I picked up a 1974 Corvette yesterday, with the base engine. The guy was in the middle of a paint job, but he decided he couldn't afford it anymore. The odometer says 86k miles, dunno about the motor. The carb is rebuilt and looks clean. I picked it up for a good price.... anyway, it hadn't been started in two months when we went to look at it. it fired up with a wee bit of starting fluid, ran okay, maybe better than okay once it warmed up. I drove it home without any problems.

Fast forward to this afternoon, when my Duster blew a leaf spring mount through the trunk floor (ouch!), so I thought I'd just transfer the plates over to the Corvette.

I hopped into the Vette to start it, and it fired up and died. did it a couple more times, then started to give it some gas to keep it running. It ran like crap. Backfiring repeatedly, even backfired through the carb a couple times. Wouldn't stay running without my foot on the gas pedal. I checked the distributor, and it's tight, and all the plug wires are on tight and routed correctly. I dunno how old the gas is, or what octane. I'm borrowing a timing light to check timing tomorrow, but I'm assuming the timing chain jumped a link. How big of a job is it on a Corvette like this to do that? And am I barking up the right tree here?

Thanks in advance for your help. I really don't want to have both of my muscle cars down at the same time, and I'm new to the world of Corvettes.

Thanks!

 

My initial thought when you say that the timing jumped would be that your timing chain is stretched or there is some other issue with the set. Sounds plausible...especially the backfire through the carb.

However, at this point its not really a scientific fact that anything happened to the timing, because you didnt know what the timing was before. When you put the light on it, you will definitely know if there is an issue presently, but perhaps it was always there and you have a couple of concurrent problems.

I would say definitely put the timing light on it, and watch for an inconsistent reading. Otherwise, turn the motor over by hand and check your valve lash. If you see inconsistencies there, investigate them..bent pushrod, worn lifter etc, although I would think these kind of issues would have been present when you first heard the car run. Pull the distributor cap and check for play in the distributor shaft itsself.

Doing the timing set is going to be like any other sbc, except I would imagine working over these fenders that the job can be a bit of a pain in the ***. Personally, if it were me and I was doing a timing set, Id be inclined to yank the intake and do a cam while I was at it.

 

FWIW: you may have run up against the classic jump timing scenario. Car runs fine; turned off; jumps a tooth or two on the restart.

 

Check the choke too. When cold there should be a 3/8" gap.

 

Umm... I can get about ten degrees play in the rotor. How bad is that?

I'm leaving now to borrow a timing light - be back in a bit. thanks for your help so far!

 

Probably a cam timing gear problem. GM used nylon cam "Quiet Gears" on these cars, that tend to come apart over the years. If you're going through the trouble of pulling the brackets, balancer and front cover for inspection, may as well have have a new timing set, seal and gaskets up front, for a quick swap out. Probably have to drop the oil pan down a bit too.

 

You will also need a dwell meter and will have to check/adjust that before the timing.

 

Sounds okay. The rotor will have a little wiggle room. Rotor and timing set are not directly related. The distributor drives off the rear of the cam. When timing jumps, the cam is not turning in sync with the crank.