Just my experience:
After about 500 miles, I found the two front cylinder head bolts loose. Also, some of the exhaust bolts needed tightening as well. A couple valves were a little loose too. Was time well spent.

X 100
yes, it sucks to take your new motor back down.
yes, it is worth the whole cost of the build to do it.
Yes, it will make a huge difference.
Yes, I am glad that some one else thinks the same way I do.

priceless

edit.
making sure that the head bolts dont have crap in the bottom. lenth of like water pump bolts.
check and re check everything. then 500 miles or I do it after warm up. 100, and 500 miles.
I have not had alot of the problems that I read about here and on other sites.

I am not sure how the factory gets this done....
I mean that a rebuild never lasts as long as factory.. after market, (starters, alt, trans, clutch, u- joints) don't seem to last as long as the factory ones do.. Not sure what to make of that....
but I will take a junk yard (say alt, or starter) over a rebuild any time.

any input on this? it would seem that with the rebuilds they would know the weak spot and fix it..

I pity the fool who don't do a retorque after a rebuild!! Uuuurrrggghhhh! <img src="/forums/images/graemlins/mrt.gif" alt="" />

I didn't know about that when I rebuilt mine <img src="/forums/images/graemlins/frown.gif" alt="" /> Basically had to do it all over again.

In my experience, you really need to check everything after 500-1k miles. The head bolts are most critical, but everything will need to be retorqued - front cover, oil pan, intake manifold, exhaust manifold...

I don't know how a person would even get to some of those intake manifold bolts when everything's hooked up?

Swivels, baby. <img src="/forums/images/graemlins/baby.gif" alt="" />

2x

>>>*Yea, without swivels, guys the size of me don't work on cars at all....*LOL**..

I will stick my poor opinion in here also, for what it is worth. When using new fastners, retorque is even more important than when reinstalling the old ones.

Either way, heating and cooling cycles cause metal molecules to move, and they can lose clamping force.

Kudos to the O/P, a good tip and we see the same regularly. Best to take the time to recheck, it can save the job down the road....*EB

So, how do the factories send out millions of vehicles that run hundreds of thousands of miles without retorquing?

Tolerance analysis and experience. Between the two of them you can figure out exactly how much you need to torque a bolt of known properties and how much it will loosen over time.