Got a line on a 400SBC motor... tossing some ideas around..

[Guest Anonymous]

Well, I got me 2 350 blocks (semi-assembled) coming this weekend for free, and my friend has a 400 he's willing to trade for the 350's..

 

He wants to build one of them into a 383, and I've heard many good things about making the 400 into a 377. He doesn't mind swapping cranks, so that's covered...

 

So, it appears I have a good starting point, no? I haven't messed with small blocks in a few years, and last time I did one, we bought it from Summit Racing..

 

My goal is right at 500hp, I was thinking of following Air Flow Research's 500HP builds... http://www.airflowresearch.com/chevy_dyno.htm

 

Questions I have (assuming the engines haven't been overbored or had the journals turned, etc..) are:

 

1. The 350 crank should drop right into the 400, right??

2. What length rods should I look for?

3. I'd rather NOT use a double-pumper carb on the street... I keep WANTING to go EFI, as I know how to tune that... opinions?

4. Anything else?

5. Yes, the block WILL be magnafluxed before I start anything... how much should I expect to pay?

6. Is a forged crank necessary? I know I will be using forged pistons, what about rods?

 

Now that you're saying "Geez Rich, shut up already!", I just wanted to thank all of you.. I love this board, and all the knowledge that is to be gained, and all the time you all spend here helping out.. I hope to one day be able to help some people as I've been helped!

[DavyZ]

Rich,

 

The journals are not the same size so therefore a 350 crank will not drop into a 400 block. There will be machining done either to the block or to the crank (and for some reason I can't think of which one--I believe the 400 has larger journals because those cranks need to be machined down to fit a 350). I would strongly suggest looking at SCAT cranks--many times you can find them listed on ebay, brand-new, for cheap from machine shops and the like. The Scat cranks are made from "cast steel" and are stronger than cast iron, but not nearly as expensive as a forged crank. Check out David Vizard's books, especially the How to Build Horsepower for the small block chevy, but look at the carbed engine book. The EFI book I'm sure is great, but I don't have it.

 

The rule (if you can call it that) seems to be that the longer the rod, the better. I would look at using at least 6 inch rods for the motor. With 500 hp, you should look at better quality rods--stock rods are good from 400-450 hp.

 

Since you are going to build an awesome motor (I'd love this one) make sure you follow the details in getting all the umph out of it and making it work the very best you can. There are so many little mods you can do, even to the short block that will make a difference. Add 'em up and BAM, 50 hp more!

 

Good luck with a great project. BTW, building a destroked 400 sbc will be more expensive in the end than building the more popular stroked 350 sbc. Food for thought. Price it all out first...

 

Davy

[Peternell]

Couple of thoughts.

First Davy is right the 350 has smaller mains (2.45) than the 400 (2.65) so you either need spacer bearings for about $40 from Powerhouse or special (& costly) oversized bearings.

 

Secondly the 377 is an interesting combo and I have the parts to build eiter a 377 or 406, but chose the 406 for a few reasons.

 

Why give up 29 cubes? The 383 is popular cause its 28 cubes larger than a .030 350 and has a longer stroke for more torque. (I know these cars don't need that much torque)

Second the longer stroke allows power to be made at a lower RPM and spining R's is expensive. Much cheaper to build an engine to survive at 6 grand than 7 grand.

 

The David Vizard book that Davy mention is great (I've got his How to build a high performance SBC on a budget book)Solid block, good rods, darn good heads, good ignition and exhaust and the RIGHT cam a lower budget 406 can get the numbers your seeking. The 377 can produce similar numbers but get ready to spend the buck$

 

Just my input, for what its worth

 

Larry (aka Peternell)

[Modern Motorsports Ltd]

I fully agree with all Larry said Why give up cubes/free power....too much talk (no offense/was in other threads) IMO about 'revving' easy...driven 327's/350's and fun is fun and more power is still fun....I'd take it at lower rpm's rather than higher and never give up cubes unless their was a HUGE reason to do so. my .02c typed quick from the office

 

nothing wrong with using those spacers either, I was all set to do a 406 or larger when my 350 roller fell on my lap and plans changed

[Guest Anonymous]

I appreciate everyone's responses.. My main reason for wanting to de-stroke the 400, was to do a long rod motor... After reading "the 350 Chevy should have built", it really turned me on to the advantages of building a long rod motor. Heck, a 350ci running 412hp, with great torque, on 87 octane pump gas is great!

 

I'm already planning on running a roller valvetrain, forged pistons, SCAT crank & rods (THANKS DAVY!), and having them all balanced, so what extra cost am I looking at to let the motor rev? I think I have the bases covered for that..

 

I love high revving motors... Guess that's why I'm a bike guy as well. The car isn't going to be a daily driver, more of a weekend "I'll run anything that comes along" fun car, and it will more than likely see some track time, so I don't mind a lumpy idle.. in fact, i am looking forward to it!

 

I just ordered the David Vizard (max power on a budget) book.. (couldn't find the EFI book you mentioned) What's this about 600hp for $3k?? What, a 300hp shot of nitrous?

[DavyZ]

Rich, I totally love that book you ordered. I swear it got me more excited than "How to SBC Racing Engines on a Budget" by Tarant(sp?) and Hawkinson. They don't call David Vizard, "Vizard the Wizard" for nothing! I would love to build a 350 or 377 ci destroked 400 sbc. I know "we should never give up cubes," but man that's a sweet motor. Might be cool just to do something different...on 87 octane no less with decent compression. Have fun building this project motor--it'll be a screamer!!!!!

 

Davy