Speed secret # 5

[jim_howard_pdx]

Ultraflow,

What I can tell you about rod ratio is this, every race engine I have ever built to run 180 mph or faster had a minimum of 2.05 rod to stroke ratio, and most had 2.1 to 2.2. After 2.2, you actually do better adding extra displacement since the burn event is pretty much over in about 40-50 degrees of crank movement.

So for the Chevy crowd running 1.5 rod ratios, my 351 at 1.78 comes out of the hole much faster and revs faster too. They have trouble building the low torque, in fact their torque curve tends to be highly peaked.

Like I said, most speed shops do not know how to build a world class race engine. When Trans Am cars were limited to 302 cubic inches, we were well into the 178 mph range on these cars. When NASCAR set their limits to 355 cubic inches, almost every team was hitting 190-210 mph in the straight aways with a two barrel 500 cfm carburetor. You gotta know they were running long rods.

Hope this helps...

My 428, when it made the finals, only lost two races. One was to a 500 cubic inch chevy, and the other race was to a 426 Hemi. Both beat me by less than 48 inches at the finish line. At this proximity, it is launch quality and reaction time that determines the winner. I ate a fine cuisine of short rod big blocks in my time, and they came up wanting..... Even the 427 Fords couldn't hang with me in my bracket. (short stroke, short rod, huge pistons, this design is called "over square". It does very well on track courses where the rpm capabilities of the 427 allowed it to dominate until the 428 and then the 429 replaced it.

The 428 was a little bit of magic with its 1.88 to 1 stock rod to stroke ratio. There are very few engines before or since with these types of ratios.

Building a 10 second car is getting relatively easy. Like I said in different thread, it is getting to be like building with lego blocks.