440,

You can get adjustable strut rod links with Heim joints (rod ends) to replace the stock bushings from Bill Reilly at bigblockdart.com. Nice pieces, and allows plenty of adjustment since you can cut/thread your strut rod to any length, and then adjust thread turns from there.

I recently visited Cameron Tilley in Australia, and he convinced me that less exh duration was the way to go on the 225, or at least it is working VERY well on his motors. His naturally aspirated road race motor has made 309 RWHP w/ a 3spd man or 286 w/ a 904 and has good manners and power range.

Lou

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Home of Slant6-powered fun machines since 1988

hey gearhead, long nice nutricious posts.
Now I understand why mar car is lame on low end... cam hasn't been degreed right. My cyl pressure drops to 120 psi when I set the lash to please the grinder's recommendation. Otherwise it has 160 psi. It's supposed to be a zero up to .08 lash lobe profile. (I don't understand lobe profiles enough to understand his recommendations, but I have the nice feeling that in about 5 of your posts I'll end up understanding cam's ABC)
Great experience you have going on, man.
You gonna help us to raise our tops. Thanks.

By the way, I'm working in a distributorless /6 ignition system with siemmens chip too. I have a 3 magnets balancer flywheel for triggering, with magnets @ tdc - 120° 240° and then other set of magnets placed 10° off (10°BTDC - 10 before 120 and 10 before 240) so my computer can read the rpm increase/decrease before the next cyl fires..., and I'm working with all-computerized stuff so I can plug in or out whatever I like too. I have a digital advance display, a dash mounted retarder/advancer $#!+... 4 diffrent programmable timing curves, locked up dist with no vac advance. I'm working also on 3 triggers at the flywheel and one coil per cylinder... so I guess I'll benefit from your experience as well.

thanks
welcome onboard.
Juan

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Thanks for the strut rod tip- but does he sell them in B-body and C-body lengths?


OK, so we now know that some OEM /6 cams had short exhaust duration, and we have a testimonial that you can get big power out of a short duration exhaust cam in a slanty.

Anyone know they physical reasoning behind that? Why is it different than a B/RB or LA engine in this respect? Yes, I know its got a long stroke and relatively short rods in comparison, but I can't see why that would explain it.

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The links are what you buy, then cut and thread your own strut rods to whatever length. Bill can set you up. Pretty sure they'll work for Bs, but not sure if C strut rods are thicker.

I'm pretty sure that the combo of the stroke/bore ratio and poor flowing head give you that shorter exh duration, but can't tell you why physically. There is still a huge unexplored territory here...

Does anyone know why a split pattern V8 cam (long exh) or even a matched pattern cam works best? I bet there are only a handful of people who understand why for sure, if anyone really does. This is a complicated problem in engine physics... I'd love to see a good reference on this.

It's really not obvious to me why having the same dur on int/exh is right for any engine. It's just a simplification so that grinding cams is easier and it's a small enough effect so that people's other modifications will make it difficult to test. Naturally, things like VVT and VLT and DOHC are the next step to making int/exh durations individually tunable.

Lou

_________________
Home of Slant6-powered fun machines since 1988

Hi again guys:

I had to go to ER yesterday for hours to help my girlfreind...she had a migrain that left her seeing things and going numb.

Then, last night, had to go with my old buds to see midnight Star Wars...I usually go to sleep before ten these days, so now I'm a little rummy and way behind in my work.

Lou:

Your ideas on ignition map vs Delta RPM(rate of change) is something I have thought about as well. Also, the use of the slope of driveshaft rpm change in conjunction with an accelerometer would allow (to some extent) a real world chasis dyno, allowing you to test for different acceleration of the car in different gears, accumulating data over a few runs should cancel out wind resistance and other facters, with the accelerometer readings used to decipher valid info based on changes in body position(climbing hills or not) etc...

I also plan on things like timing mapped to engine temperature for cold running...Many of my ideas were new and fantastic back in the 90's when I first put my mind to it...but now are what almost all systems make available...but that doesn't change the fact I want to do it myself.

