If I use the short 400 rods can I still use my 350 TRW flat top pistons and just buy a 383 crank I already have the rods or should I just buy a kit with 5.7 rods and pistons which will make more torque this motor is for a boat.

Boats are whole different animal . . . so keep in mind I'm telling you what I know from a CAR perspective.

IMO there is not a significant difference in performance between the the 5.565" rod and a 5.7" rod in a street driven 383. HOWEVER, longer rods like 6" will increase durability at sustained high RPM. There is less side loading and reduced cylinder wear with the long rod - but only by a few percent (like 4 - 5% reduction in side loading from what I've read). Remember, we're talking about a difference of only .135" between the 5.7" rod and the 5.565" rod.

The other advantage to a longer rod is increased resistance to detonation. The piston will move slightly slower through TDC and cause the piston to be slightly higher in the bore at intake valve close (IVC). This has the effect of reducing dynamic compression ratio by a hair and adding to detonation resistance. You might be able to run a 1/4-1/2 point more compression with the 6" rods than the 5.565" rods but that is JUST A GUESS - my point is that it is not that significant and would be worth while if you were talking about a race engine.

[This message has been edited by Eric68 (edited 11-25-2002).]

Ragrat,
I agree with what Eric has said. With that said, I am running a short rod 385 in my Camaro and have been running it for about 4 years. If I was starting from scratch I would opt for the longer rods. The reasong I went with the short rod was because I had good pistons and they were matched to the block. I spun a bearing in my 350 and decided to go to a 3.75 stroke crank. This thing makes good power and has been very reliable. If you already have the rods and the crank you might as well build it. I can tell you I have a 6" rod 383 and there is no difference in performance. Both engines have been in the same car and ran the same E.T.. Don't get me wrong I think the longer rod is a better way to go, if you are starting from scratch or plan to really abuse it.

Royce

ragrat i have built an run two 383s i used the 5.56 rods with the stock 350 pistons.use to be the 350 pistons was cheaper than the 383s 5.7 pistons .the other two men are right with me as far as running ,no differiance.i also dont see any diferiance in the 400s between 5.56s/5.7s.use good bolts in your rods

i agree w/ eric and the others on this one, but from all the research i have done on long rod combos, there is less improvements over longer rods than that, in all actuality. i saw a report (i can't recall where) on long vs short (stock) rod lengths where they show the improvements in piston dwell and such mathematically, and discuss it, and in conclusion they say the real world difference is extremely small. this is the sentiment of a few of the engine builders i discussed this w/ as well. but, since there is an improvement, albeit very small, if you are starting over, you might as well get a longer rod. i went w/ a 5.7 rod in my 406. my issue w/ the 6" rod in my application was that it puts the piston pin up in the oil ring lands, and you must use a support rail on them because of this. also in my opinion, of course this is just my opinion, with the piston pin higher in the piston, and overall piston top to skirt measurements remaining the same, it would make the piston slightly more prone to rock in the bore. just the oil ring issue alone was enough to make me go w/ a 5.7 rod, since any improvement w/ 6" versions are very negligable. and yes, do use GOOD rod bolts. just my opinion, good luck

[This message has been edited by 68rs406 (edited 11-25-2002).]

Here is some good info Grumpvette posted on Chevytalk...
http://www.chevytalk.org/forums/Forum64/HTML/012194.html

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383 Speed-O-Motive stroker kit with Holley 750DP, RPM intake,MSD6a box,World Products Sportsman II heads, ported and polished with 2.02/1.60 valves,64cc,TRW forged pistons with 10.7:1 compression, Comp Magnum 294s solid cam,Crane pushrods, Comp Cam 1.6 full roller rockers,MSD Pro Billet,ATI damper, 40 series Flowmasters, 4.11 gears with TH350 and Hughes 3000 stall.

Thanks for all the help this motor has to only tach to 4600-5000. and power has to be mostly of idle. I was thinking of using the comp cam xe262. and 76 cc heads with the flat tops. I cant make too much power because of the outdrive I have. thats how the 454 ended up in my camaro.I couldnt use it in my boat.