Hello all. I am building my first aluminum block big block engine. I have built iron block engines with aluminum heads in the past. I have always ran the iron blocks on the run stand up to operating temp. Then I allow the engine to cool over night and retorque the heads. What I don't know is this. Are there any considerations like this for the aluminum block? Like do I need to retorque the mains? Any first fire up tips pre and post would be greatly appreciated. Thank you, Digger73 (Mike)

Mains don’t need retorqued. I would retorque the heads after a heat cycle. I just check all other external fasteners, other than that just normal breakin procedures.

I haven’t retorqued a head in 47 years of racing and engine building

what head gaskets are you using John ?
MLS, factory shim, composition type, or all of the above ?

1008, 1009, 1039, I forget the marine gasket number, and big and small block Cometic Gaskets.

The thing about aluminum blocks, as I understand it, is that there's more expansion/contraction than an iron block.
I haven't heard head-fastener torque being an issue as much as the internal clearances.
Hopefully some serious engine builders with aluminum-block experience post their experiences.

I retorque all my stuff during the build itself. Torque as normal. Then after setting 15 minutes or so crack each fastener loose. Then tighten to spec in one pull. You'll be amazed how much further the fastener rotates from the original posistion. Then send it. no need to fire it first. Dave Koffel taught me this trick.
Doug

Exactly but that’s not what he’s talking about. Retorque on an engine stand is common practice but not after firing up the engine. I usually do it the next morning

Same here.

I may have retorrque one or two after taking them off the engine dyno just to see if any moved or loosened on iron blocks, none did.
Aluminum expands 8 times as much as regular cast iron.
I do recheck the torque readings after doing both heads while assembling them, I use oil or ARP lube on all the threads and under the heads of the bolts and on the head bolt washers also, I use the lower factory torque specs. based on hearing Tom Hoover state at one of the old Mopar Drag seminars that the upper spec is for dry bolts, fasteners and the lower spec. is for oil, lube, on the threads

Thank you all for your answers. This is just my first experience with an aluminum block and just wanted to see if there were differences I needed to know about. I have always backed the head fasteners off after torqueing the heads and hitting straight to the torque final value. When I started using aluminum heads I run the engine(s) on the run stand to temp. Then let the engine(s) cool over night and check the heads torque again. This all sets my mind at ease that I might be doing something right. Digger73 (Mike)

thank you sir.

the most important thing i would say , is get used to the way temp effects the valve lash. AMbient from 90 to 40 will tighten it a lot . Expect to see .010 or less at 70 because it will grow a lot at 180* engine temp. When building these engines in my basement in the winter , i set the lash at .008 in 50-60 degree temps. THe best thing is to get the engine uo to temp you will run it at, Check the lash on one int and exh, Let the engine cool overnight , then measure it again. Take not of the ambient temp and you have your "growth" factor .