383 vs 395

[Speedracer99]

What differences or better for Street Stock power off corner, & best over all 383 vs 395(396)?

 

Is a 6 inch rod lazy off corner? Worth using 6" for less wear and tear versus 5.7 rod?

 

 

Is 383 that much better than 355?

 

Best & lightest I-Beam rod?

[4cylfordz]

I can't tell you much about a 396 gm as haven't had any experience with one though it seems like more hassle than its worth for the extra 13 cubes personally would choose a 383 if the rules allowed as its the best bang for the buck. as far as 6vs5.7 it kinda depends on your choice of pistons and rods if you go with good stuff with coated skirts such as a mahle and a good brand of rod then I'd say short though being able to tell the difference would be tough less you were getting to the low end of the power band every lap . as far as the best and lightest I beam would probably be a lynch or Oliver or a carillo, for what your doing I would use a scat with 7/16 bolts

[fastman]

6 inch rod of course, less wear and tear on the cylinder walls. Longer rod = less force on cylinder walls / less force on cylinder walls = more HP / its a no brainer. Light weight steel rods can be anywhere form 495 gram to 550 gram, just depends how much $$ you want to spend.

[4cylfordz]

I would kinda like to see mr bishop or maybe mr spreens input on this topic I may be an engine builder though I like to see the input from from their expertise

[Alloutpc17]

383 is more of a torque motor, not a high rpm motor. I would pick the 383 for getting off the corners better on a shorter track. If I was at sas track, 355 would be me answer.

[jwmbishop]

A longer rod gives shorter TDC dwell time and longer BDC time. (dwell time is the degrees of crankshaft rotation occurring with little or no linear movement of piston - they are not equal unless of course rod length is equal to stroke).

 

More dwell time at top pretty much allows the same dynamics as increasing cam overlap. (bottom end torque and lower peak HP RPM)

 

More at bottom allows for more momentum filling of the cylinder. (top end breathing and higher peak HP RPM).

 

Most cams are R&D'ed using the 5.7 - check with your cam guy (don't just grab off shelf) before going to a 6.0.

 

The bore/stroke ratio greatly effects the area "under the curve line" of a dyno graph. In circle racing total area is more important than total peak number! (drag is quite opposite).

 

383 or 355 is always a tough question - but the best answer I've heard is this. Imagine riding a bicycle. Adding weight to your body (over boring) will increase your down stroke pressure with no extra muscle exertion. Adding length to your bell cranks will increase the leverage applied by the same amount of weight! Go for a ride on a bike and see in what conditions you want which mod!

 

How does that apply to the track? Well in the bore/stroke ratio of the 350 the torque is peaked between 1800-4800 (depending on cam and port volume) - in the 383 ratio it is between 1100 and 4300. (assuming all else is the same).

 

For short track - with small ports/carburetor rule limitations 383 running 3000-5500 RPM could be an off apex advantage. If you can go large or open port/carb - 355 spinning 3300-6000+ will get back mid straight what you "lack" off apex.

 

A good factory example is the 366 truck compared to the 396 vette engine - the 366 will pull 25000 lbs all day - in a 4000 lb car it will scream - but run out of usable RPM (where torque is increasing proportionate to RPM increase - the reason you want higher RPM is simply the % of gear - 10% gear at 5000 is 500RPM at 6500 its 650 so the proportion is better at higher RPM!)

 

Just remember - the more exotic your parts combo - the higher your maintenance costs and faster the drop off of serviceability (no more machining room to clean up wear issues)! So for that I always say stick with the 355 - the 383 is NOT going to make you a winner if you are not already there or REAL close. Spend the money on suspension so you can roll off the corner better with out needing the extra low end torque!

 

My "383" towing engine (really 387.8 as we offset ground the crank and bored to +.045) is 1.94 valved small chamber ported heads over a scat/KB kit with a well matched roller cam, 1.6 rockers and custom cast manifold. Just dynoed 412 ft lbs @ 4300 and 518 HP @ 5350 with 1000 CFM TBI (upgraded from 750 holley in prep for install into the 57). All the software gave a HUGE warning though. The cylinder pressure spike gets the same peak - but over 5500 the speed with which the pressure increases will try to barrel rock the pistons - "REV LIMIT TO 5500 to avoid broken skirts" came up many times while playing with the actual cam numbers.