how good are these? and will it be internally balanced?

 

A 400 block bored .030 over with a 350 crank = 377, and is internally balanced. A 350 block bored .030 over with a 400 crank = 383, and is externally balanced.

Popular Hot Rod did a build-up and comparison of a 377 and 383 this past fall. The 383 makes more torque up to a certain point than the 377, but the 377 makes higher peak horsepower. In order for a 377 to be faster than a 383, you have to keep the 377 RPM's high.

Either likely has more power than a 350. But, if you have a 400 shortblock already, build it up and you're better off than either a 377 or 383. All other things being equal, of course.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.73 unlimited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, TBD heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

well with any luck I will be picking up the 400 sat morning. do the 400 use 202 valves or 1.94? I plan on making it a roller motor and If it uses 1.94" valves I have a set of center bolt 350 heads I will use of course with drilling the steam holes.

 

The 624 heads from my 400 had the 1.94 intakes.

Pete

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Pete's Place
HiOutput Virtual Racing Team

 

Do not even bother with factory 400 heads. They are terrible performance heads. These engines only came with 2bbl carbs, it that's any hint.

Get some 2.02/1.60 valve heads, you already know about the steam holes.

 

I think he means a 400 with a 350 crank bored .060 over, which would make it a 383.0

I would think even then it'd make more horsepower than torque...and we all love torque

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89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-700R4 (Rebuilt) Too much done to actually list
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
-MSD 8.5 mm plug wires
-Problems every other day with the car (probably not a mod, but to me it sure makes a difference)

 

Something not mentioned yet. The 400 crank isn't a direct swap into a 350 block. The mains are too big and need to be machined down to fit in the 350 block.

When putting a 350 crank into a 400 block to make a 377, bearing spacers need to be used since the 350's mains are too small for the 400 block.

The 400's 624 or 882 heads are a very poor choice. They are thin castings and usually crack from too much heat.

Most 400's can only be bored out .030 and with the 350 crank, make a 377. The maximum allowable is .040 but even then the cylinder walls start to get too thin. Aftermarket 400 blocks "bowtie" can be taken out to .060.

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Stephen's racing page

87 IROC-Z Pro ET Bracket Race Car
383 stroker (carbed) with double hump cast iron heads and pump gas
454 Big Block buildup now in progress for the 2001 racing season

Best results before the 383 blew up
Best ET on a time slip: 11.857 altitude corrected to 11.163
Best MPH on a time slip: 117.87 altitude corrected to 126.10
Altitude corrected rear wheel HP based on power to weight ratio: 476.5
Best 60 foot: 1.662

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley