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New pistons and reconditioned rods are ready for assembly. The new pins are undersize 4340 steel and the rod ends are bushed and center hole distances matched to within .0005".

Work was done at Speed-o-motive per recommendation from Chevyman. They magnafluxed, straightened, shot peened and installed ARP bolts. This old 6 will rev with confidence now

[img]http://www.kinemation.com/Trucks/Images/piston&rod01.jpg[/img]

close up of bushed rod end.

Do those pistons have snap-rings to keep the pins centered?
It looks like they are machined for it in the wrist-pin boss.

Mechaniac,

The pins are retained with double spiral lock rings. The machined notch is in there to aid in getting the dang things out once they are put in. Without the notch, they are nearly impossible to get out without destroying something.

Ken

Ken: Looking Good! Those should do the trick. Are you still planning on future blower install on your 292? If so you might want to possibly consider having a thermal ceramic coating applied to piston tops. Hyper pistons tend to "reflect" heat and will give you hot spots. You may experience detonation problems. Detonation will more likely be experienced at the lower RPM's as the valve overlap and retarded ignition will yield there greatest net "effect" on the combustion chamber and flame front. As RPM's rise and exhaust pressures will stablize and more evenly balance the intake. The blower causes a "gulping or pumping" effect against the (lower atmospheric) exhaust side of the combustion chamber at lower speeds. Anyway you get the picture. You may want to also consider smoothing out the chambers to remove all sharp and rough edges, as they will also aggrivate detonation problems. You can also have the chambers ceramic coated. Update, and let us know your future build plans?

Think Chevy!

Chevyman,

I hadn't thought of ceramic coating. I am hoping that because I am using a Whipple style positive displacement compressor that the gulping effect will be minimal. Also, I will be running a miller cycle cam and while the absolute compression ratio is 9.5:1 with the way it is set up now, with the delayed closing of the intake valve, I am shooting for a realized mechanical compression ratio of 7.5:1 and will be running around 12 psi of boost with pump gas.

Who do you recommend for doing the ceramic coating? also, I haven't bought rings yet. Ring spacing and size were arrived at jointly between Spdomtv and Ross. But I had a brain fart and forgot to get the rings ordered. Also any thoughts on ring gap for this setup would be greatly appreciated.

Ken, those pistons are to pretty to go in an engine. For safekeeping I will be glad to hold them in storage for a few years. I know how rusty things get from all the saltwater up there.

That's a great picture Ken , what sort of digital camera are you using ??
Have you thought to use a pressure retard device like is on the Corvair Spyder to help prevent detonation ??

Hi Fred - the pistons are a lot prettier than what I took out of the motor. But those are the stock rods from a mid-60's 292 with a lot of miles. I better get them INTO the engine before they rust

Dusty, I am working on the timing / fuel injection engine management software now. I will have a manifold absolute pressure sensor that will work with the engine speed sensor to figure out spark advance - the software tweakable version of what chevy had on the spyder. I will be able to do the equivalent of changing advance curves / vacuum or pressure advance and retard on the fly. . . I will also put in safety limits in case I fat finger something on the keyboard so that I don't turn the whole works into a pile of scrap iron and aluminum. This motor is going to be a mix of something old . . . something new. A fun blend of two of my hobbies. . .

I bought a Kodak DC280 camera for work about 2 years ago for $500. It is a really good camera. A couple of weeks ago, I checked on ebay and picked another one up for $200 with all the accessories and bag for home use. I upgraded with Windows 2000 and can read the memory cards now directly in a PCMCIA slot on my laptop so getting the pictures off the camera memory card is a snap.

Ken: Never seen any information on a Miller cam but it must be a speciality design with later intake closing. This can be achieved in several ways-

1. special grind with wider LDA

2. dual pattern w/more intake lobe duration

3. special ground w/retarded intake

4. special grind w/stretched out long slower closing ramp

Most street blower set-up's use stock cam that is simply retarded. The standard thinking here is to use offset bushings. Moving the cam drive pin by about .005 offset will move cam about 1 degree, more or less.

