DavidNJ

This year it is a 434. The World block and I believe the World and ET heads are eligible. Shafts are only legal if they cam that way OEM, so I'm not sure if the ET 265 could get in.

I wonder how big you could push the bore for the competition. The deck height rule is: I don't see that as an issue though. The competition is being held at World's facilities on Long Island, and they are an engine block sponsor.

Competition would come from big blocks and Clevelands. The big blocks all have tall deck heights and lots of big flowing heads. However, for a 434, would the LS1 now be on an even par?

Link to the rules: http://www.popularhotrodding.com/eng.../0601em_rules/

There are legal Cleveland heads with 2.25 intakes and 9deg/4deg canted valves for Fords, which can use the Ford/Dart/World aftermarket blocks. So the competition will be rough.

What intake manifolds are available?

Old SStroker

To be eligible engines had to have originally been sold with a distriblutor. LSx are out.

Thoughts:

You need to go for all the little gains you can.

If you go for big bore/short stroke to keep friction hp loss down, a 4.5 in bore 3.41 stroke BBC doesn't look bad. With the power levels needed, very small bearing journals will work.

With 10.5:1 SCR detonation shouldn't be the problem it has been in the past few years. There are legal BBC heads which lend themselves to the kind of flow needed without having to do much filling. Intakes are plentiful.

Headers are a challenge, especially if you really want to work on tuning. 180* headers aren't allowed, which limits you substantially. There are probably legal ways to work with that, however.

DavidNJ

I missed that line!!!

The winning combos in the past few years have more often been long stroke small bore. The issue being less time at TDC and less shorter flame travel. All to live with 12.5 or so compression on 91 octane. I believe most also coated the pistons, valves faces, combustion chamber, exhaust valve stem, and exhaust port to help with detonation.

The fifth place engine in the last small block contest (2004) was a 8.2 deck height Ford with a 3.6" stroke and 5.47 rods. A 1.52 ratio.

That contest was also dominated by the low angle canted valve (9deg/4deg intake) aussie aftermarket Cleveland heads.

Ben R

Small Bore/Big Stroke always wins in this contest. If I were doing an LS1 I would do 4.03 x 4.250.

DavidNJ

For the challenge, yes. That would give the small blocks an advantage over the big blocks. It sounds like a Cleveland win again.

However for the street the EM has a rather constraining set of rules (2500-6500, carb, distributor, no knock sensors). Shifting the target power band and adding electronics to control detonation changes the equation significantly.

SStrokerAce

iTrader: (2)

You guys notice a big change in the rules? Maybe the compression? When you are trying to keep detonation down you need a small bore to do so.

One of the reasons why a canted valve motor has won the contest since 2003.... only way to get any valve size in a small bore is with a canted valve. 2003 Kaase=BBF, 2004 Kaase=Cleveland, 2005 Bergquist=BBC. The top 5 is usually full of canted valve heads.

Maybe a inline head can win this year.

The big deal now is they have to tell you if your head castings are legal or not... They should just open up the rocker arm rules to shaft mounts and keep the valve angle rules like they had for the first 4 years.

Either way, I don't know about you but a 10.5:1 compression ratio on a bad *** street motor is pretty lame.

Bret

Ben R

I disagree. They only care about power to 6,500, which means you have to throw a ton of piston speed at it down low (Big stroke) to take advantage of the heads they are using. They get piston speed through stroke, not RPM. IMO it doesn't have anythign to do with flame travel or anything like that.

Old SStroker

That's a concept that I have not yet understood. Please enlighten me.

You are saying piston speed is a good thing and 1700 ft/min mean PS @ 2500 is better than 1400 ft/min for breathing? I still don't see the correlation. It's not like the chunk of air being injested is attached to the piston with a string or even a spring. At 2500 rpm, with the long stroke (1700 PS) the average intake velocity is about 4.8 times the mean piston speed and with the short stroke (1400 PS) it's about 5.8 times PS. The air is rushing in many times faster than the piston is moving out of the way.

Help me out here.

chuntington101

is water injection permited??????

would allow you to run much righer comp ratios and still run on pump!

Chris.

Old SStroker

Nope.


http://www.popularhotrodding.com/eng.../0601em_rules/

DAPSUPRSLO

iTrader: (14)

I see what is being said about the pistons speed causing a larger pressure drop and hence sucking in more mixture, but if the motor size is kept constant (therefore the longer stroke motor having a smaller bore vs. the shorter stroke having a larger bore) and the same area is displaced won't the same pressure drop across the port occur (without considering the difference in instantaneous pistons speeds at top dead center do to long rod vs. short rod). Further won't the shorter stroke combination suffer less friction loss. I understand that the small bores work great for subdoing detonation but with 10.5 to 1 as a limit this year I don't think that will be as big of an issue.

How bout a large bore, short rod combination? Would keep the shrouding of valves to minimal, accelerate the piston quickly from top dead center and pull in maybe a little more charge, and not suffer big losses do to friction. Just and idea

Just some food for thought?