440:

My strut rods aren't much different than those on Big Block Dart or many of the Ford handling sites. The only real difference in mine is that I have designed the location of the rod end(bushing end of strut) to be as close to factory pivot point as possible, rather than sticking out from the frame a couple inches.

I thought about this long and hard...and decided to start with the stock location and experiment from there...I even thought of extending toward the control arm deliberately farther than the others on the market because the arc the strut would follow would be of smaller radius, which should lead to more positive caster and toe-in under hard braking or acceleration.

But I decided to build stock geometry first and measure what happens once it is all installed.

My main reason to play with suspension besides I'm cash poor but tool rich, is I kept reading about the arguments over LCA urethane...I run Urethane bushings in all my cars for 20 years now...always happy. Modern stock bushing barely last a year or two with the crap floating in our air these days, and it just seems silly to use hi-perf everything except the LCA bush and not engineer a solution.

I engineered my own then found others had at least tried...first thing I did was drill the back of the LCA pin and tap it for a locating washer...then found the obscure thread about Doc doing the same thing...not surprising...seems an obvious solution.

But then I start reading about strut arms needing adjustability or at least to be shorter, so you can achieve positive caster while adjusting for neg camber with the UCA. But I don't particularly want to pull the LCA into a bind with the bushing by pulling it forward against its will...it may work, but will put a tightness in the bushing that will transmit road harshness thru the LCA.

So I look at the assembly, and it looks to have more than enough room to just shorten the pin and bushing a 1/4" or 5/16" to move the LCA forward but keep it in its normal relationship to the LCA pin and bushing. This gets you positive caster while providing full adjustment for camber even with a lowered car.

So, why not just machine a delrin bushing instead of the urethane, since you already have nice round hardened surfaces from the old bushing shells.

Whether all this works will be seen in a couple weeks when I complete it all and install it. I'm waiting on a part for my lathe to finish the rod-end frame mounts. AND, I have a big Pontiac race next weekend to prepare for and need to concentrate on that this week.

I am doing it again myself, not because BigBlockDart desn't make a nice product, but because I'm poor at the moment, can make it myself, and all the other solutions go only part way and don't completely engineer a solution to the age old problem.

If I kit the system...and now that I have spoken, someone will probably go out and use my ideas to beat me to the punch...I would provide all of the solution in one package, with an installation DVD describing the entire proccess and animations showing the suspension geometry and what and how changes affect it for a-body apps.

Or maybe I'll be too busy with whats already on my plate...

Slant6Ram and Argentina:

My system is about 85% hardware complete...I suffered a major setback last fall that is the reason I'm a Linux user now...a virus got thru what I thought were solid defenses, and killed my hard drive...I saved almost everything except for...the work I'd just completed on the circuit board designs for the final black box...poof!!! I must start over. Also, my digital dash cad designs to have the pieces laser cut went down the same road to la la land. And for some reason, my circuits will no longer fire my Saturn 0-7000rpm tach for the large analog face of my dash...worked for months...now it doesn't, and I have to stop and figure out whats going on. And...the cool potoshop images I created to see how my Displays would look with my tach in the laser cut dash...gone!

Like Lou, I plod along slowly thru multiple projects on a limited budget and slowly get things done.

That said...none of that is so hard, just time consuming...the hard part will be upgrading the fuel system on the car. My system uses a 1 qt stainless container to store fuel near the tank pumped from a small clicker fuel pump, this then feeds the high pressure pump, leading to the fuel rail and regulator(s), then the stock line for return.

I am trying to source mil-spec threaded connecters for the firewall now...and am moving the battery to the trunk soon and rewiring the car...I also want headlights, electric fan, etc. all controlled from my system. It also has a large cpability for data acquisition and will have a USB port and IR coms in the dash for communicating to a lap top or Palm.

Also thinking about adding memory card capability. I want the tach controlled by my box so that I can playback runs.

