Well I have the Vette out of Winter Storage and have driven it a couple times. I put her away in a climate controlled garage and had a full tank of fuel from last year along with Heat and a stablizer.

When I start it up it seems to run really rich, has a hard time idleing until its warm and blows a lot of what appears to be unburnt fuel. Its not burning or leaking oil, but seems to have a knock.

When I accelerate hard the exhaust sounds a bit poppy, loud and rattles. Some slight backfiring it noticeable when I stomp on it as well. It seems like there might be a hole in the exhaust or one of the baffles is bad or causing some back pressure?

That or its misfiring, or firing on only 7 cylinders? Anyway, the acceleration is there, seems to run ok otherwise and the knock comes and goes. I'm not sure what it is.

I am replacing my entire exhaust system next week, 2 1/2" true dual to a pair of Magaflows. Once that is done it should eliminate any exhaust issues as a possible problem. Given it sounds like there is a hole somewhere, it is entirely possible that the exhaust is also loose somewhere and clunking or rattling.

Anyway, it was fine when I put her away. She generally runs really well, so this one is new. Not sure how a knock in the engine could have just surfaced, unless last years fuel is bad, or something else.

I know this information is a bit vague, but does anyone have any ideas? Thanks.

 

I would check/clean the plugs, then with the breather off start the car and check to see if the carb is flooding. May have gunk in the jets.

 

What year and what carburetor?
Look out for dirt in the float needle valve.
Take of the air cleaner and look for gasoline pouring out of the carburetor or down the air horn.
And be were careful, if it is gasoline pouring out of the carb needless to say thats a dangerous situation (been there).

 

Never even thought of that. Thanks!!! I've not given it a tune up in a while, would be a good idea to replace the plugs, wires, filters, etc anyway. Thanks!

 

1979
4bbl Quadrajet
Will do. Thanks again!

 

Turns out its the cam. Two bad lobes (worn down)... Crap.

Looks like I have an excuse to rebuild the top half of the motor. Thing that sucks is its nice out now...

 

How do you know it is the cam? If possible is provide us with a sound bite so we can all get an idea what a vehicle with wiped cam lobes sounds like.

 

A second opinion and my mechanic. What it sounds like? It ticks like a **** and runs like crap.

 

Wiped lobes seem to be rampant since the drop in ZDDP last year. Hope all is well with the rest of the motor.

 

So I've heard. Seems its worse amongst MGB/Triumph owners... ( I have an MGB too - newer cam though).

I guess I'm gonna replace the cam with an L82 and use diesel oil or race oil in the future. Live an learn. Should have the car back in no time!!!

 

Just to keep you updated, I just got the Vette back from my mechanic. New Cam, liters, timing chain, balancer, choke pull-off, gaskets, oil, filter, fuel filter, carb gaskets, and boy don't she run like a dream...

Bigger cam too! No knock, no tick... Not only where there worn lobes, the lifters were concave. Balancer was coming apart and rubbing on the timing chain cover. Anyway she runs awesome now!!!