Normally i would choose the biggest everything but when there's a size limit to the motor obviously a comprimise must be made in bore and/or stroke.

Old SStroker

That makes lots of sense to me also. Ring friction is about 70-75% of total friction hp loss, so that's a good place to pick up points.

10.5:1 SCR is probably going to give a DCR below the optimum for the 91 octane spec fuel. Shorter intake timing to increase DCR may limit how much air you get in, which is Job 1. So how about a very long rod to "dwell" the piston near TDC while the charge burns? Long rods may work this way to "crutch" too low compression.

That makes a big bore/short stroke/long rod engine a reasonable possibility. If you do the numbers for some big block standard deck heights, you get a combination like 4.500/3.410/7.00 which gives a rod/stroke ratio just over 2:1 which isn't out of line.

Do I think EMC contestants are all rushing to these kind of numbers? Not hardly.

When you get down to the last few %, which seems to happen in all serious competition, treating the single carb V8 as a bunch of single cylinder engines or at least as V4s with "corner" and "center" configurations requiring different valve and spark timing makes sense, but costs lots of $ and time to test. About the only folks with deep enough pockets are the most highly financed Cup teams. We could learn from them if they would talk about it.

If you get to read/hear anything about this from Dr. Andrew Randolph, study it thououghly. He doesn't necessarily talk like David Vizard, but with some background and study you can make sense of what he says.

SStrokerAce

iTrader: (2)

Are you guys kidding me with this piston speed thing? The heads don't care how the cubes are pulling on the intake port, just that it is pulling on it. The displacement is the reason not the piston speed. If you look at the forumulas for the average velocity of a port you can use either RPM and Displacement or piston speed AND piston area. As long as you have cubic feet per minute you are fine. The physics of filling a engine cylinder is all about high pressure going into low pressure, that's it.

The thought that piston speed is what they need is almost as good of a laugh as the use of a long stroke in those motors to make more TQ because it's a longer lever arm.

Bret

racer7088

The smaller bore engines will again win and the guys that are building to win are again going that way. Smaller chambers make more power and detonate less but with the 10.5 limit this will matter less now. The deal is to create the right port speed and do it at the right rpm window and this is where piston speed comes in. It's a concept that most people just don't get and that's really not a problem if you can't so I wouldn't worry about it too much.

You want a bore and chamber that is the smallest possible one you can make that still has sufficient airflow to totally fill the cylinders with a reasonable cam. This means you have all the ingredients to make great BSFC and win that contest. The friction is not that high at 6500 rpm on anything and thus the traditionally used "terrible" rod ratio combos that always seem to win. The ring friction has very little to do with stroke and everything to do with the bore finish and the rings being used.

SStrokerAce

iTrader: (2)

Pressure drop is created by displacement and RPM os said in other words piston area and piston speed. Cubic Feet per Min.... it's the only way you can compare the Cubic Feet per Min of average port cross sectional area and average intake velocity.

The physics of filling a engine cylinder is all about high pressure going into low pressure, that's it.

I'm starting to feel bad for the SAM kids now... they have to weed thru BS to figure out what is right and wrong in their education. The KEY to a good education is that it teaches you to question everything and not "learn" or in this case "teach" with regurgitation.

We are going to have to start breaking out the Smith & Morrison and Taylor & Taylor here soon to prove that this IS the case.

Bret

Old SStroker

Questions for you, racer:

1) Is it great BSFC that wins or is it great BMEP? .300 BSFC on a 175 psi BMEP engine probably won't make more average torque and hp than a .500 BSFC 200 psi BMEP engine.

2) Assuming that both the long stroke and short stroke builders know how to choose the "best" rings and prepare the bore finish equally well, are you saying that the long stoke engine with higher piston speed and more total ring swept area will not have more friction hp loss?

Ben R

You really are an idiot, Bret.

Ben R

You took that out of context. Erik meant that the engines that do well in this contest have good BSFC's, not that the key to winning is having a good BSFC, although it is a good thing. Good BMEP always wins a HP contest, of course.

Old SStroker

Guess I don't rate a reply form the horse's mouth.

Don't you just hate it when politicians have to have their spin doctors tell folks what the politician really meant to say? I do. That's one of the reasons I went into things mechanical rather than things political.

DavidNJ

Brett and Ben, please play nice. Just make your technical point. If one is right and one wrong, it will come out in the facts. And my guess is, if the hostility stopped, the disagreements would prove to be misunderstandings rather then conflicting concepts.

Now a question: the effect of piston speed--a function of bore/stroke, rod ratio, engine speed, and crank position--could be related to what the flow sees at any point in the stroke. A big bore keeps the piston closer to the incoming mixture. The piston displacement/speed/acceleration profile would determine what the pressure change from cylinder enlargement is at any point in the stroke.

Does this become a matter of tuning the point in the flow curve to the piston displacement curve?