I'm not sure there is a right or wrong on this subject. It depends on how long a rod you're talking about, and what the application is for the engine you're building. I'm gonna put a link here ... its a long article, but its very interesting, and there is a lot of logic in what he says IMO. Its related to some Honda modifications so you'll have to get past the honda part (about the middle of the article where it starts ... "Long rod .... You have no idea how many")
This was written by a guy some say is the Albert Enstein of engine design, and others swear is the biggest con man since P.T. Barnum.
http://www.theoldone.com/archive/crv...trokeratio.htm
Like i said its long and technical, but there is a lot one could learn here, and food for thought and probably debate too ;) :D

I brought this up to my Dad and he had a couple of interesting points.

#1 big car companies havent jumped on this band wagon because of all around engine performance.(the longrod mainly helps in max Acceleration less than 5% of normal driving)

#2 in WWII Royle's royce made some long rod airplaine engines 15000.+ rpms but had problems with deceleration and piston life due to small piston skirts.

#3 what rod ratio's are top fuel and funny car using. also indy if anyone knows.

#4 as far as the car companies why arent they using aluminum blocks and heads in all there cars and turbo's on every model.

#5 Tehnically thats what weve done by using a smaller 302 piston (height same bore)in our 351 (my street ??? car ) but that wasnt the reason why.(so we didnt really increase the rod just decreased the piston height)

#6 I would race Jim Howards race winning 428 or what ever any day of the week and we'll see who wins.(ps the drag car not my street car) boost versus long rod.

#7 race weight can help more overall that a longer rod.

its interesting but not worth the time its been given . now cams thats something i still need help with

Choose to believe or not, but my experience having been lucky enough to witness an actual dyno test of 3 motor all identical except for rod length, cough they were Chevy's but the theory is the same cough, all three motors dynoed within 10hp and ft/lbs of each other at the crank with no accessory. The only think that was noticed was while they produced the same power and relative power curves the curve it self would shift either up or down a little bit, a little bit being less then 500 rpm, but you could lay all three graphs on top of each other and they would basically all lay on top of each other if you shifted the rpm +/- the slight shift in rpm. Me personally after seeing that no longer subscribes to the theory of long rods being better... especially since the long rod shifted the rpm up without a any real power gain. Well personally I would rather make same power a little lower on the rev scale and keep my motor altogether a little longer since revs will kill your bottom end as fast as changing you oil will. Now I don't thing that the slight shift up in the revs would promote that much faster wear but if you are spending the money and are putting something to together that compared to stock will have accelerated wear anyway, why put it together with just one more thing that will cause faster wear (the slight shift in RPM's being higher).Now that all that has been said the three motors were not extreme examples of rod lengths but were common lengths used by allot of people when doing there Chevy's IE the long rod motor was a 6" rod vs. the stock 5.7 and If I remember correctly the shorter was a 5.4 just because if they were going to test the rod length theory they had to put something to together with short rods.


When he tells you it has a 400 SBC crank is he sure it is not a 400 ford crank? That was actually a popular swap before all the after market crank manufacturers started making new stroker cranks. The 400 ford crank has enough meat in it that it could be offset ground in a variety of different lengths and to the Chevy or Chrysler rod bearings and ford main bearing sizes. The 377 kit that is sold to this day by many vendors is based on a 400 crank with stock throws, Chrysler rods and Chevrolet pistons in the 9.5 deck block.

Damn!!!.......I bet your right 400 ford crank.

When I heard it had a 400 crank in I just assumed chevy since he said it had chevy rods:o

Im gonna go crawl under a rock:eek:

The thing about it is, it can't be a 400M crank in it either. They have a 4" stroke, it will not fit in a 302. And from my understanding, this is a 302 block.

The thing about it is, it can't be a 400M crank in it either. They have a 4" stroke, it will not fit in a 302. And from my understanding, this is a 302 block.