most people when it,s right they say nothing but when it,s wrong they tell the world.are they preventing a problem,who is to say it was a problem?do you get my drift?

im in.

So what's a common run-out on valve seats on a box set of heads? As I said, my Edelbrocks had .009 out of round on just the one that we checked, but I'm curious to what others find.

We bought (4) AFR 325 heads about 6 years ago for a pair of 572 builds that after 30 hours had running issues on the starboard engine. Bleed down's were great on 3 of the 4 engine banks but 1 head showed high bleed #'s. We tore that engine down and found that all 4 exhaust seats were loose and had worked their way up into the head. We shipped all the heads back to AFR for new seats and their full CNC program with a final message from Tony Mamo. Those heads have been great since. We never did find out why the exhaust seats on the 1 head had issues and the other 3 did not but I do not think a teardown when new would have caught the seat problem unless they fell out when the valves were removed. We currently have 4 new AFR heads slated for builds that will be taken apart and checked before installing because of recent threads.

Okay, here are several stand outs - not all of them manufacturer faults:

Pair of Brodix heads. One head had 2 cylinders hand finished combustion chambers, and some port work. Other 2 cyl pairing did not. Heads where ordered as cast.

Canfield BBC screw in casting plugs leaked. Wheren't reusable when takin out. Same heads had springs I wasn't comfortable with when I tested them.
This is quite normal, but worth mentioning for those who want to bolt on and go, some of the pushrods rubbed hard against the head, so those had to be ground a litttle larger.

Brand New Factory small block chevy cast iron head had no spark plug holes drilled and tapped. This was on a brand new GM Longblock. I picked it up at a local GM dealer / GMPP dealer, so this was not an imposter GM crate engine. Doh !

Bowtie small block head leaked water. Indy cylinder head leaked water.

$6000 set of small block Chevy Bowtie aluminum heads came in UPS in beat up box. Rocker studs/valve springs where facing deck surface of other head, with no protection in between. The 1 heads deck/comb chambers where f*ked up bad ! UPS denied claim. Head porter denied issues as he said they where shipped in seperate boxes, but both put into one bigger box. These where not in separate boxes. Total schit show - one off heads you could not just order another set and have that week. Took about 2 yrs, but UPS finally found out (or maybe just gave in ?) that they opened box to make sure these $6000 insured box had $6000 worth of stuff in them and when they looked up part #;s of heads, they found out they where approx $800. Not knowing about custom ported/set up cylinder heads they flagged these, as they thought someone was pulling a fast one. They delivered them late, but with a reduced insurance amt. And again, all f*ked up. So much for racing that year !

I was taught the industry standard is .001" per 1.0" of valve diameter.

"In an effort to reduce manufacturing costs on ready-to-bolt-on heads, "finished" seat rings may be installed in the heads by pressing or driving. This procedure causes the seats to go out-of-round. We have seen them out-of-round 0.014" to 0.016". The limit should be 0.002" or less."

Is anything in a production line really ready to just 'bolt on' ?
Can I buy a 'production' short block not check anything bolt my stuff up and go and have a trouble free summer? If so please send me the info I`m ready to buy.

I don't think your theory applies in the high perofrmance offshore world.

People love to brag about their toys. Powerboat owners especially like to impress. Exaggerating how many hours they run in a season, how fast thier boat goes, how long they can get a bravo drive to last, etc. But in reality they are anchored at the sand bar, lost a race to a slower boat then their claimed top speed, all while having the bravo blues. Why would the same not apply to engines?

There's plenty of proof to say that there is a problem, I think the more accurate question is, how much reliability and piece of mind will I gain for the money?

Sure some can bolt on heads without precision setup. Not everyone needs shaft rockers or piston oilers either. But when it comes to Marine High Performance Engines what's the best bang for the buck while trying to achieve ones goals?

IMO spending a few hundred on double checking and setting up heads is priceless compared to other "upgrades" that may be recommended.

To add in agreement: preventative procedures are derived from not having done them in the past and seeing the results. Knowledgeable marine engine builders are not "assuming" there might be a problem, they know there will be from past experience. Maybe not even their own, but over many years and many experiences form others, we learn what to expect and anticipate. No different than any other "school". I don't have to throw a rock at a window to know it will probably break it. Some windows are thicker, some rocks are heavier, some people throw harder...but in the end you know that if you don't want the window to break, you KNOW you probably shouldn't throw a rock at it. That's why we do this preventative, preemptive work on these engines. I like to tell customers that they will need 2000hp worth of parts for a 1000hp marine build. Not literally, but you get the message.