I will also add that when I decided to build a big inch small block, I considered everything up to 427 cubic inch. The problem with going over 406 cubic inch, everything gets tighter in the block. The clearancing for stroker cranks increases in the block and the oil pan, small base circle cams are required, piston speeds higher, rod ratio compromised, etc. I think longeivty is also compromised. The costs of all this increases the total cost exponentially. I decided the 406 was plenty for my style of driving, which requires longevity as well....because I put over 5000 miles a year on the car. At some point, a Gen 1 small block reaches a limit, and I decided that over 406 there were just too much compromise, and pushing the limits. Of course it can be done....but there is a penalty.

Figure out your realistic goals....i.e. street driving versus racetrack, and build the engine best suited for your goals. For me.....I was not going for top end power, I wanted big torque for the street. Be careful taking information from the racer crowd....as they only see things one way. As Jebby has said in the past, and I agree.....a good 406 is all the power you need on the street.

Expect there to be statements made by some who have clear difficulty in reading and writing comprehension......and say things without any real ability to make a clear input to the discussion. What I am saying is, be careful what information you use to make decisions.

 

I will be considering the 406 route for a restomod, but I have a question:
If you can't find an absolutely pristine stock block, would it make more sense to base a 406 build on a new aftermarket block?
I was thinking a non-pristine stock block might have been compromised, and that might show up later after you've spent a bunch on building it, but I don't know what the majority of experiences have been.

 

I guess it all depends on whether you can find a good block or not....and many told me it was important to get the cylinder wall sonic tested to make sure no cracks. When you add up all the costs of the testing on an old block, for me......it was better to just buy a Dart SHP block, which is more stout, and is brand new. It will also need machine work for the deck heights and bores....but so would an old block thats history is pretty much an unknown. You might save money with an old block, but you get what you get. Going to the more expensive aftermarket blocks IS a big leap in cost.....so my comments only apply to the SHP blocks which are more than adequate for the street and normal use.

 

This is the best statement I've read here in a while.....you have to know what your goal is.

 

My 400 SBC block is at my local performance machine shop getting cleaned/magna-fluxed, pressure tested, and basically checked to make sure its a good block for rebuilding. The guy asked me if I wanted to bore it out 30-over, and I said I'd like to keep it at the stock bore. he checked the cylinders while I was there, and they are all in good shape/within acceptable specs. Not sure if the cost to bore it 30-over (maybe 6 C.I. gain) is worth the cost. I really don't want to bore out good cylinders for a not-so-great cubic inch gain. Plus, keeping it at the stock bore gives me some wiggle room if something catastrophic happens in the future.

 

You want to go .030 to square the bores to the crank centerline and have the machine shop hone the block to your piston spec that you will provide them.....has nothing to do with cubes....
You need to purchase a set of pistons or the whole rotating assembly now....
By the time you clean up a 50 year old stock bore....it will be too large to run a shelf piston.
I would buy a balanced rotating assembly....
The Skip White assemblies have pistons specially designed to not have to cut a bunch off the deck to make them zero deck....something to look into....

Jebby

 

Another potential source for Rotating Assemblies is CNC Motorsports.

I will strongly suggest going with forged pistons, and VERY good rod bolts. Rod Bolts are THE most highly stressed fastners in an engine, and the longer the stroke, and the higher the RPM (and the heavier the rod/piston assembly) the higher the stresses on the rod bolts.

 

Ah, that is something I hadn't considered (obviously). Thank you.

 

I'd be slightly wary that your shop didn't suggest doing it for that reason. Is this a performance engine shop or just a rebuilder shop?

Edit: after re-reading your post, I guess if you stated you wanted stock bore before he had a chance to explain why he wanted to overbore, then that explains it.

Fun fact: the very first SBC I pulled apart myself (all of about 12 years old) was a 400 I pulled out of a 72(?) "Kingswood Estate" wagon my Pop had. It was actually a good running engine an he intended to use it as is. I thought he wanted to rebuild it, so there she was in pieces on the bench when he came home from work. Ooops.

 

Blocks warp over time. To make them square is called, "blue printing the block" It includes align boring the cam and crank bearing surfaces, decking the block and tapping the head and feasibly the main thread holes.

Whenever you bore a block, you try and do the minimal overbore to keep the cylinders as thick as possible. You might look into cooling improvements, Internally balanced, 6 inch rod rotating assemblies. Short rods have side loading issues. IMO stay away from Hyper pistons and use bigger oil pans

 

Just got a call from the machine shop. The block pressure tested good, and has no cracks. Said he was surprised the block was in such good shape. We talked for a minute, and then I asked if he had time to go ahead and bore it .030 over. I've been doing a lot of reading/research on it (maybe too much research, which is a problem I have. I like to look at stuff from all angles, and that sometimes leads to decision paralysis......).

So, looks like I will need to start researching (dammit) 4.155 rotating assemblies now........

 

they are essentially the same as 4.125. price, availability, weight, no noticeable diff.. and 406 is 1.5% more displacement...

 

In my recent build I also used CNC Motorsports for my rotating assembly. The only difference being my machinist did not want me to buy a balanced assembly. So it was an another step taking it to another shop to have it balanced . Once there it was a surprise to find that some heavy metal had to be added to balance it out. I used a Scat Crank and Rods, and Icon Pistons. Real common stuff.