Hello,

I have a mildly built 360 in my 69 Valiant with MP electronic ignition. About a year ago, I was driving and the car suddenly backfired badly through the carb and then stalled. Luckily, I was a mile from the house and was able to get it fired again long enough to limp home. The car would idle but had no power and stalled when I released the clutch unless I kept the rpms high. It felt like I had dropped a couple cylinders but the idle sounded fine. As soon as I got in front of my house, it quit. I tried to restart it and it seemed to fire but then immediately cut off. My first instinct was to check all electrical/ignition components, which I have done, but haven't had any luck. I swapped out the cap, rotor, wires, orange box, and finally the distributor. I can get the car to start up and idle, but it still has no power when you release the clutch and backfires through the carb and exhaust. The timing checks out fine when idling and all my grounds are fine as well. When I fired it up today, a bunch of fluffy black material came flying out the tailpipes and the carb caught on fire. Any thoughts on what could be wrong? I am worried it might be a valvetrain issue, but wanted to see if anyone had other ideas.

Thanks for the help!

What kind of carb do you have? I have heard of bad back fires blowing out the power valve in a holley carb. Or it may be possible to blow the cam button out? I had that happen to my 440, not sure if your small block has one. What do you plugs look like?

Others may know more to help you.

i would have had the valve covers off and see that all the rockers and pushrods are in the right place....and that all the rockers go up and down went the engine is cranked...

Any chance it jumped timing? Does your timing mark jump around much at idle? If it jumped a tooth or two, That could explain the backfiring and loss of power? With a timing light, if it jumps around a lot, I'd check that, after verifying the fuel/power valve was still good.
What do your current plugs look like?

My 383 did that after rebuild, Major vacuum leak at Intake manifold, Valley pan wasnt seated right. could be your intake leaking.

Had the same thing happen to our powerwagons 360 years ago. Its cause was a wiped cam lobe.

My vote is jumped timing chain or a wiped lobe?

didnt see what carb, but if its a holley, change out the PV.

next idea is jumped timing chain or wiped cam or bent pushrods????

Head gasket leaking between cylinders??? Seen this often. Compression or leak down test time it sounds like to me.

If you can get it to fire up and idle, forget the timing marks for the moment and just start feeding timing to it and see if it starts to run better. If it does, it is very possible the damper ring slipped on the balancer and the timing is way off.

If the timing doesnt help and you can rule out a massive vacuum leak, it sounds like it has jumped a couple of teeth on the timing chain. They will run, but not well. As others have said, pull the valve covers and check to see if you have punched any pushrods through rockers and see that they are all moving and moving about the same amount.

Well since it happened while you were driving the car and since the motor still runs it has to be narrowed down to just a few items. Most likely something with the valve train as mentioned. Probably a bad timing chain or maybe some bent pushrods. Could also be a bad cam or bad lifters. Might be something inside the distributor that came apart or some cracked sparkplugs or somthing else odd but I'd start with pulling the valve covers.

You didn't mention any engine noise though and typically bent pushrods or punched rocker arms will make a bunch of noise.

Thanks for all of the help. For those who asked, carb is an Edelbrock 750 with elec choke. I pulled the valve covers and plugs and cranked the motor over by hand. All the rockers go up and down and none of the pushrods look bent (but I didn't remove them to check). The #2 and #7 plugs are a bit sooty and all others are clean. The plugs are new, as I thought that could be the problem. I guess from here, I need to do a leakdown test to see if I have a problem with the cam. Does it make sense to focus on the #2 and #7 cylinders? Also, I checked the gasket between the carb and the intake, and for some reason some of the material was missing on the inside of the cutout. Could this be the culprit?

My bet (in order) (1) vac leak (2) new orange box is bad. I would do a compression test as it's easy but I feel that it (the problem) is elsewhere that the vacuum leak induced lean mixture IS being compressed OK.

You might have a plugged up carb. The Edelbrock carbs are sensitive to bad gas. Take the top off the carb and look inside. If you see a bunch of white crud floating around in the bowl then you know you have a plugged up carb. I had the same issue with my pickup truck a few years ago where the carb got clogged up internally and the truck ran really bad. It would start and run a bit but it would blow out black smoke and stall and didn't have any power.

Remove the rockers and check the push rods for #2 & #7 to rule out the push rods being bent or out of the lifters.Shine a light in through the opening in the heads and turn the motor and watch the lobes on those cylinders.If 2 cylinders have black fouled plugs there's a reason,cam lobes,push rods,or if you're running KB107 pistons the top ring gap was too tight and snapped the top off the pistons.Since you've checked the ignition look in those areas.

Thanks for the continued help. I have never seen a "wiped" cam lobe. What should I be looking for?

with the valve covers off, see if you see any noticeable difference in the valve height when they are open. turn the motor over and try an compare the lift on all the valves. may be subtle. maybe be really big (1/4 inch)

If a cam lobe is gone you'll have a lot of excessive play in the rocker.