It will include multiple pressure sensors(two portable, one manifold pressure) so I can plot pressure areas around the car at speed...either to test for lowering drag, or to find the best place to dump exhaust or under hood air

The point in design I am at now...is the interface. What form of menu system, its options, and how to build it expandable with little work...what type of buttons and debounce to use...Also, need to design and build the wiring harness.

I have no plans to market or sell the system...seems to me it would be a nightmare of phone calls and tech support.

But I might be willing to build a custom system or two once mine is working, tested, and trustworthy...and that, still a couple years out at this point.

440 and Lou:

I would think the main reasons for short exhaust duration working in a slant are two fold(and I've heard of a few Pontiac people running this way as well)...first, lousy intake induction efficiency...two, small bore increases exhaust velocity during blowdown leading to great scavenging.

What this suggests to me...is that instead of larger valves for both...leave the exhaust alone or only slightly larger using a smaller stem diameter valve. And a larger intake valve, perhaps offsetting its location slightly to avoid valve shrouding. If the exhaust is working that well, we should concentrate on the intake flow, and then cam for whats needed in the exhaust.

Using a smaller stem would make it easy and relatively inexpensive (since you spend to go big valves anyway)to install a solid guide, and redrill it offsetting the intake valve.

Just a couple thoughts...

Gearhead aka Karl

_________________
64 GTO...10.80's@122 on street radials
Destroked 455, Qjet, stock ign, 2400 stall

64 Valiant
Old 225, 4spd, 2.92-8.75, 2bbl, headers
dual 2.25"

I wonder if the "lousy intake induction efficiency" is really just "lousy at high RPM. Those runners are pretty long, and my guess is that they are only tuned to any degree at the low end (and they're not all equal length, anyway). Above that, they give a nice curve with no sharp bends, but you still get a lot of wall drag on the intake air. Good candidates for "extrude hone" clean-up maybe!

And lets not even bring valve shape into it.. its already too complicated! But seriously, its important and you small valve stem comment reminded me of it. Different combinations of chamber shape and port shape respond VERY differently to different valve *shapes*, but the only place you ever see this mentioned with any regularity is when Hemi builders get to talking. Hemis (the old ones) responded well to tulip valves, the wedge-heads don't. The reason being that a Hemi port has a lot of extent parallel to the valve stem and transitions to the side gently, which doesn't induce a ton of flow perpendicular to the valve stem on the back of the valve face like a wedge port does. With the wedge port, the tulip is just in the way of flow, whereas on a Hemi, it smooths and enhances the flow. Its been long enough that I don't have a good visualization of the /6 ports in my head, but looking at the lil' cutaway up at the top as I type, they look like the're pretty dog-legged, and thus shrinking the stem diameter would be a BIG help (even apart from your use of it to re-locate the valves).

I'm not *sure* that I buy the argument that small bores increase exhaust velocity, at least not directly. When you get right down to it, exhaust port velocity is a function of the cylinder volume (irrespective of shape), RPM, and the valve and port cross-section. RPM sets the time alloted to empty or fill the cylinder, and cylinder volume defines how much air has to move in that time (assuming 100% VE), and the only variable is how big a hole the air gets to move through. I think small bores and high port velocity show up together often, simply because with a small bore you can't use huge valves and thus have a huge open cross-section to reduce velocity... but its not direct a cause and effect thing. If you put a small /6 sized valve in a hypothetical huge-bore/short stroke cylinder that displaces 37.5 cubic inches and spin the crank at 3000 RPM, the average port velocity would be the same as in a 225 slant-6 cylinder spinning at 3000 RPM. Yes, the flow vs. time graph would be a little different- and maybe that's enough effect right there. But my hunch is that the real cause is that small bores limit your choice of valve sizes, not that small bores inherently move the air much differently. IOW, since you gotta live with small valves, maximize velocity, whereas you can do other things if you have room for bigger valves.


just MORE fuel for the fires... no pun intended

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I shouldn't have used the word "lousy"...it is more a comparison of capability than anything else. The shape isn't so bad as a number of other factors that affected the design criteria...not the least of which was the time period and purpose for the engine design in the first place.

