Don Terrill’s Speed-Talk

gmrocket wrote: ↑Tue Oct 08, 2019 8:55 am 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

For true, there's always an outlier; this year it was Mummert's 289" SBF. However, a 400" did win.

Still searching for the correlation, if there is any, between the higher EMC score and the relationship of the scoring algorithm, intake CFM and cylinder displacement.

Even when the 4V Mods were allowed in they were 400 CUI or close right?

Rules, piston speed, the availability of heads and manifolds that are sized more correctly for that cubic inch in that contest, the way the scoring is done( a lot of misconceptions about that btw), just to mention a few off the top of my head…...sort of an evolution, but not one that can't be broken. One hard rule change at any time can do away with a certain cubic inch advantage almost immediately.

One thing is for sure, If the Race engine challenge were to evolve and take off...and rules and scoring process were to stay similar....you wouldnt see much 400+ stuff there, unless that were to become the minimum cubic inch by rules

I did a tour of the Rotax engine factory a fews back. The engineers said then that in two stroke engines the magic number for making efficient hp in their engines was 700cc so on a twin thats 350cc cylinder. They said after that size the cylinder is tougher to fill,harder to control detonation etc. They were consistently known for the highest hp per cube in two cylcle engines. This may hold somewhat true for auto engines as well. The 400 cube motors would have over twice the size bore but the 4stroke setup gives better time to fill cylinder as two strokes but definitely the smaller bore easier to fill and control deto. Now with the electronics the two stroke bore size has been able to grow.

Seems many Euro/Foreign engines hold fairly close to that 500-600cc per cyl avg vs the EMC avg around 800+cc but then they are usually 4-5 valve ohc
2.0-2.4l 4cyl
3.0-3.6l 6cyl
4.0-4.8l 8cyl
5.0-6.0l 10/12cyl

Is this just a keeping up with the Joneses thing, packaging, emissions etc?

I may have missed it, but were the E.M.C. rules written (2) valves per cyl. max. Mark H.

tt 383 wrote: ↑Tue Oct 08, 2019 11:46 am Seems many Euro/Foreign engines hold fairly close to that 500-600cc per cyl avg vs the EMC avg around 800+cc but then they are usually 4-5 valve ohc
2.0-2.4l 4cyl
3.0-3.6l 6cyl
4.0-4.8l 8cyl
5.0-6.0l 10/12cyl

Is this just a keeping up with the Joneses thing, packaging, emissions etc?

It could be. More than likley helps to get the smaller engines into the smaller compact engine bays. Ford has taken a similar step with their smaller mod style engines. I think when they switch to small cylinder easier tocontrol emissions and make more hp/cube. Especially with 4 valve layout. The Rotax guys said when they built the 1000 twin it was a big problem to control the detonation and the harmonics associated with a 180* twin. The smaller engines could be made to perform as well with less warranty claims.

swampbuggy wrote: ↑Tue Oct 08, 2019 12:02 pm I may have missed it, but were the E.M.C. rules written (2) valves per cyl. max. Mark H.

Yes pre 68. We are just generalizing on the smaller cube setups.https://st.hotrod.com/uploads/sites/21/ ... LG-002.pdf It does not say 2valve only here however does say North American above. Dont recall any pre 68 multi valve?
I gotta say the .550 lift rule for small blocks and .600 for big is impressive for the power they made. Very cool.

As Steve K. said, I believe the small bore by the O.E.M. manufacturers is primarily driven from an emissions and packaging point of view.

I seem to remember 4" bore X 4" stroke SBF engines being a top scoring engines for a while. It would make one think the 4" bore being big enough to breath well, and an advantage to a longer stroke. The Cleveland heads probably didn't hurt much as well.

I think people put too much importance on bore/stroke in emc type of contest.

Any time the rules are restrictive it will favor less cubes. Carb size limits, lift limits, etc all restrict larger cubes more.

Be interesting to scale the rules to the cubes.
Say,... like under 365 cubes 1,40" venture size limit, under 440 cubes 1.60" venture limit, over 440 any 4500 carb that will bolt to a standard 4500 bolt pattern.
Lift limit,... under 365 cubes .600",...under 440 cubes .700" lift,..over 440 cubes no lift limit.

Valve size,... under 365 2.05" intake,... under 440 cubes 2.100, over 440 cubes no valve size limit.

Don't hold me to those sizes, but something along those lines, where there would be some decrease in the restrictions as cubes go up, and over a set cubes the rules open up to see if it makes larger cubes become the preferred engine size in the emc.

In a side note, in 2017 a 353 cube won it and a 450 cube engine was second place, so 400 cubes don't always win.

Randy

Ducati had pushed bore limits to 116mm (4.56”), but all subsequent bores are going to be 100mm (3.93”) max from now on for combustion quality.

Of course they’re trying to light off a bore that big that revs to 14,000rpm.

PackardV8 wrote: ↑Tue Oct 08, 2019 10:05 am
For true, there's always an outlier; this year it was Mummert's 289" SBF. However, a 400" did win.

Still searching for the correlation, if there is any, between the higher EMC score and the relationship of the scoring algorithm, intake CFM and cylinder displacement.

There is more left in that 289. Damn gremlins.......

Someone putting together a scoring algorithm over the past 17 years would be interesting.

Intake valve to bore size is certainly a factor, rod to stroke ratio (for what that's work) and I wonder where the number 1 cause of friction comes in, Rings ?

400" +/- just might be the "Sweet spot" for the 90* V-8

The rules have changed a lot over the years too, so that will effect whatever index you come up with. Way less run what you brung, which has caused me to lose interest, but I can understand the reason (marketing) why.

IIRC, the first year was 366" limit smblks, second year was 470" limit BB, but I don't recall if you could be smaller. 2004 was 410" max limit and I know there were a couple 383's and at least 1 Ford 393" crate engine.

This is Kaase's winning pull from his pump-gas 1.7 hp per cube 410" Cleveland (CHI Heads): I think it was 11.5:1

I've been meaning to graph this out to see the curve.