If you go with an aftermarket block, the 4.000" and 4.125" bore is the same price. Definitely get the bigger bore, it let's the valves flow more air when they are not as close to the cylinder walls.

Also, I would look at going to the 351C main bearing diameter. Definitely if you want to turn the rpm up. Maybe not if you are going max stroke and plan on keeping the rpm down.

I'm not real fond of the rod ratio when the stroke goes much over 4.0", but I haven't heard anyone claim they are prone to failure. Bent - where would you limit the rpm on these longer strokes?

The last block I had done (Chevy), I could have had a new block for about the same money. Chevy is $1000 cheaper than a Ford and as Brent said you still need to do some machining, but the aftermarket blocks are much stronger and better oiling. You don't need all the girdles, which are not cheap either. No doubt a factory block will work and it is cheaper, but the aftermarket is very tempting, especially with the 1/8" bigger bore.

I've spun the 4.100" stroke engines up over 6500 without issue. Where would I put the limit? If the rotating assembly is good quality, then I wouldn't have an issue at all with a 6500-7000 rpm setup. As you say, the Dart blocks use a 2.750" main diameter and the cranks use a SBC rod journal (2.100), so the bearing diameters lend themselves to some higher rpm action. At a 4.125-4.155 bore and a 4.100 stroke, it's still an oversquare situation and these engines make a ton of horsepower and torque both.

As stated earlier, it just comes down to budget. I wouldn't bat an eyelash at 500-550hp on a production Windsor block, so it just comes down to how much money you want to throw at a particular combination.

I have a Dart Iron Eagle block and was going to go with a 427cid but stayed with 408cid because I was using a turbo and wanted to have as much head surface as I could for the head gasket to seat on. I don't like repairing blown head gaskets. I agree on getting use to the HP, I started with 715rwhp then turned it up to 835rwhp then 924rwhp now I am over 1000rwhp. I think my cars sweet spot is around 800-835rwhp with the mods to my suspension and drag radials I can use the power in all gears need to be easy with 1st gear and just hold on in the others and I can use 93 octane with my Methanol injection system. Over 900rwhp I need to take in easy on the gas peddle until the middle of 3rd gear. The magic 427 number is important to some that want to have their car more original but I was not going for original with a turbo and stereo. These cars are not very practical so they need to be fast vintage looking SUPER-CARS!!! Just my 2 cents.

Dana E, with the Dart block I'd go with the 427 or bigger. Is your 500+ hp target fwhp or rwhp, since there is a significant difference. Cheers.

Without having to upgrade everything on the car, I've decided to go somewhat mild on the build: Dart block, 427" forged Scat rotating assembly, Brodix CNC heads, hydraulic roller. Supposed to be a 580 flywheel horsepower setup. Sure, I could have gone 468", but I didn't see the need in building the motor right at the bore/stroke limit right off the bat. May as well leave something there in case the motor needs frshened up in the future.

You'll have a lot of fun with the 427.

For future reference though, and for anyone else reading, a 454-460W is nowhere near the bore/stroke limits for a Dart block. There are a few members here that don't understand that and keep repeating it.

There is also a 4.100" crankshaft which produces a 438-445W and the extra .100" stroke makes a good bit of difference in torque.

The thing about SVO sized stroker kits is that they are all the same price, give or take a few bucks. So unless someone has to have the "427" number, I really see no reason to stop there.

So your saying the dart block is not maxed out at 460 cubes.lol:JEKYLHYDE

With a 4.250" stroke, the standard 4.125" bore gets you 454 cubes. A 4.155" bore gets you 460.

You don't have to jump all the way to 468 ci....the hp difference between 454ci and 468ci would be nominal at best. If you started with the 4.125" x 4.250" combination, you could potentially have many, many rebuilds before any "major" work needed done.

At some point, I would think you would start to think about an FE or 385.

For future reference though, and for anyone else reading, a 454-460W is nowhere near the bore/stroke limits for a Dart block

As long as you stay with Iron right? The Aluminum DART has a recommended max bore of 4.165 (.020 less than Iron), hence you are limited to ~450 max CID on the Alu block. Just asking so I understand.

You could get up over 460 cubes with the aluminum block as well. Dart says they will allow 4.165" x 4.250" with those blocks, which would be 463ci.

I've never had to take any of these blocks out to as far as we're talking. I generally do the 4.125" and 4.155" flavors. As I said, sometimes customers get hung up on numbers and instead of a 427 (4.125" x 4.000"), they'll want a 434 just to be a little different.

