Engine Masters rod ratio test results

[396project]

Curious about the longevity aspect--real time wear rates may have been more definitive.
Would measuring weight of piston rings before and after an automated break-in, using a laser scale for either combination (rod length/piston compression height) produce more definitive results than <1% in the performance department? I'd like to know how much interest I'm charging Peter long term to pay Paul $0.009.
-Mike

[Mark O'Neal]

for the ones that watched it what was your take on it? Were you surprised the shorter rods made more power?

No ... not at all.
Some people have simply kept their mouth shut because all the "experts" out there know everything; without actually testing.

Do you mean people like Reher and Morrison?

[BCjohnny]

Do you mean people like Reher and Morrison?

Paraphrasing the 'anything that connects the crank to the piston is the right ratio' phrase, concerning power, is practical for most cases

Long term wear & reliability is a different matter, when a longer rod is almost always easier on parts, not just limited to 'thrust' issues, speaking as someone who's always run the least amount of ignition advance to get the job done

[Walter R. Malik]

for the ones that watched it what was your take on it? Were you surprised the shorter rods made more power?

No ... not at all.
Some people have simply kept their mouth shut because all the "experts" out there know everything; without actually testing.

Do you mean people like Reher and Morrison?

Again; Not at all ... there are many others who could actually know but don't wish to argue with those many others who think they know.

[digger]

good thread.

is anyone here saying a 1.46 rod ratio would be better than a 1.56 rod ratio in any V8 app ?

https://www.enginebuildermag.com/2016/0 ... od-ratios/

http://www.epi-eng.com/piston_engine_te ... _to_f1.htm

rod ratios don't really exist in isolation.

[PackardV8]

good thread.

is anyone here saying a 1.46 rod ratio would be better than a 1.56 rod ratio in any V8 app ?

https://www.enginebuildermag.com/2016/0 ... od-ratios/

http://www.epi-eng.com/piston_engine_te ... _to_f1.htm

rod ratios don't really exist in isolation.

Agree, Digger. Reading the literature from the founding fathers, Harry Miller, Leo Goosen, D.R. Pye, all the way up to today, there are those who would run rod ratios of 2:1 if there were no constraints of cylinder block height, weight, engine compartment packaging, et al, but all those tradeoffs exist in the real world.

Same but different, I wasted many years of my young life trying to make horsepower with the then-new 289". When the 302" came out with shorter connecting rods, we all knew that would never work; too much side thrust. Today's checkbook 347" builds with a 1.55 R/S ratio are making enough horsepower to split the block down the middle using rods which are obviously unsuitably too short for the stroke.

[Joe-71]

I wonder how many of those 302 blocks that you day split down the middle had an aluminum stud girdle on the main caps? I have built and raced SBFs for nearly 55 years, and have never split a block. Every one I have heard of had an aluminum girdle on them. I believe it is the different expansion rate of the aluminum vs an iron girdle that promotes splitting the blocks. Joe-71

[David Redszus]

is anyone here saying a 1.46 rod ratio would be better than a 1.56 rod ratio in any V8 app ?

The term rod ratio can be misleading.

Suppose we have a fixed stroke and vary the rod length to obtain the above ratios.

That would be quite different than changing both the stroke and rod length to obtain the prescribed ratio.

rod.....stroke.....ratio
4.38.....3.0......1.46
4.46.....3.0......1.56
5.11.....3.5......1.46
5.46.....3.5......1.56

Rod ratio has no meaning unless the stroke is kept constant. Even if the ratios are the same, a
change in stroke will produce a substantial change in engine performance.

[swampbuggy]

This is information that in my strong opinion makes good sense ^^^^^^^^^^Mark H.

[396project]

Wondering if 300M (or forged titanium for that matter) for both rod 'combinations' would have resulted in more bias by their performance comparison?