Building two identical engines.....

[blykins]

When I have done serious ICL moves in EMC competitions it was working to optimize a defined power band with some surprisingly short duration, but really aggressive cams.  I ended up in places I never though I'd go (installed centerlines under 100 degrees).  It led me to go far smaller on camshaft than I used to use on street engines.  I never fully investigated the big ICL ranges on a milder build, but it could be fun.

Barry, I don't know if you have played with the iterators on computer programs, but they can return some crazy cam recommendations depending on your input.   Like 25 or 30 degrees more exhaust duration.  Seems ridiculous, but who knows?   If I were the Bill Gates of engine building I would try all that crazy stuff.   A lot of current LS cams defy our previous logic......

It's funny you mentioned installed intake centerlines and EMC engines.   EMC scoring is biased heavily to low and mid range. Sometimes when I input a desire for midrange power I get results eerily similar to some EMC cams.  Like tight LSA's and very early ICL's.   ICL's in the range of 96-100 degrees.    Seems crazy at first glance, but like you say, "engines can't read".

pl

I've tried the ridiculous duration splits (20°) vs a more conservative split on the same engine, with a horrible intake/exhaust flow ratio, on the same dyno day. A certain "custom cam grinder" wanted me to try out his cam, so I gave him all the specs, along with the camshaft that I was going to run.  Lost 28 hp and 10 average horsepower with his. 

[plovett]

When I have done serious ICL moves in EMC competitions it was working to optimize a defined power band with some surprisingly short duration, but really aggressive cams.  I ended up in places I never though I'd go (installed centerlines under 100 degrees).  It led me to go far smaller on camshaft than I used to use on street engines.  I never fully investigated the big ICL ranges on a milder build, but it could be fun.

Barry, I don't know if you have played with the iterators on computer programs, but they can return some crazy cam recommendations depending on your input.   Like 25 or 30 degrees more exhaust duration.  Seems ridiculous, but who knows?   If I were the Bill Gates of engine building I would try all that crazy stuff.   A lot of current LS cams defy our previous logic......

It's funny you mentioned installed intake centerlines and EMC engines.   EMC scoring is biased heavily to low and mid range. Sometimes when I input a desire for midrange power I get results eerily similar to some EMC cams.  Like tight LSA's and very early ICL's.   ICL's in the range of 96-100 degrees.    Seems crazy at first glance, but like you say, "engines can't read".

pl

I've tried the ridiculous duration splits (20°) vs a more conservative split on the same engine, with a horrible intake/exhaust flow ratio, on the same dyno day. A certain "custom cam grinder" wanted me to try out his cam, so I gave him all the specs, along with the camshaft that I was going to run.  Lost 28 hp and 10 average horsepower with his.

Maybe that "custom cam grinder' was using a computer program to pick his cams?  Like I said I would only try that if I were so rich I could throw money away.  Interesting though.  Thanks!

pl

[chris401]

There has been discussions on identical cubic inch engines and big bore / short stroke VS small bore / long stroke. If you had the same fuel intake, exhaust, static and dynamic compression on each.

The way I figure you change one thing it changes something else that makes it impossible to duplicate from one to the next. Have you figured out a way to equalize all the variables to settle the argument?

[blykins]

There has been discussions on identical cubic inch engines and big bore / short stroke VS small bore / long stroke. If you had the same fuel intake, exhaust, static and dynamic compression on each.

The way I figure you change one thing it changes something else that makes it impossible to duplicate from one to the next. Have you figured out a way to equalize all the variables to settle the argument?

Changing the bore and stroke would open up a bigger can of worms than what I'm interested in doing with these two.  Someone would have to pony up for some pretty custom setups.  FWIW, these are both 428's and are going to be both pretty period correct.   Both engines are going into Shelby Cobra replicas, both are 428's, both will have C6AE-R heads, both will have PI intakes, etc. 

