i want to see a test in carcraft where they build 2 performance 400's that are ABSOLUTELY IDENTICAL with the exception of the rod length. the 400's should have hydraulic flat tappet cams of around 230@.050, 10:1 comp, identical rpm intakes, edelbrock thunder carbs, regular HEI's with perhaps an aftermarket coil and module BOTH set at 36* total timing, and the same set of heads for both engines. i dont think the cobos should be "optimized" either cuz the point of doiong this test is to see which rod length is better for those of us who dont have a dyno to optimize our combos on. we want to bolt them together with off the shelf parts and have them work right. i think too often these comparisons have little, but significant, things changed that inevitably change the results also.

and im tired of seeing dyno tests start at 3000 or 4000 rpm. perhaps even skip the dyno and instead test both engines in a TYPICAL CAR, such as the disco nova. but the tests must be back to back with no other changes. id like to know the results of each engine, such as e.t. and trap speed, mpg, vacuum, does one run on 87 octane while the other requires 92, does one rev higher or drop power faster at higher rpm, is one more fun to drive etc.

i also think this same test could be done with these new friction coatings they keep coming out with. coat everyfrickenthing that moves in one engine and nothing in the other and give the results of all the possible differences listed above and any others you can think of. im confident the coated engine will make more power, last much longer and make alot more power. you should use the friction coatings on the roller rockers, valves, valve springs, cam, lifters, pistons, wristpins, bearings, timing chain and gears, fuel pump pushrod, and EVERYTHING ELSE THAT MOVES. while youre at it, since you are CARCRAFT and have pull, why not motivate someone to start making bearings out of caged roller bearings, or even grooves and ball bearings, or a combination of the 2. more ideas to come....... 

This topic is as old as the hills.  IMO, regarding a 400 sbc I think most knowledgable folks will tell you to toss the OEM rod if your building a serious combo.  From there, use either a 5.7, 6.0" or something in between.  Bottom line... don't expect significant differences unless you're building a real barn-burner.

Here's an interesting article/site regarding rod length:

http://www.iskycams.com/techtips.php

The big reason you will not be seeing roller bearing cranks any time soon is it would be less efficient. all but a select few extreme high rpm industrial setups use a hydrostatic bearing setup, the reason being that when a roller bearing is spun that fast, the weight of the roller itself, multiplied by centrifugal force causes the roller to wear rapidly due to excessive heat, and the lack of adequate lubrication ai the point of contact. By now youre probably saying "Hey dumb@ss it'll have lube!!!", hold your horses i'm getting to that part. The amount of oil required to keep a roller bearing lubed at say 7000 rpm is VASTLY different than the oil required to lube conventional bearings, not to mention that  the surfaces of these roller bearings would have to be extremely hard to live at high rpm, which would ultimately make them brittle, and intolerant of vibration. Now once again you're probably calling me that "D" word again and saying "motorcycle engines use roller bearings on the crank, hell, the ducati 749R uses em' and they don't have any problems!!!", It is at this point that i say that i am impressed with your knowledge of italian motorcycles, but unfortunately must once again dissent your argument. The diameter of said crankshaft roller bearings in the afforementioned engine is much smaller than those that would have to be used in say, a SBC, so therefore (smaller diameter rollers <less mass> + smaller O.D. <slower roller speed> + less load for bearing size <Not recip. weight but   minimal thrust load, and no belt drive ect.>= bearings live. the only real advantage I can see to a roller bearing crank  in any engine is the ability to survive light load use  without pressurized lubrication, the exact reason they are used in ducati's and HD's (tell me the last time you saw a harley holding more than squat for oil pressure at idle). Just thought i'd put that out there...sure there ARE roller bearings that COULD work in an automotive application, but the cost to retrofit the engine itself and the cost of bearing manufacture (you would have to use rollers made of a ceramic composite or synthetic quartz in order to take the heat/ vibration/ rpm) would make the bearings redundant,  that is to say would you rather spend 5000 on a supercharger and make 150 more horses, or 10k + for a modified block, crank, and rods that may only make 2 or 3 more horsepower in a street driven application? Where we are at as far as automotive bearings are concerned is what is known as "The point of diminishing returns" where it no longer makes much fiscal sense to improve upon a basically perfected technology. Oh, and by the way the Hydrostatic bearings i spoke of at the beginning of this "much longer than it probably should have been" answer are when the rotating shaft is supported by lubricant under pressure and for all intents and purposes "floats" on the oil...exactly like the ones in every automotive engine today. guess them boys in detroit were on to somethin, eh?    

 If you think i'm talking out my "4th point of contact" you can look the information i've attempted to explain here up at WWW.timken.com click on the bearings link and download rotation/speed/load/temp charts for all their popular bearings in pdf. format, or you can co to #### bearings  website and do the same...i just hope your German is good.

                                                                                 TREE

Why not optimize timing?  If I was to spend thousands to build the engine you describe, I would want to make sure the total timing was optimized.  The low buck way to determine optimal total timing is to try different settings at the track an see which one gives the best mph/ET.

Tom

i like the way you explained that tree. and no i didnt know ducati's used roller bearings.

tommy, the reason i said i think it would be better to not optimize each engine for the diff size rods is because of the "majority rules" rule. that means i dont think the majority of people would bother taking a hot street engine to the track multiple times jsut to get the timing perfect. at my local dragstrip, youd be lucky to get in 3 runs in one night. and since id want to do at least 2 runs before making changes to the timing such as diff weight springs, that means multiple trips to the track, which is far away just to get a very minor improvement in e.t.

instead i think they should put in a medium weight spring that gives them the 36* total timing and whatever inital timing the engine ends up with when it idles down, usually about 14* or so. then when they put the other engine on the dyno or in the car, just do a direct swap of the distributor from one engine to the next. please understand this is mainly to duplicate what the average joe would do, not dedicated racer guy looking of revery last 1 hp gain he can get.

Correct, old as the hills. But, the tech is there already too. The long rod motor typically has a broader torque curve. Hp doesn't hurt either. And its slightly easier on the bore walls as the rods are side loading the piston less.