Hello everyone !!I have a '69 400 Chevrolet block (377) .030 over, '72 350 crank, lingenfelter .485 custom grind cam, and mid '70's corvette heads that have been completely re-worked with new springs. Motor has a weiand tunnel ram with two Holley 450's, '69 camaro small cap dist with pertonix kit. I got the motor form a friend after he grenaded it at the strip when it was too lean with tune port on top with aluminum heads...he blew number one piston into two pieces. The only difference in my set up, and his, was the use of aluminum heads and tune port on his set up. The motor runs like a scalded ape in my rat rod. Motor had less than 5000 miles on it and was his daily driver/weekend strip car. After my first fire up with new pistons, oil pump etc...I went to adjust the valves...it was totally unadjustable. No bog down even at bottomed out rocker arms...which are stamped steel, not roller. The valve train noise is terrible...sounds like a Mazda b2000 or Plymouth volare. So i changed the lifters...still the same, but I can at least bog the motor down. Where is this noise coming from? Do I need a longer pushrod? I'm running stock 7.8's as did he, but he had Harland sharp rollers. I replaced the lifters with sealed powers from napa. I have had all my fellow Chevrolet racing builders to look and adjust running and off...we are all stumped! I hate driving it because the chatter is terrible at 2000 rpms and criusing in 4th gear. The reason I went with a fairly low compression head is because the thing weights 2000 pounds with me in it and makes plenty of power to make trash out of the 600-16 bias plies. Do I need diff heads? I had the steam holes drilled into these to run them on a 400...is the stud height different on a corvette head? I have adjusted running with a cut out valve cover, oils very well, backed nut off until chatter then tighten til stop and and extra half turn...any ideas out there?
What springs? Post the part number and / or spring rate. Is it a roller? I'm thinking the spring rate is too high and collapsing the stock lifters. Non performance lifters you get your local NAPA are only suitable for stock like lift, stock like springs and stock like duration. There is likely too much duration and spring rate which doesn't give a stock lifter enough time to fill up.