The header may be a good place for a MIG weld? Now you've got me motivated to reassemble the truck sitting in the pole shed with the 327 sitting under my work bench and the turbo 350 trans in the shop.
Why is this a topic if you need to pass inspection? I don't even think you can run a Weber DGV and pass. Unless you re-license the truck as a '74?
There is an optimum length for header primary tubes. If you go too long or too short, performance will fall off. I didn't realize how critical header design is until I bought the software and learned how to measure an individual pulse volume. You want a header tube that can hold 4, 8, 16, or 32 pulses. Collectors go at one of those margins. Dual exhaust would sound like burrito ass.
There's a single truck here for sale in MN - a '73 rustbucket listed for $1300. From my viewpoint, its a good deal even with a bad motor. Between the nice dash, the wheels, and the weber someone put a fair amount of time and money into this thing and kept good care of it.
"Will have" scored the piston, likely won't have touched the cylinder walls, definitely bent the valve, definitely beat up the head. The piston may be fine, but the head is going to get expensive to repair. Likely welding to get a seat to take after it released then pounded against the head every time the valve opened and closed. You'll need someone who can weld aluminum AND has a Serdi head bench to cut the head for a new seat. Valves are cheap.
A valve seat won't make it past the installed valve, until the head breaks off of the stem. That looks more like someone let debris get down the carb throat. Either way, the piston and cylinder wall will likely be pretty beat up - not to mention the combustion chamber, valves, seats, etc... Focus on pulling the head to make repairs.
If you want to see what's wrong, lower the piston in the cylinder around an inch and take a look.
620 with L20b. Still 2 liter displacement, no boost. Not stock however. .600" lift cam, 300+ duration, dual Weber DCOE 50's. 110.7 on the Bonneville slat flats with tons of wheel spin at 8100 rpm in 4th gear. The tach indicated the truck should have been going 151 if we could hook up. Going for 130 next year.
In an earlier life, 145+ in an Eagle Talon AWD turbo. The needle went past the gauge at 140 and out of sight at 145+.
Degree wheels are one of the most important engine building tools!!! Agreed. Checking to see if a notch lines up in a hole is silly. They're all untrustworthy reference points - especially on a motor you know has been apart prior to your service. I have 4 different cam pulleys in a bin here that are all supposed to be the same part number...???
Its true. Look at aftermarket offerings and they all share the same part numbers, which is good. It allows us 4 cylinder guys to get performance goodies like the Z guys use. The only problem I found was that the adjustable (8 hole) cam sprocket didn't have a single usable setting that worked in my race motor. I had to go nearly to the far end of adjustment on an adjustable cam sprocket, but again - it was designed for the 6 cylinder motors, so I'm grateful they are shared parts.
You will need to install some of the nuts and washers as you set the head in place, if you mount the cam to the head prior to head installation. Not a big deal - a little trickier than using stock bolts. A LOT more time consuming.