[jim_howard_pdx]

THANK GOD for go fast mercury.....and moxie.....

Thank you, thank you, thank you.....

I am sorry to bait all of you like this. I am not trying to mislead anyone. And I am not trying to b u l l s h i t anyone. I am trying to get you all to think through the steps to successful power building so you will make good engine building decisions.

Lets really discuss this thread logically, and see why rod ratio does or does not build any extra power. When you see where I end up, the light will click on and you will understand WHY certain engine configurations make hot rod magic, while others just simmer.

My real Speed Secret Number 5 should have read like this.... "If you increase your dynamic swept length, you will increase your horsepower."

Both of Moxie and go fast mercury deserve BIG bonus points on this thread.

I was wondering how long it would be before someone looked up the 428 numbers and called me out on this discussion point. I think some 300+ views took place and GO FAST MERCURY took the prize....at the end. (Like any good racers!!!)

I am not retracting anything I said about the benefits of a long rod ratio.......I am only going to explain the missing link that Richard "Isky" could only hint at!

So HERE is the entire point to my thread......, this is what you need to know when you engineer a world class engine....

Like anything about a basic engine the length of the rod divided by the length of the stroke alone does NOT tell you what horsepower you will derive from your engine. This is also true of static compression ratios. The compression ratio alone does not build horsepower or torque. That is because NO SINGLE FACTOR of your engine is responsible for ALL the horsepower you create.

Looking at static compression ratio as an illustrative example, (something I discussed on a different speed secret) I told you that to win a bracket, you match the maximum static compression ratio of the engine you are running, and then you use overlap and valve lift to create the cylinder pressure you need to power down the strip.

This is what Richard weakly pointed out in his discussion of cam timing, and how 2 degrees more intake event made more horsepower than running a longer physical rod length. SO THE DYNAMIC SWEPT LENGTH Plus proper cam timing combine to create the maximum available horsepower.

I just wondered who could explain to me why he is right???? And thank you Moxie for getting this discussion into this thread......

To simplify this information, just take the total stroke length and add the total rod length together. Compare this new sweep length against where you started. This total swept length is a great prognosticator for maximum power, but it is the rod length that most controls the piston dwell at TDC and this is where an excellent burn event combined with piston surface and stroke and rod length all add together to build the total torque and ultimately the horsepower curve of your engine.

For all of you trying to build the next killer engine, just take the total cylinder height you can play with inside your block. Then plan a way to maximize the total swept length of the stroke and rod together while maintaining the longest possible rod.

Remember Richard's warning about putting the piston pin into the oil or compression ring lands. When you reduce the blow by's ability to push out against the rings you lose piston seal and this dramatically reduces the cylinder pressure and torque production.
You need a good ring land to get good cylinder sealing.

Now look at the cam timing. You may or may not already know that your crank shaft spins the rod cap and bolts extremely close to the crank case on stroker engines. Many times we have to clearance these to clear the reciprocating parts. Did you know the same rod bolt and cap swing dangerously near your high lift, high duration camshaft????

The point Richard made was that there is a maximum lift and duration you can fit in the block with the rod and bolt combination you use. Knowing how to fit in the best cam timing, with the longest rod and the overall longest swept length will help you maximize what you can generate in horsepower.

So I am right, and Richard is right, and this points out why rod length arguments exist in the first place. Just remember that there is no one single factor of an engine that gives it all its magical power. It is really a combination of a lot of small contributing pieces that builds a racer's advantage.

Just to completely finish this thread and I promise you I am done now, unless someone really throws me something I did not expect.....this does in fact happen......Let's take all this new information I have shared and plug it into our first example.

Looking at the STOCK small block chevy we find a 3.5 inch stroke plus a 5.4 inch rod equals 8.9 inches. 8.9 inches is the dynamic swept length of the piston and rod. Now also examine the dynamic stroke ratio of 8.9 inches divided by the 3.5 inch stroke which is 2.5428!

Now look at my 351 Windsor STOCK. 3.5 stroke + 5.95 rod equals 9.45 inches of dynamic swept length, divided by 3.5 yields a 2.700 dynamic stroke ratio. So is it just the 0.16 dynamic stoke ratio that accounts for me taking every chevy 350 off the line? No it is really the 17 percent difference in the total DYNAMIC swept stroke that accounts for my coming out faster...... As long as I am not sleeping at the tree......

Now lets look at the 428 STOCK. 3.98 stroke + 6.488 rod equals 10.46. Divide by 3.98 and you get a 2.68 dynamic stroke ratio.
My favorite Ford engine is the side oiler 427. It has a combined dynamic swept length of 10.268 vs the 428's 10.46. That is why the 428 replaced the 427 wedge in Nascar racing. It was a more effective torque producer!!! The 428's dynamic rod ratio is a little shorter 2.628 to the 427's 2.7164.

That is why we liked to use a 427 side oiler block, add a 428 crank. This ended up supplying 454 cubic inches and I never frankensteined one of these that did not produce in excess of 500 flywheel horsepower with the stock 425 hp 427 cam!!!!!

In summary, it is the rod length PLUS the stroke length of the mill between you and your competitor that you should work to increase. Then make sure you are not giving up too much piston surface because that also effects ET times. Crank throw, plus rod length, plus piston surface area AND DYNAMIC COMPRESSION all combine to deliver your torque curve and horsepower curve. He with the most area under the curve generally wins.

I am sorry if I kept all these details out until the bitter end, but I really expected someone to call me on the hard numbers right away.

I am glad that Moxie and Go Fast Mercury are interested in looking over the details. Thanks guys!!!! Now we can all see how rod length works in the overall scheme of things.