I was simply referring to the relative intake design to what we all know would be better intake design...even without describing it.

But the more air you get in...the more power you can make, as long as it can be exhuasted...which the small exhuast lobe success seems to show works well in a slant six.

I think you are correct 440 if you just spun the engine on a spin tron, or only looked at the intake cycle...but the key word was blow down.

The exhuast valve opens well before the piston reaches BDC on the coming "exhaust stroke", in the case of my cam choice of 260 seat timing, installed at 102 with a lobe sep of 108...I get the exhuast valve opens 68 degrees before BDC of the power stroke.

The reason for this is blow down. Most all the exhuast will be gone by the time the engine is pumping the piston back up the bore.

It is ny thought, and completely speculative, that when the exhaust valve pops open under extreme combustion pressure while the mixture is still burning and pushing on the piston...

@ 68 degrees BBDC...

which means the piston is still 1.6 or so inches from the bottom of the bore...

That all things being equal, the small bore of the /6 helps in building extra exhaust velocity out the valve pocket by the venturi affect.

When a river gets wide it moves slow, when narrow you get rapids...

I could be wrong, but isn't one of the reasons the 340 was changed to a 360 was emissions, you just couldn't clean up the exhuast with the huge bore stroke ratio. (and I know that is a whole nother discussion)

If the exhuast was non expanding gas being pushed out the cyl by the piston...your point would be well taken.

I don't think I've explained my thoughts well on this one...but its all I've got time for...got to get to work now...

gearhead

_________________
64 GTO...10.80's@122 on street radials
Destroked 455, Qjet, stock ign, 2400 stall

64 Valiant
Old 225, 4spd, 2.92-8.75, 2bbl, headers
dual 2.25"

Gearhead, I find most of what you're posting incredibly fascinating, even if I don't understand half of it.

Gotta love an old GTO too.

_________________
Official Cookie and Mater Tormentor.

My understanding regarding big bores and emissions is that its mainly a matter of "quench area"- big bore combustion chambers have more total surface area composed of (relatively) cool metal than "square" cylinders, and area = quench, which increases HC emissions. Also, its harder to maintain a uniform flame-front across a wide/thin combustion chamber than it is a narrower/thicker chamber. Most engines today have gone back from very "oversquare" cylinders like a 340, 383, or Buick 455 to a more nearly "square" chamber, and a few are even "undersquare" like an Olds 455 was (one of the ultimate examples of a small-bore/long stroke powerplant). You have to walk a fine line between surface area, valve size, and added friction from long-stroke designs when pushing the envelope with efficiency and emissions like modern engines have to do.

On "blow down," you may well be right. Things are very different when combustion dynamics are added to simple engine parts motion.

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Thanks for the comments SlantZilla:

And yes, I do love my old Goat...it was built in Oct of 63 and so was I...

My claim to fame is going very quick while remaining extremely drivable...even now with 600hp on tap...(and more built into the engine but not made available yet)...aside from being fairly radical sounding because of the full 3" pipes out the back and big engine...is that if you drove it around...it is very docile and runs like a mid 13 sec car around town. Idles at 800 in gear(even with only a 2200 stall 10" convertor), runs at 165 degrees in all conditions...even traffic jam mid summer, gets good milage, for what it is(12 around town, 14 at 70mph).

I have 255 60 15 rear 245 60 15 front, disk brakes, and urathane bushings front and rear. Heavily modified rear suspension to aid traction.

Anyway, it handles really nice whether cruising around, or mountain roads, (although its no vette killer) it doesn't feel at all like a 10 second drag car...Until...that is, you nail the throttle, at which point you get one hell of a ride, still pulling as hard in high gear as first...even at 120 across the line. Traction is awesome even on the street, and the engines power band was carefully designed by me to make the traction very controllable.

Only picture on the net right now is in the upper left corner of the animation on my useless web page:

http://www.ponchopower.com

Its an awesome car and I love it!!!

Argentina:

Here is a picture of my own locked out distributor I cobbled together.


