running lean when I picked it up. After several instances to double check it, they gave me some BS story about the engine needed new gaskets and that the carb was fine.
When driving it home... the engine started to "pop" under load. At idle its fine, but when accelerating the car does not perform well and there is a popping sound coming from the engine. I contacted the shop... brought it back and they told me it was running lean.... which to their idiocy they admit some error on their part. However, now they state the engine has a flat spot on the cam and will need a new cam, push rods and a valve job. Does this sound right?
Can a carb with the float not adjusted or the air fuel mixture not set properly cause engine problem? Or is it all coincidence and 350 small block engines have failures like this all to common?
Appreciate any advice.
I had taken my Vette to a specialty corvette shop back in April for some repairs on wiring in my dash.
After close to 6 months, and picking up the car twice due to sloppy work I finally got my car back.
They repaired and overhauled the carburetor, however my car was running lean when I picked it up. After several instances to double check it, they gave me some BS story about the engine needed new gaskets and that the carb was fine.
When driving it home... the engine started to "pop" under load. At idle its fine, but when accelerating the car does not perform well and there is a popping sound coming from the engine. I contacted the shop... brought it back and they told me it was running lean.... which to their idiocy they admit some error on their part. However, now they state the engine has a flat spot on the cam and will need a new cam, push rods and a valve job. Does this sound right?
Can a carb with the float not adjusted or the air fuel mixture not set properly cause engine problem? Or is it all coincidence and 350 small block engines have failures like this all to common?
Appreciate any advice.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
do 2nd opinion yourself. pull valve covers. have someone crank engine and watch all 16 rockers. if one is barely moving, they are telling the truth. if not, they are either incompetent or crooks. in neither case do they deserve more of your money. doubtful they would fake it by removing a pushrod, but... if lobe is really wiped, they didn't do it. BUT, it doesn't wipe overnight. a garage is sometimes a whorehouse. go there, pay money, get screwed.
Thread Starter
Instructor
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Thanks. But question is if they incorrectly put the carb on, could that damage the engine if I run it? If I run the car lean, I thought that would destroy the engine. Could the flat spot on the cam be a result of running the car with the carburetor fuel air mixture and float not set properly?
Thread Starter
Instructor
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I just don't know what would cause a flat spot on the cam.
I've driven this car for 12 years, has 75000 miles and baby it.
The only thing that comes to mind for the popping sound and poor engine performance is because they gave me the back back with it running lean.
I've driven this car for 12 years, has 75000 miles and baby it.
The only thing that comes to mind for the popping sound and poor engine performance is because they gave me the back back with it running lean.
Last edited by 78stan; Nov 8, 2017 at 04:24 PM.
Burning Brakes
Joined: May 2013
Posts: 789
Likes: 129
From: Los Banos CA
Thanks. But question is if they incorrectly put the carb on, could that damage the engine if I run it? If I run the car lean, I thought that would destroy the engine. Could the flat spot on the cam be a result of running the car with the carburetor fuel air mixture and float not set properly?
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
Cams die from mileage only. If it is wiped lobe, they didn't do it in any way. If they took pushrod off, or replaced 1 with a bent one? That isn't incompetence. Pull valve covers. Get and replace the carb gasket. Lean at low rpm's and load won't hurt engine. Get it at 5000 full throttle and have it go lean then? You get roasted pistons. That is mainly a boat issue.
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Thread Starter
Instructor
Joined: Jul 2008
Posts: 167
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Very unlikely that running it lean would do any damage to the cam (in fact, I would say almost impossible, unless the lean condition caused it to overheat). Cam lobes do 'go flat', but usually due to just general wear, or other mechanical problems with the engine. My guess would be that they rebuilt the carb incorrectly, or installed something incorrectly. I'd definitely find another shop. If you give your location, someone in your area might be able to give you shop suggestions.
I thought it was the carb too... but the way this car pops under load is crazy. See link here...
Does this sound like a flat spot on the cam?
Racer
Joined: Mar 2012
Posts: 476
Likes: 37
From: Lynnwood WA
I thought it might be simple till I saw the video. Did you demonstrate this to the shop that had the car? Can you tell what part or even side of the engine it is coming from?
You need to find a new shop.
You need to find a new shop.
Last edited by Zorro O; Nov 8, 2017 at 05:49 PM.
Thread Starter
Instructor
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I swear the engine never sounded like that when I took it in. I feel the way the car was given to me with the carb not adjusted properly and running lean did it in.
Racer
Joined: Mar 2012
Posts: 476
Likes: 37
From: Lynnwood WA
It’s hard to tell from the audio on a video but it does sound like a rocker arm or push rod. I would not run it anymore until you pull the valve cover and take a look. Check to see if anything is bent or lose.
Racer
Joined: Mar 2012
Posts: 476
Likes: 37
From: Lynnwood WA
Pull the valve cover before you do anything, check for broken rocker, broken spring, bent or broken push rod, look for debris. If all these seem good pull the plugs and turn the engine over by hand and see if all the rockers are moving up and down the same. If the rattling noise is separate from the other noise it could just be your PCV valve.
Racer
Joined: Mar 2012
Posts: 476
Likes: 37
From: Lynnwood WA
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
Rod knock. Bad rod knock. They took that car and hammered the stuffins out of it. And they will say "Wasn't me!" And you will have no way to prove anything or get a nickel from them. Did you pay with credit card? If so, at least you can get that back...maybe.
Last edited by derekderek; Nov 8, 2017 at 09:23 PM.