Carb backfire and Timing mark off 79 Chevy 350

[bd]

You won't have to remove a cylinder head, but the intake will need to be removed. 

454 is right.  Even when a lifter is totally collapsed, there's some vertical motion of the pushrod.  No movement of the pushrod translates to a totally flat cam lobe.  There's a good chance the lifters will be difficult to remove due to varnish and subtle mushrooming.  But, rest assured, with some coaxing, they will come out. 

You will need to pull the intake to assess the damage; but anticipate a recam with all new lifters, a timing chain/gear set, break-in oil, a new filter, and related materials.

[jcjoggerst]

454 is right.  Even when a lifter is totally collapsed, there's some vertical motion of the pushrod.  No movement of the pushrod translates to a totally flat cam lobe.  There's a good chance the lifters will be difficult to remove due to varnish and subtle mushrooming.  But, rest assured, with some coaxing, they will come out. 

You will need to pull the intake to assess the damage; but anticipate a recam with all new lifters, a timing chain/gear set, break-in oil, a new filter, and related materials.

Oh that stinks I was hoping from something easier. But thanks guys for all the help. I'll dig in hopefully tomorrow. I'll post results...

[bd]

You'll need to partially strip peripherals from the front of the engine, including the harmonic balancer, in order to recam.  You might as well fix the timing mark issue at the same time. 

[jcjoggerst]

You'll need to partially strip peripherals from the front of the engine, including the harmonic balancer, in order to recam.  You might as well fix the timing mark issue at the same time. 

Oh yeah good idea. I'll definitely do that. Thanks again!

[jcjoggerst]

OK so here's a couple pics of the lifter that wasn't lifting. The bottom is slightly concave, but since my pushrod didn't lift at all, I think it must be a worn cam lobe. I looked down at the cam as I turned the engine with a wrench, it definitely looked worn. So replacing the cam, etc will be my next step.

ALSO, the #8 spark plug smashed! No gap at all. What would cause that?? I can't see anything in the chamber, but I guess there must be something in there maybe a piece of piston.

Oh and I did my own compression test and it's not pretty. The front 4 cylinders are about 100-110 psi, but the back 4 are about 75, and one is 60.   Any ideas what would cause the back four to be different than the front four?? I suspect bad rings all around.

With all this, I'm not sure exactly what I'm going to do with the engine. I just bought this truck for $700 just for fun. So maybe I'll just patch the engine as cheap as possible and resell. I wanted it to be my long term project, but I don't even know if this engine is worth messing with.

[Boone83K10]

if timing mark is at 12 o clock on TDC... could be a later engine than a 79. but it looks like you have larger problems to deal with.

[454Man]

Slap a Lil cam in there and have fun!:-)  maybe change the valve springs to match.

[bake74]

With all this, I'm not sure exactly what I'm going to do with the engine. I just bought this truck for $700 just for fun. So maybe I'll just patch the engine as cheap as possible and resell. I wanted it to be my long term project, but I don't even know if this engine is worth messing with.

     If you wanted a long term project why not rebuild engine or have it rebuilt ( the top end should not cost that much to get redone ), or swap engine.  If you bought it for $700.00, You are not to bad off.
     I do not recall your specific plans for the truck, unless you are not willing to put any money into it.
     If you sell it I hope you would tell potential buyers at least what you know.

[bd]

OK so here's a couple pics of the lifter that wasn't lifting. The bottom is slightly concave, but since my pushrod didn't lift at all, I think it must be a worn cam lobe. I looked down at the cam as I turned the engine with a wrench, it definitely looked worn. So replacing the cam, etc will be my next step.

ALSO, the #8 spark plug smashed! No gap at all. What would cause that?? I can't see anything in the chamber, but I guess there must be something in there maybe a piece of piston.

Oh and I did my own compression test and it's not pretty. The front 4 cylinders are about 100-110 psi, but the back 4 are about 75, and one is 60.   Any ideas what would cause the back four to be different than the front four?? I suspect bad rings all around.

With all this, I'm not sure exactly what I'm going to do with the engine. I just bought this truck for $700 just for fun. So maybe I'll just patch the engine as cheap as possible and resell. I wanted it to be my long term project, but I don't even know if this engine is worth messing with.

That poor motor has been abused!  There's no question that something hammered the plug.  How many miles show on the odometer? 

To check the rings, one-at-a-time, pump ~3 squirts of motor oil into each cylinder and recheck the compression.  If the rings are simply worn, the compression should be considerably greater running the test with oil in the cylinders.  If compression doesn't increase, damage is more severe.

To determine if you have piston damage, either borrow a bore scope, or pull the cylinder head.  But, one way or another you'll need to get a good look at the cylinder wall and piston.  If you manage to procure a bore scope, check all the cylinders.  It's not uncommon for debris to bounce between cylinders through the intake manifold.

Ultimately, I think you may find some cylinder scoring, detonation damage and seized rings.

[Blazin]

It would be making a ticking sound most likely if it was a lifter. I'd say new cam, lifters, and timing chain at the least. Shouldn't have to take the heads off at all.