December 2010 Chevy High Performance Q & A

Kevin McClelland Nov 15, 2010 0 Comment(s)
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Inches Are Us
Q: What advantage does a 377ci (destroked 400) have over a 383ci with a 4-inch bore? I have a circa-'78 400 block and crank, machine shop checked, and all is good (still stock bore at 4.125 inch) with the castings centered. Rods, slugs, and heads were deep-sixed. What combo would be most reliable yet give best performance on a typical budget, let's say around $1,500. I'm open to any parts suggestions. Thanks, hope to hear from you.
Mike Helbig
Airville, PA

A: Back in the day, the 4.125-inch bore ruled for big airflow. The larger bore would unshroud the intake valve and you could stuff more air into the engine. Shortening the stroke to the standard 3.48-inch 350 stroke gave you the 377ci. These things would sing and rev really nice. Then along came the shortage of good 400 blocks and everyone started building 383s (4-inch bore with 3.75-inch stroke). These ended up being the mainstay of small-block engine builds for the past 10 to 15 years. Today, with the affordable aftermarket blocks from Dart and World Products, a 400-plus-inch small-blocks are becoming the norm.

Several years ago, David Reher from Reher/Morrison Racing Engines commented that with the cylinder head technology available today, he would always go for the inches either with bore or with stroke. The selection of cylinder heads around today will give you the ability to feed almost any bore size over 4-inches.

We would build some variant of your 400 combination. Obviously, for budgetary reasons the simple answer is bore the engine 0.030-inch over and put your 406 together. The components necessary to screw together a 400 are plentiful and very affordable. Spend your money on the best cylinder heads you can afford. This will give you the best horsepower for the dollars.

You didn't mention what you were building your engine for. For all-around good performance, pick up a set of 190cc-inlet-port-size aluminum heads. This will give you a good balance of torque and horsepower from your 406.

Q: I have an '86 S-10 pickup with a 388 that I think is about 10.5:1 compression with a Comp Cams 268 Xtreme Energy cam, a set of Brodix Street heads, 170cc intake runners with 69cc chambers, and a cast 400 crank with 5.560-inch rods and flat-top forged TRW pistons. The engine is topped off with a Performer intake and a 750 Speed Demon mechanical secondary carb, and is backed by a TH350 trans with a stock converter. The truck has a Dana 60 full spool and 4.10:1 gears and 35-spline axles. This may be a little overkill, but no worries with the Cal Trac bars. I shift the truck at 5,300 and have a 5,800 high-side chip in the MSD. What is max rpm with this crank and rod? I have a 2,300 to 2,700-stall converter; would this help or hurt the truck? It has run as fast as 8.05 in the eighth-mile, and 10.31 at 100 in the 1,000-ft on a true 275/60 street tire with 4.10:1 gears. Also, would a set of 15/8 long-tube headers help, and roller rockers? I'm currently running stamped steel rockers and I also thought about switching to an Edelbrock Air-Gap Performer RPM. The truck is now a toy, as it was my daily driver for 31/2 years. Any info would be great.
Brian Parker
Barling, AR

A: Nifty little truck you have there. The only problem is they aren't as light as you might expect. Obviously, there are many models and options of S-10 trucks, but the lightest curb weight of a V-6-equipped S-10 is around 3,400 pounds. Slap in an aluminum-headed small-block and a Dana 60 rearend and you're probably in the 3,500-plus-pound range. Back in the day, we would stuff small-blocks in the very lightweight Chevy LUV trucks. Those were a handful when you dropped in a 400 small-block, TH350, and a 12-bolt rear. You're going in the right direction with your parts selection. Let's take a look.


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