Ouch - I think I need a rebuild

[klgray]

Earlier I posted about my engine making a knocking sound. I think I may have munched a cylinder. I'm depressed. I've owned my vette for 2 years, and now I can't drive it - its summer in Alaska, and our corvette driving season is really short.

Can you give me some input on how difficult a rebuild is to accomplish? How much time it takes, and also about some idea of the cost. Is it easier/cheaper/smarter to buy a crate motor and start over?

Any advice would be helpful! Thanks for the help.

 

[6880 Mike]

Do you have a computer scanner? First thing to do is to determine exactly what has happened. You may need a rebuild; you may not. Set up the scanner and see what error codes are stored in the computer.

 

[Vettehead Mikey]

What basic investigation and troubleshooting have you done? Could be a 5 minute no cost adjustment or a new crate engine plus labour. Or anywhere in between.

 

[klgray]

Troubleshooting

Hi 6880Mike and Vettehead Mikey

I don't have a scanner, though as I recall the 81 ODB plug is a bit strange - can you buy one at Shucks? I'm happy to buy one if so.

Basic troubleshooting: Listened with coolant hose to isolate the cylinder "knocking" at rear passenger side of engine. Loss of power on startup with hesitation, no smoking though. Knocking sound follows motor RPMs. Had a friend who knows motors listen to it, and he's not sure if it is a lifter issue or something more serious.

Thanks for the help so far!

 

[Dunzvett81]

Well, I think you just desrcibed a bad cam with worn lobes. If that is the original it wouldn't surprise me. GM had a lot of trouble with cams in the early 80's. I repalced mine 2 years ago. It had the exact symptoms as you describe. The lobes were worn so bad that one cylinder was just along for the ride. I bet you dollars to donuts that is your problem. It is somewhat labour intensive (especially if you do it yourself) but well worth it. When I did mine I repalced the cam, lifters, springs, harmonic balancer, timing chain and a few other components. a lot easier to replace these things when you have it torn down. It now runs very strong, lots of power (well at least for a stock 81!!) no hesitation etc... Mine cost about $500.00 if I had of taken it to a shop would be looking at about $1500 - $1800. I thought about a crate motor, which would be awesome - more hp but this was about all the purse strings could afford at the time.

 

[6880 Mike]

Check valve adjustment.

 

[LannyL81]

Take the valve cover off that side and check rocker arms. You could have a rocker stud that has pulled out of the head.
Easy fix...just not permenent....hammer back in...but if it came out once, it will come out again...but quicker.
If you have the original stock heads....throw them away and get a decent set, either GM or after market ones.

 

[klgray]

Looks like it was the camshaft

Took the car in to an old hot-rodder - took the valve covers off, and cranked it over - the rockers on Pistion #8 didn't move. Took the crankshaft out and the lobe is completely gone. Looks like the person before me tightened down the valves too far. About 46,000 miles on the car.

 

[KANE]

Took the car in to an old hot-rodder - took the valve covers off, and cranked it over - the rockers on Pistion #8 didn't move. Took the crankshaft out and the lobe is completely gone. Looks like the person before me tightened down the valves too far. About 46,000 miles on the car.

Sounds like you are at a crossroads.;squint:

Will you go OEM rebuild or custom?


Either way- keep us posted!

 

[black_81_vette]

You can swap cams but dont go crazy with the lift and duration.Some thing with around 260 deg of duration would be good with say 450 lift.Any more than that and it will hurt power with the engine being stock otherwise.Over the winter you could to a complete top end swap with smaller chamber heads add headers ect and have a decent running car for what you would pay to have had a stock long block bought for it and still make more power. Its easy to do it on a budget just shop smart buy good used heads a intake and whatever else you can find cheap. You dont have to spend a kings ransom to have a strong car if you use your head.

 

[klgray]

I'm back

Well - I had a new cam installed, carb cleaned up/rebuilt, new plugs, new front brake calipers, and general clean up done to the motor. Now it runs beautifully - I wonder how long that cam had been going out?

Fun to drive again - only thing is - in Alaska, I've probably only got another month to drive it!

Thanks for everyone's help/suggestions.