My insurance ran out in February 2020 on my 40. With everything shut down for COVID I decided not to renew and instead do my P/S conversion. When I parked it the recently installed 1972 350 4-bolt main SBC was running perfectly.
Fast forward to now. After reinsuring and getting it back on the road, I noticed it had developed a slight tapping noise under certain conditions at 2000+ rpm. My instincts were that one of the valves was a bit loose.
I’ve now adjusted all the flat tapper hydraulic valves to zero plus 1/4 turn. The tap is gone. When cold it seems to have a bit of a miss. At idle the vacuum gauge has quite a noticeable flicker. It seems to go away under light throttle. As the engine warms up the miss seems to get worse.
When trying to narrow down the issue I replaced all the relatively new plugs. All looked good with a light tan colour except for #7 which was black with possible oil residue.
After a 1/2 hour drive the new plug is also black. I previous found that pulling the plug wires out of the distributor cap made a difference to the idle for all cylinders except for #7.
Any thoughts of what went wrong while it wasn’t being driven? I’ve also added Seafoam to the oil to try and loosen things up.
Motor is out of a ‘72 Chevy pickup that has 72k miles on it. I installed a lower mileage RV cam into it along with the lifters that were with that cam. Also a new timing chain as it was loosing bits of nylon gear.
Could one of the used lifters be failing? Did I loose a cam lobe? What should I check next?
Fast forward to now. After reinsuring and getting it back on the road, I noticed it had developed a slight tapping noise under certain conditions at 2000+ rpm. My instincts were that one of the valves was a bit loose.
I’ve now adjusted all the flat tapper hydraulic valves to zero plus 1/4 turn. The tap is gone. When cold it seems to have a bit of a miss. At idle the vacuum gauge has quite a noticeable flicker. It seems to go away under light throttle. As the engine warms up the miss seems to get worse.
When trying to narrow down the issue I replaced all the relatively new plugs. All looked good with a light tan colour except for #7 which was black with possible oil residue.
After a 1/2 hour drive the new plug is also black. I previous found that pulling the plug wires out of the distributor cap made a difference to the idle for all cylinders except for #7.
Any thoughts of what went wrong while it wasn’t being driven? I’ve also added Seafoam to the oil to try and loosen things up.
Motor is out of a ‘72 Chevy pickup that has 72k miles on it. I installed a lower mileage RV cam into it along with the lifters that were with that cam. Also a new timing chain as it was loosing bits of nylon gear.
Could one of the used lifters be failing? Did I loose a cam lobe? What should I check next?
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