[Cliff R]

Did you drill holes in the air cleaner lids? Not only will that do NOTHING to improve power anyplace it allows butt-loads of unfiltered air into the engine and will destroy it.

Knurling valves guides is a cheap and poor way to tighten up clearances. It was a "quick-fix" decades ago but we all found out that displacing metal and leaving a spiral groove behind reduced surface area and the fix is short lived.

I tried that repair WAY back when I first got into the hobby and it wasn't a few thousand miles before they guides were worn out and the heads had to come back off for full length hardened iron replacement guides.

Over the years bronze guides have become very popular and a good repair provided you use top quality material. The debate has raged on for decades about what to use and no one can agree on any of it. There are many types of bronze guides and folks that chose one type vs another pretty much stand behind their choice when those topics come up for discussion. At this point in time and on this thread pretty much wasting space to cover the options and benefits of each type, then you have to throw the valve material into the equation, etc.

In any case I NEVER knurl valve guides or recommend it. It's just not a good long term repair and more of a cheap "crutch" fix offered by shops to save the customer some money and get them on down the road for a bit....IMHO

As far as the 041 cam and duration, you have to look at how they measured the duration, here are the specs right from the Melling catalog:

SPC-8 INT. 3 BTC 48ABC 231 32 BTC 92 ABC 304 .313 .469 112 HYD

EXH. 54 BBC 6 ATC 240 84 BBC 51 ATC 315 .313 .469 115 HYD

The specs for all the Melling Pontiac cams can be found here:

https://www.melling.com/wp-content/u...ck-294-304.pdf