Varying the compression ratio a half point, or changing the cam timing 6° will be easy while keeping everything else constant.  I will even use the same carb between engines.

[GerryP]

There has been discussions on identical cubic inch engines and big bore / short stroke VS small bore / long stroke. If you had the same fuel intake, exhaust, static and dynamic compression on each.

The way I figure you change one thing it changes something else that makes it impossible to duplicate from one to the next. Have you figured out a way to equalize all the variables to settle the argument?

Intake considerations become more critical when you gain cubics by way of stroke.  The reason for that is as you increase stroke, you also increase piston velocity as it moves away from TDC.  You can easily run out of plenum volume.  Something like a Performer RPM with a spacer might not be very sensitive to it even as a dual plane design, but something like a Streetmaster with a tiny plenum might suffer a bit even being a single plane and using a spacer.  This is where people who do this kind of stuff for a living can address the issues in the overall combination.  We who are just pikers think it's a humdinger and never know about what we're leaving on the table.

So, if this case, you'd have more than just displacement to consider since it does matter how you got that displacement.  Imagine another test where you had engines of equal displacement but of different configuration.  There are some configurations that have a natural advantage and the V8 is not one of them.

[DuckRyder]

I think engine masters (of the Motor Trend on demand Variety) did something with both bore stroke and ICL

I think:

3.  Aggressive cam lobes vs. non-aggressive cam lobes, keeping .050" duration, LSA, ICL, and lift the same between the two

Would be most interesting.

I know it is outside of the scope of what you're talking about here, but I'll throw it out there on the off chance someone could figure out a way to do it - what would be really interesting is to run them for a long time like 100,000 miles and see if the super aggressive lobe was in fact as hard on parts as it is thought to be sometimes....

[frnkeore]

Varying the compression ratio a half point, or changing the cam timing 6° will be easy while keeping everything else constant.  I will even use the same carb between engines.

What will be the duration and lift?

[blykins]

I think engine masters (of the Motor Trend on demand Variety) did something with both bore stroke and ICL

I think:

3.  Aggressive cam lobes vs. non-aggressive cam lobes, keeping .050" duration, LSA, ICL, and lift the same between the two

Would be most interesting.

I know it is outside of the scope of what you're talking about here, but I'll throw it out there on the off chance someone could figure out a way to do it - what would be really interesting is to run them for a long time like 100,000 miles and see if the super aggressive lobe was in fact as hard on parts as it is thought to be sometimes....

I think we have a pretty good handle on that one already.   You can *hear* an aggressive lobe and added NVH usually isn't desired because of the outcome.  In addition, the spring pressure requirements are higher.  That may or may not be a deal breaker in and of itself, but in an application with say, 3/8" stem large valves, the spring pressure requirements go up considerably.  Twelve years ago, FE's with hydraulic rollers hit a wall at 5500 rpm because most guys were running heavy valves in combination with aggressive lobes, such as the Comp XE or XFI lobes.  Adding spring pressure helped, but you got to a point where you could overcome the lifter function.

Changing to a much less aggressive lobe enabled the rpm range to go up because you didn't have the valve weight to overcome with spring pressure.   Changing to lighter valves on top of that opened the envelope up even more. 

If you notice, most "aggressive" lobes are indeed made for more modern applications with 7mm or 8mm valve stems, etc.  The aftermarket LS and Gen 3 Hemi guys can start to get into that sort of thing because their parts are a lot lighter in comparison to an FE, but a 100k miles is a long time. 

Even if you got a handle on the valvetrain weights (most of your SBF aftermarket heads come with 7mm or 5/16" stem valves and beehive springs with light retainers), an aggressive lobe can smack the valves against the seats harder/faster.   

[blykins]

Varying the compression ratio a half point, or changing the cam timing 6° will be easy while keeping everything else constant.  I will even use the same carb between engines.

What will be the duration and lift?

Haven't got that far yet.  Takes me a good bit to sit down and look at everything.