My system only uses three magnets and calculates rpm for two pulses(120 degrees engine rotation), then fires the same timing for two cylinders in a row, while starting a new rpm calculation while the second spark plug fires. I spent alot of time thinking about various trigger methods and resolution I wanted and such...I'm sure...much as you did... and some of my original thoughts took me to a design almost exactly like yours. But I wanted to simplify things as much as possible for this first system, figuring if it works, I will more than likely take what I learn with this one, and redisign for extreme everything!!!!

My main thought, was that even with the rpm changing at say 1000 rpm per second in first gear(and this would be a value representative of a race car in first gear)...this means the rpm changes 100/per tenth sec, or 10 rpm per .01 sec, or 1 rpm every .001.

As you can see from this chart I did:


If you go even to a fairly high rpm near shift point of say 5000rpm, then the crank rotates 1 degree in .00003333 seconds. Multiply this by 120 degrees and you get .0039 or basically 4 thousandths of a second. So for any 120 degrees of revolution the rpm only changes 4 rpm(1 degree per .001 times numder of seconds between firing of plugs... .004 sec x 1 rpm/sec) even at 5000, with an acceleration rate of the engine of 1000 rpm per second.

This acceleration rate is probably well above even a good running, low geared, typical slant six...so I'm being conservative.

So even if I measure the rpm over a 120 degree sweep of the magnets, then wait and fire the next two cylinders in a row without changing the ignition timing value, the rpm will only change by a conservative 8 rpm between my softwares decision making about ignition timing...and, it will be less of a change for every other gear as the rate of change of engine rpm slows down.

I figure this is a huge improvement over the accuracy of the stock distributior with the associated timing chain slop, cam flex, cam movement back and forth(which changes timing as gear mesh changes), crankshaft torsional twist and its affect on piston position...etc.

So its good enough for me and saves alot of overhead from the black box brain.

That said, there is more than one way to do almost anything, and your system simply gives even more resolution, which can't be a bad thing.

my software operates from a basic timing curve, that then gets modified by what the value of sensors and such say. This also saves over trying to create a 3D ignition map, it simplyruns thru a decision tree each pass and adds or subtracts from the base curve.

My plan is to install the digital dash to test the electronics in the car, then install the digital timing but thru a distributor(the one in the pic) to play with that...then when dialed, install the dual throttle bodies and experiment and learn...then redesign the system for port injection and distributorless ignition.

My distributor sends its VR signal(the sine wave signal that comes out of a stock electronic Mopar distributor) to a 7 pin GM HEI module. this module takes the signal and sends out a 5 volt square wave to the computer, and waits for me to send back a pulse that is when I want the spark to fire...in the mean time, the HEI module has been charging the coil and waiting for the return signal.

Very simple elegant solution.

Karl

_________________
64 GTO...10.80's@122 on street radials
Destroked 455, Qjet, stock ign, 2400 stall

64 Valiant
Old 225, 4spd, 2.92-8.75, 2bbl, headers
dual 2.25"

I think thats part of it 440...

I knew that mentioning that example wasn't the best...but...part of why the extra quench(cool areas in the chamber) can result in this problem, is because a big bore engine is constantly exposing much more cylinder area for any given piston position in the cyl compared to a small bore engine, this means that the conbustion gases have a more dificult time burning completely through...however, it also means more pressure on the piston during critical crank angle positions(hence broad torque curve in small bore and peaky in big bore(again simplified)...so my point is that for any given piston position in the bore, the smaller bore tends to promote more complete burning while the mixture is trapped in a smaller area that is not increasing in size as quickly as the piston is pushed down the bore...

I think modern engines get away with it mostly due to much more efficient combustion chamber design.

Anyway...good thoughts 440...yum...stimulating...

Karl

I'm outta time and must go...

_________________
64 GTO...10.80's@122 on street radials
Destroked 455, Qjet, stock ign, 2400 stall

64 Valiant
Old 225, 4spd, 2.92-8.75, 2bbl, headers
dual 2.25"