This is a good argument for, if you're buying heads from somewhere other than a shop known for quality cylinder head prep..... It's probably a good idea to have someone familiar with what you're building to have a look at them before bolting them on.

This set was bought from some interweb seller, and just bolted on.
There has been some porting done, so perhaps the seller made the impression they were a head shop.

They had been run before they came into my shop........ And had already had a problem.

Unfortunately, nobody picked up on this before they got bolted on......

1.88 ex/2.25 int......... Not quite enough room for that combo.
Additionally, they're the wrong length....... About .250 too long, which I'm sure contributed to the severely worn guides. A couple were bell mouthed out to about .009 clearance at the top and bottom.