Your 292, any what you are trying to achieve as a finished engine are a (how can I put this in a nice way) a peculiarity! I don't mean this in a bad way. It's just that your build up would be much more simple with lower compression (static) to begin with. Running with 9.5 in NA trim would be fine. But when you install the blower with 12 psi boost, you have to retard ignition and intake closing so radically to achieve enough lower dynamic compression to make it run. Jumping from (9.5 static to 7.5 dynamic) with such late closing will shift your powerband very high in the rpm's. Also with this late closing you move the maximum torque up higher in the revs, right where you don't need it, at least on street anyway.

What the late closing effect will be is an engine with (blown) lots of power up high 3500/4500 rpm range, but no bottom end and poor mid range power. It will stuff you in the seat with wide open throttle to be sure, but may be very hard to idle and start. You will also have to consider (I think you are going to stuff this mill in the Burb aren't you?) vehicle weight and rear gearing. An engine like this would work best wide open, and with a stick shift, like a dragster. An auto would shift too early, and you won't have the necessary torque to recover.

If this was a drag car it would be simple. But it's not. You could just change cams when you install the blower. Because of the different requirements needed by adding the blower later, this complicates matters. If you want your engine to perform well NA, then build accordingly. The 9.5 comp seems ideal. But when you add the blower your base comp is way too high, and I feel that you will simply be moving your detonation problem just higher in the rpm's. You can't have it both
ways. This is not a drag engine that you will be tearing back down after 20 runs. It has to last and run cool enough, and responsive enough and be managable enough to be a everyday driver. With such late closing there is less time to fill the cylinder, and in "theory" less time for spontaneous combustion (detonation) to occur, but it may still and possibly with serious damaging effects at 4000 rpm!

Not trying to discourage you, but I think you should discuss all your build plans with maybe Speedo, someone knowledgable with street blower set-up's for advise on this so you will enjoy the end result and be happy with it. Also check with them on ceramic coating as I think they can have this done for you. They should advise you on rings also.

Think Chevy!

Chevyman,

You are not the first to question the approach I am planning. But nothing ventured, nothing gained. I have done a lot of reading on Miller cycle cams and talked with a couple of guys who have experience with this approach - when I called Iskendarian cams, they knew just what I was talking about and reported that they had done Miller cycle cam grinds for a number of different engines.

The reading I have done has been specifically about the Mazda Millenia and work done by Jaguar, Toyota and Nissan in recent years. The argument is that when the compression of the air/fuel mixture is equally shared between an efficient supercharger (aka Whipple design) and the subsequent compression of the charge by the piston, that maximum efficiency and performance can be had.

Low speed idle is reported to be smooth and bottom end torque is actually up to 30% higher than a NA motor. This is all documented by a variety of sources - in print (Corky Bell's book "Supercharging") and on the web in numerous automotive engineering "white papers".

I know it is not conventional - and that is why I went with the 9.5:1 compression ratio in the first place. It is ideal for NA application if my Miller experiment doesn't work, and optimum for the Miller approach as well.

The pressure balance point during the intake cycle where the intake charge stops entering the cylinder is actually between 25 and 35 degrees past BDC. If you run a standard grind, you are slamming the intake valve shut well before the cylinder has reached the same pressure as that of the supercharger induced pressure in the intake plenum. By delaying the closing of the intake valve, the cylinder pressure reaches equilibrium with the plenum pressure without any heating due to mechanical compression. Then, as the piston compresses the charge for the remaining 65 - 70 degrees of crank rotation, you have much less heating than if you had a full 85 or 90 degrees of compression stroke.

Does this make sense to you now or do you think I should save my money and put a 390 cfm four bbl on it?

Here is one link on the miller cycle engine.

Ken, I find your plans very interesting. I've been helping-looking over the shoulder of Leo Santuci who built a 292 turbo alcohol injected modified 53 coupe. Early results are encouraging, with boost set low, still dialing it in, ran 10.11 @ 130MPH. If you don't already have a copy of his book you might find it interesting. He runs a near stock cam and 3.73 gears. He is trying to persuade me to huff my 261. Just wonder about the rest of my drivetrain (T-5???) Please keep us posted on your project.