o, shows how much i kno.. sry

 

If you want a 4 spd. auto you might look at the 700R or the 200-4R. Either are 4 spd autos. I think the 200 has a lower 1st gear. Monster sells the 700R for $1200. Rated for 500 HP.

 

o, thx. ill look into it

 

I just grabbed those off of some engine builders site, I checked the math and a 4.125x3.48 is a destroked 400 giving a 373 ci. Most people building higher end racers don't like the 400 bore (4.125) as the walls are very thin and they can not be bored much more if damaged. The cylinders are siamesed as well which doesn't dissapate heat as easy.
I'm not sure if the transmissions were different through the years for the TH400, but those were used behind late 60's bigblocks. I dunno what GM rates them to handle. I've never had problems with the 10 bolt, but on my LS1 Trans-am, people have said once they get a little over stock (350hp+) they lose reliability. I plan on cutting down a 12 bolt from a truck to use, but I havnt fiddled with them before. I'd prefer to go with a 700R on my current one when I get to that point.

 

Hmmm. Lots of people love 400 blocks. How do you think you get a 434,427,or 454 small block. Ain't happinin with a 4" bore. Only 400 blocks are siamese huh? Congrats your up to 9 posts in 3 years.

 

400s are like any other block, you can get thick or thin walls depending on the casting. I have one that is bored 20 over and is sonic checked at 145 on the thrust wall, so I would feel comfortable in taking another 20 out if needed. It doesn't heat up any worse than a 350 on hormones.

 

A simple test to determine if a small block Chevy is a good block is to check the soft plug bosses at the rear. (under the bellhousing area) If the soft plugs are situated as close to center in the boss, then the cores didn't shift when it was cast, and it will allow maximum boring if needed. If you look at the cam boss and the two freeze plug bosses at the rear you can measure the distance around the boss and see how far off the casting is. I've seen some that were major amounts off center.
I had an old machinist friend who used to hold the F stock title in a Dodge Dart show me that trick when he was building the 283 in my '55 Chevy. He said he wouldn't even waste time doing major engine work on a SBC that showed signs of the cores shifting, as the walls would be thin on one side and it would have cooling issues when bored.

 

Is was being sarcastic on the siamese stuff. The core shift stuff is new though. I'm going to definitly try and remember that the next time shoppin for a block. Makes me wonder how bad my 383 is off. Kind of bummed I didn't think about that though. I have be working with castings in some form or another my whole life.

 

The problems I've have with 400 sbc's aren't with the bores but with the lifter valleys and the deck. You'll usually see cracks in the lifter valley or between the steam and bolt holes across the deck before you get too far along. A lot of engine builders will put plugs in the deck before decking and boring to add strength and durability. My old 400 had 3 - 4 cracks running down the lifter valley though and I've known others to do the same.

 

Every engine has some quirk; it's just finding those engines that have the least. I've always thought the 283, 327, and 350 were the most reliable basis for a small block Chevy build. They all have vitues that make them great choices, but in today's market the 350 is head and shoulders the best choice since you get more bang for the buck.
Jumping to a 383 is a nice choice, but not exactly a buget build motor. Taking a 350 and boring it out, then going with some great heads, cam, and pistons is about the cheapest way to make a lot of power that you'll ever find in a SBC. It's just tough to beat the 350 for HP per dollar spent.