My doomed 408 build

flyfish said

This was my first thought as well...the springs that come with the Eddy heads are made for flat tappet lifters. They are not made to handle a much heavier roller lifter. Even mild roller cams like what the OP described would need more spring. I would not go back to that builder again....

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There are 2 version of springs that you can buy from Edelbrock on their heads setup OOTB: one set for flat tappet and a different set for rollers. They have different assembly PN's for the 2 different spring sets on a given casting. So it depends on what Edelbrock PN was purchased; that hopefully could be found on the original build list. If they originally were for the flat tappets and the rollers were put in with those springs, then, it might well be some valve float or valvetrain resonances going on now.

Back on page 1 it was said that the shop cleaned and re-assembled the engine for the 2nd go-around. But you just don't know if they did a good job of it. I'd assume at this point that they did not. #8 exhaust lifter is the first lifter that the oil reaches after leaving the pump and filter. This MIGHT make it a bit more likely to catch debris as it comes into the oil gallery; or maybe when the engine is off, any debris in that gallery settles into the back end near the #8 exhaust lifter.

I'd be pulling the oil filter first and cutting it open for examination for debris. BTW, don't use the so-called race filters... they have a much more 'open' media that passes lots bigger particles.