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Author Topic:   Jr Motorsports 377, 383 and 406's
Dirt Freak

Total posts: 248
posted January 24, 2002 04:08 PM
For a street stock, what is the difference between a 377 and a 383? I'm looking at Jr Motorsports shortblocks and wonder what the advantages of each are. Also, what about a 406, any disadvantages to a 406? I've heard 406's aren't real durable, but thats just what I've heard. I want a reliable motor more than I want a horsepower monster.

Also, I've seen some sing the praises of Jr shortblocks, anyone got any complaints?

[This message has been edited by WesternAuto17 (edited January 25, 2002).]

Dirt Full Roller

Total posts: 37
posted January 24, 2002 04:25 PM
a 377 is a rpm motor you've got to twist the #@$% out of it. in other words it makes its hp at a higher rpm. the 383 & 406 makes hp on the bottom of it,s rpm range. i run a 406 . they last if you keep your rpms down. make sure you use 5.7 or 6.0 rods. the 5.565 rods are the weak point in a 406. i've heard nothing but good about jr. short blocks.

Dirt Freak

Total posts: 285
posted January 24, 2002 07:05 PM UIN: 40696038
377 is a 400 block with a 350 crank a 383 is a 350 block with a 400 crank if i remember right

Dirt Freak

Total posts: 310
posted January 24, 2002 10:01 PM
agree on the 406 6000 maybe 6200 not much more on a sustained level

Dirt Freak

Total posts: 237
posted January 25, 2002 07:46 AM
I live within a short driving distance to JRs, in fact I buy a LOT of my parts there. They've even done some machine work for me, although I've never actually bought a shortblock from them.


Recently, they've messed up a couple of my machineshop projects. Enough that I'll take my machineshop work somewhere else next time.

Want an example? How about leaving an old freeze plug inside the block after cleaning and installing a new freeze plug right over the top? Or forgetting to install the little plug above the rear main cap? Or loosing 2 of my Scat rods?

Dirt Maniac

Total posts: 115
posted January 26, 2002 08:48 PM
Which engine you use depends on what kind of power range your looking for. I personally like a 350 engine with a high RPM range, but most of the tracks I race limit us to a 350. I have tried 400 block engines and have not had much success with them. I would run a 350-383 engine. If your rules allow the 383, go with it. Use all good parts in the rotating assy and you can turn 6500-7000 rpm. Use as long of rod as possible in which ever engine you decide to use. It relieves alot of side pressure on the cylinder wall and the piston both, which will help the engine to rev better and last longer, especially with the 400 block.

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