Don Terrill’s Speed-Talk

I've asked this question before and haven't gotten an answer I can understand, but there's something at work in the formula which favors building to 400". So one more time, WIGO?

Maybe it's the builder?

It doesn't always.

Ours was 353ci last year.

Rick

Rick360 wrote: ↑Fri Oct 05, 2018 5:16 pm It doesn't always. Ours was 353ci last year. Rick

For true, Rick. I should have titled it, "Why does 400" win EMC most every year?"

More 400s than any other size?

I think it's the near optimum size given the rule limitations of the cylinder heads and rpm range.

There are probably opposing forces pushing things towards 400".

Things like carb limits, lift limits, cam limits, some years mufflers, etc, would tend to favor less cubes.

But the power to run the valve train, bearing friction, etc would "tend" to be close to the same amount of power for a 450 cube engine as it would be for a 350 cube engine, so those forces would tend to favor bigger cubes because the power taken by those things would be less percentage of a bigger cube than smaller cube.

Last year when the 353" won, the rules were kinda restrictive, but the second place engine was 451 cubes.
So the top 2 averages 400" LOL


Randy

One year BES Tony commented on how he browsed through his historical dyno sheets and right around 400 cubes was a sweet spot.

hoffman900 wrote: ↑Sat Oct 06, 2018 11:45 am I think it's the near optimum size given the rule limitations of the cylinder heads and rpm range.

YEP ... that is the opinion I have. The rules limitations mostly favor an engine combination around that size.

That is one reason I think they should go back to requiring every brand have the same C.I.D. as the others that year; smaller and larger than 400.
More different combinations would probably win.

Rather than start a new thread and still trying to understand the EMC internal scoring logic, I'll ask the same question a different way.

From all the past years of EMC, can we postulate a formula which correlates head CFM with cylinder displacement with Early Iron EMC results?

For example, a BBC, with available OEM iron heads can be built anywhere from 366" to 454", so which would you choose and why?

If the Studebaker V8 heads flow 200-225 CFM, would you expect to score higher with a 224" or a 310" or something in between?

For

PackardV8 wrote: ↑Mon Oct 07, 2019 10:48 am Rather than start a new thread and still trying to understand the EMC internal scoring logic, I'll ask the same question a different way.

From all the past years of EMC, can we postulate a formula which correlates head CFM with cylinder displacement with Early Iron EMC results?

For example, a BBC, with available OEM iron heads can be built anywhere from 366" to 454", so which would you choose and why?

If the Studebaker V8 heads flow 200-225 CFM, would you expect to score higher with a 224" or a 310" or something in between?

For

All the numbers BELOW peak torque is a function of the EMC scoring. Smaller engines NEED to be torquey engines so, a lot of mass air flow down there is somewhat counterproductive for those; getting the right balance is imperative.

I've thought about this a bunch and I'm wondering if the longer stroke, ~3.75 avg., gives you more piston speed to activate the intake tract when you can't weld the runners for length but increasing the bore much beyond the 400 cubes (give or take...) simply starts outpacing the cylinder head limitations.

That's the roadblock I kept hitting when contemplating an AMC build for the contest.

Jack,
Might want to talk with Mummert who is a member here. His 289 sbf came in second place and not where out of first.

390 FE (400") 2,511

289" (296") 2,504

427" BBC (429") 2,448 ( Jon Kaase)

404" BBC 2,412

Stan

Dyno sheet from testing

https://i1043.photobucket.com/albums/b4 ... sqdz8w.jpg

Congrats, Mummert! I remember him posting about that 289 in the other Engine Masters thread. Wow!

The 400 inch range thing isn't some magic number . I think it's just because those builders who have won with 400 is because that's what they usually build and are comfortable in that cube range

I remember when this topic first started...I mentioned back then that if that was true, how did Joe Carroll sneak right in there with a 302 Chevy? It wasn't some one year fluke,, he was always right there with all the 400's

he Debunked that theory