Rod, yes, at some point you would look to a big block. I wouldn't necessarily look to an FE, but the 385 series engines will make unreal amounts of naturally aspirated horsepower and torque. Of course it all comes down to what you want, what you're doing, the style you want, etc.

Thanks Brent, good to know :)

Dana what happened to the 393? It would seem like that made at least 500HP.
Lou
The KC Brodix is a very nice head. the 210 would fit nice with a 427. The AFR also is a nice head.
Lou

Go with the AFR head if your going the 427w route, in some cases the trick flow head, blykins knows best.

In the short time I had the 393 on the road, it sure drove nice and seemed to make good power.

The shop that built the motor used the wrong camshaft thrust plate resulting in excessive endplay. The cam and distributor gear were wiped out in less that 175 miles. I saw that he tossed in some used pushrods when he built the motor so I figured I better check everything. Crank, bearings, pistons and cylinder walls were undamaged. Measured all the clearances, CC'd the heads, etc. Everything checked out as per the build sheet.....except for the used, mismatched pushrods which were .080" too short, one of which was bent. That pretty much put me over the edge since by this time I had missed out on all the summer cruises, etc. I replaced all the damaged parts in the 393, a friend made me an offer on the motor to replace the 347 in his Mustang, so off it went.

We have two of Keith Crafts 408W in our club. They make 530 plus hp and 540 plus tq. Coach Mike has several thousands of miles on his, three years of driving year round. No problems. Very street-able motors, meaning they idle correctly, do not over heat, no oil leaks, no problems. Just drop in and drive.

I picked up the last motor a couple of weeks ago. 408W 531 hp & 540 Tq, cost $8375. If you will add up the cost of the parts your going to buy and the machine work, you will spend close to $8000. Keith uses parts that he has proven will work.

His shops are clean and orderly. He has all the machines needed to build a motor. We have five of his motors in our group and everyone loves them.
I can't say enough about the horsepower and dependable of his motors.

Check him out. Keith Craft Performance Engines

Dwight

Both configurations are overkill for these cars. Get the one that's cheaper to buy, maintain and repair. I have a version of the Keith Craft 408 (not sure any 2 are exactly alike) and have not had any problem in 7 years 14k+ miles. Did a 260 mile cruise yesterday. Motor was flawless. Brakes need some work.....

.
I'm going with the Brodix KC 210 heads for a couple of reasons: the exhaust port location is close to the location of the Dart Pro 1 heads that were on the 393 so the exhaust should bolt up without work and the Brodix heads outflow the AFR's...at least according to the published flow charts for both heads. I'll probably have my machinist check them on his flowbench.
.
I don't doubt Keith Craft builds a nice motor, but I prefer, and I'm more than capable, of building my own. It's my therapy. The one and only "crate motor" I bought in my life didn't make it 175 miles. My machinist friends are great. They know I have the tools to check the work as accurately as they can....and I will check.

Thanks to some serious shopping and some good deals, I can build an all new Dart block 427, with a forged Scat rotating assembly, using Keith Crafts' Brodix 210 heads and his hydraulic roller cam for about the same price as a factory block 408.

As Brent suggested, going bigger than 427" would not really cost much more for the engine parts, and you could make more power. In my case, I already had the new manifold and carburetor from the 393, I didn't want to shell out the dough to have new headers made and I don't have enough room under the hood to use a taller intake manifold. If I was starting from square one, building a 460+ inch motor would be very tempting. All in all if this motor can hit close to the advertised power numbers, not come apart on the dyno, and last more than 175 miles, I'll be happy.

It should be a nice build. Keep us posted.
I found that my KC 195 heads raised my exhaust at the 4 pipe flange about 1/8". A 120 emery spool and a electric drill worked perfect to contour the body. Also the head valve cover rails were a little higher. The oil filler tube had to be cut 1/4 for cap clearance, again 5 minute job with a cutting wheel. I widened my Edelbrock RPM intake coolant passages to better match the head. The Aluminum heads have a shorter passage than the World Windsor Sr. which was taller. There is a thin tab in the intake coolant passage. It looks like it was meant for trimming. A quick port match showed that taking some [not all] of this tab away made for better coolant flow. Again very quickly done with a burr tool. I ran the car yesterday and all went well. I definitely felt the power difference through the whole RPM range. Check your Rocker pushrod geometry! I used the Mid Lift method and it worked great. PM me on this if you want.
Good Luck.
Lou

If you don't have the parts, don't let the heads and intake stop you from adding cubes. Those 210 heads will work just fine on a larger engine and you can use the shorter intake. Torque is your friend in a street car...